JP6283945B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus that cools a plurality of showcases, refrigerators, and the like using a refrigerator in a supermarket or the like.

2. Description of the Related Art Conventionally, a refrigeration apparatus including a refrigerator and a refrigerator such as a freezer / refrigerated showcase or a prefabricated refrigerator used in a supermarket or the like is known.
In this type of system, when configuring a large-scale refrigeration system, systematize the coolers such as the above-mentioned showcases according to the required capacity of the refrigerator and the required capacity, and install multiple units for the required system. ing.
The defrosting of the evaporator in the conventional refrigeration system is performed by first stopping the refrigeration system of the defrosting system, dissolving the frost adhering to each evaporator of the system with a heater, etc., and then operating the refrigeration system of the system again. The method (hereinafter referred to as collective defrosting) is generally used. In this operation method, since the pull-down operation of the refrigeration apparatus is performed collectively after the completion of defrosting, the load on the refrigerator is temporarily increased.
Then, it is necessary to control the refrigerator so that the capacity control function from the minimum load to the maximum load of all the systems of the cooling device is achieved, and a refrigerator having a wider capacity control range is required.

  On the other hand, a defrosting operation (hereinafter, referred to as sequential defrosting) in which a plurality of showcases are grouped and the evaporator is defrosted step by step for each group has been proposed (see, for example, Patent Document 1). .)

JP-A-11-83216

However, a refrigeration cycle using a supercritical fluid as a refrigerant, such as carbon dioxide, becomes a supercritical cycle when the outside air temperature exceeds the critical temperature, and the total volume of the refrigerant increases as compared with a case where the temperature is lower than the critical temperature.
For this reason, when sequential defrosting (sequential defrosting) is performed for each group using a supercritical fluid, the high-pressure side pressure increases due to excess refrigerant during the defrosting operation. Conventionally, a refrigerant recovery tank has been installed to avoid abnormally high pressure.

On the other hand, when the outside air temperature decreases, the refrigeration cycle becomes a saturation cycle. Since the outside air temperature is low, the cooling load of the cooling device is also small.
When sequential defrosting is performed in this state, a case where the value falls below the minimum load corresponding to the refrigerator occurs, and the compressor frequently repeats start and stop.
At the time of starting the compressor, the equilibrium pressure start is performed to improve the startability, but the operation that does not contribute to cooling continues until the evaporation temperature on the low pressure side that has increased due to the pressure equalization is equivalent to the internal temperature. There is a problem that causes an increase in electric power.
An object of the present invention is to provide a refrigeration apparatus that solves the problems of the conventional techniques described above and can realize power saving, peak power reduction, and stabilization of cooling capacity.

The present invention relates to a refrigeration apparatus using a refrigeration cycle that uses a supercritical fluid as a refrigerant, a refrigerator, a plurality of cooling apparatuses that cool items using the refrigerant supplied from the refrigerator, and an outside air temperature detection A defrosting mode in which the plurality of cooling devices are collectively defrosted based on the detection result of the outside air temperature detecting unit and the outside air temperature detecting unit, or the plurality of cooling devices are grouped into groups. A defrost control unit that switches to any one of the sequential defrost modes that perform defrosting step by step, wherein the defrost control unit detects the temperature of the outside air temperature detection unit of the supercritical fluid. When the temperature is higher than a first threshold temperature determined in relation to the critical temperature, the sequential defrosting mode is executed.
In this invention, when the outside air temperature exceeds the first threshold temperature Ta1, the collective defrosting mode is switched to the sequential defrosting mode. Therefore, the pull-down operation after the completion of the defrosting is performed for each group. An increase in load can be avoided, saving power and reducing peak power especially in summer.

