JP2013190154A - Refrigeration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration apparatus capable of stably obtaining a high COP by suppressing an influence of an ambient temperature irrespective of a refrigeration cycle using carbon dioxide as coolant.SOLUTION: The refrigeration apparatus 10 includes a first refrigeration cycle 12 which comprises a first compressor 18, a first heat radiator 20, a second compressor 22, a second heat radiator 24 connected with the discharge side of the second compressor 22, a heat exchanger 16 connected with the outlet side of the second heat radiator 24, an expansion device 26 connected with the outlet side of the heat exchanger 16 and a heat sink 28, and uses carbon dioxide as coolant, and a second refrigeration cycle 14 which comprises a compressor 36, a heat radiator 38 and an expansion device 40, and connects a heat exchanger 16 between the outlet side of the expansion device 40 and the compressor 36, wherein the heat exchanger 16 is configured so as to make the coolant of the first refrigeration cycle 12 and the coolant of the second refrigeration cycle 14 heat-exchangeable to each other.

Description

  The present invention relates to a refrigeration apparatus using two systems of refrigeration cycles having a compressor, a radiator, an expansion device, and a heat absorber as main components.

  FIG. 2 shows a basic configuration diagram of the refrigeration apparatus 100 that has been widely used conventionally. In the refrigeration apparatus 100, main components such as a compressor 102, a radiator (condenser) 104, an expansion device 106, and a heat absorber (evaporator) 108 are connected by a pipe 110, and a refrigerant is sealed inside. In such a refrigeration apparatus 100, the refrigerant that has been adiabatically compressed by the compressor 102 and cooled to high temperature and high pressure is cooled (heat dissipated) by the radiator 104, and then adiabatically expanded by the expansion device 106 to obtain low temperature and low pressure. A cycle (refrigeration cycle) is formed in which the refrigerant is heated (absorbed) by the heat absorber 108 and then returned to the compressor 102.

  As a general installation method of the refrigeration apparatus 100, the expansion device 106 and the heat absorber 108 are installed in a device (use site) for the purpose of refrigeration and cooling, such as a refrigeration showcase, and the product is cooled to a predetermined temperature. The compressor 102 and the radiator 104, which are other constituent devices, are installed in a machine compartment such as a refrigeration showcase as a unit, or are installed outdoors.

  The refrigerant of the refrigeration apparatus 100 is generally a chlorofluorocarbon refrigerant or a natural refrigerant such as ammonia or hydrocarbon. However, since the chlorofluorocarbon refrigerant has a great influence on global warming, its use reduction is required. . On the other hand, natural refrigerants have problems such as toxicity and strong flammability, resulting in high equipment costs. Therefore, in recent years, carbon dioxide (carbon dioxide) has been used as a refrigerant in consideration of danger, safety, and the like because it has little influence on global warming.

  Carbon dioxide is characterized by a low triple point temperature (about 30.9 ° C.) and high pressure (about 7.4 MPa) according to a generally known ph (pressure-enthalpy) diagram. In order to obtain a high cooling amount in the refrigeration cycle, it is necessary to increase the pressure to a very high pressure (for example, about 10 MPa) compared to other refrigerants. For this reason, the refrigeration cycle using a carbon dioxide refrigerant has a problem that the refrigeration efficiency (COP) indicated by the amount of cooling heat / compression power is low and the refrigerant temperature at the compressor outlet is high. In particular, when the ambient temperature is high, the amount of heat for cooling becomes small, and in order to make the refrigerant higher than the ambient temperature, the pressure must be increased to a higher pressure. Will do.

  Regarding such a problem with the carbon dioxide refrigerant, for example, in Patent Document 1, a branch portion is provided in a pipe between the radiator and the expansion device to divert the carbon dioxide refrigerant, and another refrigerant on the branch side is expanded. A configuration is disclosed in which the main stream side carbon dioxide refrigerant is cooled by being expanded by an apparatus and passing through a heat exchanger to exchange heat with the main stream side carbon dioxide refrigerant. In Patent Document 2, the carbon dioxide refrigerant discharged from the compressor is radiated by a radiator, then expanded by a first expansion device, cooled by cooling water, and then the second expansion device. The structure which expand | swells by this and introduce | transduces into an evaporator is disclosed. Further, Patent Document 3 includes a refrigeration cycle using a fluorocarbon R22 as a refrigerant and a refrigeration cycle using carbon dioxide as a refrigerant, and exchanges heat between the R22 side evaporator and the carbon dioxide side condenser. A possible configuration is disclosed.

