Cooling device using non-azeotropic coolant mixture

Abstract

This cooling device using a non-azeotropic coolant mixture comprises: a cooling circuit that includes a compressor for compressing the non-azeotropic coolant mixture and a heat exchanger for performing heat exchange with the non-azeotropic coolant mixture; a pressure sensor for measuring the pressure of the non-azeotropic coolant mixture; a temperature sensor for measuring the temperature of the non-azeotropic coolant mixture; and a control unit for specifying the concentration of a low-boiling-point gas coolant in the cooling circuit on the basis of the pressure of the non-azeotropic coolant mixture and the temperature of the non-azeotropic coolant mixture in the vicinity of a condenser as measured by the temperature sensor.

Description

Cooling device using azeotropic refrigerant mixture

[0001] This invention relates to a cooling device using an azeotropic refrigerant mixture.

[0002] Conventionally, a refrigeration and air conditioning device (cooling device) using an azeotropic refrigerant mixture, which is a refrigerant in which a low-boiling refrigerant and a high-boiling refrigerant are mixed, is known. Such a device is disclosed in, for example, Japanese Patent Laid-Open No. 8-75280.

[0003] Japanese Patent Laid-Open No. 8-75280 discloses a refrigeration and air conditioning device provided with a bypass pipe, a capillary tube, a double-tube heat exchanger, and a composition calculator in addition to a refrigeration cycle using an azeotropic refrigerant mixture which is a refrigerant in which a low-boiling refrigerant and a high-boiling refrigerant are mixed. In the refrigeration and air conditioning device of Japanese Patent Laid-Open No. 8-75280, a part of the azeotropic refrigerant mixture discharged from the compressor included in the refrigeration cycle flows into the bypass pipe, is condensed and liquefied by the double-tube heat exchanger, and is depressurized by the capillary tube. In Japanese Patent Laid-Open No. 8-75280, the composition calculator takes in the temperature and pressure of the azeotropic refrigerant mixture in a low-pressure and saturated state detected by a temperature detector and a pressure detector. Here, the composition calculator of Japanese Patent Laid-Open No. 8-75280 stores the relationship between the temperature and pressure of the azeotropic refrigerant mixture and the circulation composition (concentration ratio of each refrigerant to be mixed) of the azeotropic refrigerant mixture in the refrigeration cycle. Thereby, the composition calculator of Japanese Patent Laid-Open No. 8-75280 specifies the circulation composition of the azeotropic refrigerant mixture flowing through the bypass pipe and the like added to the refrigeration cycle based on the taken-in temperature and pressure of the azeotropic refrigerant mixture.

[0004] Japanese Patent Laid-Open No. 8-75280

[0005] As described in Japanese Patent Publication No. 8-75280, the composition calculator determines the circulating composition of the refrigerant flowing through bypass piping and other components added to the refrigeration cycle based on the temperature and pressure of the non-azeotropic mixed refrigerant that has been taken in. However, in Japanese Patent Publication No. 8-75280, it is necessary to add components such as bypass piping, capillary tubes, and double-tube heat exchangers, separate from the refrigeration cycle, in order to determine the composition of the non-azeotropic mixed refrigerant. This results in the disadvantage of making the refrigeration and air conditioning system (cooling system) larger and more complex. For this reason, there is a need for a cooling system that uses a non-azeotropic mixed refrigerant and can determine the composition of the non-azeotropic mixed refrigerant while suppressing the increase in size and complexity of the system.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a cooling device using a non-azeotropic refrigerant mixture that can identify the composition of the non-azeotropic refrigerant mixture while suppressing the increase in size and complexity of the device.

[0007] To achieve the above objective, a cooling device using a non-azeotropic mixed refrigerant according to the first aspect of this invention comprises a cooling circuit including a compressor for compressing a non-azeotropic mixed refrigerant, which is a mixture of a low-boiling-point refrigerant and a high-boiling-point refrigerant, and a heat exchanger for performing heat exchange of the non-azeotropic mixed refrigerant; a pressure sensor for measuring the pressure of the non-azeotropic mixed refrigerant, a temperature sensor for measuring the temperature of the non-azeotropic mixed refrigerant, and a control unit that determines the concentration of the low-boiling-point refrigerant in the cooling circuit based on the pressure of the non-azeotropic mixed refrigerant flowing into the heat exchanger measured by the pressure sensor and the temperature of the non-azeotropic mixed refrigerant near the heat exchanger measured by the temperature sensor. Here, "temperature of the non-azeotropic mixed refrigerant near the heat exchanger measured by the temperature sensor" in this invention is a broad concept that includes the temperature of the non-azeotropic mixed refrigerant, the temperature of the heat exchanger, and the temperature of the piping near the heat exchanger.

[0008] The cooling device using a non-azeotropic refrigerant mixture according to the first aspect of this invention includes a control unit that determines the concentration of the low-boiling-point refrigerant in the cooling circuit based on the pressure of the non-azeotropic refrigerant mixture flowing into the heat exchanger, measured by a pressure sensor placed in the cooling circuit, and the temperature of the non-azeotropic refrigerant mixture near the heat exchanger, measured by a temperature sensor. As a result, the concentration of the low-boiling-point refrigerant in the cooling circuit is determined based on the pressure and temperature of the non-azeotropic refrigerant mixture in the cooling circuit, eliminating the need for additional circuits (additional configurations) separate from the cooling circuit. Consequently, the composition of the non-azeotropic refrigerant mixture can be determined while suppressing the increase in size and complexity of the device.

[0009] In a cooling system using a non-azeotropic refrigerant mixture according to the first aspect described above, preferably, the control unit stores relational information showing the correspondence between the pressure of the non-azeotropic refrigerant mixture flowing into the heat exchanger, measured by a pressure sensor, the temperature of the non-azeotropic refrigerant mixture near the heat exchanger, measured by a temperature sensor, and the concentration of the low-boiling-point refrigerant in the cooling circuit. Based on this relational information, the control unit is configured to perform control to identify the concentration of the low-boiling-point refrigerant in the cooling circuit. With this configuration, the control unit can easily identify the concentration of the low-boiling-point refrigerant in the cooling circuit based on the relational information stored in advance.

[0010] In this case, preferably, the heat exchanger includes a condenser that condenses the non-azeotropic refrigerant mixture discharged by the compressor, and the control unit is configured to determine the concentration of the low-boiling-point refrigerant in the cooling circuit based on the pressure of the non-azeotropic refrigerant mixture flowing into the compressor or condenser measured by a pressure sensor, the saturation temperature of the non-azeotropic refrigerant mixture in the condenser, and related information. With this configuration, since the temperature sensor measures the non-azeotropic refrigerant mixture in a gaseous state flowing into the condenser, it is possible to measure the saturation temperature of the non-azeotropic refrigerant mixture more easily than when measuring the non-azeotropic refrigerant mixture in which gaseous and liquid states are mixed, such as in the part near the outlet side of the condenser. Here, "saturation temperature of the non-azeotropic refrigerant mixture in the condenser" refers to the saturation temperature of the non-azeotropic refrigerant mixture in a gaseous state in the condenser.

[0011] In a cooling system that uses a non-azeotropic mixed refrigerant and includes a condenser, the control unit is preferably configured to perform concentration reduction operation control to lower the concentration of the low-boiling-point refrigerant in the cooling circuit when a state value determined from the pressure of the non-azeotropic mixed refrigerant flowing into the condenser and the casing temperature of the compressor exceeds a concentration-specific threshold set according to the concentration of the low-boiling-point refrigerant in the cooling circuit. With this configuration, even when it is desired to suppress an increase in the concentration of the low-boiling-point refrigerant in the cooling circuit, the concentration increase can be appropriately suppressed in response to the relationship between the pressure of the non-azeotropic mixed refrigerant flowing into the condenser and the casing temperature of the compressor exceeding a concentration-specific threshold.

[0012] In this case, preferably, the control unit is configured to perform a concentration reduction operation control when the state value exceeds a concentration threshold, thereby increasing the superheating degree of the non-azeotropic mixed refrigerant flowing into the compressor. With this configuration, as the superheating degree increases, the evaporation of the non-azeotropic mixed refrigerant in the liquid portion where the high-boiling point refrigerant tends to accumulate is promoted, and the amount of gaseous high-boiling point refrigerant in the cooling circuit increases, thereby reducing the concentration of gaseous low-boiling point refrigerant in the cooling circuit.

[0013] In a cooling system using a non-azeotropic refrigerant, where the above-mentioned concentration reduction operation control involves increasing the superheating degree of the non-azeotropic refrigerant mixture flowing into the compressor, the control unit is preferably configured to reduce the compressor rotation speed if the state value exceeds a concentration-specific threshold even after the control has increased the superheating degree of the non-azeotropic refrigerant mixture flowing into the compressor. With this configuration, for example, if it is desired to avoid the low-boiling-point refrigerant becoming high temperature and high pressure even after the control has increased the superheating degree of the non-azeotropic refrigerant mixture flowing into the compressor, the pressure and temperature in the cooling circuit can be reduced by reducing the compressor rotation speed.

[0014] In a cooling system using a non-azeotropic mixed refrigerant that performs the concentration reduction operation control described above, the control unit is preferably configured to control the degree of superheating of the non-azeotropic mixed refrigerant flowing into the compressor, or the rotational speed of the compressor, so that the concentration of the low-boiling-point refrigerant in the cooling circuit approaches the concentration threshold, but within a range that does not exceed the concentration threshold. With this configuration, the concentration of the low-boiling-point refrigerant can be increased by bringing it closer to the concentration threshold. As a result, for example, if the cooling performance of the low-boiling-point refrigerant is superior to that of the high-boiling-point refrigerant, more efficient cooling can be achieved by increasing the concentration of the low-boiling-point refrigerant.

[0015] In a cooling system using a non-azeotropic refrigerant mixture, the heat exchanger described above includes a condenser, and preferably, a fan is further provided to blow air onto the condenser. The control unit is configured to increase the fan speed to increase the amount of heat dissipated by the condenser when the temperature of the non-azeotropic refrigerant mixture near the inlet side of the condenser is not at the saturation temperature. Here, since the non-azeotropic refrigerant mixture in a gaseous state becomes liquid somewhere along the path through the condenser, it is difficult to determine at which part of the condenser the non-azeotropic refrigerant mixture is at the saturation temperature. In contrast, with the above configuration, the position at which the non-azeotropic refrigerant mixture reaches the saturation temperature can be adjusted by increasing the amount of heat dissipated by the condenser using the fan. Therefore, it is possible to confirm that the non-azeotropic refrigerant mixture reaches the saturation temperature at a predetermined position without having to prepare many temperature sensors to determine the exact position at which the non-azeotropic refrigerant mixture reaches the saturation temperature. As a result, the concentration of low-boiling-point refrigerant in the cooling circuit can be easily determined based on the saturation temperature.

[0016] In a cooling system using a non-azeotropic mixed refrigerant that controls the concentration of the low-boiling-point refrigerant in the cooling circuit based on the above-mentioned relational information, preferably, the relational information includes table data showing the correspondence between the pressure of the non-azeotropic mixed refrigerant flowing into the heat exchanger measured by a pressure sensor, the temperature of the non-azeotropic mixed refrigerant near the heat exchanger measured by a temperature sensor, and the concentration of the low-boiling-point refrigerant in the cooling circuit. With this configuration, the concentration of the low-boiling-point refrigerant in the cooling circuit can be more easily determined based on the stored table data.

[0017] In a cooling system using a non-azeotropic refrigerant mixture according to the first aspect described above, preferably, the heat exchanger includes an evaporator for evaporating the non-azeotropic refrigerant mixture, an accumulator for temporarily storing the non-azeotropic refrigerant mixture discharged from the evaporator, and a liquid level gauge for measuring the liquid level of the non-azeotropic refrigerant mixture stored in the accumulator. The control unit is configured to perform control to identify the concentration of the low-boiling-point refrigerant in the cooling circuit based on relational information indicating the correspondence between the liquid level of the non-azeotropic refrigerant mixture in the accumulator placed in the cooling circuit, as measured by the liquid level gauge, and the concentration of the low-boiling-point refrigerant in the cooling circuit. With this configuration, for example, even if a pressure sensor or temperature sensor fails and the concentration of the low-boiling-point refrigerant in the cooling circuit cannot be identified, the concentration of the low-boiling-point refrigerant in the cooling circuit can still be identified based on relational information indicating the correspondence between the liquid level of the accumulator placed in the cooling circuit and the concentration of the low-boiling-point refrigerant in the cooling circuit.

[0018] In this case, preferably, the control unit is configured to perform concentration reduction operation control such that the concentration of low-boiling-point refrigerant in the cooling circuit is reduced when the liquid level of the non-azeotropic mixed refrigerant in the accumulator located in the cooling circuit, as measured by the liquid level gauge, exceeds a predetermined liquid level threshold. With this configuration, even when it is desired to suppress an increase in the concentration of low-boiling-point refrigerant in the cooling circuit, the concentration of low-boiling-point refrigerant in the cooling circuit can be appropriately reduced based on the measured liquid level exceeding the liquid level threshold.