In the present invention, the defrost control unit may execute the collective defrost mode when the temperature falls below a second threshold temperature lower than the first threshold temperature.
The second threshold temperature may be determined in relation to the outside air temperature when the load falls below the minimum capacity control rate of the refrigerator.
In the present invention, when the outside air temperature falls below the second threshold temperature Ta2, the sequential defrosting mode is switched to the batch defrosting mode, so that the situation where the refrigerator 10 falls below the minimum capacity control rate is reduced, and repetition of start / stop is small. Become. Therefore, the number of times of starting the equilibrium pressure using the bypass pipe 131 is reduced, and thereby an increase in power consumption can be suppressed.

The defrosting control unit may perform the defrosting operation in the collective defrosting mode in an intermediate temperature zone between the second threshold temperature Ta2 and the first threshold temperature Ta1 while the outside air temperature is rising.
The defrosting control unit may perform a defrosting operation in a sequential defrosting mode in an intermediate temperature range between the second threshold temperature Ta2 and the first threshold temperature Ta1 while the outside air temperature is decreasing.
The intermediate temperature zone between the second threshold temperature Ta2 and the first threshold temperature Ta1 may basically be the sequential defrost mode or the collective defrost mode.
In the present invention, for example, in the middle temperature range in which the outside air temperature is rising such as in summer, the defrosting operation is performed in the batch defrost mode, and in the middle in which the outside air temperature is falling in the winter season. In the temperature zone, the defrosting operation is performed in the summer in the collective defrost mode, so the sequential defrost mode is maintained and the sequential defrost mode is executed as it is.
In this invention, switching between the sequential defrost mode and the collective defrost mode can be executed stably and smoothly.

  In the present invention, when the outside air temperature exceeds the first threshold temperature, the collective defrosting mode is switched to the sequential defrosting mode. Therefore, the pull-down operation after the completion of the defrosting is performed for each group. Increase in power consumption can be avoided, and it is possible to save power and reduce peak power especially in summer.

It is a refrigerating cycle figure showing an embodiment of a refrigerating device concerning the present invention. It is a flowchart of the defrost control in this embodiment. AD is a figure which shows the operation | movement of the defrost control in this embodiment. It is a schematic diagram of the gas cooler of a refrigerator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram of a refrigeration cycle showing an embodiment of a refrigeration apparatus according to the present invention.
The refrigeration apparatus includes a refrigerator 10 that cools the refrigerant, and a showcase (cooling apparatus) 40 that is cooled by the refrigerant sent from the refrigerator 10.
In this refrigeration cycle, carbon dioxide whose refrigerant pressure (high pressure) on the high pressure side is equal to or higher than its critical pressure (supercritical) is used as the refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and takes into consideration flammability and toxicity. As the oil as the lubricating oil, existing oils such as mineral oil (mineral oil), alkylbenzene oil, ether oil, ester oil, and PAG (polyalkyl glycol) are used.

The refrigerator 10 includes a compressor 11 that is compressed in two stages.
The compressor 11 is an internal intermediate pressure type multi-stage compression rotary compressor, and a low-stage rotary compression driven by an electric element as a driving element and a rotating shaft of the electric element in a cylindrical sealed container made of a steel plate. The rotary compression mechanism part which consists of an element and a high stage side rotary compression element is provided.
A refrigeration side heat exchanger 12 is connected to the compressor 11 via a refrigerant pipe 13, and the refrigeration side heat exchanger 12 includes a gas cooler 14, an intercooler 15, an oil cooler 16, and a blower fan 17. It is configured.

