Refrigerating cycle by liquid nitrogen condensation

Abstract

To provide a refrigerating cycle capable of achieving required high cooling capacity in a saved space even when a target temperature of circulation liquid for controlling a temperature control object to a prescribed temperature is extremely low.SOLUTION: A refrigerant is condensed in a condenser 5 using liquid nitrogen in a refrigerating cycle which repeats a cycle in which a circulation circuit 1 having an evaporator 7 for cooling circulation liquid to a target temperature or below by heat exchange by vaporizing the refrigerant, a compressor 4 for compressing the vaporized refrigerant to have condensable high pressure and high temperature, a condenser 5 for condensing the high pressure and high temperature refrigerant, and an expansion valve 6 for making the condensed refrigerant have low pressure and low temperature is used. The refrigerant is vaporized within the evaporator 7 while being circulated, the vaporized refrigerant is compressed by the compressor 4 to have high pressure and high temperature, the refrigerant made to have the high pressure and high temperature is cooled by cooling liquid in the condenser 5 and is liquefied to have high pressure and high temperature, the liquefied refrigerant is expanded by the expansion valve 6 to have low pressure and low temperature, and the refrigerant having the low pressure and the low temperature is vaporized by the evaporator 7 again.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multistage refrigeration cycle used to control the temperature of a cryogenic process in a semiconductor manufacturing device or the like, and relates to a refrigeration cycle for realizing miniaturization of the device. [Background technology]

[0002] As is well known, in semiconductor manufacturing, it is necessary to control the temperature at a constant level within each process. For this purpose, a temperature control device is used to control the temperature by circulating a circulating fluid whose liquid temperature is controlled. This temperature control device is generally called a chiller.

[0003] Chillers generally have a refrigeration cycle for adjusting the temperature of a circulating fluid supplied to a process or the like that is the subject of temperature control to a predetermined temperature (hereinafter referred to as the "target temperature"). This refrigeration cycle circulates a refrigerant in a circulation circuit equipped with a compressor, condenser, expansion valve, and evaporator. During the circulation process, the refrigerant is compressed, condensed, expanded, and evaporated repeatedly by the compressor, condenser, expansion valve, and evaporator, thereby cooling the temperature of the circulating fluid, and the temperature of the circulating fluid is adjusted to the target temperature by a heater or the like.

[0004] For example, Figure 5 shows a typical chiller, in which reference numeral 31 denotes a circulation circuit for circulating a refrigerant. As is well known, this circulation circuit 31 comprises a compressor 32, a condenser 33, an expansion valve 34, and an evaporator 35 connected by circulation piping 36, and the refrigerant is circulated within the piping 36. A circulating fluid circuit 37 for cooling the circulating fluid with vaporized refrigerant is connected to the evaporator 35, and a cooling fluid circuit 38 for cooling the refrigerant is connected to the condenser 33. The circulating fluid circuit 37 includes a supply path 37a for supplying the circulating fluid to the evaporator and a circulation path 37b for returning the circulating fluid adjusted to a target temperature to a process or the like that is the subject of temperature control. Furthermore, the cooling fluid circuit 38 includes a supply path 38a for supplying cooling water to the condenser 33 and a return path 38b for returning the cooling water, which has condensed the refrigerant, to the cooling water supply source.

[0005] Then, while the refrigerant is circulated in the pipe 36, the refrigerant is vaporized in the evaporator 35, the vaporized refrigerant in the evaporator 35 is compressed by the compressor to a high pressure and high temperature, the high pressure and high temperature refrigerant is cooled and condensed in the condenser to a high pressure liquid, the liquefied refrigerant is expanded by the expansion valve to a low pressure and low temperature, and the low pressure and low temperature refrigerant is vaporized again in the evaporator, and the heat of vaporization absorbs heat from the circulating liquid in the evaporator, thereby raising the temperature of the circulating liquid to the target temperature, repeating this refrigeration cycle.

[0006] Incidentally, the target temperature of the circulating fluid adjusted by the chiller may be as low as minus 70 to minus 80 degrees Celsius, or even minus 100 degrees Celsius. Therefore, when the temperature of the object to be cooled is extremely low, a normal single-stage refrigeration cycle cannot cool the circulating fluid to the target temperature.