[0019] In a cooling system using a non-azeotropic mixed refrigerant, which performs concentration reduction operation control to lower the concentration of the low-boiling-point refrigerant in the cooling circuit when the liquid level of the non-azeotropic mixed refrigerant in the accumulator exceeds a predetermined liquid level threshold, preferably the system further includes a bypass pipe that draws in the liquid non-azeotropic mixed refrigerant stored in the accumulator, converts it into a gaseous non-azeotropic mixed refrigerant, and draws it into the compressor, the control unit is configured to perform at least one of the following as concentration reduction operation control when the liquid level measured by the liquid level gauge exceeds the liquid level threshold: control to increase the degree of superheating of the non-azeotropic mixed refrigerant flowing into the compressor, control to decrease the rotational speed of the compressor, or control to draw the liquid stored in the accumulator into the compressor via the bypass pipe. With this configuration, controlling the superheating of the non-azeotropic refrigerant mixture flowing into the compressor promotes the evaporation of the non-azeotropic refrigerant mixture in the liquid portion where high-boiling point refrigerant tends to accumulate. This increases the amount of gaseous high-boiling point refrigerant in the cooling circuit, thus reducing the concentration of gaseous low-boiling point refrigerant in the cooling circuit. Furthermore, controlling the compressor's rotational speed reduces the pressure and temperature in the cooling circuit, for example, when it is desirable to avoid high temperature and pressure for the low-boiling point refrigerant. Additionally, controlling the system to draw the liquid stored in the accumulator into the compressor via a bypass pipe allows the non-azeotropic refrigerant mixture in the liquid portion of the accumulator, where high-boiling point refrigerant tends to accumulate, to be drawn into the compressor as a gaseous state via the bypass pipe and flow into the cooling circuit. As a result, the amount of gaseous high-boiling point refrigerant in the cooling circuit increases, thus reducing the concentration of gaseous low-boiling point refrigerant in the cooling circuit.

[0020] In a cooling system using a non-azeotropic refrigerant mixture, the heat exchanger preferably includes a condenser and a plurality of inlet temperature sensors located on the inlet side of the condenser and a plurality of outlet temperature sensors located on the outlet side of the condenser. The control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on a plurality of temperatures of the non-azeotropic refrigerant mixture in the condenser measured by the plurality of inlet temperature sensors and a plurality of temperatures of the non-azeotropic refrigerant mixture in the condenser measured by the plurality of outlet temperature sensors. With this configuration, it is possible to compare the temperature measurement results of the plurality of temperature sensors located on the inlet side of the condenser, where the measured temperature gradient is relatively large, with the temperature measurement results of the plurality of temperature sensors located on the outlet side of the condenser, where the measured temperature gradient is relatively small. As a result, it becomes easier to calculate the saturation temperature at which the temperature gradient of the non-azeotropic refrigerant mixture begins to decrease. In this invention, "inlet side of the condenser" refers to the half of the cooling coils included in the condenser that is closer to the compressor, and "outlet side of the condenser" refers to the half of the cooling coils included in the condenser that is closer to the expansion valve.

[0021] In this case, preferably, the control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on the difference in the positions of the two inlet-side temperature sensors and the difference in the temperature of the non-azeotropic refrigerant mixture in the condenser measured by each of the two inlet-side temperature sensors, and the difference in the positions of the two outlet-side temperature sensors and the difference in the temperature of the non-azeotropic refrigerant mixture in the condenser measured by each of the two outlet-side temperature sensors. With this configuration, the cooling rate can be calculated as a temperature gradient corresponding to the difference (distance) between the two temperature sensors on both the inlet and outlet sides of the condenser. Therefore, the saturation temperature at which the change in the cooling rate of the non-azeotropic refrigerant mixture begins to decrease can be appropriately calculated using the cooling rates on both the inlet and outlet sides of the condenser.

[0022] In a cooling system using a non-azeotropic mixed refrigerant, including the above-mentioned inlet-side temperature sensor and outlet-side temperature sensor, preferably, the condenser is provided with an ambient temperature sensor that measures the temperature of the environment surrounding the condenser, and this ambient temperature sensor also serves as the outlet-side temperature sensor. With this configuration, the number of outlet-side temperature sensors to be added to the condenser can be reduced. As a result, an increase in the number of parts in the cooling system can be suppressed.

[0023] In a cooling system using a non-azeotropic refrigerant mixture, including the above-described inlet and outlet temperature sensors, the control unit is preferably configured such that, when the temperature difference between the non-azeotropic refrigerant mixture measured by two of the multiple inlet temperature sensors is less than a predetermined threshold, the temperature of the non-azeotropic refrigerant mixture measured by the inlet temperature sensor closer to the inlet side of the condenser is identified as the saturation temperature of the non-azeotropic refrigerant mixture in the condenser. With this configuration, the saturation temperature of the non-azeotropic refrigerant mixture can be easily identified using only the multiple temperature sensors located on the inlet side of the condenser, without having to compare the temperature measurement results of multiple temperature sensors located on both the inlet and outlet sides of the condenser.

[0024] In a cooling system using a non-azeotropic refrigerant mixture, the heat exchanger includes a condenser, preferably the temperature sensor includes a thermograph, and the control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on the temperatures of the non-azeotropic refrigerant mixture at multiple points on the inlet side of the condenser measured by the thermograph and the temperatures of the non-azeotropic refrigerant mixture at multiple points on the outlet side of the condenser measured by the thermograph. With this configuration, the temperature of the entire condenser can be easily obtained by the thermograph, making it easy to determine the saturation temperature of the non-azeotropic refrigerant mixture. Furthermore, the device configuration can be simplified compared to, for example, the case where multiple contact-type temperature sensors are placed in the condenser.

[0025] To achieve the above objective, a cooling device using a non-azeotropic mixed refrigerant according to the second aspect of this invention comprises a cooling circuit including a compressor for compressing a non-azeotropic mixed refrigerant, which is a mixture of a low-boiling-point refrigerant and a high-boiling-point refrigerant, and a heat exchanger for performing heat exchange of the non-azeotropic mixed refrigerant; a temperature sensor for measuring the temperature of the non-azeotropic mixed refrigerant; and a control unit that identifies the concentration of the low-boiling-point refrigerant in the cooling circuit based on the saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger measured by the temperature sensor, the liquid saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger, and relational information showing the correspondence between the saturation temperature and the liquid saturation temperature and the concentration of the low-boiling-point refrigerant in the cooling circuit. Here, "liquid saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger" refers to the temperature at which the temperature appears to be saturated when the rate of temperature decrease becomes small after heat has been removed by the heat exchanger and the non-azeotropic mixed refrigerant has become liquid.

[0026] The cooling device using a non-azeotropic mixed refrigerant according to the second aspect of this invention includes a control unit that determines the concentration of the low-boiling-point refrigerant in the cooling circuit based on the saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger measured by a temperature sensor, the liquid saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger, and relational information showing the correspondence between the saturation temperature and the liquid saturation temperature and the concentration of the low-boiling-point refrigerant in the cooling circuit. This makes it possible to easily determine the concentration of the low-boiling-point refrigerant in the cooling circuit based on relational information showing the correspondence between the temperature difference between the saturation temperature and the liquid saturation temperature and the concentration of the low-boiling-point refrigerant in the cooling circuit, even if the pressure in the cooling circuit is unknown.

[0027] To achieve the above objective, a cooling device using a non-azeotropic mixed refrigerant according to the third aspect of this invention comprises a compressor for compressing a non-azeotropic mixed refrigerant, which is a mixture of a low-boiling-point refrigerant and a high-boiling-point refrigerant; an evaporator for evaporating the non-azeotropic mixed refrigerant; an accumulator for temporarily storing the non-azeotropic mixed refrigerant discharged from the evaporator; a liquid level gauge for measuring the liquid level of the non-azeotropic mixed refrigerant stored in the accumulator; and a control unit for determining the concentration of the low-boiling-point refrigerant in the cooling circuit based on relational information showing the correspondence between the liquid level of the non-azeotropic mixed refrigerant in the accumulator arranged in the cooling circuit, as measured by the liquid level gauge, and the concentration of the low-boiling-point refrigerant in the cooling circuit.

[0028] The cooling device using a non-azeotropic mixed refrigerant according to the third aspect of this invention includes a control unit that identifies the concentration of the low-boiling-point refrigerant in the cooling circuit based on relational information showing the correspondence between the liquid level height of the non-azeotropic mixed refrigerant in an accumulator placed in the cooling circuit, measured by a liquid level gauge, and the concentration of the low-boiling-point refrigerant in the cooling circuit. As a result, the concentration of the low-boiling-point refrigerant in the cooling circuit is identified based on relational information showing the correspondence between the liquid level height of the accumulator placed in the cooling circuit and the concentration of the low-boiling-point refrigerant in the cooling circuit, eliminating the need for additional circuits (additional configurations) separate from the cooling circuit. Consequently, it is possible to provide a cooling device that can identify the composition of a non-azeotropic mixed refrigerant while suppressing the increase in size and complexity of the device.

[0029] According to the present invention, it is possible to provide a cooling device using a non-azeotropic mixed refrigerant that can identify the composition of the non-azeotropic mixed refrigerant while suppressing an increase in the size and complexity of the device.

[0030] This is a block diagram of a cooling device according to the first embodiment of the present invention. This is a diagram showing the cooling circuit of a cooling device according to the first embodiment of the present invention. This is a diagram for explaining the accumulator of a cooling device according to the first embodiment of the present invention. This is a diagram for explaining the condenser of a cooling device according to the first embodiment of the present invention. This is a diagram for explaining how to obtain the saturation temperature of a non-azeotropic mixed refrigerant in the cooling circuit of a cooling device according to the first embodiment of the present invention. This is a diagram for explaining a table as relational information stored by the control unit of a cooling device according to the first embodiment of the present invention. This is a diagram for explaining the state values ​​obtained by the control unit of a cooling device according to the first embodiment of the present invention. This is a block diagram of a cooling device according to the second embodiment of the present invention. This is a diagram for explaining the cooling circuit of a cooling device according to the second embodiment of the present invention. This is a diagram for explaining how to calculate the low boiling point refrigerant concentration of a cooling device according to the second embodiment of the present invention. This is a diagram for explaining how to calculate the storage liquid refrigerant ratio of a cooling device according to the second embodiment of the present invention. This is a diagram for explaining the arrangement relationship between the condenser and the temperature sensor according to the third embodiment of the present invention. This is a diagram for explaining how to calculate the saturation temperature of a non-azeotropic mixed refrigerant in a condenser when the ambient temperature is relatively high, according to the third embodiment of the present invention. This is a diagram illustrating a method for calculating the saturation temperature of a non-azeotropic refrigerant mixture in a condenser when the ambient temperature is relatively low, according to the third embodiment of the present invention. This is a diagram illustrating the arrangement relationship between the condenser and the temperature sensor, according to the fourth embodiment of the present invention. This is a diagram illustrating a method for calculating the saturation temperature of a non-azeotropic refrigerant mixture in a condenser, according to the fourth embodiment of the present invention. This is a block diagram of a cooling device, according to the fifth embodiment of the present invention. This is a diagram illustrating the temperature distribution of the non-azeotropic refrigerant in the condenser, according to the fifth embodiment of the present invention. This is a diagram illustrating a method for calculating the saturation temperature of a non-azeotropic refrigerant mixture in a condenser, according to the fifth embodiment of the present invention. This is a block diagram of a cooling device, according to the sixth embodiment of the present invention. This is a diagram illustrating a table of relational information stored by the control unit of the cooling device, according to the sixth embodiment of the present invention. This is a diagram illustrating a method for calculating the saturation temperature and liquid saturation temperature of a non-azeotropic refrigerant mixture in a condenser, according to the sixth embodiment of the present invention. This is a block diagram of a cooling device, according to the seventh embodiment of the present invention.This is a diagram illustrating the arrangement relationship between the condenser and the temperature sensor according to the seventh embodiment of the present invention. This is a diagram illustrating the method for calculating the saturation temperature of a non-azeotropic refrigerant mixture in a condenser according to the seventh embodiment of the present invention. This is a diagram illustrating the mathematical formula as relational information stored in the control unit of the cooling device according to the first modification of the present invention. This is a diagram illustrating the arrangement relationship between the condenser and the temperature sensor according to the second modification of the present invention. This is a diagram illustrating the method for calculating the saturation temperature of a non-azeotropic refrigerant mixture in a condenser third modification of the present invention.

[0031] [First Embodiment] Hereinafter, a first embodiment embodying the present invention will be described based on the drawings.

[0032] (Configuration of the cooling device) The configuration of the cooling device 100 according to the first embodiment will be described with reference to Figures 1 to 7. Note that the cooling device 100 is an example of a "cooling device using a non-azeotropic mixed refrigerant" as defined in the claims.

[0033] In the first embodiment, the cooling device 100 includes a compressor 1, a condenser 2, a fan 2a, an expansion valve 3, an evaporator 4, a fan 4a, an accumulator 5, a pressure sensor 6, a temperature sensor 7, a housing temperature sensor 8, a cooling circuit 101 consisting of piping 101a to piping 101e, and a control unit 10. As shown in Figure 2, the cooling circuit 101 is a closed circuit that completes one loop.

[0034] A non-azeotropic mixed refrigerant 20, which includes a high-boiling-point gaseous refrigerant 21a (see Figure 3), a low-boiling-point gaseous refrigerant 22a (see Figure 3), a high-boiling-point liquid refrigerant 21b (see Figure 3), and a low-boiling-point liquid refrigerant 22b (see Figure 3), circulates within the cooling circuit 101 of the cooling device 100. The cooling device 100 is configured to cool the interior of a cooling chamber (not shown) by performing heat exchange of the non-azeotropic mixed refrigerant 20. The cooling device 100 is, for example, a display case. Note that the high-boiling-point gaseous refrigerant 21a and the high-boiling-point liquid refrigerant 21b are examples of "high-boiling-point refrigerants" in the claims, and the low-boiling-point gaseous refrigerant 22a and the low-boiling-point liquid refrigerant 22b are examples of "low-boiling-point refrigerants" in the claims.