The compressor 11 is provided with a first suction port 20 and a first discharge port 21 in the first-stage compression mechanism 11a, and a second suction port 22 and a second discharge port 23 in the second-stage compression mechanism 11b. Is provided. The first suction port 20 of the compressor 11 sucks the refrigerant sent from the evaporator 41 of the showcase 40, compresses it to an intermediate pressure by the first-stage compression mechanism 11 a, and discharges it from the first discharge port 21. It is configured.
The first discharge port 21 of the compressor 11 is connected to the inlet side of the intercooler 15 via the refrigerant pipe 13, and the second suction port of the compressor 11 is connected to the outlet side of the intercooler 15 via the refrigerant pipe 13. 22 is connected. The second discharge port 23 of the compressor 11 is connected to the oil separator 24 via the refrigerant pipe 13, and the oil separator 24 is connected to the gas cooler 14 via the refrigerant pipe 13. The oil separator 24 separates and stores the oil in the refrigerant. The oil separator 24 is connected to the inlet side of the oil cooler 16 via the oil feed pipe 25, and the outlet side of the oil cooler 16 is The compressor 11 is connected to the compressor 11 through an oil return pipe 26.

The refrigerant discharged from the first discharge port 21 of the compressor 11 flows into the intercooler 15 through the refrigerant pipe 13 and is cooled by exchanging heat with the outside air by operating the blower fan 17 in the intercooler 15. Returned to the second inlet 22 of the machine 11. Then, the compressor 11 is compressed to a required pressure by the second-stage compression mechanism 11 b and is discharged from the second discharge port 23, and merges and is sent to the gas cooler 14 through the oil separator 24.
The oil separator 24 separates and stores the oil in the refrigerant. The oil in the oil separator 24 is sent to the oil cooler 16 through the oil feed pipe 25, and the air cooler 16 is cooled by exchanging heat with the outside air by operating the blower fan 17. To the intermediate stage of the compressor 11.
The gas cooler 14 cools the refrigerant sent from the compressor 11 by exchanging heat with the outside air by operating the blower fan 17.

  A split heat exchanger 30 is connected to the gas cooler 14 via the refrigerant pipe 13. The refrigerant pipe 13 on the inlet side of the split heat exchanger 30 is provided with a branch pipe (first branch pipe) 31 branched from the refrigerant pipe 13, and the branch pipe 31 passes through a branch pipe expansion valve 32. Are connected to the split heat exchanger 30. In the split heat exchanger 30, the refrigerant pipe 13 and the branch pipe 31 are arranged so that the refrigerant flows in opposite directions, and the refrigerant flowing through the refrigerant pipe 13 and the refrigerant flowing through the branch pipe 31 are combined. It is configured so that heat can be exchanged efficiently.

  The outlet side of the branch pipe 31 of the split heat exchanger 30 is connected to the outlet side of the intercooler 15. The branch pipe expansion valve 32 decompresses the high-pressure refrigerant on the inlet side of the split heat exchanger 30 and expands it to an intermediate pressure level. The split heat exchanger 30 cools the high-pressure refrigerant by exchanging heat between the high-pressure refrigerant flowing through the refrigerant pipe 13 and the decompressed refrigerant flowing through the branch pipe 31. The decompressed refrigerant after the heat exchange joins with the refrigerant on the outlet side of the intercooler 15 and is sent to the compressor 11 from the second suction port 22 respectively, and the temperature and intermediate pressure of the refrigerant discharged from the compressor 11 are optimized. Is achieved.

A branch pipe (second branch pipe) 35 is connected to the outlet side of the refrigerant pipe 13 of the split heat exchanger 30, and the branch pipe 35 is connected to the inlet side of the refrigerant recovery tank 34.
Two pipes 134 and 135 are connected to the outlet side of the refrigerant recovery tank 34, and the two pipes 134 and 135 are connected to the outlet side of the refrigerant pipe 13 of the split heat exchanger 30. Reference numeral 36 denotes an electric expansion valve, reference numerals 37 and 38 denote electromagnetic valves, and reference numeral 39 denotes a capillary tube.