[0007] That is, in order to condense the refrigerant, which has been heated to a high pressure and temperature by a compressor, into a high pressure and high temperature liquid in a condenser, the refrigerant is generally cooled using cold water. For example, assuming that the target temperature is -40°C or higher, in this case, the evaporation temperature of the refrigerant is about -45°C and the condensation temperature is about 30°C, so the condensation temperature for condensing and liquefying the high pressure and high temperature refrigerant supplied from the compressor is about 30°C, and condensation with air or water is possible.

[0008] However, when the target temperature is an extremely low temperature of minus 70 degrees or below, it is difficult to cool the circulating fluid to below the target temperature using the single-stage refrigeration cycle described above. For example, if the target temperature is between minus 70 and minus 80 degrees, the evaporation temperature must be minus 80 degrees or below, and the refrigerant condensation temperature must be minus 10 degrees or below. Because refrigerant condensation is impossible with water or air, a chiller using a multi-stage refrigeration cycle, which combines multiple single-stage refrigeration cycles, is required.

[0009] To explain this multi-stage refrigeration cycle, for example, if the temperature to be cooled is -60°C, the evaporation temperature is about -70°C and the condensation temperature is about -10°C. Therefore, when the high-pressure, high-temperature gas supplied from the compressor is condensed in the condenser, the condensation temperature is about -10°C, and condensation using water or air is impossible, so in a single-stage refrigeration cycle, it is difficult to raise the temperature of the circulating fluid to the target temperature.

[0010] Therefore, in a multi-stage refrigeration cycle, the refrigeration cycle is divided into two stages, for example, a low-stage refrigeration cycle and a high-stage refrigeration cycle (two-stage refrigeration cycle), and the evaporator of the high-stage refrigeration cycle is combined with the condenser of the low-stage refrigeration cycle, so that the refrigerant in the low-stage refrigeration cycle is condensed with the refrigerant of the high-stage refrigeration cycle; or, the refrigeration cycle is divided into three stages, for example, a low-stage refrigeration cycle, a middle-stage refrigeration cycle, and a high-stage refrigeration cycle (three-stage refrigeration cycle circuit), and the condenser of the low-stage refrigeration cycle is combined with the evaporator of the middle-stage refrigeration cycle, and further, the condenser of the middle-stage refrigeration cycle is combined with the evaporator of the high-stage refrigeration cycle, so that the refrigerant in the low-stage refrigeration cycle is condensed with the refrigerant of the middle-stage refrigeration cycle, and the refrigerant in the middle-stage refrigeration cycle is condensed with the refrigerant of the high-stage refrigeration cycle, making it possible to fully respond even when the target temperature of the circulating liquid is extremely low.

[0011] 3 shows the circuit configuration of a two-stage refrigeration cycle, which is configured by connecting a low-stage refrigeration cycle 41a and a high-stage refrigeration cycle 41c. The low-stage refrigeration cycle 41a has a compressor 32a, a condenser 33a, an expansion valve 34a, and an evaporator 35a. A circulating fluid supply circuit 37a and a circulating fluid circulation circuit 37b are connected to the evaporator 35a, and heat exchange occurs between the refrigerant and the circulating fluid inside the evaporator 35a.

[0012] The high-stage refrigeration cycle 41c also has a compressor 32c, a condenser 33c, an expansion valve 34c, and an evaporator 35c, and the evaporator 35c is also used as the condenser 33a in the low-stage refrigeration cycle 41a, and the refrigerant that has been pressurized and heated to a high temperature by the compressor 32a in the low-stage refrigeration cycle 41a is condensed in the evaporator 35c in the high-stage refrigeration cycle 41c (the condenser 33a in the low-stage refrigeration cycle 41a).

[0013] Furthermore, a coolant supply circuit 38a and a coolant return circuit 38b are connected to the condenser 33c in the high-stage refrigeration cycle 41c, and the refrigerant heated to a high temperature and high pressure by the compressor 32c in the high-stage refrigeration cycle 41c is condensed with the coolant. Note that the condensation in this case can be not only water but also air.

