JP5436631B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus configured with a two-way refrigeration cycle.

  Adopting a dual refrigeration cycle that uses outdoor air as a heat source and divides the vapor compression cycle into a low-end side and a high-end side and connects them with a cascade heat exchanger when the object to be cooled is cooled to minus tens of degrees Celsius in a freezer. May be. The aim is to improve the operation efficiency by reducing the compression ratio in the high and low vapor compression cycles.

  However, under the low outdoor air conditions that occur in winter, if the dual operation that operates both the low-source compressor of the low-source refrigeration cycle and the high-source compressor of the high-source refrigeration cycle is performed, the compression ratio becomes too small. Operation efficiency may deteriorate. For this reason, a method has been proposed in which unit operation (operation that operates only the low-source compressor and operation that stops the high-source compressor) and dual operation are switched according to the outside air temperature.

  As a refrigeration system that performs this type of operation, for example, a part of an outdoor heat exchanger that is a radiator of a high-source refrigeration cycle is divided and used as a radiator of a low-source refrigeration cycle. There is known a refrigeration apparatus that can be switched between (see, for example, Patent Document 1). In this refrigeration apparatus, during unit operation, the low-source refrigeration cycle uses the divided part of the outdoor heat exchanger to radiate outside air. During dual operation, the low-source refrigeration cycle shuts off the refrigerant flow to the split part of the outdoor heat exchanger and flows the refrigerant to the cascade heat exchanger side, and performs heat dissipation on the cascade heat exchanger side. In the high-source refrigeration cycle, heat is radiated from the outside air by a portion other than the divided portion of the outdoor heat exchanger.

  In addition, by disposing the radiator of the high-source refrigeration cycle at a position higher than the cascade heat exchanger, even if the high-source compressor is stopped, the refrigerant naturally circulates in the high-source refrigeration cycle by gravity, There is known a refrigeration apparatus that allows a high-source refrigeration cycle to function during unit operation (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2000-274848 (page 6, FIG. 1) JP-A-8-189713 (page 5, FIG. 2)

  However, in the configuration as shown in Patent Document 1, the divided part of the outdoor heat exchanger that is divided and used as a radiator of the low-source refrigeration cycle is used exclusively for unit operation, In the dual operation, the refrigerant is not flowed to the divided portion. Therefore, in the dual operation, only the portion other than the divided portion can be used in the outdoor radiator, and the outdoor radiator cannot be used to the maximum extent. In addition, since the outdoor heat exchanger can only be partially used even in unit operation, there is a problem that sufficient heat dissipation performance to the outside air cannot be obtained.

  Further, as shown in Patent Document 2, in the method of performing the refrigerant natural circulation of the high-source refrigeration cycle and the vapor compression operation of only the low-source refrigeration cycle during unit operation, The temperature of the original refrigerant (refrigerant circulating in the high-source refrigeration cycle) is about 5 to 10 ° C. higher than the outside air temperature. For this reason, even if it exchanges heat with a high original refrigerant, a low original refrigerant (refrigerant that circulates in a low original refrigeration cycle) cannot be cooled to a temperature close to the outside air temperature, and sufficient heat radiation capacity to the outside air cannot be obtained. There's a problem.

  The present invention has been made to solve the above-described problems, and is a refrigeration capable of improving the operation efficiency by securing a sufficient heat radiation capacity to the outside air in both the two-way operation and the one-way operation. The object is to obtain a device.

  A refrigeration apparatus according to the present invention includes a high-source refrigeration cycle configured by connecting a high-source compressor, a first outdoor radiator, a high-source expansion valve, and an evaporation section of a cascade heat exchanger, An original compressor, a second outdoor radiator, a condensing part of a cascade heat exchanger, a low original expansion valve, and a cooler connected to each other, a low original refrigeration cycle, a low original compressor and a high The second outdoor operation determines the distribution order of the refrigerant that has flowed out of the low-source compressor in the two-way operation that operates both the original compressor and the single-unit operation that operates the low-source compressor and stops the high-source compressor. A flow path switching valve that switches from the radiator to the condensing part of the cascade heat exchanger and the reverse order thereof, and cascade heat exchange with the first outdoor radiator by bypassing the high-source compressor in the high-source refrigeration cycle during unit operation And a natural circulation cycle in which the refrigerant is naturally circulated in the evaporation section of the vessel.

