Cooling device

Abstract

To provide a cooler capable of efficiently performing defrosting without excess or deficiency while suppressing rise in air temperature during defrosting.SOLUTION: A cooler 100 comprises a control unit 10 that when defrosting is performed by the flow of air sent from a blower 6 to a heat transfer surface of a cooling evaporator 5, controls the end of defrosting based on a blast temperature that is a temperature of air sent from the blower 6 to the cooling evaporator 5, a surface temperature that is a temperature of the surface of the cooling evaporator 5, and a blowout temperature that is a temperature of air blown out from the cooling evaporator 5.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a cooling device, and more particularly to a cooling device that defrosts a cooling evaporator. [Background technology]

[0002] 2. Description of the Related Art Conventionally, cooling devices that defrost a cooling evaporator are known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a cooling device that defrosts a cooling evaporator. The cooling device includes a compressor, a condenser, an expansion valve, an evaporator, and a blower. The compressor compresses a refrigerant. The condenser condenses the refrigerant discharged from the compressor. The expansion valve expands the refrigerant condensed in the condenser. The evaporator evaporates the refrigerant expanded by the expansion valve. The blower sends air to the surface of the evaporator.

[0004] In the cooling device of Patent Document 1, frost adhering to the surface of the evaporator is sublimated and peeled off by blowing air onto the surface of the evaporator with a blower. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-18035 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the cooling device of the above Patent Document 1, in order to suppress the rise in the air temperature during defrosting, the evaporator is not heated by a heater, but the frost is sublimated and peeled off by sending air to the surface of the evaporator, so that the temperature change of the evaporator during defrosting is small. Here, in the cooling device of the above Patent Document 1, although it is not specified in the above Patent Document 1, if the temperature change of the evaporator during defrosting is small, it is considered to be difficult to detect the temperature drop of the evaporator due to heat exchange between the evaporator and the air and determine the end of defrosting, so it is considered to perform defrosting by setting the defrosting time in advance. However, when the defrosting time is set in advance, if the set defrosting time is long, the efficiency of the defrosting process is deteriorated due to defrosting being performed even after the frost is completely removed. In addition, if the set defrosting time is short, the frost remains, so it is difficult to perform defrosting efficiently without excess or deficiency. For these reasons, it is desired that the cooling device described in the above Patent Document 1 perform defrosting efficiently without excess or deficiency while suppressing the rise in the air temperature during defrosting.

[0007] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a cooling device that can perform defrosting efficiently and without excess or deficiency while suppressing an increase in air temperature during defrosting. [Means for solving the problem]

[0008] A cooling device according to one aspect of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant discharged from the compressor, an expansion section that expands the refrigerant condensed by the condenser, a cooling evaporator that evaporates the refrigerant expanded by the expansion section, a blower that blows air to a surface of the cooling evaporator, and a control section that performs control to terminate defrosting based on a blowing temperature that is the temperature of air blown from the blower to the cooling evaporator, a surface temperature that is the temperature of the surface of the cooling evaporator, and a blowing temperature that is the temperature of air blown out from the cooling evaporator, when defrosting is performed by a flow of air blown from the blower to a heat transfer surface of the cooling evaporator. The control unit is configured to obtain a heat transfer change index value that changes with a change in a heat transfer value indicating the ease of heat transfer from the cooling evaporator to air, which changes with defrosting of frost adhering to the cooling evaporator, based on the blowing air temperature, the surface temperature, and the blowing temperature, and to perform control to terminate defrosting when the heat transfer change index value or a change in the heat transfer change index value becomes equal to or less than a threshold value. .

[0009] In the cooling device according to one aspect of the present invention, as described above, a control unit is provided that controls defrosting by the flow of air sent from the blower to the heat transfer surface of the cooling evaporator. As a result, defrosting can be performed by sublimation and peeling due to the air flow, so there is no need to excessively increase the temperature of the cooling evaporator during defrosting. Therefore, it is possible to suppress an increase in the air temperature during defrosting. Also, as described above, the control unit controls to end defrosting based on the blowing air temperature, which is the temperature of the air sent from the blower to the cooling evaporator, the surface temperature, which is the temperature of the surface of the cooling evaporator, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator. As a result, by performing calculations using the blowing air temperature, the surface temperature, and the blowing temperature, it is possible to obtain, for example, a heat transfer value (overall heat transfer coefficient) indicating the ease of heat transfer from the cooling evaporator to the air that changes with defrosting. As a result, even if the temperature change of the cooling evaporator is small when defrosting is performed by sublimation and peeling due to the air flow, the defrosting can be terminated based on the above calculation result (for example, the heat transfer value (overall heat transfer coefficient)), so the progress of the defrosting can be accurately detected based on the above calculation result, and defrosting can be performed efficiently without excess or deficiency. As a result, defrosting can be performed efficiently without excess or deficiency while suppressing the air temperature from rising during defrosting. Furthermore, since the end of defrosting can be detected based on a comparison between the heat transfer change index value and a threshold value, it is possible to prevent the process for detecting the end of defrosting from becoming complicated.