[0014] The two-stage refrigeration cycle in Fig. 3 is a circuit in which the target temperature of the circulating fluid is set to minus 70 to minus 80 degrees Celsius, and the refrigerant used in the low-stage refrigeration cycle 41a is R23, which has a boiling point of minus 82 degrees Celsius, and the refrigerant used in the high-stage refrigeration cycle 41c for condensing this R23 is R410a, which has a boiling point of minus 51.4 degrees Celsius. The refrigerant (R410a) in the high-stage refrigeration cycle 41c is condensed using a cooling liquid.

[0015] 4 is a diagram showing the circuit configuration of a three-stage refrigeration cycle, which includes a low-stage refrigeration cycle 41a, a middle-stage refrigeration cycle 41b, and a high-stage refrigeration cycle 41c. The low-stage refrigeration cycle 41a includes a compressor 32a, a condenser 33a, an expansion valve 34a, and an evaporator 35a. A circulating fluid supply circuit 37a and a circulating fluid circulation circuit 37b are connected to the evaporator 35a, and heat exchange occurs between the refrigerant and the circulating fluid inside the evaporator 35a.

[0016] The middle-stage refrigeration cycle 41b also has a compressor 32b, a condenser 33b, an expansion valve 34b, and an evaporator 35b, and the evaporator 35b is also used as the condenser 33a in the low-stage refrigeration cycle 41a, and the refrigerant that has been heated to high pressure and temperature by the compressor 32a in the low-stage refrigeration cycle 41a is condensed in the evaporator 35b in the middle-stage refrigeration cycle 41b (the condenser 33a in the low-stage refrigeration cycle).

[0017] Furthermore, the high-stage refrigeration cycle 41c also has a compressor 32c, a condenser 33c, an expansion valve 34c, and an evaporator 35c, and the evaporator 35c is also used as the condenser 33b in the middle-stage refrigeration cycle 41b, and the refrigerant that has been heated to high pressure and temperature by the compressor 32b in the middle-stage refrigeration cycle 41b is condensed in the evaporator 35c in the high-stage refrigeration cycle 41c (condenser 33b in the middle-stage refrigeration cycle 41b).

[0018] A coolant supply circuit 38a and a coolant return circuit 38b are connected to the condenser 33c in the high-stage refrigeration cycle 41c, and the refrigerant heated to a high temperature and high pressure in the compressor 32 in the high-stage refrigeration cycle 41c is condensed with the coolant. Note that the condensation in this case can be not only water but also air.

[0019] The three-stage refrigeration cycle shown in Figure 4 is a circuit in which the target temperature of the circulating liquid is minus 100 degrees, and the refrigerant used in the low-stage refrigeration cycle 41a is R14, which has a boiling point of minus 128 degrees, the refrigerant used in the middle-stage refrigeration cycle 41b for condensing this R14 is R23, which has a boiling point of minus 82 degrees, and the refrigerant used in the high-stage refrigeration cycle 41c for condensing this R23 is R410a, which has a boiling point of minus 51.4 degrees, so that the condensation of the refrigerant (R410a) in the high-stage refrigeration cycle 41c is performed using the cooling liquid.

[0020] Therefore, by using these multi-stage refrigeration cycles, it is possible to adequately cope with cases where the temperature of the circulating fluid is extremely low. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-20509 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-148852 [Patent Document 3] Japanese Patent Publication No. 2022-26751 Summary of the Invention [Problem to be solved by the invention]

[0022] In recent years, chillers have been required to have extremely low temperatures for circulating fluid, high cooling capacity, and space-saving design. However, the use of the multi-stage refrigeration cycle described above presents a problem in that it is unavoidable to go against these requirements.

[0023] For example, in the case of a two-stage refrigeration cycle system with a low-stage refrigeration cycle 41a using R23, which has a boiling point of -82°C, and a high-stage refrigeration cycle 41c using R410a, which has a boiling point of -51.4°C, where the target temperature of the circulating fluid is -70 to -80°C, as described above, the boiling point of the refrigerant (R23) used in the low-stage refrigeration cycle 41a is close to the target temperature of the circulating fluid, so the heat exchange temperature difference is small. In this case, the expansion valve must be throttled to reduce the refrigerant pressure to near zero and lower the refrigerant's boiling point. This reduces the amount of refrigerant circulating through the refrigeration cycle, requiring larger compressors and evaporators to ensure sufficient cooling capacity. This increases the size of the chiller, making it impossible to achieve the space-saving requirement.