[0035] As shown in Figure 2, the compressor 1 is configured to compress a non-azeotropic refrigerant mixture 20. The compressor 1 is controlled by an inverter (not shown). The compressor 1 is configured to allow adjustment of the flow rate of the non-azeotropic refrigerant mixture 20 discharged from the compressor 1. In this first embodiment, the compressor 1 is located below the cooling chamber housing (not shown).

[0036] The condenser 2 is a heat exchanger located outside the cooling chamber (not shown). The condenser 2 is configured to condense the refrigerant discharged from the compressor 1. The condenser 2 is equipped with a fan 2a, which is configured to supply air to the condenser 2. Heat is then transferred from the non-azeotropic refrigerant mixture 20 in the condenser 2 to the air supplied by the fan 2a, and heat is removed from the non-azeotropic refrigerant mixture 20. Note that the condenser 2 is an example of a "heat exchanger" as defined in the claims. The detailed configuration of the condenser 2 will be described later.

[0037] The expansion valve 3 is configured to expand the non-azeotropic refrigerant mixture 20 condensed by the condenser 2. In this first embodiment, the expansion valve 3 is an electronic expansion valve operated by, for example, a stepping motor (not shown). By adjusting the opening degree of the expansion valve 3, the amount of non-azeotropic refrigerant mixture 20 supplied to the evaporator 4 located downstream of the cooling circuit 101 is adjusted. The opening degree of the expansion valve 3 is adjusted by a stepping motor that receives a control command output from the control unit 10.

[0038] The evaporator 4 is configured to evaporate the non-azeotropic refrigerant mixture 20 that has been expanded by the expansion valve 3. The evaporator 4 also includes a fan 4a. The evaporator 4 removes heat from the non-azeotropic refrigerant mixture 20 by air supplied to the evaporator 4 body from the fan 4a. Note that the evaporator 4 is an example of a "heat exchanger" as defined in the claims.

[0039] The accumulator 5 is positioned between the compressor 1 and the evaporator 4 and is provided to prevent the non-azeotropic refrigerant mixture 20 from being drawn into the compressor 1 in a liquid state. The accumulator 5 is also configured to temporarily store the non-azeotropic refrigerant mixture 20 discharged from the evaporator 4. As a result, the accumulator 5 is configured to keep the pressure of the non-azeotropic refrigerant mixture 20 inside the cooling circuit 101 close to a constant pressure, even when fluctuations occur in the cooling load.

[0040] As shown in Figure 3, the accumulator 5 contains piping 101e connected to the evaporator 4 (see Figure 1) and piping 101a connected to the compressor 1 (see Figure 1). The non-azeotropic mixed refrigerant 20 inside the accumulator 5 includes a high-boiling point gaseous refrigerant 21a and a low-boiling point gaseous refrigerant 22a, and a high-boiling point liquid refrigerant 21b and a low-boiling point liquid refrigerant 22b. In this case, the low-boiling point liquid refrigerant 22b preferentially evaporates from the non-azeotropic mixed refrigerant 20 liquid in which the high-boiling point liquid refrigerant 21b (see Figure 4) and the low-boiling point liquid refrigerant 22b are mixed inside the accumulator 5, so the proportion of low-boiling point gaseous refrigerant 22a in the space increases. As a result, the concentration of low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 drawn in by the compressor 1 increases, and the concentration of low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 throughout the entire cooling circuit 101 may increase. The operation of the control unit 10 in suppressing the increase in the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 will be described later.

[0041] The pressure sensor 6 shown in Figure 2 is, for example, located in the piping 101b connecting the compressor 1 and the condenser 2, and continuously measures the pressure of the non-azeotropic refrigerant mixture 20 flowing into the condenser 2. The pressure sensor 6 is also configured to communicate with the control unit 10 and transmits the measured pressure of the non-azeotropic refrigerant mixture 20 in the piping 101b to the control unit 10.

[0042] The temperature sensor 7 is arranged, for example, on the condenser 2 and is configured to constantly measure the temperature of the zeotropic mixture refrigerant 20 flowing into the condenser 2. In this first embodiment, a plurality of temperature sensors 7 are arranged. Further, the temperature sensor 7 is configured to be communicable with the control unit 10 and transmits the temperature of the zeotropic mixture refrigerant 20 flowing into the condenser 2 to the control unit 10. The detailed configuration of the temperature sensor 7 will be described later.

[0043] The housing temperature sensor 8 is arranged, for example, on the compressor 1 and measures the housing temperature of the compressor 1. Note that the housing temperature of the compressor 1 and the temperature of the zeotropic mixture refrigerant 20 inside the compressor 1 are substantially equal values. Further, the housing temperature sensor 8 is configured to be communicable with the control unit 10 and transmits the measured pressure of the zeotropic mixture refrigerant 20 inside the compressor 1 to the control unit 10.

[0044] The control unit 10 includes arithmetic units (not shown) such as a CPU (Central Processing Unit) as a processor, a ROM (Read Only Memory), and a RAM (Random Access Memory). In this first embodiment, the control unit 10 is configured to acquire the detection values of the pressure sensor 6, the temperature sensor 7, and the housing temperature sensor 8, and is also configured to control the operations of the compressor 1, the fan 2a, the fan 4a, and the expansion valve 3. Further, the control unit 10 includes a storage unit (not shown) such as a hard disk drive or a semiconductor storage device, and stores programs for operating various components and table data D1 (see FIG. 6) as relationship information to be described later.

[0045] The pipes 101a to 101e are metal pipes through which the zeotropic mixture refrigerant 20 flows, and are formed of a metal having relatively high thermal conductivity such as copper, for example. In this first embodiment, the pipe connecting the accumulator 5 and the compressor 1 is the pipe 101a, the pipe connecting the compressor 1 and the condenser 2 is the pipe 101b, the pipe connecting the condenser 2 and the expansion valve 3 is the pipe 101c, the pipe connecting the expansion valve 3 and the evaporator 4 is the pipe 101d, and the pipe connecting the evaporator 4 and the accumulator 5 is the pipe 101e.

[0046] Here, the detailed configurations of the condenser 2 and the temperature sensor 7 will be described with reference to FIG. 4. As shown in FIG. 4, the condenser 2 includes a cooling coil 2b disposed at a position where the cooling air generated by the fan 2a hits, and cooling fins 2c. In this first embodiment, the condenser 2 is a so-called fin-and-coil type heat exchanger. The heat of the zeotropic mixture refrigerant 20 flowing in the cooling coil 2b that has flowed in from the pipe 101b is radiated through the cooling fins 2c, and further, the heat radiation is promoted by the fan 2a. As a result, the temperature of the zeotropic mixture refrigerant 20 flowing in the cooling coil 2b decreases, and the zeotropic mixture refrigerant 20 condenses into a liquid.

[0047] Here, in this first embodiment, the temperature sensor 7 includes a temperature sensor 7a, a temperature sensor 7b, and a temperature sensor 7c, and is arranged in this order, for example, near the inlet side of the condenser 2. Therefore, the temperature measured by the temperature sensor 7a is a temperature equal to or higher than the temperature measured by the temperature sensor 7b, and the temperature measured by the temperature sensor 7b is a temperature equal to or higher than the temperature measured by the temperature sensor 7a. In addition, the locations where each of the temperature sensor 7a, the temperature sensor 7b, and the temperature sensor 7c is arranged are arranged, for example, at a position about 1 / 4 of the total length of the cooling coil 2b from the connection position between the cooling coil 2b and the pipe 101b.

[0048] (Specific operation of low-boiling-point gas refrigerant) Next, a method for measuring the saturation temperature of the zeotropic mixture refrigerant 20 will be described with reference to FIGS. 1 to 7. In this first embodiment, the control unit 10 shown in FIG. 1 determines that the saturation temperature of the zeotropic mixture refrigerant 20 in the condenser 2 is the value measured by the temperature sensor 7b if the difference between the temperature measured by the temperature sensor 7b (see FIG. 4) and the temperature measured by the temperature sensor 7c is within 0.5°C. Further, when the difference between the temperature measured by the temperature sensor 7b and the temperature measured by the temperature sensor 7c exceeds 0.5°C, the control unit 10 determines that the temperature of the zeotropic mixture refrigerant 20 in the condenser 2 has not reached the saturation temperature, and performs control to increase the rotation speed of the fan 2a.

[0049] Here, for example, as shown in Figure 5, suppose the temperature measured by temperature sensor 7a is 48.0°C and the temperature measured by temperature sensor 7b is 46.0°C. In this case, if the temperature T1 measured by temperature sensor 7c is 44.5°C, the control unit 10 increases the rotation speed of fan 2a based on the fact that the difference between the temperature measured by temperature sensor 7b and the temperature measured by temperature sensor 7c is 1.5°C, which is greater than 0.5°C. As a result, the amount of heat dissipated from condenser 2 increases, and the temperature of the non-azeotropic refrigerant mixture 20 decreases at an earlier timing.

[0050] Then, after the rotation speed of fan 2a increases, if the temperature T2 measured by temperature sensor 7c is 45.7°C, the control unit 10 determines that the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 is 46.0°C, based on the fact that the difference between the temperature measured by temperature sensor 7b and the temperature measured by temperature sensor 7c is within 0.5°C. As mentioned above, the control unit 10 also acquires the pressure of the non-azeotropic refrigerant mixture 20 in the piping 101b measured by pressure sensor 6.

[0051] Here, the control unit 10 stores table data D1, as shown in Figure 6, as pre-acquired data. Table data D1 shows the correspondence between the saturation temperature and pressure of the non-azeotropic refrigerant mixture 20 in the piping 101b of the cooling circuit 101 and the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic refrigerant mixture 20. For example, if the saturation temperature of the non-azeotropic refrigerant mixture 20 is 46.0°C and the pressure is 1.7 MPa, the control unit 10 can determine that the concentration of the low-boiling point gaseous refrigerant 22a in the gaseous non-azeotropic refrigerant mixture 20 is 35.0%. In this way, the composition of the gaseous non-azeotropic refrigerant mixture 20 (the concentration ratio of high-boiling point gaseous refrigerant 21a to low-boiling point gaseous refrigerant 22a) can be determined. In other words, the control unit 10 does not directly measure the concentration of the low-boiling-point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20, but instead uses so-called soft sensing, indirectly determining the concentration of the low-boiling-point gaseous refrigerant 22a based on the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 and the saturation temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2, using table data D1. Table data D1 is an example of "relevant information" in the claims.

[0052] (Concentration adjustment operation of low-boiling point gaseous refrigerant) Here, for example, if the low-boiling point gaseous refrigerant 22a is flammable or corrosive, it is necessary to suppress the increase in the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101. For this reason, the control unit 10 is configured to perform a concentration reduction operation control to lower the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 when the state value determined from the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 and the housing temperature of the compressor 1 exceeds a concentration threshold including a first concentration threshold, a second concentration threshold, and a third concentration threshold, which are set according to the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101.

[0053] Here, the control unit 10 stores the correspondence between state values ​​and concentration threshold values ​​as pre-acquired data. In this first embodiment, for example, the first concentration threshold value, which is one of the concentration threshold values, is the threshold value when the concentration of the low-boiling point gaseous refrigerant 22a is 35%, the second concentration threshold value is the threshold value when the concentration of the low-boiling point gaseous refrigerant 22a is 40%, and the third concentration threshold value is the threshold value when the concentration of the low-boiling point gaseous refrigerant 22a is 45%.

[0054] In this first embodiment, we will describe the case where, for example, the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 is 40.0%. The control unit 10 also obtains information from the housing temperature sensor 8, which measures the temperature of the compressor 1, that the housing temperature of the compressor 1 is 45°C. As a result, the state value takes the value shown at point S1 in Figure 7. At this time, point S1 as the state value is a position that does not exceed the second concentration threshold when the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 is 40.0%, so the control unit 10 does not need to perform concentration reduction operation control.

[0055] Here, for example, if there is a reason such as a large latent heat of vaporization of the low-boiling point gaseous refrigerant 22a (high cooling performance), it may be desirable to increase the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101. In this case, the control unit 10 controls the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 to approach the second concentration threshold, without exceeding the second concentration threshold, which is a threshold value for each concentration. To this end, the control unit 10 is configured to perform controls such as issuing a signal to adjust the opening degree of the expansion valve 3, thereby reducing the degree of superheating of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, or increasing the rotational speed of the compressor 1.

[0056] Next, we will explain the case where, as a result of the control unit 10 performing the above control, the state value transitions from point S1 to point S2, as shown in Figure 7. At this time, point S2 as the state value is a position that exceeds the second concentration threshold when the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 is 40.0%, so the control unit 10 needs to perform concentration reduction operation control.

[0057] At this time, the control unit 10 performs control to increase the superheating of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, for example by issuing a signal to adjust the opening degree of the expansion valve 3 as a concentration reduction operation control. This promotes the evaporation of the high-boiling-point liquid refrigerant 21b accumulated in the piping 101a to piping 101e and the accumulator 5. Based on the saturation temperature and pressure of the non-azeotropic mixed refrigerant 20, the control unit 10 calculates the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 and continues the above control so that the state value does not exceed a concentration threshold corresponding to the concentration of the low-boiling-point gaseous refrigerant 22a.

[0058] Furthermore, if the state value exceeds a concentration-specific threshold corresponding to the concentration of the low-boiling-point gaseous refrigerant 22a even after performing the above concentration reduction operation control, a command is given to an inverter (not shown) that operates the compressor 1 to reduce the rotational speed of the compressor 1. As a result, the pressure in the cooling circuit 101 decreases, and the state value is adjusted so that it does not exceed a concentration-specific threshold corresponding to the concentration of the low-boiling-point gaseous refrigerant 22a.

[0059] (Effects of the First Embodiment) Next, the effects of the first embodiment described above will be explained.