[0010] In addition, in the cooling device according to the above aspect, preferably, the cooling device further includes a blowing temperature sensor for measuring the blowing temperature, a surface temperature sensor for measuring the surface temperature, and a blowing temperature sensor for measuring the blowing temperature, and the control unit is configured to control the defrosting to end based on the blowing temperature measured by the blowing temperature sensor, the surface temperature measured by the surface temperature sensor, and the blowing temperature measured by the blowing temperature sensor. With this configuration, the blowing temperature can be directly measured by the blowing temperature sensor, the surface temperature can be directly measured by the surface temperature sensor, and the blowing temperature can be directly measured by the blowing temperature sensor, so that the calculation result using the blowing temperature, the surface temperature, and the blowing temperature can be accurately calculated. As a result, the progress of the defrosting can be detected more accurately, so that the defrosting can be performed more efficiently without excess or deficiency.

[0012] In the cooling device according to the above aspect, Preferably, the control unit is configured to perform control to calculate a change in heat transfer value accompanying defrosting of frost adhering to the cooling evaporator based on a value obtained by dividing the inlet / outlet air temperature difference calculated by the difference between the supply air temperature and the blowing temperature by the inlet evaporator temperature difference calculated by the difference between the supply air temperature and the surface temperature. With this configuration, the change (trend) in the heat transfer value (overall heat transfer coefficient) that cannot be directly measured by the sensor can be calculated based on the supply air temperature, surface temperature, and blowing temperature that can be measured by the sensor, so that the defrosting process based on the heat transfer change index value can be easily performed.

[0013] in this case,Preferably, the control unit is configured to perform control to calculate a heat transfer change index value that changes with a change in the heat transfer value based on the difference between a value obtained by dividing the inlet / outlet air temperature difference by the inlet evaporator temperature difference in an ideal state in which the surface temperature and the blowing temperature are equal after defrosting is completed and the value obtained by dividing the current inlet / outlet air temperature difference by the inlet evaporator temperature difference. With this configuration, the change (trend) of the heat transfer change index value that changes with the change (trend) of the heat transfer value (overall heat transfer coefficient) that cannot be directly measured by the sensor can be calculated based on the blowing air temperature, surface temperature, and blowing temperature that can be measured by the sensor, so that defrosting processing based on the heat transfer change index value can be realized.

[0014] In the cooling device according to the above aspect, Preferably, the control unit is configured to change the threshold value based on the output of the blower. With this configuration, the heat transfer value (overall heat transfer coefficient) changes depending on the wind speed that changes with the output of the blower, so that the threshold value can be changed to an appropriate value.

[0015] In the cooling device according to the above aspect, Preferably, the control unit is configured to control the start of defrosting at predetermined time intervals or when the change in the heat transfer change index value reaches or exceeds a predetermined value. With this configuration, defrosting can be reliably performed before excessive frost forms on the cooling evaporator, thereby suppressing a decrease in the cooling performance of the cooling evaporator.

[0016] In the cooling device according to the above aspect, the control unit is preferably configured to perform control to estimate the surface temperature of the cooling evaporator based on the degree of superheat of the cooling evaporator. With this configuration, a more accurate surface temperature can be obtained, and therefore the calculation result using the blowing air temperature, the surface temperature, and the blowing temperature can be calculated more accurately. Effect of the Invention

[0017] According to the present invention, as described above, it is possible to perform defrosting efficiently without excessive or insufficient while suppressing an increase in air temperature during defrosting. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a configuration of a cooling device according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a perspective view showing a cooling evaporator of a cooling device according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a cooling evaporator of the cooling device according to the first embodiment of the present invention. [Figure 4] 4 is a graph showing changes in a heat transfer change index value in the cooling device according to the first embodiment of the present invention. [Diagram 5] 1 is a graph showing an example of a change in the moisture content of air when wind pressure defrosting is performed. [Figure 6] 4 is a flowchart showing an air pressure defrosting process of the cooling device according to the first embodiment of the present invention. [Figure 7] FIG. 6 is a schematic diagram showing a cooling evaporator of a cooling device according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a schematic diagram showing a cooling evaporator of a cooling device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0020] [First embodiment] The configuration of a cooling device 100 according to a first embodiment will be described with reference to FIGS.

[0021] The cooling device 100 is configured to cool a cooling space. Specifically, the cooling device 100 is configured to cool the cooling space to a temperature of 0°C or lower. For example, the cooling device 100 is configured to cool the cooling space to a temperature of about -20°C. The cooling device 100 is configured to cool the inside of a showcase, a refrigerator, a freezer, a storehouse, or a room as the cooling space. For example, the cooling device 100 is an ice showcase in which the top of the cooling space is open and which cools frozen foods and ice creams.