  According to the present invention, it is possible to dissipate the outside air from each of the first outdoor radiator of the high-source refrigeration cycle and the second outdoor radiator of the low-source refrigeration cycle in both the binary operation and the unit operation. Thus, it is possible to obtain a refrigeration apparatus that can secure sufficient heat dissipation capability to the outside air and improve the operation efficiency.

It is a refrigerant circuit figure which shows an example of the freezing apparatus in one embodiment of this invention. It is a figure which shows the structural example of the high original heat radiator of the refrigeration apparatus of FIG. 1, and a low original heat radiator. It is a figure which shows the flow of the refrigerant | coolant at the time of the binary operation of the freezing apparatus of FIG. FIG. 4 is a pressure-specific enthalpy diagram showing the refrigeration cycle operation of the refrigeration apparatus of FIG. 3. It is a figure which shows an example of the operation efficiency characteristic with respect to the compression ratio of the refrigerant compressor generally used. It is a figure which shows the flow of the refrigerant | coolant at the time of unit operation of the freezing apparatus of FIG. FIG. 7 is a pressure-specific enthalpy diagram showing the refrigeration cycle operation of the refrigeration apparatus of FIG. 6.

FIG. 1 is a refrigerant circuit diagram illustrating an example of a refrigeration apparatus according to an embodiment of the present invention. First, the configuration of the refrigeration apparatus will be described with reference to FIG.
The refrigeration apparatus includes an outdoor unit 1 and a plurality of cooling units 2. A plurality of cooling units 2 are installed in a refrigeration warehouse where cooling objects are placed, and are connected to the outdoor unit 1 by connecting pipes 3 and 4.

  The outdoor unit 1 includes a high-source compressor 5, a high-source radiator 6 that is a first outdoor radiator, a high-source expansion valve 8, and a cascade heat exchanger 9. A high-source refrigeration cycle is configured by connecting the high-source compressor 5, the high-source heat radiator 6, the high-source expansion valve 8, and the evaporation section 9a of the cascade heat exchanger 9 with pipes. In the high-source refrigeration cycle, a bypass circuit 17 that bypasses the high-source compressor 5 and a bypass valve 17a that opens and closes the bypass circuit 17 are provided, and a natural circulation cycle described later is configured. The high-source refrigeration cycle further includes a bypass circuit 18 that bypasses the high-source expansion valve 8 and a bypass valve 18 a that opens and closes the bypass circuit 18.

  The outdoor unit 1 is configured by connecting a low-source compressor 10, a flow switching valve 11, a low-source radiator 12 that is a second outdoor radiator, and a condensing part 9 b of the cascade heat exchanger 9 with pipes. The heat dissipation part of the low-source refrigeration cycle is provided. Further, the outdoor unit 1 includes an outdoor fan 7 for promoting and adjusting heat exchange by blowing outdoor air to each of the high-source radiator 6 and the low-source radiator 12, and an outside air temperature for detecting the outside air temperature. A sensor 19 is provided.

  For example, as shown in FIG. 2, the high-source radiator 6 and the low-source radiator 12 are configured integrally with a plate fin tube type heat exchanger that is formed by penetrating a heat transfer tube 22 through a flat heat transfer fin 21. Yes. The heat transfer fins 21 may or may not be divided into a portion that becomes the high-source radiator 6 and a portion that becomes the low-source radiator 12. In the case where the heat transfer fins 21 are divided, the thermal insulation effect is increased, so that both can dissipate heat more efficiently.

  In addition, when the high-source radiator 6 and the low-source radiator 12 are integrated, the high-source radiator 6 is disposed at the top to increase the refrigerant flow rate during natural circulation by increasing the head difference as much as possible. The original radiator 12 side is arranged in the lower part.