[0060] The cooling device 100 of the first embodiment described above includes a compressor 1 for compressing a non-azeotropic mixed refrigerant 20 containing a high-boiling-point gaseous refrigerant 21a, a low-boiling-point gaseous refrigerant 22a, a high-boiling-point liquid refrigerant 21b, and a low-boiling-point liquid refrigerant 22b; a cooling circuit 101 including a condenser 2 and an evaporator 4 as heat exchangers for heat exchange of the non-azeotropic mixed refrigerant 20; a pressure sensor 6 disposed in the compressor 1 or the piping 101b of the cooling circuit 101 connecting the compressor 1 and the evaporator 4 for measuring the pressure of the non-azeotropic mixed refrigerant 20; a temperature sensor 7 disposed in the condenser 2 for measuring the temperature of the non-azeotropic mixed refrigerant 20; and a control unit 10 that determines the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 based on the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6 and the temperature of the non-azeotropic mixed refrigerant 20 near the condenser 2 measured by the temperature sensor 7. As a result, the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 is determined based on the pressure and temperature of the non-azeotropic mixed refrigerant 20 in the cooling circuit 101, eliminating the need for additional circuits (additional configurations) separate from the cooling circuit 101. Consequently, the composition of the non-azeotropic mixed refrigerant 20 can be determined while suppressing the enlargement and complexity of the cooling device 100.

[0061] In the first embodiment described above, the control unit 10 stores table data D1 as relational information showing the correspondence between the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6, the temperature of the non-azeotropic mixed refrigerant 20 near the heat exchanger measured by the temperature sensor 7, and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101. The control unit 10 is configured to perform control to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the table data D1. As a result, the control unit 10 can easily identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the table data D1 that has been stored in advance.

[0062] Furthermore, in the first embodiment described above, the heat exchanger includes a condenser 2 that condenses the non-azeotropic mixed refrigerant 20 discharged by the compressor 1, and the control unit 10 is configured to determine the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the pressure of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1 or condenser 2 measured by the pressure sensor 6, the saturation temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2, and the table data D1. As a result, since the temperature sensor 7 measures the non-azeotropic mixed refrigerant 20 in a gaseous state flowing into the condenser 2, it is possible to measure the saturation temperature of the non-azeotropic mixed refrigerant 20 more easily than when measuring the non-azeotropic mixed refrigerant 20 in a mixture of gaseous and liquid states, such as in the part near the outlet side of the condenser 2.

[0063] Furthermore, in the first embodiment described above, the control unit 10 is configured to perform concentration reduction operation control to lower the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 when the state value determined from the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 and the housing temperature of the compressor 1 exceeds a concentration threshold set according to the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101. This makes it possible to appropriately suppress the concentration increase of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101, even when it is desired to suppress the increase in concentration.

[0064] Furthermore, in the first embodiment described above, the control unit 10 is configured to perform a concentration reduction operation control when the state value exceeds a concentration threshold, thereby increasing the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1. As a result, increasing the superheating degree promotes the evaporation of the non-azeotropic mixed refrigerant 20 in the liquid portion where the high-boiling-point liquid refrigerant 21b tends to accumulate, increasing the amount of gaseous high-boiling-point refrigerant in the cooling circuit 101, and thus reducing the concentration of gaseous low-boiling-point gaseous refrigerant 22a in the cooling circuit 101.

[0065] Furthermore, in the first embodiment described above, the control unit 10 is configured to reduce the rotational speed of the compressor 1 if the state value exceeds a concentration threshold even after it has controlled to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1. This allows, for example, the pressure and temperature in the cooling circuit 101 to be lowered by reducing the rotational speed of the compressor 1 when it is desired to avoid the low boiling point gaseous refrigerant 22a becoming high temperature and high pressure even after it has controlled to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1.

[0066] Furthermore, in the first embodiment described above, the control unit 10 is configured to control the degree of superheating of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, or the rotational speed of the compressor 1, so as to bring the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 closer to the concentration threshold, but within a range that does not exceed the concentration threshold. This allows the concentration of the low-boiling-point gaseous refrigerant 22a to be increased by bringing it closer to the concentration threshold. As a result, for example, if the cooling performance of the low-boiling-point gaseous refrigerant 22a is superior to that of the high-boiling-point gaseous refrigerant 21a, more efficient cooling can be achieved by increasing the concentration of the low-boiling-point gaseous refrigerant 22a.

[0067] Furthermore, in the first embodiment described above, a fan 2a is provided to blow air into the condenser 2, and the control unit 10 is configured to increase the rotation speed of the fan 2a to increase the amount of heat dissipated by the condenser 2 when the temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2 is not at the saturation temperature. Here, since the non-azeotropic mixed refrigerant 20 in a gaseous state becomes a liquid state somewhere along the path through the condenser 2, it is difficult to determine at which part of the condenser 2 the non-azeotropic mixed refrigerant 20 is at the saturation temperature. In contrast, with the above configuration, the position at which the non-azeotropic mixed refrigerant 20 reaches the saturation temperature can be adjusted by increasing the amount of heat dissipated by the condenser 2 with the fan 2a. Therefore, it is possible to confirm that the non-azeotropic mixed refrigerant 20 reaches the saturation temperature at a predetermined position without having to prepare many temperature detectors to determine the exact position at which the non-azeotropic mixed refrigerant 20 reaches the saturation temperature. As a result, the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 can be easily determined based on the saturation temperature.

[0068] Furthermore, in the first embodiment described above, the related information includes table data D1 that shows the correspondence between the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6, the temperature of the non-azeotropic mixed refrigerant 20 near the heat exchanger measured by the temperature sensor 7, and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101. This makes it easier to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the stored table data D1.

[0069] [Second Embodiment] Next, with reference to Figures 8 to 11, the configuration of the cooling device 100a according to the second embodiment of the present invention will be described. In this second embodiment, for example, even if the pressure sensor 6 or temperature sensor 7 fails and the control unit 10a is unable to measure the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102, a configuration will be described in which the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102 is determined in a different manner from that of the first embodiment.

[0070] (Cooling Circuit Structure) The cooling device 100a shown in Figure 8 has the same configuration as the cooling device 100 shown in the first embodiment, except that a liquid level gauge 5a, a valve 5b, and piping 101f are additionally provided in the cooling circuit 102. Note that the second embodiment does not need to be explained in relation to the first embodiment. Note that piping 101f is an example of a "bypass pipe" as defined in the claims.

[0071] As shown in Figure 9, the liquid level gauge 5a is configured to measure the liquid level of the non-azeotropic mixed refrigerant 20 stored inside the accumulator 5. The liquid level gauge 5a is also configured to communicate with the control unit 10 and transmits the measured liquid level information to the control unit 10.

[0072] Furthermore, near the bottom of the accumulator 5, there is a pipe 101f connected to a pipe 101a that connects the accumulator 5 and the compressor 1 via a valve 5b. The valve 5b is configured to be controlled by the control unit 10. The pipe 101f is, for example, a copper pipe and is equipped with a pipe heater (not shown) and is configured to change the non-azeotropic mixed refrigerant 20 drawn into the accumulator 5 in a liquid state into a gaseous state.

[0073] (Identification of low-boiling point gaseous refrigerant concentration and control of concentration reduction operation) Here, the control unit 10 stores the stored liquid refrigerant ratio to the liquid level height acquired in advance, as shown in Figure 10, and calculates the stored liquid refrigerant ratio based on the acquired liquid level height. The control unit 10 can calculate the amount (volume) of non-azeotropic mixed refrigerant 20 stored in liquid form in the accumulator 5 by multiplying the liquid level height measured by the liquid level gauge 5a by the bottom area of ​​the accumulator 5, which is set in advance by the user or the like. The stored liquid refrigerant ratio indicates the ratio of the non-azeotropic mixed refrigerant 20 stored in liquid form in the accumulator 5 to the total amount of non-azeotropic mixed refrigerant 20 sealed in the cooling circuit 102.

[0074] Furthermore, in this second embodiment, the control unit 10 stores mathematical formula data D2 as relational information showing the correspondence between the previously acquired stored liquid refrigerant ratio and the concentration of the low-boiling point gaseous refrigerant 22a, as shown in Figure 11. The mathematical formula data D2 is a function represented by y = f(x), with the stored liquid refrigerant ratio on the x-axis and the low-boiling point refrigerant concentration on the y-axis. This makes it possible to determine the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 based on the liquid level height of the non-azeotropic mixed refrigerant 20 in the liquid state in the accumulator, which is determined by the liquid level gauge 5a. For example, based on the mathematical formula data D2, the control unit 10 determines that if the stored liquid refrigerant ratio is 12%, the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 is 33%.

[0075] Here, the control unit 10 performs concentration reduction operation control to lower the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102 when the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5 located in the cooling circuit 102, as measured by the liquid level gauge 5a, exceeds a predetermined liquid level threshold h1, so that the concentration of the low-boiling-point gaseous refrigerant 22a does not exceed a predetermined concentration. Specifically, the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5 is set to be smaller than the liquid level threshold h1 which corresponds to the stored liquid refrigerant ratio R that is the concentration threshold C of the low-boiling-point gaseous refrigerant 22a shown in Figure 11, so that the concentration of the low-boiling-point gaseous refrigerant 22a does not exceed the concentration threshold C shown in Figure 11. Note that this liquid level threshold h1 differs depending on the state value.

[0076] The control unit 10 is configured to perform at least one of the following controls as a concentration reduction operation control when the liquid level of the non-azeotropic refrigerant mixture 20 in the accumulator 5 exceeds the liquid level threshold h1: increasing the superheating of the non-azeotropic refrigerant mixture 20 flowing into the compressor 1, decreasing the rotational speed of the compressor 1, or causing the liquid non-azeotropic refrigerant mixture 20 stored in the accumulator 5 to be drawn into the compressor 1 via the piping 101f. In this second embodiment, the control unit 10 controls the intake of the liquid non-azeotropic refrigerant mixture 20 stored in the accumulator 5 into the compressor 1 via the piping 101f. After turning on a heater (not shown) that heats the piping 101f, the control unit 10 controls the valve 5b to open so that the gaseous non-azeotropic refrigerant mixture 20 can flow into the compressor 1. This reduces the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102.

[0077] (Effects of the second embodiment) Next, the effects of the second embodiment will be described.

[0078] In the cooling device 100a of the second embodiment described above, the heat exchanger includes an evaporator 4 for evaporating a non-azeotropic mixed refrigerant 20, an accumulator 5 for temporarily storing the non-azeotropic mixed refrigerant 20 discharged from the evaporator 4, and a liquid level gauge 5a for measuring the liquid level of the non-azeotropic mixed refrigerant 20 stored in the accumulator 5. The control unit 10a is configured to perform control to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 based on mathematical formula data D2 as relational information showing the correspondence between the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5 located in the cooling circuit 102, as measured by the liquid level gauge 5a, and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102. This allows the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102 to be determined, even if, for example, the pressure sensor 6 or temperature sensor 7 malfunctions and the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102 cannot be determined, based on mathematical data D2 which shows the correspondence between the liquid level of the accumulator 5 located in the cooling circuit 102 and the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102.

[0079] In the cooling device 100a of the second embodiment described above, the control unit 10a is configured to perform concentration reduction operation control to reduce the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 when the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5 located in the cooling circuit 102, as measured by the liquid level gauge 5a, exceeds a predetermined liquid level threshold h1. This makes it possible to appropriately reduce the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 based on the measured liquid level exceeding the liquid level threshold h1, even when it is desired to suppress an increase in the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102.

[0080] The cooling device 100a of the second embodiment described above is further equipped with a pipe 101f that draws in the liquid non-azeotropic mixed refrigerant 20 stored in the accumulator 5 and converts it into a gaseous non-azeotropic mixed refrigerant 20 for intake into the compressor 1. The control unit 10a is configured to perform at least one of the following controls as a concentration reduction operation control when the liquid level height measured by the liquid level gauge 5a exceeds the liquid level threshold h1: control to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, control to decrease the rotational speed of the compressor 1, or control to draw the liquid stored in the accumulator 5 into the compressor 1 via the pipe 101f. This allows control to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, thereby promoting the evaporation of the non-azeotropic mixed refrigerant 20 in the liquid portion where the high-boiling point liquid refrigerant 21b tends to accumulate. This increases the amount of gaseous high-boiling point gaseous refrigerant 21a in the cooling circuit 102, thus lowering the concentration of gaseous low-boiling point gaseous refrigerant 22a in the cooling circuit 102. Additionally, by controlling the rotation speed of the compressor 1 to decrease, for example, when it is desirable to avoid the low-boiling point gaseous refrigerant 22a becoming high temperature and pressure, the pressure and temperature in the cooling circuit 102 can be lowered. Furthermore, by controlling the liquid stored in the accumulator 5 to be drawn into the compressor 1 via piping 101f, the non-azeotropic mixed refrigerant 20 in the liquid portion of the accumulator 5, where the high-boiling point liquid refrigerant 21b tends to accumulate, can be drawn into the compressor 1 in a gaseous state via piping 101f and flow into the cooling circuit 102. As a result, the amount of high-boiling-point gaseous refrigerant 21a in the cooling circuit 102 increases, which in turn reduces the concentration of low-boiling-point gaseous refrigerant 22a in the cooling circuit 102.

[0081] Furthermore, the other effects of the second embodiment are the same as those of the first embodiment.