[0024] Furthermore, if the target temperature of the circulating fluid is between -70 and -80 degrees and R14, which has a boiling point of -128 degrees, is used as the refrigerant, even if the evaporation temperature of the refrigerant is set to, for example, -90 degrees, the temperature difference between the boiling point and evaporation temperature of the refrigerant can be large, so the required amount of refrigerant circulated can be secured without increasing the size of the compressor or evaporator.However, this results in a three-stage refrigeration cycle in which the middle stage refrigeration cycle that condenses the R14 uses R23, and the high stage refrigeration cycle that condenses the R23 uses R410a, which again creates the problem of the chiller becoming larger and not being able to be made smaller.

[0025] Furthermore, when the target temperature of the circulating fluid is minus 100 degrees, as described above, the system will be configured as a three-way refrigeration cycle, with a low-stage refrigeration cycle 41a using R14, which has a boiling point of minus 128 degrees, as a refrigerant, a middle-stage refrigeration cycle 41b using R23, which has a boiling point of minus 82 degrees, as a refrigerant, and a high-stage refrigeration cycle 41c using R410a, which has a boiling point of minus 51.4 degrees, as a refrigerant. This will result in the chiller becoming larger and making it impossible to make the chiller smaller.

[0026] Therefore, an object of the present invention is to provide a refrigeration cycle that can prevent the chiller from becoming larger and achieve the required high cooling capacity in a small space, even when the target temperature of the circulating fluid is extremely low. [Means for solving the problem]

[0027] The refrigeration cycle using liquid nitrogen condensation of the present invention is as follows: A refrigeration cycle is used to maintain a temperature of a control target, such as various devices or processes, at a preset temperature by circulating a circulating fluid adjusted to a very low temperature through the control target, A circulation circuit is provided in the middle of a piping for circulating a refrigerant, and the circulation circuit is connected to the piping for circulating the refrigerant, and the evaporator is configured to cool the circulating liquid to a target temperature or lower by vaporizing the refrigerant, the compressor is configured to compress the vaporized refrigerant to a high pressure and high temperature at which the refrigerant can be condensed, and the condenser is configured to condense the refrigerant compressed to a high pressure and high temperature by the compressor through heat exchange with the coolant supplied by the coolant supply circuit, and the expansion valve is configured to lower the high pressure and high temperature refrigerant liquefied by the condenser and supply the low pressure and low temperature refrigerant to the evaporator. A refrigeration cycle in which a refrigerant is circulated in a loop circuit, the circulating refrigerant is vaporized in an evaporator, the heat of vaporization absorbs heat from the circulating liquid in the evaporator to lower the temperature of the circulating liquid below a target temperature, the vaporized refrigerant in the evaporator is compressed to a high pressure and high temperature by a compressor so that it can be condensed, the high pressure and high temperature refrigerant is cooled with a coolant in a condenser to condense it into a high pressure and high temperature liquid, the liquefied refrigerant is expanded by an expansion valve to a low pressure and low temperature, the low pressure and low temperature refrigerant is vaporized again in the evaporator, and the heat of vaporization absorbs heat from the circulating liquid in the evaporator to lower the temperature of the circulating liquid below the target temperature, repeating this cycle. In order to condense the refrigerant in the condenser, liquid nitrogen is flowed through the coolant supply circuit for supplying the coolant to the condenser, and the refrigerant is condensed by the liquid nitrogen in the condenser. [Effects of the Invention]

[0028] The liquid nitrogen condensation refrigeration cycle of the present invention is a refrigeration cycle that aims to keep the circulating liquid at an extremely low temperature of minus 70 degrees or below, and is characterized in that the refrigerant, which has been pressurized and heated by a compressor, is condensed using liquid nitrogen.