  In FIG. 2, the solid line arrow indicates the refrigerant flow direction, and the white arrow indicates the outside air flow. As shown in FIG. 2, it is folded from the downstream side to the upstream side with respect to the outside air flow direction. It is preferable to flow a refrigerant. Thereby, since the refrigerant | coolant of the latter half of a refrigerant | coolant flow heat-exchanges with the external air before heat exchange, a sufficient temperature difference with external air can be ensured, and external air heat radiation can be performed stably. The high heat radiator 6 and the low heat radiator 12 are preferably integrated from the viewpoint of compactness, but are not limited to the integral type.

  Returning to the description of FIG. The cooling unit 2 includes an endothermic part of a low-source refrigeration cycle. The heat absorption part of the low-source refrigeration cycle is configured by connecting the liquid electromagnetic valve 13, the low-source expansion valve 14, and the cooler 15 with piping. And the heat absorption part of the low-source refrigeration cycle is connected to the heat-radiation part of the low-source refrigeration cycle by connection pipes 3 and 4 so that the refrigerant circulates. The cooling unit 2 is further provided with a cooling fan 16 that blows air to the cooler 15.

  In the high-source refrigeration cycle of this refrigeration apparatus, for example, combustible R290 is enclosed as a refrigerant, and, for example, carbon dioxide is enclosed as a refrigerant in the low-source refrigeration cycle. The high-source refrigeration cycle filled with flammable refrigerant is closed in the outdoor unit 1, so there is no need to put in and out the refrigerant during installation work or removal work, reducing the risk of explosion accidents due to refrigerant leakage Can do. In addition, the low-source refrigeration cycle in which the amount of refrigerant needs to be adjusted on-site does not cause a major accident even if the refrigerant leaks because the refrigerant is carbon dioxide, and it also has a significant impact on global warming. small.

  The refrigeration apparatus further includes a control device 20 that controls the entire refrigeration apparatus. The control device 20 is composed of a microcomputer and includes a CPU, a RAM, a ROM, and the like. When the outside air temperature detected by the outside air temperature sensor 19 is higher than a predetermined temperature, the control device 20 performs a two-way operation that operates both the low-source compressor 10 and the high-source compressor 5, and the outside air temperature is In the case of low outside air below a predetermined temperature, a single unit operation is performed in which only the low-source compressor 10 is operated and the high-source compressor 5 is stopped.

  In addition, the control device 20 performs control such as switching the flow path switching valve 11 between two-way operation and unit operation, and opening and closing the bypass valves 17a and 18a. In addition, the control apparatus 20 may be provided in the outdoor unit 1, may be provided in the cooling unit 2, or is configured separately for each unit and configured to perform mutual processing. good.

  Next, the refrigeration cycle operation during the two-way operation will be described with reference to FIG.

[Two-way operation]
FIG. 3 is a diagram illustrating the refrigerant flow during the binary operation of the refrigeration apparatus of FIG. 1. In FIG. 3, the solid line arrows indicate the refrigerant flow in the low-source refrigeration cycle, and the dotted lines indicate the refrigerant flow in the high-source refrigeration cycle. FIG. 4 is a pressure-specific enthalpy diagram showing the refrigeration cycle operation of the refrigeration apparatus of FIG. Since the refrigerant is different between the high-source refrigeration cycle and the low-source refrigeration cycle, the pressure with respect to the saturation temperature is originally different, but in FIG. 4, the horizontal axis is corrected so that each refrigerant has the same saturation temperature with respect to the pressure. The specific enthalpy is corrected for the same saturation line. In FIG. 4, 31 indicates a saturation curve, 32 indicates an outside air temperature isotherm, 33 indicates a low-source refrigeration cycle, and 34 indicates a high-source refrigeration cycle. A to I in FIG. 4 indicate refrigerant states at the respective piping positions shown in A to I in FIG. FIG. 4 shows the operation when the outside air temperature is 35 ° C. and the cooler target temperature −30 ° C. together with the temperature of each state.