[0022] As shown in Figures 1 and 2, the cooling device 100 includes a compressor 1, a condenser 2, a blower 3, multiple expansion valves 4, multiple cooling evaporators 5, a blower 6, a blowing temperature sensor 7 (see Figure 3), a surface temperature sensor 8 (see Figure 3), a blowing temperature sensor 9 (see Figure 3), and a control unit 10.

[0023] The compressor 1 is configured to compress a refrigerant. The compressor 1 is controlled by an inverter (not shown). As a result, the compressor 1 is configured to be able to adjust the flow rate of the refrigerant discharged from the compressor 1. The refrigerant is, for example, R410A, R404A, R32, carbon dioxide (CO2), or the like.

[0024] The condenser 2 is configured to condense the refrigerant discharged from the compressor 1. The blower 3 is configured to send air to the condenser 2. As a result, heat is transferred from the refrigerant in the condenser 2 to the air sent by the blower 3.

[0025] The multiple expansion valves 4 are configured to expand the refrigerant condensed by the condenser 2. Each of the multiple expansion valves 4 is configured, for example, as a needle valve. The opening degree of each of the multiple expansion valves 4 is adjusted by a stepping motor (not shown) attached to each of the multiple expansion valves 4. By adjusting the opening degrees of the multiple expansion valves 4, the flow rates of the refrigerant in the multiple cooling evaporators 5 provided downstream of each of the multiple expansion valves 4 are adjusted.

[0026] 2 and 3, each of the cooling evaporators 5 is configured to evaporate the refrigerant expanded by each of the expansion valves 4. Each of the cooling evaporators 5 is arranged in parallel with one another. Each of the cooling evaporators 5 has a plurality of flat plates 51 and a refrigerant flow path 52.

[0027] Each of the flat plates 51 is made of a metal such as aluminum. The front and back surfaces of each of the flat plates 51 are heat transfer surfaces. The coolant flow passage 52 penetrates the flat plates 51 and is provided in a serpentine manner.

[0028] The blower 6 is configured to send air to the cooling evaporator 5. This transfers heat from the refrigerant in the cooling evaporator 5 to the air sent by the blower 6. The blower temperature sensor 7 is, for example, a thermistor. The blower temperature sensor 7 measures the blowing temperature of the air flowing from the blower 6 toward the cooling evaporator 5. The surface temperature sensor 8 is, for example, a thermistor. The surface temperature sensor 8 measures the surface temperature of the electric heating surface of the cooling evaporator 5. The blowing temperature sensor 9 is, for example, a thermistor. The blowing temperature sensor 9 measures the blowing temperature of the air blown out from the cooling evaporator 5.

[0029] (Control unit) The control unit 10 includes a CPU (Central Processing Unit, not shown) and a storage unit (not shown) having a RAM (Random Access Memory) and a ROM (Read Only Memory), etc. The storage unit stores an air pressure defrosting program for performing air pressure defrosting in which the frost adhering to the cooling evaporator 5 is removed by peeling and sublimation without melting it, by blowing air through the cooling evaporator 5 with the air blower 6. The control unit 10 is also configured to control the air blower 6 with a preset output so that the air speed of the air blower 6 is constant, according to the air pressure defrosting program.

[0030] Here, wind pressure defrosting by the blower 6 is performed at predetermined time intervals. That is, the control unit 10 is configured to control the start of defrosting at predetermined time intervals. In wind pressure defrosting, frost is removed by peeling and sublimation, and it is preferable to remove frost mainly by sublimation. However, when frost is removed mainly by sublimation, the time required to remove frost becomes relatively long, so it is important to determine the timing when defrosting has ended.

[0031] Therefore, the control unit 10 of the first embodiment is configured to perform control to terminate defrosting based on the blowing air temperature, which is the temperature of the air sent from the blower 6 to the cooling evaporator 5, the surface temperature, which is the temperature of the surface of the cooling evaporator 5, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator 5, when defrosting is performed by the flow of air sent from the blower 6 to the cooling evaporator 5, the surface temperature, which is the temperature of the surface of the cooling evaporator 5, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator 5. That is, the control unit 10 is configured to perform control to terminate defrosting based on the three temperatures, namely the blowing air temperature, the surface temperature, and the blowing temperature, when performing wind pressure defrosting in which frost is removed by peeling and sublimation without melting it by supplying an air flow from the blower 6 while controlling the temperature to near 0°C.