[0082] [Third Embodiment] Next, the configuration of the cooling device 100b (see Figure 12) according to the third embodiment of the present invention will be described with reference to Figures 12 to 14. In this third embodiment, the temperature sensor 7 is placed in a different position relative to the condenser 2 than in the first embodiment, thereby determining the saturation temperature of the non-azeotropic mixed refrigerant 20 in the condenser 2 and determining the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101. Note that the cooling device 100b according to the third embodiment of the present invention has the same configuration as the cooling device 100 of the first embodiment (see Figure 1), except for the change in the placement of the temperature sensor 7. Points common to the first embodiment in the third embodiment will not be explained.

[0083] (Arrangement of temperature sensors) As shown in Figure 12, the cooling device 100b of the third embodiment has temperature sensors 7a, 7b, 7d, and 7e arranged in the condenser 2. Temperature sensors 7a and 7b are examples of the "multiple inlet-side temperature sensors" in the claims, and temperature sensors 7c and 7d are examples of the "multiple outlet-side temperature sensors" in the claims.

[0084] The inlet-side temperature sensors, temperature sensors 7a and 7b, are positioned on the inlet side of the cooling coil 2b of the condenser 2, beyond the halfway point of its total length. Specifically, temperature sensors 7a and 7b are positioned, for example, from the connection point between the cooling coil 2b and the piping 101b to a point approximately one-quarter of the way along the total length of the cooling coil 2b. More specifically, temperature sensor 7a is positioned at bend number b1, which is the connection point between the cooling coil 2b and the piping 101b, and temperature sensor 7a is positioned at bend number b2, which is the first bend in the cooling coil 2b. Although bend number b1 is not strictly a bend, it is described as a bend for convenience. The distances between each bend number are approximately equal.

[0085] The outlet-side temperature sensors, temperature sensors 7d and 7e, are positioned on the outlet side of the cooling coil 2b of the condenser 2, beyond the halfway point of its total length. Specifically, temperature sensors 7d and 7e are positioned, for example, from the connection point between the cooling coil 2b and the piping 101c to a point approximately halfway through the total length of the cooling coil 2b. More specifically, temperature sensor 7d is positioned at bend number b20, which is the 20th bend from the inlet side of the cooling coil 2b, and temperature sensor 7e is positioned at bend number b23, which is the 23rd bend from the inlet side of the cooling coil 2b.

[0086] (Determination of Saturation Temperature) Here, the control unit 10 (see Figure 1) determines the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on multiple temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by multiple inlet-side temperature sensors 7 and multiple temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by multiple outlet-side temperature sensors 7. Specifically, the control unit 10 (see Figure 1) will explain an example in which it calculates (determines) the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 using the temperatures of the non-azeotropic refrigerant mixture 20 measured by temperature sensors 7a, 7b, 7d, and 7e, respectively, in the summer when the ambient temperature of the location where the condenser 2 is installed is relatively high. Note that in the summer when the ambient temperature of the location where the condenser 2 is installed is relatively high, the temperature gradient of the non-azeotropic refrigerant mixture 20 on the inlet side of the condenser 2 is relatively large.

[0087] In Figure 13, the horizontal axis represents the bend numbers arranged at equal intervals, and the vertical axis represents the temperature [°C] measured by the temperature sensor 7. At bend number b1, located on the inlet side of condenser 2, the temperature T11 is measured by temperature sensor 7a (see Figure 12), and at bend number b2, the temperature T12 is measured by temperature sensor 7b (see Figure 12). Furthermore, at bend number b20, located on the outlet side of condenser 2, the temperature T13 is measured by temperature sensor 7d (see Figure 12), and at bend number b23, the temperature T14 is measured by temperature sensor 7e (see Figure 12).

[0088] Here, the control unit 10 (see Figure 1) determines the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on the difference in the positions of the two inlet-side temperature sensors 7a and 7b, the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the two inlet-side temperature sensors 7a and 7b, and the difference in the positions of the two outlet-side temperature sensors 7d and 7e, and the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the two outlet-side temperature sensors 7d and 7e. Specifically, the control unit 10 first determines the cooling rate of the non-azeotropic refrigerant mixture 20 on the inlet side of the condenser 2 based on the difference in the positions of the two inlet-side temperature sensors 7a and 7b, and the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the two inlet-side temperature sensors 7a and 7b. Furthermore, the cooling rate of the non-azeotropic refrigerant mixture 20 on the outlet side of the condenser 2 is determined based on the difference in the positions of the two outlet-side temperature sensors 7d and 7e, and the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by the two outlet-side temperature sensors 7d and 7e.

[0089] Here, the distances between each bend number shown on the horizontal axis are approximately equal. For example, if the distance between bend number b1 and bend number b2 is "1", then the distance between bend number b20 and bend number b23 is represented as "3". That is, the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1 to bend number b2, which is the inlet side of the condenser 2, is (T12 - T11) / 1, and the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20 to bend number b23, which is the outlet side of the condenser 2, is (T14 - T13) / 3.

[0090] Next, the control unit 10 (see Figure 1) extends the straight lines passing through coordinates (b1, T11) and (b2, T12), which are obtained based on the cooling rate on the inlet side, to determine the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2. Also, as shown in Figure 13, the control unit 10 calculates a relational expression that extends the straight lines passing through coordinates (b20, T13) and (b23, T14), which are obtained based on the cooling rate on the outlet side. Then, the control unit 10 identifies the intersection point of the extensions of the straight lines on the inlet side and the outlet side as the saturation temperature Ts of the non-azeotropic refrigerant mixture 20 in the condenser 2. Subsequently, similar to the first embodiment, the composition of the non-azeotropic mixed refrigerant 20 in a gaseous state (the concentration ratio of high-boiling point gaseous refrigerant 21a to low-boiling point gaseous refrigerant 22a) is determined based on the saturation temperature Ts of the non-azeotropic mixed refrigerant 20, the pressure of the non-azeotropic mixed refrigerant 20 in the piping 101b (see Figure 1) measured by the pressure sensor 6, and the table data D1 (see Figure 6).

[0091] Furthermore, using Figure 14, an example will be explained in which the control unit 10 (see Figure 1) calculates (determines) the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 using the temperatures of the non-azeotropic refrigerant mixture 20 measured by temperature sensors 7a, 7b, 7d, and 7e, respectively, in winter when the ambient temperature of the location where the condenser 2 is installed is relatively low. Note that in winter when the ambient temperature of the location where the condenser 2 is installed is relatively low, the temperature gradient of the non-azeotropic refrigerant mixture 20 on the inlet side of the condenser 2 becomes relatively small.

[0092] In this case as well, the control unit 10 calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1 to bend number b2, which is the inlet side of the condenser 2, as (T22 - T21) / 1, and calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20 to bend number b23, which is the outlet side of the condenser 2, as (T24 - T23) / 3. In this case, both the cooling rate of the non-azeotropic refrigerant mixture 20 on the inlet side of the condenser 2 and the cooling rate of the non-azeotropic refrigerant mixture 20 on the outlet side of the condenser 2 are gentler than the slopes of the respective cooling rates on the inlet and outlet sides shown in Figure 13. The control unit 10 then identifies the intersection point on the extensions of the straight lines on the inlet and outlet sides as the saturation temperature Tsa of the non-azeotropic refrigerant mixture 20 in the condenser 2. In this way, the control unit 10 appropriately calculates (identifies) the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2, regardless of the surrounding environment of the condenser 2. The subsequent processing is carried out in the same manner as described above.

[0093] (Effects of the third embodiment) Next, the effects of the third embodiment will be described.

[0094] In the cooling device 100b of the third embodiment described above, the temperature sensor 7 includes a plurality of inlet-side temperature sensors 7a and 7b arranged on the inlet side of the condenser 2, and a plurality of outlet-side temperature sensors 7d and 7e arranged on the outlet side of the condenser 2. The control unit 10 is configured to determine the saturation temperature Ts or Tsa of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on a plurality of temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by the plurality of inlet-side temperature sensors 7a and 7b, and a plurality of temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by the plurality of outlet-side temperature sensors 7d and 7e. This makes it possible to compare the temperature measurement results of the plurality of temperature sensors 7a and 7b arranged on the inlet side of the condenser 2, where the measured temperature gradient is relatively large, and the plurality of temperature sensors 7d and 7e arranged on the outlet side of the condenser 2, where the measured temperature gradient is relatively small. As a result, it becomes easier to calculate the saturation temperature Ts or Tsa at which the temperature gradient of the non-azeotropic refrigerant mixture 20 begins to decrease.

[0095] Furthermore, in the cooling device 100b of the third embodiment described above, the control unit 10 is configured to determine the saturation temperature Ts or Tsa of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on the difference in the positions of the two inlet-side temperature sensors 7a and 7b, the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the two inlet-side temperature sensors 7a and 7b, and the difference in the positions of the two outlet-side temperature sensors 7d and 7e, and the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the two outlet-side temperature sensors 7d and 7e. This makes it possible to calculate the cooling rate as a temperature gradient corresponding to the difference (distance) between the two temperature sensors 7a and 7b, or between the temperature sensors 7d and 7e, on both the inlet and outlet sides of the condenser 2. Therefore, it is possible to appropriately calculate the saturation temperature Ts or Tsa at which the change in the cooling rate of the non-azeotropic refrigerant mixture 20 begins to decrease, using the cooling rates on both the inlet and outlet sides of the condenser 2.

[0096] Furthermore, the other effects of the third embodiment are the same as those of the first embodiment.

[0097] [Fourth Embodiment] Next, the configuration of the cooling device 100c (see Figure 15) according to the fourth embodiment of the present invention will be described with reference to Figures 15 and 16. In this fourth embodiment, a temperature sensor 7e is not provided for the condenser 2, and the ambient temperature sensor 9 is used (shared) as the temperature sensor 7e on the outlet side to determine the saturation temperature of the non-azeotropic mixed refrigerant 20 in the condenser 2, thereby determining the concentration of the low boiling point gaseous refrigerant 22a in the cooling circuit 101. Note that the cooling device 100c according to the fourth embodiment of the present invention has the same configuration as the cooling device 100b (see Figure 12) of the third embodiment, except for the points mentioned above. Points common to the third embodiment in the fourth embodiment will not be explained.

[0098] (Temperature Sensor Arrangement) As shown in Figure 15, in the cooling device 100c of the fourth embodiment, temperature sensors 7a, 7b, and 7d are arranged in the condenser 2. In addition, an ambient temperature sensor 9 is arranged in the condenser 2 to measure the temperature around the condenser 2. The ambient temperature sensor 9 is configured to communicate with the control unit 10 and transmits the temperature around the condenser 2 to the control unit 10.

[0099] In this fourth embodiment, the condenser 2 is configured to draw in ambient air in the X1 direction in order to measure the temperature of the surrounding environment using the ambient temperature sensor 9. The condenser 2 also discharges heat from its Y-direction end through a heat dissipation mechanism (not shown). Therefore, if, for example, the ambient temperature sensor 9 were placed at the Y-direction end of the condenser 2, a short circuit would occur, making it impossible to properly measure the ambient air temperature. Accordingly, in the fourth embodiment, the ambient temperature sensor 9 is positioned near the center of the condenser 2 in the Y-direction.

[0100] The ambient temperature sensor 9 measures the ambient temperature near the outlet side of the condenser 2, and therefore effectively measures the temperature of the non-azeotropic refrigerant mixture 20 at bend number b24, which is the connection point between the cooling coil 2b and the piping 101c. In other words, the ambient temperature sensor 9 functions as a temperature sensor 7f on the outlet side of the condenser 2. Although bend number b24 is not strictly a bend, it is described as a bend for convenience. Also, the distances between each bend number are approximately equal.

[0101] (Determination of saturation temperature) Similar to the third embodiment, as shown in Figure 16, the control unit 10 (see Figure 1) calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1 to bend number b2, which are on the inlet side of the condenser 2, as (T32 - T31) / 1, and calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20 to bend number b24, which are on the outlet side of the condenser 2, as (T34 - T33) / 4. In the fourth embodiment, although the position (bend number) of the temperature sensor 7 on the outlet side is closer to the outlet side than in the third embodiment, there is no significant change in the cooling rate of the non-azeotropic refrigerant mixture 20 on the outlet side of the condenser 2.

[0102] The control unit 10 then identifies the intersection point on the extensions of the straight lines corresponding to the respective cooling rates on the inlet and outlet sides as the saturation temperature Tsb of the non-azeotropic mixed refrigerant 20 in the condenser 2. Subsequently, similar to the first and third embodiments, the control unit 10 identifies the composition of the non-azeotropic mixed refrigerant 20 in a gaseous state (the concentration ratio of high-boiling point gaseous refrigerant 21a to low-boiling point gaseous refrigerant 22a) based on the saturation temperature Tsb of the non-azeotropic mixed refrigerant 20, the pressure of the non-azeotropic mixed refrigerant 20 in the piping 101b (see Figure 1) measured by the pressure sensor 6, and the table data D1 (see Figure 6).

[0103] (Effects of the fourth embodiment) Next, the effects of the fourth embodiment will be described.

[0104] In the cooling device 100c of the fourth embodiment described above, the condenser 2 is provided with an ambient temperature sensor 9 that measures the temperature of the environment surrounding the condenser 2, and the ambient temperature sensor 9 also serves as the outlet-side temperature sensor 7f. This reduces the number of outlet-side temperature sensors 7 that need to be added to the condenser 2. As a result, it is possible to suppress an increase in the number of parts of the cooling device 100.

[0105] Furthermore, the other effects of the fourth embodiment are the same as those of the third embodiment.