(Two-way operation-low-source refrigeration cycle)
In the low-source refrigeration cycle in which the carbon dioxide refrigerant is sealed, the compressor operation is performed regardless of the outside air temperature. In the dual operation, the flow path switching valve 11 is switched to the solid line side in FIG. The rotation speed of the low-source compressor 10 is adjusted so that the low-pressure saturation temperature becomes −30 ° C. The intake refrigerant (state A) of the low-source compressor 10 is pressurized to a pressure corresponding to a saturation temperature of 15 ° C. to become a high-temperature refrigerant (state B). This high-temperature refrigerant is first guided to the low-source radiator 12 via the flow path switching valve 11. Since the high-temperature refrigerant led to the low-source radiator 12 is about 90 ° C. and is sufficiently hotter than the outside air, by radiating heat to the outside air, the temperature is close to the outside air temperature (state C) as shown in FIG. To be cooled.

  The refrigerant of the low-source refrigeration cycle cooled to a temperature close to the outside air temperature then flows into the condensing unit 9b of the cascade heat exchanger 9 and exchanges heat with the high-source refrigerant passing through the evaporation unit 9a, so that the state D And flows into the cooling unit 2 via the connection pipe 3. The refrigerant flowing into the cooling unit 2 passes through the opened liquid electromagnetic valve 13, is depressurized to a saturation temperature of −30 ° C. by the low original expansion valve 14 (state E), and flows into the cooler 15. The refrigerant that has flowed into the cooler 15 exchanges heat with the air in the refrigeration warehouse to cool the refrigeration warehouse, and then enters the low-pressure gas state A again. Then, the refrigerant in the low-pressure gas state A is sucked into the low-source compressor 10 again via the connection pipe 4.

(Two-way operation-high-source refrigeration cycle)
In the high-source refrigeration cycle in which R290 is enclosed, the high-temperature and high-pressure refrigerant (state G) that has flowed out of the high-source compressor 5 radiates heat to the outside air at 35 ° C. in the high-source radiator 6 and reaches a saturation temperature of 50 ° C. Then, the refrigerant is further cooled to a temperature close to the outside air temperature to become a high-pressure liquid refrigerant (state H). Then, the high-pressure liquid refrigerant is depressurized to a saturation temperature of about 10 ° C. by the high original expansion valve 8 (state I). During the dual operation, the bypass valves 17a and 18a are closed.

  The refrigerant decompressed by the high original expansion valve 8 exchanges heat with a low original refrigerant having a saturation temperature of 15 ° C. in the evaporation section 9a of the cascade heat exchanger 9, evaporates into a low pressure gas refrigerant (state F), It is sucked into the original compressor 10. At this time, the high compressor 5 is adjusted so that the saturation temperature of the suction pressure is about 10 ° C., and the high temperature compressor 5 is heated so that the suction gas refrigerant superheat degree is about 5 degrees. The opening degree of the expansion valve 8 is adjusted.

  Thus, under the operating conditions in which the refrigerant temperature on the heat radiation side is 50 ° C. and the refrigerant temperature on the heat absorption side is −30 ° C., for example, when the unit operation is performed with R290 refrigerant, the compression ratio exceeds 10. FIG. 5 is an example of the operation efficiency characteristic with respect to the compression ratio of a refrigerant compressor that is generally used. However, the operation efficiency becomes maximum when the compression ratio is about 3 to 4, and the efficiency decreases at a compression ratio higher than that. Therefore, in an operation where the compression ratio exceeds 10, the operation efficiency is greatly reduced. Therefore, as described above, the refrigeration cycle is divided into the low-source refrigeration cycle and the high-source refrigeration cycle, and the two-way operation can reduce the respective compression ratios to about 3 to 4, thereby improving the operation efficiency. Can do.

[Unit operation]
Next, the refrigeration cycle operation during unit operation will be described. In the case of low outside air whose outside air temperature is equal to or lower than a predetermined temperature, if the two-way operation is performed, the compression ratio decreases for both the high and low sources, so that the operation efficiency also decreases in this case. In order to avoid this, in the present embodiment, only the low-source compressor 10 is operated and the high-source compressor 5 is stopped during low outside air. In the unit operation, the flow path switching valve 11 is switched to the dotted line side in FIG.