[0032] Specifically, the control unit 10 is configured to perform control to terminate the defrosting based on the blowing air temperature measured by the blowing air temperature sensor 7, the surface temperature measured by the surface temperature sensor 8, and the blowing air temperature measured by the blowing air temperature sensor 9. In this way, not only the surface temperature but also the blowing air temperature and the blowing air temperature are used to determine the completion of defrosting.

[0033] Here, the frost adhering to the surface of the cooling evaporator 5 impedes the transfer of heat from the cooling evaporator 5 to the air. That is, as the amount of frost adhering to the surface of the cooling evaporator 5 increases, it becomes more difficult for heat to be transferred from the cooling evaporator 5 to the air, and as the amount of frost adhering to the surface of the cooling evaporator 5 decreases, it becomes easier for heat to be transferred from the cooling evaporator 5 to the air. In this way, by capturing the change in the ease of transfer of heat from the cooling evaporator 5 to the air (change in thermal resistance), it is possible to obtain the change in the amount of frost adhering to the surface of the cooling evaporator 5.

[0034] The ease of heat transfer from the cooling evaporator 5 to the air is indicated by the heat transfer value, which is the overall heat transfer coefficient. That is, the heat transfer value (overall heat transfer coefficient) decreases as the amount of frost adhering to the surface of the cooling evaporator 5 increases, making it difficult for heat to be transferred between the cooling evaporator 5 and the air. The heat transfer value (overall heat transfer coefficient) increases as the amount of frost adhering to the surface of the cooling evaporator 5 decreases, making it easier for heat to be transferred between the cooling evaporator 5 and the air. In this way, by capturing the change in the heat transfer value (overall heat transfer coefficient), it is possible to obtain the change in the amount of frost adhering to the surface of the cooling evaporator 5.

[0035] Here, the formula for heat transfer from the cooling evaporator 5 to the air is expressed as Q=-k*A*ΔT0. Q is the amount of heat exchanged between the cooling evaporator 5 and the air, k is the heat transfer value (overall heat transfer coefficient), A is the heat transfer area of ​​the cooling evaporator 5, and ΔT0 is the inlet evaporator temperature difference (temperature difference between the blown air temperature and the surface temperature). Q is the air specific heat C p , the inlet / outlet air temperature difference (temperature difference between the supply air temperature and the blown air temperature) ΔT air , and q, the air mass flow rate m Therefore, Q=C p *q m *ΔT air Since it is shown by C p *ΔT air =-k*A*ΔT0. This means that ΔT air / ΔT0=k*A / (C p *q m ) is expressed as A / (C p *q m ) is an almost constant value, the change in the heat transfer value (overall heat transfer coefficient) k is obtained by the supply air temperature, surface temperature, and blown-out temperature.

[0036] As a result, the change (trend) in the amount of frost adhering to the surface of the cooling evaporator 5 can be obtained from the blowing air temperature, the surface temperature, and the blowing temperature. Therefore, the completion of defrosting can be determined from the blowing air temperature, the surface temperature, and the blowing temperature.

[0037] That is, the control unit 10 is configured to obtain a heat transfer change index value that changes in accordance with a change in the heat transfer value indicating the ease of heat transfer from the cooling evaporator 5 to the air, which changes in accordance with the defrosting of frost adhering to the cooling evaporator 5 based on the supply air temperature, surface temperature and blowing temperature, and to perform control to terminate defrosting based on the heat transfer change index value becoming equal to or lower than the threshold value Th.

[0038] Specifically, the control unit 10 calculates the inlet / outlet air temperature difference ΔT air The system is configured to perform control to calculate the change in heat transfer value (overall heat transfer coefficient) associated with the defrosting of frost adhering to the cooling evaporator 5 based on the value obtained by dividing the above by the inlet evaporator temperature difference ΔT0 calculated from the difference between the supply air temperature and the surface temperature.

[0039] That is, the control unit 10 calculates the inlet / outlet air temperature difference ΔT in an ideal state where the surface temperature and the blown temperature are equal after defrosting is completed. air is divided by the inlet evaporator temperature difference, ΔT0, and the current inlet / outlet air temperature difference ΔT air The control is configured to calculate a heat transfer change index value that changes with the change in the heat transfer value based on the difference between the value obtained by dividing the inlet evaporator temperature difference ΔT0 and the value obtained by dividing the inlet evaporator temperature difference ΔT1. Here, in an ideal state, the surface temperature and the blowing temperature become equal, so that ΔT air / ΔT0 becomes 1. As a result, the control unit 10 air The heat transfer change index value is calculated based on the formula: 1-(ΔT air / ΔT0), the calculated value approaches 0 as the amount of frost adhering to the cooling evaporator 5 decreases, and the calculated value increases as the amount of frost adhering to the cooling evaporator 5 increases. Note that G is a gain for adjusting the scale of the heat transfer change index value.