[0029] As is well known, the temperature of liquid nitrogen is minus 196 degrees Celsius, and the present invention, which uses this liquid nitrogen to condense the refrigerant, can sufficiently condense the refrigerant even when using refrigerants such as R14 or R23, which have extremely low boiling points and condensation temperatures that cannot be condensed with water or air, without configuring multiple refrigeration cycles such as a multi-stage refrigeration cycle. Therefore, even if the target temperature of the circulating fluid is, for example, minus 80 degrees Celsius or minus 100 degrees Celsius, there is no need to configure multiple refrigeration cycles, and the circulating fluid can be cooled to the target temperature in a single stage, achieving high cooling capacity and space savings. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a block diagram for explaining a circulation circuit used in an embodiment of a refrigeration cycle using liquid nitrogen condensation according to the present invention. [Figure 2] FIG. 10 is a diagram showing the parameterization of the compressor operating frequency and the opening degree of the electronic expansion valve according to the target temperature of the circulating fluid divided into multiple areas in an embodiment of the refrigeration cycle using liquid nitrogen condensation of the present invention. [Figure 3] FIG. 2 is a block diagram for explaining a two-stage refrigeration cycle. [Figure 4] FIG. 2 is a block diagram for explaining a three-stage refrigeration cycle. [Figure 5] FIG. 1 is a block diagram illustrating a typical chiller. DETAILED DESCRIPTION OF THE INVENTION

[0031] The refrigeration cycle using liquid nitrogen condensation of the present invention is a refrigeration cycle using a circulation circuit in which a circulating liquid flow path through which the circulating liquid circulates is connected midway through a circulation pipe for circulating the refrigerant, and which is connected to an evaporator for cooling the circulating liquid to a temperature below a target by vaporizing the refrigerant, a compressor for compressing the vaporized refrigerant to a high pressure and high temperature, and a cooling liquid supply circuit for supplying a cooling liquid, and which is connected to a condenser for condensing by heat exchange the refrigerant that has been made high pressure and high temperature by the compressor using the cooling liquid supplied by the cooling liquid supply circuit, and an expansion valve for reducing the pressure and temperature of the refrigerant liquefied in the condenser and supplying the low pressure and low temperature refrigerant to the evaporator.

[0032] The refrigerant is circulated in the circulation circuit, and the circulating refrigerant is vaporized in an evaporator. The heat of vaporization absorbs heat from the circulating liquid in the evaporator, raising the temperature of the circulating liquid to a target temperature. The vaporized refrigerant in the evaporator is compressed in a compressor to a high pressure and high temperature. The high-pressure, high-temperature refrigerant is then cooled and condensed with a cooling liquid in a condenser to become a high-pressure, high-temperature liquid. The liquefied refrigerant is expanded in an expansion valve to a low pressure and low temperature. The low-pressure, low-temperature refrigerant is then vaporized again in the evaporator, absorbing heat from the circulating liquid in the evaporator due to the heat of vaporization, raising the temperature of the circulating liquid to the target temperature. This refrigeration cycle repeats this cycle.

[0033] In the refrigeration cycle of the present invention, liquid nitrogen is used as the coolant to be supplied to the condenser to condense the refrigerant in the condenser, and this liquid nitrogen is supplied to the condenser through a coolant supply circuit, so that the refrigerant is condensed by the liquid nitrogen in the condenser.

[0034] Preferably, an inverter compressor is used as the compressor and an electronic expansion valve is used as the expansion valve. When an inverter compressor is used as the compressor and an electronic expansion valve is used as the expansion valve, the target temperature of the circulating fluid is divided into a plurality of areas in advance, the operating frequency of the inverter compressor and the aperture of the electronic expansion valve are set as parameters according to the plurality of divided target temperature areas of the circulating fluid, and the operating frequency of the inverter compressor and the aperture of the electronic expansion valve are automatically adjusted according to the parameters according to the target temperature of the circulating fluid. This makes it possible to maintain the circulating fluid at the target temperature even when the target temperature range of the circulating fluid varies over a wide range, for example, from -100°C to 30°C.

[0035] Furthermore, when setting each parameter, it is advisable to make it possible to remotely control the chiller via the Internet or the like, so that the parameters for the inverter compressor operating frequency and the opening degree of the electronic expansion valve can be set remotely, which also makes it possible to perform remote maintenance on the chiller equipment. [Example]

[0036] An embodiment of the refrigeration cycle using liquid nitrogen condensation (hereinafter simply referred to as the "refrigeration cycle") of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining a circulation circuit used to implement the refrigeration cycle of this embodiment, and in the figure, reference numeral 1 denotes the circulation circuit.