[0106] [Fifth Embodiment] Next, the configuration of the cooling device 100d (see Figure 17) according to the fifth embodiment of the present invention will be described with reference to Figures 17 to 19. In this fifth embodiment, a temperature sensor 7 is not provided for the condenser 2, and the concentration of the low boiling point gaseous refrigerant 22a in the cooling circuit 101 is determined by using a thermograph 7t (see Figure 17) to determine the saturation temperature of the non-azeotropic mixed refrigerant 20 in the condenser 2. Note that the cooling device 100d according to the fifth embodiment of the present invention has the same configuration as the cooling device 100b (see Figure 12) of the third embodiment, except for the points mentioned above. Points that are common to the third embodiment in the fifth embodiment will not be explained.

[0107] As shown in Figure 17, the cooling device 100d of the fifth embodiment is equipped with a thermographic camera 7t as a temperature sensor 7. The thermographic camera 7t is configured to detect infrared radiation emitted from an object without contact, and generates a temperature distribution based on the amount (intensity) of infrared radiation detected by imaging the object. In the fifth embodiment, the thermographic camera 7t is positioned to image the entire condenser 2, and generates a temperature distribution of the cooling coil 2b (see Figure 18) in the condenser 2. The control unit 10 is configured to acquire the temperature at a predetermined position in the cooling coil 2b of the condenser 2 based on the temperature image captured by the thermographic camera 7t.

[0108] Figure 18 is a temperature distribution map of the condenser 2 captured by thermography 7t. For simplicity, the temperature distribution of parts other than the cooling coil 2b is not shown. As shown in Figure 18, for example, at bend number b1 of the cooling coil 2b connected to piping 101b, the temperature of the cooling coil 2b (non-azeotropic refrigerant mixture 20) is a relatively high T41 [°C]. Subsequently, the non-azeotropic refrigerant mixture 20 flowing through the cooling coil 2b is cooled by the condenser 2 and its temperature decreases. For example, at bend number b2, the temperature of the non-azeotropic refrigerant mixture 20 is T42 [°C], which is lower than T41 [°C]. At bend number b20, it is T43 [°C], which is lower than T42 [°C], and at bend number b23, it is T44 [°C], which is lower than T43 [°C]. The control unit 10 (see Figure 17) acquires the temperature at each bend number location detected by the thermographic camera 7t.

[0109] (Determination of saturation temperature) As shown in Figure 19, the control unit 10 calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1 to bend number b2, which are the inlet side of the condenser 2, as (T42 - T41) / 1, and the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20 to bend number b23, which are the outlet side of the condenser 2, as (T44 - T43) / 3. The control unit 10 then identifies the intersection point of the extensions of the lines corresponding to the respective cooling rates on the inlet and outlet sides as the saturation temperature Tsc of the non-azeotropic refrigerant mixture 20 in the condenser 2. Subsequently, similar to the first to fourth embodiments, the composition of the non-azeotropic mixed refrigerant 20 in a gaseous state (the concentration ratio of high-boiling point gaseous refrigerant 21a to low-boiling point gaseous refrigerant 22a) is determined based on the saturation temperature Tsc of the non-azeotropic mixed refrigerant 20, the pressure of the non-azeotropic mixed refrigerant 20 in the piping 101b (see Figure 1) measured by the pressure sensor 6, and the table data D1 (see Figure 6).

[0110] (Effects of the Fifth Embodiment) Next, the effects of the fifth embodiment will be described.

[0111] In the cooling device 100d of the fifth embodiment described above, the temperature sensor 7 includes a thermograph 7t, and the control unit 10 is configured to determine the saturation temperature Tsc of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on the temperatures T41 and T42 of the non-azeotropic refrigerant mixture 20 at multiple points on the inlet side of the condenser 2 (bend numbers b1 and b2) measured by the thermograph 7t, and the temperatures T43 and T44 of the non-azeotropic refrigerant mixture 20 at multiple points on the outlet side of the condenser 2 (bend numbers b20 and b23) measured by the thermograph 7t. As a result, the temperature of the entire condenser 2 can be easily obtained by the thermograph 7t, and the saturation temperature Tsc of the non-azeotropic refrigerant mixture 20 can be easily determined. Furthermore, the device configuration can be simplified compared to, for example, the case where multiple contact-type temperature sensors 7 are placed in the condenser 2.

[0112] Furthermore, the other effects of the fifth embodiment are the same as those of the third embodiment.

[0113] [Sixth Embodiment] Next, with reference to Figures 20 to 22, a cooling device 100e (see Figure 20) according to the sixth embodiment of the present invention will be described. In this sixth embodiment, there is no configuration for detecting pressure, eight temperature sensors 7 are arranged on the cooling coil 2b of the condenser 2, and a storage unit included in the control unit 10b stores table data D3 (see Figure 21) as relational information. In the sixth embodiment, an example will be described in which the non-azeotropic mixed refrigerant 20 is cooled by the condenser 2 and, after becoming completely liquid, its temperature further decreases. Note that the cooling device 100e according to the sixth embodiment of the present invention has the same configuration as the cooling device 100b (see Figure 12) of the third embodiment, except for the points mentioned above. Points common to the third embodiment in the sixth embodiment will not be explained.

[0114] (Table Data) The control unit 10b (see Figure 20) stores table data D3, as shown in Figure 21, as pre-acquired data. Table data D3 shows the correspondence between the saturation temperature Tsd (see Figure 22) of the non-azeotropic mixed refrigerant 20 in the condenser 2, the liquid saturation temperature Tse (see Figure 22) of the non-azeotropic mixed refrigerant 20 in the condenser 2, and the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20. For example, if the saturation temperature of the non-azeotropic mixed refrigerant 20 in the condenser 2 is 46.0°C and the liquid saturation temperature is 37.0°C, the control unit 10b (see Figure 20) can use this table data D3 to determine that the concentration of the low-boiling point gaseous refrigerant 22a in the gaseous non-azeotropic mixed refrigerant 20 is 35.0%. In other words, the control unit 10b does not directly measure the concentration of the low-boiling-point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20, but instead uses so-called soft sensing, indirectly determining the concentration of the low-boiling-point gaseous refrigerant 22a based on the saturation temperature Tsd and liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2 using table data D3. Table data D3 is an example of the "relevant information" in the claims.

[0115] (Identification of Saturation Temperature) As shown in Figure 22, the control unit 10b (see Figure 20) acquires the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 as T51 to T58, corresponding to bend numbers b1, b2, b13, b15, b20, b21, b23, and b24, respectively. In the sixth embodiment, the control unit 10b calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1 to bend number b2, which are the inlet side of the condenser 2, as (T52 - T51) / 1, and the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b13 to bend number b15, which are the outlet side of the condenser 2, as (T54 - T53) / 2. The control unit 10b then identifies the intersection point on the extension of the straight lines corresponding to the respective cooling rates on the inlet and outlet sides as the saturation temperature Tsd of the non-azeotropic refrigerant mixture 20 in the condenser 2.

[0116] (Determination of Liquid Saturation Temperature) In the sixth embodiment, the control unit 10b determines the liquid saturation temperature in addition to the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2. The control unit 10b acquires the temperatures of multiple bend numbers located on the outlet side, for example, from the connection point between the cooling coil 2b and the piping 101c (see Figure 12) to a point about 1 / 4 of the total length of the cooling coil 2b. In the sixth embodiment, the control unit 10b calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20 to bend number b21 as (T56 - T55) / 1, and calculates the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b23 to bend number b24, which are on the outlet side of the condenser 2, as (T58 - T57) / 1. The control unit 10b then identifies the intersection point on the extensions of the lines corresponding to these two cooling rates as the liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2.

[0117] Subsequently, the control unit 10b determines the composition of the non-azeotropic mixed refrigerant 20 in the gaseous state (the concentration ratio of high-boiling point gaseous refrigerant 21a and low-boiling point gaseous refrigerant 22a) based on the saturation temperature Tsd and the liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2, and the table data D3.

[0118] (Effects of the sixth embodiment) Next, the effects of the sixth embodiment will be described.

[0119] The cooling device 100e of the sixth embodiment described above includes a compressor 1 for compressing a non-azeotropic mixed refrigerant 20 containing a high-boiling-point gaseous refrigerant 21a, a low-boiling-point gaseous refrigerant 22a, a high-boiling-point liquid refrigerant 21b, and a low-boiling-point liquid refrigerant 22b; a cooling circuit 101 including a condenser 2 and an evaporator 4 as heat exchangers for heat exchange of the non-azeotropic mixed refrigerant 20; a temperature sensor 7 for measuring the temperature of the non-azeotropic mixed refrigerant 20; a control unit 10b for determining the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 based on the saturation temperature Tsd of the non-azeotropic mixed refrigerant 20 in the condenser 2 measured by the temperature sensor 7, the liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2; and table data D3 showing the correspondence between the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 and the saturation temperature Tsd and the liquid saturation temperature Tse. This makes it possible to easily determine the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101, for example, even if the pressure inside the cooling circuit 101 is unknown, based on table data D3 which shows the correspondence between the temperature difference between the saturation temperature Tsd and the liquid saturation temperature Tse and the concentration of the low-boiling-point gaseous refrigerant 22a inside the cooling circuit 101.

[0120] Furthermore, the other effects of the sixth embodiment are the same as those of the third embodiment.

[0121] [Seventh Embodiment] Next, the configuration of the cooling device 100f (see Figure 23) according to the seventh embodiment of the present invention will be described with reference to Figures 23 to 25. In this seventh embodiment, an example will be described in which the control unit 10c corrects the bend number as the acquisition position of the temperature sensor 7 when the distance between bends of the condenser 12 is longer than that of the condenser 2 (see Figure 12) of the third embodiment. Note that the cooling device 100f according to the seventh embodiment of the present invention has the same configuration as the cooling device 100b (see Figure 12) of the third embodiment, except for the points mentioned above. Points that are common to the third embodiment in the seventh embodiment will not be explained.

[0122] As shown in Figure 23, the cooling device 100f of the seventh embodiment includes a condenser 12. The condenser 12 is a heat exchanger located outside a cooling chamber (not shown). The condenser 12 is configured to condense the refrigerant discharged from the compressor 1. The condenser 12 is provided with a fan 12a, which is configured to supply air to the condenser 12. Heat is then transferred from the non-azeotropic refrigerant mixture 20 in the condenser 12 to the air supplied by the fan 12a, and heat is removed from the non-azeotropic refrigerant mixture 20. The condenser 12 also includes a cooling coil 12b and cooling fins 12c, which are positioned where they are exposed to the cooling air generated by the fan 12a. In this seventh embodiment, the condenser 12 is a so-called fin-coil type heat exchanger. Note that the condenser 12 is an example of a "heat exchanger" as defined in the claims.

[0123] Furthermore, the temperature sensors 7a and 7b are positioned on the inlet side of the cooling coil 12b of the condenser 12, beyond the halfway point of the total length of the cooling coil 12b of the condenser 12. More specifically, temperature sensor 7a is positioned at bend number b1, which is the connection point between the cooling coil 12b and the piping 101b, and temperature sensor 7a is positioned at bend number b2, which is the first bend in the cooling coil 12b. Additionally, temperature sensors 7d and 7e are positioned on the outlet side of the cooling coil 12b, beyond the halfway point of the total length of the cooling coil 12b of the condenser 12. Specifically, temperature sensor 7d is positioned at bend number b20, which is the 20th bend in the cooling coil 12b counting from the inlet side, and temperature sensor 7e is positioned at bend number b23, which is the 23rd bend in the cooling coil 12b counting from the inlet side.

[0124] Here, the condenser 12 of the seventh embodiment has, for example, 1.5 times the width of the condenser 2 of the third embodiment (see Figure 12). As a result, the distance between the bends of the condenser 12 becomes 1.5 times longer, and the temperature drop of the non-azeotropic refrigerant mixture 20 in the cooling coil 12b between each bend becomes very large. In this case, the control unit 10c (see Figure 23) is pre-programmed by the user to perform correction processing on the relationship between the temperature detected by the temperature sensor 7 and the bend number, using the condenser 2 of the third embodiment as a reference.

[0125] As shown in Figure 25, the control unit 10c (see Figure 23) acquires the temperature of bend number b1 as temperature T61 and the temperature of bend number b2 as temperature T62 using the inlet-side temperature sensor 7. At this time, the control unit 10c sets a virtual bend number b2a at a position 2 / 3 of the way between bend number b1 and bend number b2. Note that the position of this virtual bend number b2a varies depending on the width of the condenser 12 which is set in advance. In the seventh embodiment, the distance between bends of the condenser 12 has a width that is, for example, 3 / 2 times (1.5 times) that of the condenser 2 of the third embodiment (see Figure 12), so the reciprocal of the width ratio is 2 / 3.

[0126] The control unit 10c then acquires a point x2 where the temperature is T62 at a virtual bend number b2a, rather than at the position of point x1 where the temperature is T62 at the originally acquired bend number b2. Therefore, the control unit 10c also uses this virtual point x2 to calculate the cooling rate in the condenser 2. That is, the cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b1, which is the inlet side of the condenser 12, to the virtual bend number b2a is calculated as (T62 - T61) / (2 / 3). The cooling rate of the non-azeotropic refrigerant mixture 20 from bend number b20, which is the outlet side of the condenser 2, to bend number b23 is (T64 - T63) / 3. The control unit 10b then identifies the intersection point on the extensions of the lines corresponding to the respective cooling rates on the inlet and outlet sides as the saturation temperature Tsf of the non-azeotropic refrigerant mixture 20 in the condenser 2.

[0127] Subsequently, similar to the third embodiment, the composition of the non-azeotropic mixed refrigerant 20 in a gaseous state (the concentration ratio of high-boiling point gaseous refrigerant 21a to low-boiling point gaseous refrigerant 22a) is determined based on the saturation temperature Tsf of the non-azeotropic mixed refrigerant 20, the pressure of the non-azeotropic mixed refrigerant 20 in the piping 101b (see Figure 1) measured by the pressure sensor 6, and the table data D1 (see Figure 6).