[0040] In this way, the control unit 10 is configured to determine that the amount of frost adhering to the cooling evaporator 5 has been sufficiently reduced based on the heat transfer change index value becoming equal to or less than the threshold value Th, and to perform control to terminate the defrosting. That is, the control unit 10 is configured to determine that the amount of frost adhering to the cooling evaporator 5 has been sufficiently reduced based on the heat transfer change index value becoming equal to or less than the threshold value Th, and to terminate the defrosting at time t a The defrosting process is terminated at the time of the defrosting.

[0041] FIG. 5 shows a graph showing the change in the moisture content of the air when wind pressure defrosting is performed with a humidity sensor attached downstream of the cooling evaporator 5. Comparing the graphs in FIG. 4 and FIG. 5, it can be seen that similar changes (trends) have been obtained. Here, the time t a and the time t when wind pressure defrosting ends in the graph of FIG. b is approximately the same as that shown in FIG. 1. In this way, since a graph similar to the change in the air moisture content can be obtained by using the heat transfer change index value, it is understood that the temperature sensor can perform detection equivalent to that of a humidity sensor. Therefore, it is understood that the end of defrosting can be accurately determined by using the temperature sensor. As a result, the amount of frost adhering to the cooling evaporator 5 can be accurately detected without using a humidity sensor, and by using a temperature sensor instead of a humidity sensor, the reliability of the detection accuracy can be maintained.

[0042] (Wind pressure defrosting process) The wind pressure defrosting process by the control unit 10 will be described below with reference to Fig. 6. The wind pressure defrosting process is a process for performing wind pressure defrosting by the blower 6.

[0043] In step S1, the control unit 10 determines whether or not a predetermined time has elapsed. If the predetermined time has elapsed, the process proceeds to step S2, and if the predetermined time has not elapsed, step S1 is repeated. In step S2, the control unit 10 starts blowing air by the blower 6. The blower 6 blows air at an output preset by the control unit 10 so as to maintain a constant wind speed. In step S3, the control unit 10 acquires the blowing air temperature, surface temperature, and discharge temperature. The blowing air temperature is the temperature measured by the blowing temperature sensor 7. The surface temperature is the temperature measured by the surface temperature sensor. The discharge temperature is the temperature measured by the discharge temperature sensor 9.

[0044] In step S4, the control unit 10 calculates a heat transfer change index value. That is, the control unit 10 calculates a heat transfer change index value based on the acquired blowing air temperature, surface temperature, and blowing temperature by: (1-(ΔT air / ΔT0))*G is calculated. In step S5, the control unit 10 judges whether the heat transfer change index value is equal to or less than the threshold value Th. If the heat transfer change index value is equal to or less than the threshold value Th, the process proceeds to step S6, and after the defrosting by the blower 6 is completed, the process returns to step S1. If the heat transfer change index value exceeds the threshold value Th, the process returns to step S3.

[0045] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0046] In the first embodiment, as described above, the cooling device 100 includes a control unit 10 that performs control to terminate defrosting based on the blowing air temperature, which is the temperature of the air sent from the blower 6 to the cooling evaporator 5, the surface temperature, which is the temperature of the surface of the cooling evaporator 5, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator 5, when defrosting is performed by the flow of air sent from the blower 6 to the heat transfer surface of the cooling evaporator 5. This makes it possible to defrost by sublimation and peeling due to the air flow, so there is no need to excessively increase the temperature of the cooling evaporator 5 during defrosting. Therefore, it is possible to suppress the temperature of the air from increasing during defrosting. In addition, by performing a calculation using the blowing air temperature, the surface temperature, and the blowing temperature, it is possible to obtain a heat transfer value (overall heat transfer coefficient) that indicates the ease of heat transfer from the cooling evaporator 5 to the air, which changes with defrosting, for example. As a result, even if the temperature change of the cooling evaporator 5 is small when defrosting is performed by sublimation and peeling due to the air flow, the defrosting can be terminated based on the above calculation results (for example, the heat transfer value (overall heat transfer coefficient)), so the progress of the defrosting can be detected accurately based on the above calculation results and defrosting can be performed efficiently without excess or deficiency. As a result, defrosting can be performed efficiently without excess or deficiency while suppressing the air temperature from rising during defrosting.

[0047] In the first embodiment, as described above, the cooling device 100 includes the blowing temperature sensor 7 for measuring the blowing temperature, the surface temperature sensor 8 for measuring the surface temperature, and the blowing temperature sensor 9 for measuring the blowing temperature. The control unit 10 is configured to perform control to terminate defrosting based on the blowing temperature measured by the blowing temperature sensor 7, the surface temperature measured by the surface temperature sensor 8, and the blowing temperature measured by the blowing temperature sensor 9. As a result, the blowing temperature can be directly measured by the blowing temperature sensor 7, the surface temperature can be directly measured by the surface temperature sensor 8, and the blowing temperature can be directly measured by the blowing temperature sensor 9, so that the calculation result using the blowing temperature, the surface temperature, and the blowing temperature can be accurately calculated. As a result, the progress of defrosting can be detected more accurately, so that defrosting can be performed more efficiently without excess or deficiency.