[0037] The refrigeration cycle of this embodiment is implemented using a circulation circuit 1 similar to that of a commonly used refrigerator.

[0038] 1, the circulation circuit 1 used in this embodiment has a refrigerant circulation pipe 3 for circulating a refrigerant, similar to a circulation circuit generally used to implement a refrigeration cycle. An evaporator 7 is provided in the pipe 3 for vaporizing the refrigerant to cool the circulating liquid to a target temperature or lower. A circulating liquid circuit 9 is connected to the evaporator 7, and the circulating liquid circuit 9 is used to circulate the circulating liquid between the circulating liquid and a control target, such as various devices or processes, that require temperature control, thereby maintaining the control target at a preset temperature.

[0039] The evaporator 7 is connected to a compressor 4 via a pipe 3, and the compressor 4 is used to compress the refrigerant vaporized in the evaporator 7 to a high pressure and a high temperature.

[0040] Also, the compressor 4 is connected via a pipe 3 to a condenser 5 for cooling and condensing the refrigerant, which has been brought to a high pressure and temperature by the compressor 4, by heat exchange. A coolant supply circuit 8 is connected to the condenser 5, and the high pressure and high temperature refrigerant supplied from the compressor 4 is cooled and condensed by supplying a coolant to the condenser 5 via the coolant supply circuit 8. In this embodiment, liquid nitrogen is used as the coolant supplied to the condenser 5.

[0041] Next, an expansion valve 6 is connected to the condenser 5 via piping 3, and the expansion valve 6 is used to reduce the pressure and temperature of the refrigerant liquefied in the condenser 5 and supply the reduced pressure and temperature refrigerant to the evaporator 7.

[0042] In the circulation circuit 21 configured as described above, as is well known, the low-pressure, low-temperature gas vaporized by the evaporator 7 is converted into a high-pressure, high-temperature gas by the compressor 4, and this high-pressure, high-temperature gas is then condensed with liquid nitrogen in the condenser 5 to become a high-pressure, high-temperature liquid. The refrigerant condensed into a liquid by the condenser 5 is then converted into a low-pressure, low-temperature liquid by the expansion valve 6, and the refrigerant supplied from the expansion valve 6 is vaporized again in the evaporator 7 and cools the circulating liquid by the heat of vaporization, after which this refrigeration cycle is repeated. In this embodiment, an inverter-controllable compressor is used as the compressor 4, and an electronic expansion valve is used as the expansion valve 6.

[0043] The coolant circulation circuit 8 is used to condense the refrigerant, which has been heated to a high pressure and temperature by the compressor 4, in the condenser 5 by heat exchange, and includes a coolant supply circuit 801 that supplies the coolant to the condenser 5, and a coolant return circuit 802 that returns the coolant (gas) after heat exchange with the refrigerant in the condenser 5 to the coolant supply source.

[0044] Furthermore, the circulating fluid circulation circuit 9 is used to circulate the circulating fluid between a controlled object whose temperature is to be controlled, such as a semiconductor etching process, and the evaporator 7, and to supply the controlled object with the circulating fluid cooled to a preset temperature in the evaporator 7. The circulating fluid circulation circuit 9 has a circulating fluid supply circuit 901 for supplying the controlled object with the circulating fluid cooled to a target temperature or lower in the evaporator 7, a circulating fluid return circuit 902 for returning the circulating fluid whose temperature has been raised in the controlled object to the evaporator 7, and a pump 17.

[0045] In the figure, reference numeral 17 denotes a circulation pump that circulates the circulating fluid through a controlled object whose temperature is to be controlled, such as a semiconductor etching process, and reference numeral 18 denotes a heater that controls the temperature of the circulating fluid that has been cooled to a target temperature or lower by the evaporator 7 to the target temperature. That is, in the circulation circuit 1 used in this embodiment, the temperature of the circulating fluid is cooled to a target temperature or lower, and then the heater 18 is used to control the circulating fluid to the target temperature.