[0128] (Effects of the seventh embodiment) Next, the effects of the seventh embodiment will be described.

[0129] In the cooling device 100f of the seventh embodiment described above, the control unit 10c sets a virtual bend number b2a according to the width of the condenser 12, and calculates the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 12 based on the temperature at the virtual bend number b2a. This makes it possible to appropriately calculate the saturation temperature Tsf of the non-azeotropic refrigerant mixture 20 in the condenser 12 even when the distance between bends of the condenser 12 is relatively long.

[0130] Furthermore, the other effects of the seventh embodiment are the same as those of the third embodiment.

[0131] [Modifications] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and further includes all modifications (modifications) within the meaning and scope equivalent to the claims.

[0132] For example, in the first and second embodiments described above, the control unit 10 is configured to store relational information showing the correspondence between the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6, the temperature of the non-azeotropic mixed refrigerant 20 near the heat exchanger measured by the temperature sensor 7, and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101, and to perform control to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the relational information. However, the present invention is not limited to this. In the present invention, for example, the control unit 10 may acquire relational information by communication from another external device without storing the relational information, and perform control to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the relational information.

[0133] Furthermore, in the first to fifth embodiments and the seventh embodiment described above, the heat exchanger includes a condenser 2 that condenses the non-azeotropic mixed refrigerant 20 discharged by the compressor 1, and the control unit 10 is configured to determine the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2, the saturation temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2, and related information. However, the present invention is not limited to this. In the present invention, the control unit 10 may, for example, determine the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on the pressure of the compressor 1 measured by the pressure sensor 6, the saturation temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2, and related information. Furthermore, the control unit 10 may determine the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 based on, for example, the pressure of the non-azeotropic mixed refrigerant 20 flowing out of the evaporator 4 measured by the pressure sensor 6, the saturation temperature of the non-azeotropic mixed refrigerant 20 near the evaporator 4, and related information.

[0134] Furthermore, in the first to seventh embodiments described above, the control unit 10 is configured to perform concentration reduction operation control such that when a state value determined from the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 and the housing temperature of the compressor 1 exceeds a concentration threshold set according to the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101, the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 is reduced. However, the present invention is not limited to this. In the present invention, for example, when the state value exceeds a concentration threshold, control may be performed to reduce the pressure of the non-azeotropic mixed refrigerant 20 in the cooling circuit 101 without reducing the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101.

[0135] Furthermore, in the first to seventh embodiments described above, the control unit 10 is configured to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1 as a concentration reduction operation control when the state value exceeds a concentration threshold, but the present invention is not limited to this. In the present invention, for example, control may be performed to reduce the pressure of the non-azeotropic mixed refrigerant 20 in the cooling circuit 101 without adjusting the superheating degree.

[0136] Furthermore, in the first to seventh embodiments described above, the control unit 10 is configured to reduce the rotational speed of the compressor 1 if the state value exceeds a concentration threshold even after it has performed control to increase the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1. However, the present invention is not limited to this. In the present invention, the control unit 10 may reduce the rotational speed of the compressor 1 without increasing the superheating degree of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1. The control unit 10 may also stop the compressor 1.

[0137] Furthermore, in the first to seventh embodiments described above, the control unit 10 is configured to control the degree of superheating of the non-azeotropic mixed refrigerant 20 flowing into the compressor 1, or the rotational speed of the compressor 1, so as to bring the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 closer to the concentration threshold, but not exceeding the concentration threshold. However, the present invention is not limited to these examples. In the present invention, the control unit 10 may perform control to maintain the current concentration as long as the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101 does not exceed the concentration threshold. Alternatively, the control unit 10 may perform control to bring the concentration closer to a concentration arbitrarily set by the user or the like.

[0138] Furthermore, in the first and second embodiments described above, an example was shown in which a fan 2a is further provided to blow air into the condenser 2, and the control unit 10 is configured to increase the rotation speed of the fan 2a in order to increase the amount of heat dissipated by the condenser 2 when the temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2 is not at the saturation temperature, but the present invention is not limited thereto. In the present invention, for example, a cooling means other than the fan 2a may be used to bring the temperature of the non-azeotropic mixed refrigerant 20 near the inlet side of the condenser 2 closer to the saturation temperature, or the temperature of the non-azeotropic mixed refrigerant 20 near the outlet side of the condenser 2 may be considered as the saturation temperature.

[0139] Furthermore, in the first embodiment described above, the relational information included an example in which table data D1 showing the correspondence between the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6, the temperature of the non-azeotropic mixed refrigerant 20 near the heat exchanger measured by the temperature sensor 7, and the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101. However, the present invention is not limited to this. In the present invention, the control unit 10 may store mathematical formula data D4 as relational information, for example, as shown in Figure 26, which shows the correspondence between the pressure of the non-azeotropic mixed refrigerant 20 flowing into the condenser 2 measured by the pressure sensor 6, the temperature of the non-azeotropic mixed refrigerant 20 near the heat exchanger measured by the temperature sensor 7, and the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 101. The mathematical formula data D4 is, for example, a function that shows the relationship between the saturation temperature on the x-axis and the concentration of the low-boiling-point gaseous refrigerant 22a on the y-axis, according to the pressure of multiple patterns of piping 101b. Specifically, the formula is expressed as follows: when the pressure in pipe 101b is pressure P1, y = f1(x); when the pressure in pipe 101b is pressure P2, y = f2(x); and when the pressure in pipe 101b is pressure P3, y = f3(x).

[0140] Furthermore, in the second embodiment described above, the heat exchanger includes an evaporator 4 for evaporating a non-azeotropic mixed refrigerant 20, an accumulator 5 for temporarily storing the non-azeotropic mixed refrigerant 20 discharged from the evaporator 4, and a liquid level gauge 5a for measuring the liquid level of the non-azeotropic mixed refrigerant 20 stored in the accumulator 5. The control unit 10a is configured to perform control to identify the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 based on mathematical formula data D2 as relational information showing the correspondence between the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5, which is located in the cooling circuit 102 and measured by the liquid level gauge 5a, and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102. However, the present invention is not limited to this example. In the present invention, the control unit 10 may perform control to determine the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102 based on table data from which information similar to that of mathematical formula data D2 can be obtained as relational information showing the correspondence between the liquid level height of the non-azeotropic mixed refrigerant 20 in the accumulator 5 and the concentration of the low-boiling-point gaseous refrigerant 22a in the cooling circuit 102.

[0141] Furthermore, in the second embodiment described above, the control unit 10a is configured to perform concentration reduction operation control such that when the liquid level of the non-azeotropic mixed refrigerant 20 in the accumulator 5 located in the cooling circuit 102, as measured by the liquid level gauge 5a, exceeds a predetermined liquid level threshold h1, it reduces the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102. However, the present invention is not limited to this. In the present invention, for example, when the liquid level exceeds a predetermined liquid level threshold h1, control may be performed to reduce the pressure of the non-azeotropic mixed refrigerant 20 in the cooling circuit 101 without reducing the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 101.

[0142] Furthermore, in the second embodiment described above, the invention is further provided with a pipe 101f that draws in the liquid non-azeotropic refrigerant mixture 20 stored in the accumulator 5 and converts it into a gaseous non-azeotropic refrigerant mixture 20 for intake into the compressor 1. The control unit 10a is configured to perform at least one of the following controls as a concentration reduction operation control when the liquid level measured by the liquid level gauge 5a exceeds the liquid level threshold h1: increasing the superheating degree of the non-azeotropic refrigerant mixture 20 flowing into the compressor 1, decreasing the rotational speed of the compressor 1, or drawing the liquid stored in the accumulator 5 into the compressor 1 via the pipe 101f. However, the present invention is not limited to this. In the present invention, for example, without providing the pipe 101f and valve 5b, at least one of the following controls may be performed when the liquid level exceeds the liquid level threshold h1: increasing the superheating degree of the non-azeotropic refrigerant mixture 20 flowing into the compressor 1, or decreasing the rotational speed of the compressor 1.

[0143] Furthermore, although the second embodiment described above shows an example in which the cooling device 100a is equipped with a pressure sensor 6, a temperature sensor 7, and a liquid level gauge 5a, the present invention is not limited thereto. In the present invention, for example, the device may be configured to determine the concentration of the low-boiling point gaseous refrigerant 22a in the non-azeotropic mixed refrigerant 20 based solely on the liquid level height measured by the liquid level gauge 5a, without the pressure sensor 6 and the temperature sensor 7. That is, the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102 is determined based on relational information showing the correspondence between the liquid level height of the accumulator 5 arranged in the cooling circuit 102 and the concentration of the low-boiling point gaseous refrigerant 22a in the cooling circuit 102, so there is no need to provide an additional circuit (additional configuration) separate from the cooling circuit 102. As a result, the composition of the non-azeotropic mixed refrigerant 20 can be determined while suppressing the enlargement and complexity of the device.

[0144] Furthermore, in the first embodiment described above, the control unit 10 identifies the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 as the value measured by temperature sensor 7b if the difference between the temperature measured by temperature sensor 7b and the temperature measured by temperature sensor 7c is within 0.5°C, and considers that the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 has not reached the saturation temperature if the difference between the temperature measured by temperature sensor 7b and the temperature measured by temperature sensor 7c exceeds 0.5°C. However, the present invention is not limited to this. In the present invention, the difference between the temperature measured by temperature sensor 7b and the temperature measured by temperature sensor 7c, used to identify the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 as the value measured by temperature sensor 7b, may be arbitrarily determined by the user according to the characteristics of the non-azeotropic refrigerant mixture 20.

[0145] Furthermore, in the third to seventh embodiments described above, the control unit 10 is configured to determine the saturation temperature Ts or Tsa of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on multiple temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by multiple inlet-side temperature sensors 7a and 7b, and multiple temperatures of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by multiple outlet-side temperature sensors 7d and 7e, etc., but the present invention is not limited thereto. In the present invention, for example, temperature sensors 7 may be placed at all bends of the condenser 2, and a user or the like may determine the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on all the detected temperatures.

[0146] Furthermore, in the third to seventh embodiments described above, an example was shown in which the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 is determined using the temperature at bend number b1, where the temperature sensor 7 is located. However, the present invention is not limited to this. In the present invention, the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 may be determined using the temperature at the location in the condenser 2 where the temperature sensor 7 is located. For example, as shown in Figure 27, each of the temperature sensors 7a, 7b, 7d, and 7e may detect the temperatures (T71 to T74) at the inlet positions p1 and p2 and the outlet positions p3 and p4 of the cooling coil 2b, respectively, to determine the saturation temperature Tsg. In this case, the data of the detected temperature plot will be a graph corresponding to the distance from the condensation start position p0, which is the boundary between the piping 101b and the condenser 2. Specifically, as shown in Figure 28, the horizontal axis is set to "distance from condensation start position p0," and the temperature at the location where each temperature sensor 7 is located is plotted. For example, distance d1 is the distance from the condensation start position p0 to position p1 in Figure 27. Therefore, the control unit 10 (see Figure 1) derives the cooling rate of the non-azeotropic mixed refrigerant 20 on the inlet side of the condenser 2 as (T72 - T71) / (d2 - d1), and the cooling rate of the non-azeotropic mixed refrigerant 20 on the outlet side of the condenser 2 as (T74 - T73) / (d4 - d3). The other configurations are the same as in the third embodiment.

[0147] Furthermore, in the third to seventh embodiments described above, an example was shown in which the saturation temperature Ts or Tsa of the non-azeotropic refrigerant mixture 20 in the condenser 2 is determined based on the difference in the positions (bend numbers) of the inlet-side temperature sensors 7a and 7b, the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the inlet-side temperature sensors 7a and 7b, and the difference in the positions (bend numbers) of the outlet-side temperature sensors 7d and 7e, and the difference in the temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2 measured by each of the outlet-side temperature sensors 7d and 7e. However, the present invention is not limited thereto. In the present invention, for example, the control unit 10 may be configured to determine the temperature of the non-azeotropic refrigerant mixture 20 measured by the inlet-side temperature sensor 7a, which is closer to the inlet side of the condenser 2, as the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2, when the difference in the temperature of the non-azeotropic refrigerant mixture 20 measured by the two inlet-side temperature sensors 7a and 7b is smaller than a predetermined threshold.

[0148] Furthermore, in the third to seventh embodiments described above, an example was shown in which two temperature sensors 7 are placed on each of the inlet and outlet sides of the condenser 2, and the control unit 10 (see Figure 1) determines the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2. However, the present invention is not limited to this. In the present invention, for example, more than two temperature sensors 7 may be placed on each of the inlet and outlet sides of the condenser 2, and the control unit 10 may determine the saturation temperature of the non-azeotropic refrigerant mixture 20 in the condenser 2. Specifically, as shown in Figure 29, three temperature sensors 7 may be placed on each of the inlet side (bend numbers b1 to b3) and outlet side (bend numbers b19, b21, and b24) of the condenser 2, and the temperature T81 to T86 at each position may be detected to determine the saturation temperature Tsh. In this case, the control unit 10 may derive an approximate linear equation using the least squares method for plotting three points on the inlet side of the condenser 2, and may also derive an approximate linear equation using the least squares method for plotting three points on the outlet side. The other configurations are the same as in the third embodiment.

[0149] Furthermore, in the fourth embodiment described above, the condenser 2 is provided with an ambient temperature sensor 9 for measuring the temperature of the environment surrounding the condenser 2, and the ambient temperature sensor 9 also serves as the outlet-side temperature sensor 7f. However, the present invention is not limited to this. In the present invention, regardless of whether or not the ambient temperature sensor 9 is present, an outlet-side temperature sensor may be added as needed.