(Refrigerant recovery operation)
In the case of carbon dioxide refrigerant, supercritical cycle operation is performed in which the refrigerant in the refrigerant circuit does not liquefy when the outside air temperature becomes high. In this case, there is a risk that the high pressure side in the refrigerant circuit may become abnormally high pressure due to the surplus refrigerant.
When it is determined that the high-pressure side pressure has abnormally increased, a refrigerant recovery operation is performed. In this refrigerant recovery operation, the electric expansion valve 36 and the electromagnetic valve 37 are opened with the electromagnetic valve 38 closed. By opening the electromagnetic valve 37, the pressure in the refrigerant recovery tank 34 is released to the outside of the tank via the pipe 134. The refrigerant in the refrigerant recovery tank 34 decreases and the refrigerant flowing into the tank liquefies and accumulates in the refrigerant recovery tank 34.
That is, when the pressure in the refrigerant recovery tank 34 drops below the supercritical pressure, the refrigerant changes from the gas region to the saturation region, and the liquid level is secured. In this state, the refrigerant is recovered to the refrigerant recovery tank 34 via the branch pipe 35. Thereby, the overload driving | operation of the compressors 11 and 11 by a high voltage | pressure abnormality can be prevented.

(Refrigerant holding operation)
In this refrigerant holding operation, the electromagnetic valve 38 is kept closed, the electromagnetic valve 37 is closed, and the opening of the electric expansion valve 36 is maintained in the previous refrigerant recovery operation.
When the electromagnetic valve 37 is closed, the liquid level in the refrigerant recovery tank 34 is maintained by the pressure by the high pressure side region of the refrigerant circuit via the opened electric expansion valve 36. Therefore, liquid sealing in the refrigerant recovery tank 34 can be avoided, and safety can be ensured. Thereby, the circulation refrigerant | coolant amount in a refrigerant circuit can be maintained appropriately.
(Refrigerant release operation)
When it is determined that the refrigerant in the refrigerant circuit is insufficient, the refrigerant discharge operation is executed. In this refrigerant discharge operation, the electric expansion valve 36 and the electromagnetic valve 37 are closed, and the electromagnetic valve 38 is opened.
As a result, the liquid refrigerant accumulated in the refrigerant recovery tank 34 is reduced to an intermediate pressure via the pipe 135 connected to the lower part of the refrigerant recovery tank 34 and the capillary tube 39, and is released into the refrigerant circuit. .
In the present embodiment, (refrigerant recovery operation) − (refrigerant holding operation) − (refrigerant discharging operation) − (refrigerant holding operation) is repeated based on the high-pressure side pressure value. Therefore, refrigerant recovery / release can be controlled based on the high pressure side pressure. Therefore, high pressure protection and overload operation can be prevented accurately. As a result, the amount of refrigerant flowing in the refrigerant circuit becomes an optimum state, and it becomes possible to optimize energy efficiency.

  One end of a bypass pipe 131 is connected to the refrigerant pipe 13 on the outlet side of the intercooler 15, and the other end of the pipe 135 is connected to the refrigerant pipe 13 connected to the first suction port 20 of the compressor 11. An electromagnetic valve 132 is interposed in the bypass pipe 131.

  An evaporator 41 of a plurality of showcases 40 is connected to the refrigerant pipe 13 on the outlet side of the split heat exchanger 30 via an expansion valve 42, and the refrigerant and the warehouse sent from the refrigerant pipe 13 by the evaporator 41 are stored. Heat is exchanged with the air inside, and the interior of each showcase 40 is cooled. The outlet side of the evaporator 41 is connected to the first suction port 20 of the compressor 11 via the refrigerant pipe 13.

In the present embodiment, the defrosting operation of the showcase 40 is performed.
The defrosting operation of the showcase 40 is performed by the control device (defrost control unit) 136.
In the present embodiment, the control device 136 divides all the showcases 40 into a plurality of fine groups including a plurality of showcases 40 and a batch defrosting mode in which the defrosting operation of all the showcases 40 is performed at once. The sequential defrosting mode in which the defrosting operation is performed step by step for each group is switched according to the outside air temperature.
In the present embodiment, an example in which ten showcases 40 are divided into three groups (Gr1 to Gr3) is shown.
The three groups are grouped so that the sum of the refrigeration loads of the devices belonging to each group is made as uniform as possible, and the loads are almost equal.