[0046] Also in the figure, reference numeral 11 denotes a hot gas supply circuit for supplying hot gas to the evaporator 7 before the evaporator 7, and 12 denotes an electronic expansion valve for controlling the flow rate of the hot gas. Also in the figure, reference numeral 13 denotes a cooling refrigerant supply circuit for supplying refrigerant to the compressor 4 to cool it, and 14 denotes an electronic expansion valve for controlling the flow rate of the cooling refrigerant supplied to the compressor 4. Furthermore, reference numeral 15 denotes a flow control valve for adjusting the flow rate of the cooling liquid flowing to the condenser 5, and 16 denotes a pressure sensor for checking the pressure of the refrigeration cycle.

[0047] Next, the refrigeration cycle of this embodiment using the circulation circuit configured as described above will be explained. In the refrigeration cycle of this embodiment, as described above, the refrigerant is circulated within the circulation circuit 1, and the cycle of evaporation, compression, condensation, and expansion of the refrigerant is repeated. Liquid nitrogen is flowed into the coolant supply circuit 8, and the refrigerant, which has been heated to a high pressure and temperature by the compressor, is condensed using the liquid nitrogen.

[0048] As is well known, the temperature of liquid nitrogen is minus 196 degrees Celsius. In the refrigeration cycle of this embodiment, which is characterized by using this liquid nitrogen to condense the refrigerant, even when the target temperature of the circulating liquid is minus 80 degrees Celsius or minus 100 degrees Celsius and a refrigerant with an extremely low boiling point such as R14 is used as the refrigerant, it is possible to condense the refrigerant in a single-stage refrigeration cycle without using a multi-stage refrigeration cycle, thereby achieving high cooling capacity and space saving.

[0049] In the refrigeration cycle of this embodiment, the target temperature of the circulating fluid that may be set is divided into a plurality of areas in advance, and the operating frequency of the compressor 4 and the openings of the electronic expansion valves 6, 12, and 14 are set as parameters for each area so that the temperature of the circulating fluid can be set to the target temperature.

[0050] Figure 2 shows the set target of the circulating fluid divided into multiple areas, and the state in which the operating frequency of the compressor 4 and the opening of the electronic expansion valves 6, 12, and 14 are parameterized so that the temperature of the circulating fluid can be set to the target temperature for each area. CMP indicates the operating frequency of the compressor 4, and DEV indicates the opening of the electronic expansion valves 6, 12, and 14.

[0051] After the target temperature of the circulating fluid is set, the operating frequency of the compressor 4 and the openings of the electronic expansion valves 6, 12, and 14 are automatically set to values ​​that are pre-parameterized and set according to the area to which the set target temperature of the circulating fluid belongs. This makes it possible to more efficiently cool the temperature of the circulating fluid to the target temperature with a simple component configuration.

[0052] That is, in order to lower the temperature of the object to be cooled to below the target temperature, it is necessary to control the evaporation temperature of the refrigerant. In this embodiment, however, since an electronic expansion valve is used, it is possible to control the evaporation temperature of the refrigerant to the intended temperature.

[0053] Furthermore, to ensure the required cooling capacity, it is necessary to adjust the amount of refrigerant circulating by controlling the operating frequency of the compressor. However, in this embodiment, an inverter-controllable compressor is used, and therefore, unlike conventional devices that use a constant-speed compressor, operate the compressor at maximum capacity, and cool the circulating liquid by using various adjustment valves, etc., the operating frequency of the compressor can be controlled to ensure the amount of refrigerant circulating required for the cooling capacity. This makes it possible to achieve energy savings by avoiding cooling the circulating liquid more than necessary.

[0054] Furthermore, in the case of a chiller that can handle extremely low temperatures, the control temperature range is very wide, from extremely low temperatures (for example, minus 100 degrees) to room temperature (for example, 30 degrees), but in this embodiment, the operating frequency of compressor 4 and the opening of electronic expansion valves 6, 12, and 14 are set to optimal values ​​depending on the target temperature, so the circulating fluid can be cooled to the target temperature more efficiently.