[0048] Furthermore, in the first embodiment, as described above, the control unit 10 is configured to acquire a heat transfer change index value that changes with a change in the heat transfer value indicating the ease of heat transfer from the cooling evaporator 5 to the air, which changes with defrosting of frost adhering to the cooling evaporator 5, based on the blowing air temperature, the surface temperature, and the blowing temperature, and to perform control to terminate defrosting based on the heat transfer change index value becoming equal to or less than the threshold value Th. This makes it possible to detect the end of defrosting based on a comparison between the heat transfer change index value and the threshold value Th, thereby making it possible to prevent the process for detecting the end of defrosting from becoming complicated.

[0049] In the first embodiment, as described above, in this case, preferably, the control unit 10 calculates the inlet / outlet air temperature difference ΔT airThe controller is configured to perform control to calculate a change in heat transfer value accompanying defrosting of frost adhering to the cooling evaporator 5 based on a value obtained by dividing the above by the inlet evaporator temperature difference ΔT0 calculated from the difference between the supply air temperature and the surface temperature. This allows the change (trend) in the heat transfer value (overall heat transfer coefficient) that cannot be directly measured by a sensor to be calculated based on the supply air temperature, surface temperature, and blown-out temperature that can be measured by the sensors, making it possible to easily perform defrosting processing based on the heat transfer value (overall heat transfer coefficient).

[0050] In the first embodiment, as described above, the control unit 10 calculates the inlet / outlet air temperature difference ΔT in an ideal state in which the surface temperature and the blown air temperature are equal after defrosting is completed. air is divided by the inlet evaporator temperature difference ΔT0, and the current inlet / outlet air temperature difference ΔT air and a control is performed to calculate a heat transfer change index value that changes with a change in the heat transfer value based on the difference between the value obtained by dividing the inlet evaporator temperature difference ΔT0 and the value obtained by dividing the inlet evaporator temperature difference ΔT0. This makes it possible to calculate the change (trend) in the heat transfer change index value that changes with the change (trend) in the heat transfer value (overall heat transfer coefficient) that cannot be directly measured by a sensor, based on the blowing air temperature, surface temperature, and blowing temperature that can be measured by a sensor, and therefore makes it possible to easily perform a defrosting process based on the heat transfer change index value.

[0051] In the first embodiment, as described above, the control unit 10 is configured to perform control to start defrosting at predetermined time intervals. This allows defrosting to be reliably performed before excessive frost forms on the cooling evaporator 5, thereby suppressing a decrease in the cooling performance of the cooling evaporator 5.

[0052] [Second embodiment] Next, a cooling device 200 of a second embodiment will be described with reference to Fig. 1 and Fig. 7. In detail, unlike the cooling device 100 of the first embodiment that includes a blower 6 controlled at a constant output, the cooling device 200 of the second embodiment controls the blower 6 with the output being changed. Note that in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0053] 1 and 7, a cooling device 200 of the second embodiment includes a compressor 1, a condenser 2, a blower 3, a plurality of expansion valves 4, a plurality of cooling evaporators 5, a blower 6, a blowing temperature sensor 7, a surface temperature sensor 8, a blowing temperature sensor 9, a current sensor 201, and a control unit 210. The current sensor 201 is a sensor that measures a current supplied from the control unit 210 to the blower 6.

[0054] (Control unit) The control unit 210 of the second embodiment is configured to perform control to change the threshold value Th based on the output of the blower 6. That is, the heat transfer value (overall heat transfer coefficient) changes due to a change in heat transfer from the cooling evaporator 5 to the air. The heat transfer from the cooling evaporator 5 to the air depends on the wind speed of the blower 6. That is, the heat transfer from the cooling evaporator 5 to the air becomes easier as the wind speed of the blower 6 increases. Also, the heat transfer from the cooling evaporator 5 to the air becomes harder as the wind speed of the blower 6 decreases. For this reason, the control unit 210 is configured to calculate the output of the blower 6 based on the current value measured by the current sensor 201, and to change the threshold value Th based on the output of the blower 6. Note that other configurations of the second embodiment are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0055] (Effects of the second embodiment) In the second embodiment, the following effects can be obtained.

[0056] In the second embodiment, as described above, the cooling device 200 includes a control unit 210 that performs control to terminate defrosting when defrosting is performed by the flow of air sent from the blower 6 to the heat transfer surface of the cooling evaporator 5, based on the blowing air temperature, which is the temperature of the air sent from the blower 6 to the cooling evaporator 5, the surface temperature, which is the temperature of the surface of the cooling evaporator 5, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator 5. This makes it possible to perform defrosting efficiently without excess or deficiency while suppressing an increase in the air temperature during defrosting.