FIG. 2 shows a processing flow.
The control device 136 acquires the outside air temperature (S1). This outside air temperature is compared with the first threshold temperature Ta1, and it is determined whether or not the outside air temperature has become lower than the first threshold temperature Ta1 to be equal to or higher than the first threshold temperature Ta1 (S2). When it becomes, it switches to sequential defrost mode (S3).
If the outside air temperature does not become lower than the first threshold temperature Ta1 from less than the first threshold temperature Ta1, the outside air temperature is compared with the second threshold temperature Ta2. It is determined whether or not the outside air temperature is lower than the second threshold temperature Ta2 from a state higher than the second threshold temperature Ta2 (S4), and when it is equal to or lower than the second threshold temperature Ta2, the batch defrost mode is switched. (S5). Further, when the outside air temperature is not lower than the second threshold temperature Ta2 from a state higher than the second threshold temperature Ta2, defrosting is performed in the same defrost mode as before the determination (S6).

FIG. 3 is an operation explanatory diagram according to this embodiment.
In the present embodiment, as shown in FIG. 3D, a first threshold temperature Ta1 and a second threshold temperature Ta2 having a temperature lower than the first threshold temperature Ta1 are set as the outside air temperature during mode switching.
For example, when it goes to summer, the outside air temperature is rising (curve that rises to the right), and the control device 136 performs the defrosting operation in the collective defrosting mode. In the collective defrosting mode, the three groups are simultaneously defrosted as shown in FIGS.
In FIG. 3D, when the outside air temperature exceeds the first threshold temperature Ta1, the control device 136 switches from the collective defrost mode to the sequential defrost mode. In the sequential defrosting mode, as shown in FIGS. 3A to 3C, the control device 136 performs defrosting operation on the three groups Gr1, Gr2, and Gr3 step by step.
For example, the control device 136 maintains the sequential defrosting mode while the outside air temperature is decreasing toward the winter season (curved downward curve). When the outside air temperature continues to decrease and falls below the second threshold temperature Ta2, the sequential defrost mode is switched to the batch defrost mode.
Then, the control device 136 maintains the collective defrosting mode until the outside air temperature rises again exceeding the first threshold temperature Ta1.

FIG. 4 is a schematic diagram of the gas cooler 14 of the refrigerator.
The first threshold temperature Ta1 is set to, for example, 30 ° C. for the carbon dioxide refrigerant so that the refrigerant temperature Tout at the outlet of the gas cooler 14 is lower than the critical temperature. Here, the first threshold temperature Ta1 is determined from the heat exchange performance and the critical temperature so that the refrigerant temperature Tout at the outlet of the gas cooler 14 is less than the critical temperature.
A refrigeration cycle using a supercritical fluid as a refrigerant, such as carbon dioxide, becomes a supercritical cycle when the outside air temperature exceeds the critical temperature, and the total volume of the refrigerant increases as compared with a case where the temperature is lower than the critical temperature. For this reason, when the outside air temperature exceeds the critical temperature, if the sequential defrosting (sequential defrosting) of the groups Gr1 to Gr3 is performed, the high-pressure side pressure increases due to the excess refrigerant. In order to avoid abnormally high pressure, the refrigerant recovery tank 34 is installed, but there are many groups that perform defrosting sequentially so that the excess refrigerant at the time of defrosting can be absorbed by the recovery tank. It is necessary to reduce the excess refrigerant.

In the present embodiment, when the outside air temperature exceeds the first threshold temperature Ta1 in FIG. 3D, the batch defrost mode is switched to the sequential defrost mode, and defrosting is performed for each of the groups Gr1 to Gr3 in the sequential defrost mode.
In this configuration, the showcase 40 is divided into three groups Gr1 to Gr3, and the sum of the refrigeration loads of the devices belonging to the groups Gr1 to Gr3 is made as uniform as possible. The amount can be dispersed.
Therefore, in the sequential defrost mode, an increase in the high-pressure side pressure can be suppressed without increasing the volume of the refrigerant recovery tank 34.