  As described above, since the high unit compressor 5 is stopped in the unit operation, if the refrigerant does not flow into the evaporation section 9a of the cascade heat exchanger 9, the heat can be dissipated only by the low source radiator 12 in the low source refrigeration cycle. Disappear. Therefore, the heat dissipation capability is greatly reduced. Therefore, in the present embodiment, the refrigerant circulates in the high-source refrigeration cycle by natural refrigerant circulation, and the heat of the refrigerant flowing through the condensing unit 9b of the low-source refrigeration cycle is converted by the cascade heat exchanger 9 The heat dissipation capability is improved by absorbing the heat to the side and dissipating heat to the outside air with the high-source radiator 6. Hereinafter, this unit operation will be described with reference to FIGS.

  FIG. 6 is a diagram showing the refrigerant flow during unit operation of the refrigeration apparatus of FIG. 1. In FIG. 6, the solid line arrow indicates the refrigerant flow in the low-source refrigeration cycle, and the dotted line indicates the refrigerant flow in the high-source refrigeration cycle. FIG. 7 is a pressure-specific enthalpy diagram showing the refrigeration cycle operation of the refrigeration apparatus of FIG. 6, and similarly to FIG. 3, the difference in saturation temperature and pressure due to different refrigerants at the high and low sources is the same. It is corrected and illustrated as an operation with a refrigerant. In FIG. 7, 31 indicates a saturation curve, 32 indicates an outside air temperature isotherm, 33 indicates a low-source refrigeration cycle, and 34 indicates a high-source refrigeration cycle. A to E and J to L in FIG. 7 indicate refrigerant states at the respective piping positions indicated by A to E and J to L in FIG. 6. Moreover, in FIG. 7, operation | movement in case the outside temperature 0 degreeC and a cooler target temperature-30 degreeC is shown with the temperature of each state.

(Unit operation-low refrigeration cycle)
In the low-source refrigeration cycle, the rotational speed of the low-source compressor 10 is adjusted so that the low-pressure saturation temperature becomes −30 ° C., as in the high outside air condition. The intake refrigerant (state A) of the low-source compressor 10 is pressurized to become a high-temperature refrigerant (state B), and is first sent to the condensing unit 9b of the cascade heat exchanger 9 via the flow path switching valve 11. The refrigerant that has flowed into the condenser 9b of the cascade heat exchanger 9 dissipates heat to the high-source refrigerant on the high-source refrigeration cycle that passes through the evaporator 9a, condenses at 15 ° C., and enters state C. Then, the refrigerant in the state C flows into the low heat radiator 12 and exchanges heat with the outside air at 0 ° C., and is cooled to a temperature close to the outside air temperature 0 ° C. (here, 2 ° C.) (state D).

  The refrigerant that has flowed out of the low heat radiator 12 flows into the cooling unit 2 through the connection pipe 3, passes through the opened liquid electromagnetic valve 13, and is depressurized to a saturation temperature of −30 ° C. by the low original expansion valve 14. (State E). The refrigerant decompressed by the low original expansion valve 14 flows into the cooler 15 and heat-exchanges with the air in the freezer warehouse to cool the inside of the freezer warehouse. The refrigerant that has cooled the inside of the freezer warehouse again enters the low-pressure gas state A, and then is sucked into the low-source compressor 10 again via the connection pipe 4.

(Unit operation-high refrigeration cycle)
On the other hand, in the high-source refrigeration cycle, the high-source compressor 5 is stopped in a state where the outdoor blower 7 is operated, and the bypass valve 17a is opened. Further, the high expansion valve 8 is fully opened or the bypass valve 18a is opened. As a result, a circulation cycle (natural circulation cycle) is formed in which the high-source heat radiator 6 and the cascade heat exchanger 9 are directly connected to bypass the high-source compressor 5.