[0150] Furthermore, in the fifth embodiment described above, the temperature sensor 7 includes a thermograph 7t, and the control unit 10 is configured to determine the saturation temperature Tsc of the non-azeotropic refrigerant mixture 20 in the condenser 2 based on the temperatures T41 and T42 of the non-azeotropic refrigerant mixture 20 at multiple points on the inlet side of the condenser 2 (bend numbers b1 and b2) measured by the thermograph 7t, and the temperatures T43 and T44 of the non-azeotropic refrigerant mixture 20 at multiple points on the outlet side of the condenser 2 (bend numbers b20 and b23) measured by the thermograph 7t. However, the present invention is not limited to this. In the present invention, for example, the saturation temperature may be determined by the user by visually viewing a temperature distribution image captured using the thermograph 7t.

[0151] Furthermore, in the sixth embodiment described above, an example was shown in which a control unit 10b identifies the concentration of low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 based on the saturation temperature Tsd of the non-azeotropic mixed refrigerant 20 in the condenser 2 measured by a temperature sensor 7, the liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2, and table data D3 showing the correspondence between the saturation temperature Tsd and the liquid saturation temperature Tse and the concentration of low-boiling-point gaseous refrigerant 22a in the cooling circuit 101. However, the present invention is not limited thereto. In the present invention, for example, the control unit may identify the concentration of low-boiling-point gaseous refrigerant 22a in the cooling circuit 101 using table data showing the correspondence between the temperature difference between the saturation temperature Tsd of the non-azeotropic mixed refrigerant 20 in the condenser 2 and the liquid saturation temperature Tse of the non-azeotropic mixed refrigerant 20 in the condenser 2 and the concentration of low-boiling-point gaseous refrigerant 22a in the cooling circuit 101.

[0152] Furthermore, in the seventh embodiment described above, the control unit 10c sets a virtual bend number b2a according to the width of the condenser 12, and calculates (specifies) the saturation temperature of the non-azeotropic mixed refrigerant 20 in the condenser 12 based on the temperature at the virtual bend number b2a. However, the present invention is not limited to this. In the present invention, if the distance between bends of the cooling coil 12b in the condenser 12 is relatively long, a temperature sensor 7 may be placed in the straight portion between the bends of the cooling coil 12b, and the distance between the temperature sensors 7 may be taken as the cooling distance. By detecting the temperature drop corresponding to the cooling distance, the cooling rate may be derived and the saturation temperature may be specified.

[0153] Furthermore, in the third to seventh embodiments described above, the temperature sensor 7 on the inlet side of the condenser 2 is positioned at a location approximately 1 / 4 of the total length of the cooling coil 2b from the connection point between the cooling coil 2b and the piping 101b, specifically at the positions of bend numbers b1 and b2. However, the present invention is not limited to this. In the present invention, the temperature sensor 7 on the inlet side may be positioned at a location other than bend numbers b1 and b2, as long as it is positioned between the connection point between the cooling coil 2b and the piping 101b and 1 / 2 of the total length of the cooling coil 2b. However, since the cooling rate of the non-azeotropic mixed refrigerant 20 often changes significantly on the inlet side of the condenser 2, it is preferable that multiple inlet-side temperature sensors 7 be positioned as close to the piping 101b side of the condenser 2 as possible.

[0154] 1 Compressor 2 Condenser 2a Fan 3 Expansion valve 4 Evaporator 4a Fan 5 Accumulator 5a Level gauge 5b Valve 6 Pressure sensor 7, 7a, 7b, 7c, 7d, 7e, 7f Temperature sensor 7t Thermography (temperature sensor) 8 Enclosure temperature sensor 9 Ambient temperature sensor 10, 10a, 10b, 10c Control unit 20 Non-azeotropic mixed refrigerant 21a High boiling point gaseous refrigerant (high boiling point refrigerant) 21b High boiling point liquid refrigerant (high boiling point refrigerant) 22a Low boiling point gaseous refrigerant (low boiling point refrigerant) 22b Low boiling point liquid refrigerant (low boiling point refrigerant) 100, 100a-100f Cooling device (cooling device using non-azeotropic mixed refrigerant) 101, 102 Cooling circuit 101a, 101b, 101c, 101d, 101e, 101f Piping D1, D3 Table data (related information) D2, D4 Formula data (related information) Ts, Tsa~Tsd, Tsf~Tsh Saturation temperature (of non-azeotropic refrigerant mixture) Tse Liquid saturation temperature (of non-azeotropic refrigerant mixture)

Claims

1. A cooling device using a non-azeotropic refrigerant mixture, comprising: a compressor for compressing a non-azeotropic refrigerant mixture comprising a low-boiling-point refrigerant and a high-boiling-point refrigerant; a cooling circuit including a heat exchanger for performing heat exchange of the non-azeotropic refrigerant mixture; a pressure sensor disposed in the compressor or in the piping of the cooling circuit connecting the compressor and the heat exchanger for measuring the pressure of the non-azeotropic refrigerant mixture; a temperature sensor for measuring the temperature of the non-azeotropic refrigerant mixture; and a control unit that determines the concentration of the low-boiling-point refrigerant in the cooling circuit based on the pressure of the non-azeotropic refrigerant mixture flowing into the heat exchanger measured by the pressure sensor disposed in the cooling circuit, and the temperature of the non-azeotropic refrigerant mixture near the heat exchanger measured by the temperature sensor.

2. The control unit is configured to store relational information showing the correspondence between the pressure of the non-azeotropic mixed refrigerant flowing into the heat exchanger measured by the pressure sensor, the temperature of the non-azeotropic mixed refrigerant near the heat exchanger measured by the temperature sensor, and the concentration of the low-boiling point refrigerant in the cooling circuit, and to perform control to determine the concentration of the low-boiling point refrigerant in the cooling circuit based on the relational information, as described in claim 1.

3. The cooling device using a non-azeotropic refrigerant mixture according to claim 2, wherein the heat exchanger includes a condenser for condensing the non-azeotropic refrigerant mixture discharged by the compressor, and the control unit is configured to determine the concentration of the low-boiling-point refrigerant in the cooling circuit based on the pressure of the non-azeotropic refrigerant mixture flowing into the compressor or the condenser measured by the pressure sensor, the saturation temperature of the non-azeotropic refrigerant mixture in the condenser, and the related information.

4. The cooling apparatus using a non-azeotropic mixed refrigerant according to claim 3, wherein the control unit is configured to perform concentration reduction operation control such that the concentration of the low-boiling point refrigerant in the cooling circuit is reduced when a state value determined from the pressure of the non-azeotropic mixed refrigerant flowing into the condenser and the housing temperature of the compressor exceeds a concentration threshold set according to the concentration of the low-boiling point refrigerant in the cooling circuit.

5. The cooling device using a non-azeotropic mixed refrigerant according to claim 4, wherein the control unit is configured to perform control to increase the degree of superheating of the non-azeotropic mixed refrigerant flowing into the compressor as the concentration reduction operation control when the state value exceeds the concentration threshold.

6. The cooling device using a non-azeotropic mixed refrigerant according to claim 5, wherein the control unit is configured to reduce the rotational speed of the compressor if the state value exceeds the concentration threshold even after it has performed control to increase the degree of superheating of the non-azeotropic mixed refrigerant flowing into the compressor.

7. The cooling device using a non-azeotropic mixed refrigerant according to claim 4, wherein the control unit is configured to control the degree of superheating of the non-azeotropic mixed refrigerant flowing into the compressor, or the rotational speed of the compressor, so as to bring the concentration of the low boiling point refrigerant in the cooling circuit closer to the concentration threshold, but within a range that does not exceed the concentration threshold.

8. The cooling device using a non-azeotropic mixed refrigerant according to claim 3, further comprising a fan for blowing air onto the condenser, wherein the control unit is configured to increase the rotational speed of the fan to increase the amount of heat dissipated by the condenser when the temperature of the non-azeotropic mixed refrigerant near the inlet side of the condenser is not at the saturation temperature.

9. The cooling apparatus using a non-azeotropic refrigerant mixture according to claim 2, wherein the relational information includes table data showing the correspondence between the pressure of the non-azeotropic refrigerant mixture flowing into the heat exchanger as measured by the pressure sensor, the temperature of the non-azeotropic refrigerant mixture near the heat exchanger as measured by the temperature sensor, and the concentration of the low-boiling point refrigerant in the cooling circuit.

10. The cooling device using a non-azeotropic refrigerant according to claim 1, wherein the heat exchanger includes an evaporator for evaporating the non-azeotropic refrigerant mixture, further comprising an accumulator for temporarily storing the non-azeotropic refrigerant mixture discharged from the evaporator, and a liquid level gauge for measuring the liquid level of the non-azeotropic refrigerant mixture stored in the accumulator, and the control unit is configured to perform control to identify the concentration of the low-boiling-point refrigerant in the cooling circuit based on relational information indicating the correspondence between the liquid level of the non-azeotropic refrigerant mixture in the accumulator arranged in the cooling circuit and the concentration of the low-boiling-point refrigerant in the cooling circuit, as measured by the liquid level gauge.

11. The cooling device using a non-azeotropic mixed refrigerant according to claim 10, wherein the control unit is configured to perform a concentration reduction operation control such that the concentration of the low boiling point refrigerant in the cooling circuit is reduced when the liquid level height of the non-azeotropic mixed refrigerant in the accumulator arranged in the cooling circuit, as measured by the liquid level gauge, exceeds a predetermined liquid level threshold.

12. The cooling device using a non-azeotropic refrigerant mixture according to claim 11, further comprising a bypass pipe that draws in the liquid state of the non-azeotropic refrigerant mixture stored in the accumulator and converts it into a gaseous state for intake into the compressor, wherein the control unit is configured to perform at least one of the following controls as the concentration reduction operation control when the liquid level measured by the liquid level gauge exceeds the liquid level threshold: increasing the degree of superheating of the non-azeotropic refrigerant mixture flowing into the compressor, decreasing the rotational speed of the compressor, or causing the liquid stored in the accumulator to be drawn into the compressor via the bypass pipe.

13. The cooling device using a non-azeotropic refrigerant mixture according to claim 3, wherein the temperature sensor includes a plurality of inlet temperature sensors arranged on the inlet side of the condenser and a plurality of outlet temperature sensors arranged on the outlet side of the condenser, and the control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on a plurality of temperatures of the non-azeotropic refrigerant mixture in the condenser measured by the plurality of inlet temperature sensors and a plurality of temperatures of the non-azeotropic refrigerant mixture in the condenser measured by the plurality of outlet temperature sensors.

14. The cooling device using a non-azeotropic refrigerant mixture according to claim 13, wherein the control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on the difference in the positions of the two inlet-side temperature sensors and the difference in the temperature of the non-azeotropic refrigerant mixture in the condenser measured by each of the two inlet-side temperature sensors, and the difference in the positions of the two outlet-side temperature sensors and the difference in the temperature of the non-azeotropic refrigerant mixture in the condenser measured by each of the two outlet-side temperature sensors.

15. The cooling device using a non-azeotropic mixed refrigerant according to claim 13, wherein the condenser is provided with an ambient temperature sensor for measuring the temperature of the environment surrounding the condenser, and the ambient temperature sensor also serves as the outlet side temperature sensor.

16. The cooling device using a non-azeotropic refrigerant mixture according to claim 13, wherein the control unit is configured to determine the temperature of the non-azeotropic refrigerant mixture measured by the inlet temperature sensor closer to the inlet side of the condenser as the saturation temperature of the non-azeotropic refrigerant mixture in the condenser, when the difference in temperature of the non-azeotropic refrigerant mixture measured by two of the plurality of inlet temperature sensors is less than a predetermined threshold.

17. The cooling device using a non-azeotropic refrigerant mixture according to claim 3, wherein the temperature sensor includes a thermograph, and the control unit is configured to determine the saturation temperature of the non-azeotropic refrigerant mixture in the condenser based on the temperature of each of the non-azeotropic refrigerant mixtures at a plurality of points on the inlet side of the condenser measured by the thermograph and the temperature of each of the non-azeotropic refrigerant mixtures at a plurality of points on the outlet side of the condenser measured by the thermograph.

18. A cooling device using a non-azeotropic refrigerant, comprising: a compressor for compressing a non-azeotropic mixed refrigerant comprising a low-boiling point refrigerant and a high-boiling point refrigerant; a cooling circuit including a heat exchanger for performing heat exchange of the non-azeotropic mixed refrigerant; a temperature sensor for measuring the temperature of the non-azeotropic mixed refrigerant; and a control unit for determining the concentration of the low-boiling point refrigerant in the cooling circuit based on the saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger measured by the temperature sensor, the liquid saturation temperature of the non-azeotropic mixed refrigerant in the heat exchanger, and relational information indicating the correspondence between the saturation temperature and the liquid saturation temperature and the concentration of the low-boiling point refrigerant in the cooling circuit.

19. A cooling device using a non-azeotropic refrigerant, comprising: a compressor for compressing a non-azeotropic refrigerant mixture comprising a low-boiling point refrigerant and a high-boiling point refrigerant; an evaporator for evaporating the non-azeotropic refrigerant mixture; an accumulator for temporarily storing the non-azeotropic refrigerant mixture discharged from the evaporator; a liquid level gauge for measuring the liquid level of the non-azeotropic refrigerant mixture stored in the accumulator; and a control unit for determining the concentration of the low-boiling point refrigerant in the cooling circuit based on relational information indicating the correspondence between the liquid level of the non-azeotropic refrigerant mixture in the accumulator arranged in the cooling circuit and the concentration of the low-boiling point refrigerant in the cooling circuit, as measured by the liquid level gauge.

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