  In the collective defrosting mode described above, the pull-down operation in the refrigeration apparatus is performed collectively, for example, in three groups after defrosting is completed, so that the load on the refrigerator 10 temporarily increases considerably, increasing the peak power in summer. There is a fear.

In the present embodiment, in FIG. 3D, when the outside air temperature exceeds the first threshold temperature Ta1, the control device 136 switches from the collective defrost mode to the sequential defrost mode. In sequential defrost mode, defrosting is executed step by step for each group, so even if pull-down operation is executed after the completion of defrosting, it is pull-down operation for each group, and a sudden increase in cooling load is avoided. Power saving, peak power reduction, and cooling capacity can be stabilized.
Since the three groups are grouped so that the load is almost equal, the increase in cooling load during pull-down operation for each group is equalized, a sudden increase in cooling load is avoided, power saving, and peak Reduces power consumption and stabilizes cooling capacity.
In this embodiment, by switching from the collective defrosting mode to the sequential defrosting mode, a sudden increase in cooling load can be avoided, and the maximum load equivalent of the cooling device can be reduced. That is, it is not necessary to determine the maximum load equivalent in anticipation of the pull-down operation in the collective defrosting mode. Therefore, it is not necessary to control the refrigerator 10 so as to perform the capacity control function from the equivalent of the minimum load to the equivalent of the maximum load expecting the pull-down operation, and the capacity control range of the refrigerator 10 can be set small.
Since the three groups are grouped so that the load is almost equal, the equivalent of the maximum load that anticipates the execution of pull-down operation for each group is equalized, from the equivalent of the minimum load to the equivalent of the equalized maximum load. It is only necessary to fulfill the capacity control function, and the capacity control range of the refrigerator 10 can be set smaller.

In the present embodiment, the second threshold temperature Ta2 is set to a temperature at which the refrigerator 10 may repeatedly start and stop when the outside air temperature falls below a predetermined temperature.
In a refrigeration cycle that uses a supercritical fluid as a refrigerant, such as carbon dioxide, when the outside air temperature decreases as in winter, the refrigerant liquefies and the refrigeration cycle becomes a saturation cycle. In this case, the cooling load of the cooling device is also small. In this state, when sequential defrosting is performed and the pull-down operation after completion of defrosting is controlled so as not to overlap, there may be a case where the value falls below the minimum load equivalent of the refrigerator 10, and the compressor 11 may frequently start and stop repeatedly. There is.

The second threshold temperature Ta2 is a temperature lower than the first threshold temperature Ta1 (for example, 20 ° C.), and the second threshold temperature Ta2 is related to the outside air temperature when the load falls below the minimum capacity control rate of the refrigerator 10. It has been decided. If determined in this way, when the outside air temperature falls below the second threshold temperature Ta2, the refrigerator 10 falls below the minimum capacity control rate, and the refrigerator 10 stops.
At the time of starting the stopped compressor 11, in order to improve the startability, the above-described bypass pipe 131 is used to perform an equilibrium pressure start that equalizes the intermediate pressure side region and the low pressure side region of the refrigerant circuit. Since the operation that does not contribute to cooling continues until the evaporation temperature on the low-pressure side that has risen due to the above becomes equivalent to the internal temperature, if the compressor 11 repeatedly starts and stops, the power consumption increases accordingly.
In the present embodiment, when the outside air temperature falls below the second threshold temperature Ta2, the control device 136 switches from the sequential defrost mode to the batch defrost mode. When the mode is switched to the collective defrosting mode, the situation of falling below the minimum capacity control rate (corresponding to the minimum load) of the refrigerator 10 is reduced, and the increase and decrease in power consumption can be suppressed without frequently repeating start and stop.