  The high-source-side refrigerant R290 is cooled by releasing heat to the outside air temperature of 0 ° C. in the high-source radiator 6, and then flows into the evaporator 9a of the cascade heat exchanger 9 and passes through the condenser 9b side. It is heated by the discharge gas refrigerant of the compressor 10. Therefore, if the high heat radiator 6 is installed at a position higher than the cascade heat exchanger 9, a temperature difference occurs in the refrigerant between the high heat radiator 6 and the evaporation part 9a of the cascade heat exchanger 9, The refrigerant naturally circulates in the natural circulation cycle. In this natural circulation cycle, the saturation temperature of the high-source refrigerant in the evaporation section 9a of the cascade heat exchanger 9 is an intermediate saturation temperature between the outside air temperature 0 ° C. and the condensation temperature 15 ° C. of the low-source refrigeration cycle (here, 8 ° C. )

  In the natural circulation cycle provided in the high-source refrigeration cycle, the refrigerant bypassing the high-source compressor 5 condenses at 8 ° C. in the high-source radiator 6 to become a liquid refrigerant (state K), and cascade heat exchange is performed depending on its weight. It descends toward the vessel 9 and flows into the evaporator 9a of the cascade heat exchanger 9. The liquid refrigerant condensed in the high heat radiator 6 (state K) becomes a high-pressure liquid refrigerant (state L) by the amount corresponding to the liquid head at the inlet of the evaporation section 9a of the cascade heat exchanger 9 below it. This liquid refrigerant is heated by the low original refrigerant of 15 ° C. that passes through the condensing part 9b of the cascade heat exchanger 9, evaporates at 8 ° C., and becomes a gas refrigerant (state J). This gas refrigerant is pushed up from the evaporation section 9a of the cascade heat exchanger 9 and rises, passes through the bypass valve 17a, and flows again into the high-source radiator 6 inlet located above.

  In this way, in the natural circulation cycle provided in the high-source refrigeration cycle, the high-source refrigerant naturally circulates only by the operation of the outdoor blower 7 without driving the high-source compressor 5, so that the outside air can be dissipated. Cooling operation with low power consumption.

  In unit operation in which the high-source refrigeration cycle is simply stopped without performing natural circulation, heat radiation to the outside air is performed only by the low-source heat radiator 12, so that the heat radiation capability is insufficient. However, in the present embodiment, it is possible to dissipate the outside air using both the high-source radiator 6 and the low-source radiator 12, and thus sufficient heat dissipation performance can be ensured.

  Moreover, since the flow order of the low-source refrigerant in the low-source refrigeration cycle during the unit operation is changed from the cascade heat exchanger 9 to the low-source radiator 12 by switching the flow path switching valve 11, the low-source refrigerant The temperature can be lowered to near the outside temperature. Further, in the two-way operation, since the outside air temperature is higher than the condensation temperature in the condensing unit 9b of the cascade heat exchanger 9, the low-source refrigerant is supplied to the low-source refrigerant before the cascade heat exchanger 9 in the low-source refrigeration cycle. It is possible to dissipate the outside air by passing it through, and the low-source heat radiator 12 can be used effectively.

  As described above, according to the present embodiment, since the two-way operation and the one-way operation can be selected, it is possible to avoid the deterioration of the operation efficiency due to the compression ratio becoming too small under the low outside air condition. .

  Further, the low-source radiator 12 of the low-source refrigeration cycle and the high-source radiator 6 of the high-source refrigeration cycle are configured to be able to dissipate the outside air, and the high-source radiator 6 also has a refrigerant when the high-source compressor 5 is stopped. The following effects can be obtained because it is configured to pass through by natural circulation. That is, since it becomes possible to radiate the outside air using both the high-source radiator 6 and the low-source radiator 12 during unit operation, sufficient heat radiation performance can be ensured. In other words, the heat dissipation performance of the outdoor heat exchanger (high-source radiator 6, low-source radiator 12) can be utilized to the maximum, the operating efficiency can be improved under low outdoor air conditions, and the energy saving performance can be improved. Can do.

  In Patent Document 1 in which a part of the outdoor heat exchanger is used exclusively for unit operation, the outdoor heat exchanger cannot be used to the maximum during two-way operation. The outside air can be radiated by both the high-source radiator 6 and the low-source radiator 12 during the original operation. That is, the outdoor heat exchanger can be used to the maximum, and sufficient heat radiation performance can be ensured even during dual operation, thereby improving the energy saving performance.