[0055] As described above, in this embodiment, the operating frequency of the compressor and the opening of the electronic expansion valve are set as parameters according to a plurality of areas divided according to the target temperature of the circulating fluid, but when setting these various parameters, in addition to directly operating the chiller, it is also possible to set the chiller remotely via the Internet or the like, and enable the various parameters to be set remotely. In this way, in addition to the initial setting of the parameters, remote maintenance is also possible when it becomes necessary to modify the various parameters due to changes in the operating environment of the device. [Industrial Applicability]

[0056] The present invention can bring the circulating fluid to the target temperature without using a multi-stage refrigeration cycle, even when the target temperature of the circulating fluid is an extremely low temperature, and therefore can be applied to all refrigeration cycles with an extremely low target temperature. [Explanation of symbols]

[0057] 1 Circulation circuit 3. Piping for refrigerant circulation 4. Compressor 5. Condenser 6. Electronic expansion valve 7 Heat exchanger (evaporator) 8 Coolant circulation circuit 801 Coolant supply path 802 Coolant return path 9 Circulating fluid circulation circuit 901 Circulating fluid supply path 902 Circulating fluid return path 11 Hot gas supply line 12 Electronic expansion valve 13 Cooling refrigerant supply path 14 Electronic expansion valve 15 Water control valve 16 Pressure Sensor 17 Pump 18 Heater

Claims

1. A refrigeration cycle is used to maintain a temperature of a control target, such as various devices or processes, at a preset temperature by circulating a circulating fluid adjusted to a very low temperature through the control target, It is arranged in the middle of a circulation pipe (3) for circulating a refrigerant. an evaporator (7) connected to a circulating fluid circuit (9) through which the circulating fluid circulates, for cooling the circulating fluid to a target temperature by vaporizing a refrigerant; A compressor (4) for compressing the vaporized refrigerant to high pressure and high temperature; a condenser (5) connected to a coolant supply circuit (8) for supplying a coolant, and for condensing, by heat exchange, the refrigerant that has been made high-pressure and high-temperature by the compressor (4) using the coolant supplied by the coolant supply circuit (8); a circulation circuit (1) including an expansion valve (6) for lowering the pressure and temperature of the refrigerant liquefied in the condenser (5) and supplying the low-pressure and low-temperature refrigerant to the evaporator (7), While circulating a refrigerant in a circulation circuit (1), the circulating refrigerant is The circulating liquid is vaporized in the evaporator (7), and the heat of vaporization absorbs heat from the circulating liquid in the evaporator (7) to reduce the temperature of the circulating liquid to a target temperature or lower, and then the heater (18) controls the temperature of the circulating liquid to the target temperature. In a refrigeration cycle, the refrigerant vaporized in the evaporator (7) is compressed by the compressor (4) to a high pressure and high temperature at which it can be condensed, the high pressure and high temperature refrigerant is cooled and condensed by a cooling liquid in the condenser (5) to become a high pressure liquid, the liquefied refrigerant is expanded by an expansion valve (6) to become a low pressure and low temperature refrigerant, the low pressure and low temperature refrigerant is vaporized again in the evaporator (7), the evaporator absorbs heat from the circulating liquid to make the temperature of the circulating liquid below a target temperature, and the heater (18) makes it to the target temperature, and the cycle is repeated. To condense the refrigerant in the condenser, A refrigeration cycle using liquid nitrogen condensation, characterized in that liquid nitrogen is flowed through the coolant supply circuit (8) for supplying a coolant to a condenser (5), and the refrigerant is condensed by the liquid nitrogen in the condenser (5).

2. 2. The refrigeration cycle using liquid nitrogen condensation according to claim 1, wherein the target temperature of the circulating fluid is minus 70 degrees Celsius or less.

3. 3. The refrigeration cycle using liquid nitrogen condensation according to claim 1, wherein an inverter compressor is used as the compressor (4) and an electronic expansion valve is used as the expansion valve (6).

4. 4. The refrigeration cycle using liquid nitrogen condensation according to claim 3, wherein a target temperature of the circulating fluid is divided into a plurality of areas in advance, and the operating frequency of the inverter compressor (4) and the aperture of the electronic expansion valve (6, 12, 14) are set as parameters according to the divided areas, and the operating frequency of the inverter compressor (4) and the aperture of the electronic expansion valve (6, 12, 14) are automatically adjusted according to the parameters according to the target temperature of the circulating fluid.

5. 5. The refrigeration cycle using liquid nitrogen condensation according to claim 4, wherein the operating frequency of the inverter compressor (4) and the opening parameters of the electronic expansion valves (6, 12, 14) can be set by remote control.

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