[0057] In the second embodiment, as described above, the control unit 210 is configured to perform control to change the threshold value Th based on the output of the blower 6. As a result, the heat transfer value (overall heat transfer coefficient) changes depending on the wind speed which changes with the output of the blower 6, so that the threshold value Th can be changed to an appropriate value. Note that other effects of the second embodiment are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0058] [Third embodiment] Next, a cooling device 300 of a third embodiment will be described with reference to Fig. 1 and Fig. 8. In detail, unlike the cooling device 100 of the first embodiment which uses the surface temperature measured by the surface temperature sensor 8 as it is, the cooling device 300 of the third embodiment performs control to estimate the surface temperature measured by the surface temperature sensor 8 based on the degree of superheat of the cooling evaporator 5. In the third embodiment, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0059] 1 and 8, a cooling device 300 of the third embodiment includes a compressor 1, a condenser 2, a blower 3, a plurality of expansion valves 4, a plurality of cooling evaporators 5, a blower 6, a blowing temperature sensor 7, an inlet surface temperature sensor 301, an outlet surface temperature sensor 302, a blowing temperature sensor 9, a current sensor 303, and a control unit 310. The current sensor 303 is a sensor that measures a current supplied from the control unit 310 to the blower 6.

[0060] The inlet surface temperature sensor 301 measures the temperature of the refrigerant flowing into the cooling evaporator 5. The inlet surface temperature sensor 301 is a thermistor. The outlet surface temperature sensor 302 measures the temperature of the refrigerant flowing out from the cooling evaporator 5. The outlet surface temperature sensor 302 is a thermistor. Since the refrigerant changes from liquid phase to gas phase in the cooling evaporator 5, the degree of superheat of the cooling evaporator 5 is calculated from the difference between the temperature measured by the inlet surface temperature sensor 301 and the temperature measured by the outlet surface temperature sensor 302. Here, if there is no degree of superheat of the cooling evaporator 5 (if the degree of superheat is about 0), it is considered that the temperature distribution of the cooling evaporator 5 is approximately uniform. However, if there is a degree of superheat of the cooling evaporator 5 (if it is other than about 0), it is considered that there is a bias in the temperature distribution of the cooling evaporator 5.

[0061] (Control unit) Therefore, the control unit 310 of the third embodiment is configured to perform control to estimate the surface temperature of the cooling evaporator 5 based on the degree of superheat of the cooling evaporator 5. That is, the control unit 310 is configured to perform control to estimate the temperature of the refrigerant inside the cooling evaporator 5 based on the degree of superheat of the cooling evaporator 5. The control unit 310 is also configured to perform control to estimate the surface temperature of the cooling evaporator 5 based on the estimated temperature of the refrigerant inside the cooling evaporator 5. Note that other configurations of the third embodiment are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0062] (Effects of the third embodiment) In the third embodiment, the following effects can be obtained.

[0063] In the third embodiment, as described above, the cooling device 300 includes a control unit 310 that performs control to terminate defrosting when defrosting is performed by the flow of air sent from the blower 6 to the heat transfer surface of the cooling evaporator 5, based on the blowing air temperature, which is the temperature of the air sent from the blower 6 to the cooling evaporator 5, the surface temperature, which is the temperature of the surface of the cooling evaporator 5, and the blowing temperature, which is the temperature of the air blown out from the cooling evaporator 5. This makes it possible to perform defrosting efficiently without excess or deficiency while suppressing an increase in the air temperature during defrosting.

[0064] In the third embodiment, as described above, the control unit 310 is configured to perform control to estimate the surface temperature of the cooling evaporator 5 based on the degree of superheat of the cooling evaporator 5. This makes it possible to obtain a more accurate surface temperature, and therefore makes it possible to more accurately calculate the calculation result using the blowing air temperature, the surface temperature, and the blowing temperature. Note that other effects of the third embodiment are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0065] [Variations] The first to third embodiments disclosed herein should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the description of the first to third embodiments, and further includes all modifications (variations) within the meaning and scope equivalent to the claims.

[0066] For example, in the above first to third embodiments, the control unit 10 (210, 310) is configured to perform control to start defrosting at predetermined time intervals, but the present invention is not limited to this. In the present invention, the control unit may be configured to perform control to start defrosting based on the change in the heat transfer change index value becoming equal to or greater than a predetermined value.

[0067] In the above first to third embodiments, the control unit 10 (210, 310) is configured to perform control to end defrosting when the heat transfer change index value becomes equal to or less than the threshold value Th, but the present invention is not limited to this. In the present invention, the control unit may be configured to perform control to end defrosting when the amount of change in the heat transfer change index value becomes equal to or less than the threshold value.