  Further, in the low-source refrigeration cycle, the distribution order of the low-source heat radiator 12 and the cascade heat exchanger 9 can be selected, and the refrigerant discharged from the low-source compressor 10 during the single unit operation is first supplied to the cascade heat exchanger 9. Then, the following effect is obtained. That is, during unit operation, the high-pressure refrigerant in the low-source refrigeration cycle can be reduced to near the outside air temperature. Further, when viewed from the high-source refrigeration cycle, the outside refrigerant heat dissipation performance of the high-source radiator 6 is improved by raising the outlet refrigerant of the evaporator 9a of the cascade heat exchanger 9 to near the discharge gas temperature of the low-source refrigeration cycle. Can be made. As a result, driving efficiency can be increased.

  Further, as shown in FIG. 1, in the binary operation, the cascade heat exchanger 9 is configured to perform heat exchange between the low-source refrigerant and the high-source refrigerant in a parallel flow, so that the intake refrigerant of the high-source compressor 5 is Abnormal overheating can be prevented.

  In the unit operation, the low-source refrigerant and the high-source refrigerant exchange heat in the cascade heat exchanger 9 in a counterflow. For this reason, since the refrigerant on the outlet side of the high-end cascade heat exchanger 9 exchanges heat with the discharge gas of the low-source compressor 10, a sufficient degree of superheat can be secured on the gas side of the natural circulation cycle, and the outside air heat radiation performance Will improve.

  1 outdoor unit, 2 cooling unit, 3 connection piping, 4 connection piping, 5 high compressor, 6 high heat radiator, 7 outdoor blower, 8 high expansion valve, 9 cascade heat exchanger, 9a evaporation section, 9b condensation 10 Low compressor, 11 Flow switching valve, 12 Low heat radiator, 13 Liquid solenoid valve, 14 Low expansion valve, 15 Cooler, 16 Cooling fan, 17 Bypass circuit, 17a Bypass valve, 18 Bypass circuit , 18a Bypass valve, 19 Outside temperature sensor, 20 Control device, 21 Heat transfer fin, 22 Heat transfer tube.

Claims (5)

A high-source refrigeration cycle configured by connecting a high-source compressor, a first outdoor radiator, a high-source expansion valve, and an evaporation section of a cascade heat exchanger;
A low-source refrigeration cycle configured by connecting a low-source compressor, a second outdoor radiator, a condensing unit of a cascade heat exchanger, a low-source expansion valve, and a cooler;
Outflow from the low-source compressor in a dual operation that operates both the low-source compressor and the high-source compressor, and a single-unit operation that operates the low-source compressor and stops the high-source compressor A flow path switching valve that switches the flow order of the refrigerant from the second outdoor radiator to the order of the condensing part of the cascade heat exchanger and the reverse order thereof,
A natural circulation cycle that bypasses the high-compressor compressor in the high-source refrigeration cycle during the unit operation and naturally circulates the refrigerant between the first outdoor radiator and the evaporation section of the cascade heat exchanger; A refrigeration apparatus characterized by. An outside temperature sensor for detecting the outside temperature;
The refrigeration apparatus according to claim 1, further comprising a control device that selectively performs the two-way operation and the single-unit operation based on an outside air temperature detected by the outside air temperature sensor.   The refrigeration according to claim 2, wherein the control device selects the unit operation when the outside air temperature is equal to or lower than a predetermined temperature, and selects the two-way operation when the outside air temperature is higher than the predetermined temperature. apparatus.   The natural circulation cycle includes a bypass circuit that bypasses the high-source compressor in the high-source refrigeration cycle, and a bypass valve that is provided in the bypass circuit and is opened during the unit operation. The apparatus is arranged at a position higher than the evaporation part of the cascade heat exchanger, and is configured so that the refrigerant circulates between the first outdoor radiator and the evaporation part of the cascade heat exchanger. The refrigeration apparatus according to any one of claims 1 to 3.   In the single unit operation, the refrigerant flowing through the condensing unit and the refrigerant flowing through the evaporating unit exchange heat in the cascade heat exchanger in a counter flow, and in the dual operation, the refrigerant flows through the condensing unit in the cascade heat exchanger. The refrigeration apparatus according to any one of claims 1 to 4, wherein the refrigerant and the refrigerant flowing through the evaporation section exchange heat in parallel flow.

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