As described above, according to the embodiment to which the present invention is applied, when the outside air temperature exceeds the first threshold temperature Ta1, the batch defrosting mode is switched to the sequential defrosting mode. Therefore, it is performed for each group. Therefore, a rapid increase in cooling load can be avoided, and power saving and peak power reduction can be achieved.
Further, when the outside air temperature falls below the second threshold temperature Ta2, since the sequential defrost mode is switched to the batch defrost mode, the situation where the refrigerator 10 falls below the minimum capacity control rate is reduced, and the repetition of start and stop is reduced. The number of times of starting the equilibrium pressure using the bypass pipe 131 is reduced, thereby suppressing an increase in power consumption.

The intermediate temperature zone between the second threshold temperature Ta2 and the first threshold temperature Ta1 may be the sequential defrost mode or the collective defrost mode.
In the present embodiment, for example, in the middle temperature range in which the outside air temperature is rising (curved upward in FIG. 3), such as in summer, the defrosting operation is performed in the collective defrosting mode and heads for winter. In such an intermediate temperature zone during which the outside air temperature is decreasing (curve of lower right in FIG. 3), the defrosting operation is being executed in the summer in the batch defrost mode, so the sequential defrost mode is maintained, The sequential defrost mode is executed as it is.
By doing so, switching between the sequential defrost mode and the collective defrost mode can be performed stably and smoothly.
With the above configuration, it is possible to provide a refrigeration apparatus that can realize power saving, peak power reduction, and stabilization of cooling capacity.
In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention.

DESCRIPTION OF SYMBOLS 10 Refrigerator 11 Compressor 12 Refrigeration side heat exchanger 13 Refrigerant piping 14 Gas cooler 15 Intercooler 16 Oil cooler 17 Blower fan 20 1st inlet 21 First outlet 22 Second inlet 23 Oil outlet 30 Split Heat exchanger 31 Branch pipe 32 Branch pipe expansion valve 33 Second branch pipe 34 Refrigerant recovery tank 35 Refrigerant return pipe 36 Controller 40 Showcase 41 Evaporator 42 Expansion valve Ta1 First threshold temperature Ta2 Second threshold temperature

Claims (6)

In a refrigeration system using a refrigeration cycle that uses a supercritical fluid as a refrigerant,
A refrigerator,
A plurality of cooling devices for cooling the item using the refrigerant supplied from the refrigerator;
An outside temperature detector for detecting the outside temperature;
Based on the detection result of the outside air temperature detection unit, a batch defrosting mode in which the plurality of cooling devices are collectively defrosted, or a sequence in which the plurality of cooling devices are grouped and defrosted step by step. A defrost control unit that switches to any one of the defrost modes,
With
The defrosting control unit executes the sequential defrosting mode when the detected temperature of the outside air temperature detecting unit is higher than a first threshold temperature determined in relation to the critical temperature of the supercritical fluid. apparatus.   2. The refrigeration apparatus according to claim 1, wherein the defrost control unit executes the collective defrost mode when the temperature falls below a second threshold temperature lower than the first threshold temperature.   3. The refrigeration apparatus according to claim 2, wherein the second threshold temperature is determined in relation to an outside air temperature when a load is lower than a minimum capacity control rate of the refrigerator.   The defrosting control unit performs a defrosting operation in a collective defrosting mode in an intermediate temperature range between the second threshold temperature Ta2 and the first threshold temperature Ta1 while the outside air temperature is rising. The refrigeration apparatus according to any one of claims 1 to 3.   The defrosting control unit performs a defrosting operation in a sequential defrosting mode in an intermediate temperature range between the second threshold temperature Ta2 and the first threshold temperature Ta1 while the outside air temperature is decreasing. The refrigeration apparatus according to any one of claims 1 to 4.   The refrigeration apparatus according to any one of claims 1 to 5, wherein the loads of the plurality of cooling apparatuses are equally divided.

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