[0068] In addition, in the above first to third embodiments, an example of a configuration in which three cooling evaporators 5 for cooling are provided is shown, but the present invention is not limited to this. In the present invention, one, two, or four or more cooling evaporators for cooling may be provided.

[0069] In addition, in the above first to third embodiments, an example of a configuration in which the expansion valve 4 is used as the expansion section is shown, but the present invention is not limited to this. In the present invention, a member other than the expansion valve, such as an ejector, may be used as the expansion section.

[0070] In the above second embodiment, an example has been shown in which control unit 210 is configured to calculate the output of blower 6 based on the current value measured by current sensor 201 and change threshold value Th based on the output of blower 6, but the present invention is not limited to this. In the present invention, the control unit may be configured to calculate the output of the blower based on the pressure value measured by the differential pressure gauge and change the threshold value based on the output of the blower. Also, the control unit may be configured to change the threshold value based on the output of the blower that is preset in the blower.

[0071] In the above first to third embodiments, for convenience of explanation, the control process of the control unit 10 (210, 310) is explained using a flow-driven flowchart in which the process is performed in order according to the process flow, but the present invention is not limited to this. In the present invention, the control process of the control unit may be performed by an event-driven process in which the process is executed on an event-by-event basis. In this case, the control process may be performed completely in an event-driven manner, or may be performed in a combination of event-driven and flow-driven. [Explanation of symbols]

[0072] 1 Compressor 2 Condenser 3. Blower 4 Expansion valve 5. Cooling evaporator 6. Blower 7. Blower temperature sensor 8 Surface temperature sensor 9. Air outlet temperature sensor 10, 210, 310 Control unit 100, 200, 300 chillers Th Threshold ΔT0 inlet evaporator temperature difference ΔT air Inlet / outlet air temperature difference

Claims

1. A compressor that compresses a refrigerant; a condenser that condenses the refrigerant discharged from the compressor; an expansion section that expands the refrigerant condensed by the condenser; a cooling evaporator that evaporates the refrigerant expanded by the expansion section; A blower that blows air onto the surface of the cooling evaporator; a control unit that performs control to terminate defrosting based on a blowing temperature, which is the temperature of the air sent from the blower to the cooling evaporator, a surface temperature, which is the temperature of the surface of the cooling evaporator, and a blowing temperature, which is the temperature of the air blown out from the cooling evaporator, when defrosting is performed by a flow of air sent from the blower to the heat transfer surface of the cooling evaporator, The control unit is configured to obtain a heat transfer change index value that changes in accordance with a change in a heat transfer value that indicates the ease of heat transfer from the cooling evaporator to the air, which changes in accordance with defrosting of frost adhering to the cooling evaporator, based on the supply air temperature, the surface temperature, and the blowing temperature, and to control to terminate defrosting based on the heat transfer change index value or an amount of change in the heat transfer change index value becoming equal to or less than a threshold value.

2. A blowing air temperature sensor that measures the blowing air temperature; a surface temperature sensor for measuring the surface temperature; A blowout temperature sensor that measures the blowout temperature is further provided, The cooling device according to claim 1, wherein the control unit is configured to control the termination of defrosting based on the supply air temperature measured by the supply air temperature sensor, the surface temperature measured by the surface temperature sensor, and the blowing air temperature measured by the blowing air temperature sensor.

3. The cooling device according to claim 1, wherein the control unit is configured to perform control to calculate a change in the heat transfer value associated with defrosting of frost adhering to the cooling evaporator based on a value obtained by dividing an inlet / outlet air temperature difference calculated by the difference between the supply air temperature and the discharge temperature by an inlet evaporator temperature difference calculated by the difference between the supply air temperature and the surface temperature.

4. 4. The cooling device according to claim 3, wherein the control unit is configured to perform control to calculate the heat transfer change index value, which changes with a change in the heat transfer value, based on a difference between a value obtained by dividing the inlet / outlet air temperature difference by the inlet evaporator temperature difference in an ideal state in which defrosting is completed and the surface temperature and the blowing temperature are equal, and a value obtained by dividing the acquired current inlet / outlet air temperature difference by the inlet evaporator temperature difference.

5. The cooling device according to claim 1 , 3 or 4 , wherein the control unit is configured to perform control for changing the threshold value based on an output of the blower.

6. The cooling device according to claim 1 , 3 , 4 , or 5 , wherein the control unit is configured to perform control to start defrosting at predetermined time intervals or when a change in the heat transfer change index value reaches or exceeds a predetermined value.

7. The cooling device according to any one of claims 1 to 6, wherein the control unit is configured to perform control to estimate the surface temperature of the cooling evaporator based on the degree of superheat of the cooling evaporator.

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