Japanese Patent No. 4207235 Japanese Patent Laid-Open No. 2006-194568 Japanese Patent Laid-Open No. 11-14172

  However, in the configuration of Patent Document 1, it is necessary to change the amount of refrigerant to be diverted depending on the ambient temperature, it is difficult to control to obtain stable efficiency, and the diverted side refrigerant is also carbon dioxide. Therefore, the refrigeration efficiency is low, and it is difficult to improve the efficiency of the entire system. In addition, the configuration of Patent Document 2 requires a separate cooling water production system in order to secure low-temperature cooling water, which increases costs and uses water, so the cooling temperature cannot be lowered to below freezing point. Efficiency gains throughout the system are limited. Furthermore, in the configuration of Patent Document 3, the condenser of the refrigeration cycle using the carbon dioxide refrigerant is directly cooled by the second refrigerant (CFC-based R22). Therefore, a large amount of the second refrigerant is used for cooling. Necessary, causing an increase in the size of the apparatus configuration of the refrigeration cycle using the second refrigerant.

  The present invention has been made in view of the above-described problems of the prior art. Even in a refrigeration cycle using carbon dioxide as a refrigerant, it is possible to stably obtain a high COP while suppressing the influence of the ambient temperature. An object is to provide a refrigeration apparatus.

  A refrigeration apparatus according to the present invention includes a first compressor, a first radiator connected to a discharge side of the first compressor, a second compressor connected to an outlet side of the first radiator, A second radiator connected to the discharge side of the second compressor, a heat exchanger connected to the outlet side of the second radiator, and a first expansion device connected to the outlet side of the heat exchanger And a heat sink connected to the outlet side of the first expansion device, a first refrigeration cycle using carbon dioxide as a refrigerant, a compressor, and a radiator connected to the discharge side of the compressor And a second expansion device connected to the outlet side of the radiator, and a second refrigeration cycle in which the heat exchanger is connected between the outlet side of the second expansion device and the compressor. The heat exchanger can exchange heat between the refrigerant of the first refrigeration cycle and the refrigerant of the second refrigeration cycle.

  According to such a configuration, the carbon dioxide refrigerant flowing through the heat exchanger immediately before flowing into the first expansion device on the first refrigeration cycle side is absorbed by the heat absorption when the refrigerant on the second refrigeration cycle side evaporates in the heat exchanger. Since it can cool by the action, the temperature of the carbon dioxide refrigerant in the first refrigeration cycle can be made lower than the ambient temperature, and the COP of the first refrigeration cycle using the carbon dioxide refrigerant can be increased. In the second refrigeration cycle, since a refrigerant having a high COP such as a general chlorofluorocarbon can be used, the COP of the entire system can be increased. Moreover, since the temperature immediately before the first expansion device of the carbon dioxide refrigerant can be stabilized by the heat exchanger regardless of the ambient temperature, it is possible to stably obtain a high COP even in the summer when the ambient temperature is high. Can do.

  When the heat exchanger is a counterflow type heat exchanger in which the refrigerant of the first refrigeration cycle and the refrigerant of the second refrigeration cycle are counterflowed, the heat exchange efficiency is improved and the heat exchanger The temperature of the carbon dioxide refrigerant in the first refrigeration cycle flowing out can be lowered to near the temperature of the refrigerant in the second refrigeration cycle flowing into the heat exchanger, and COP can be further improved.

  It is preferable that a refrigerant other than carbon dioxide is used for the second refrigeration cycle because COP in the entire system can be improved. As the refrigerant other than carbon dioxide, for example, a refrigerant having a COP higher than that of carbon dioxide such as a fluorocarbon refrigerant or a natural refrigerant may be used.

  When a control device is provided that controls the operating state of the second refrigeration cycle based on the refrigerant temperature in the first refrigeration cycle, the operation of the second refrigeration cycle is stopped based on the refrigerant temperature in the first refrigeration cycle. Since it can be performed, the efficiency of the entire system can be further increased.

  In this case, the control device detects the refrigerant temperature at the outlet of the heat exchanger in the first refrigeration cycle, and controls the operating state of the compressor in the second refrigeration cycle based on the detected refrigerant temperature. It is preferable to adopt a configuration to Then, the temperature of the carbon dioxide refrigerant exiting the heat exchanger can be optimally managed by the second refrigeration cycle, and the operation of the compressor of the second refrigeration cycle is stopped depending on the situation of the carbon dioxide refrigerant, or Since the rotational speed can be reduced or increased, the efficiency of the entire system can be further increased.

  According to the present invention, the carbon dioxide refrigerant flowing through the heat exchanger immediately before flowing into the first expansion device on the first refrigeration cycle side is absorbed by the endothermic action when the refrigerant on the second refrigeration cycle side evaporates in the heat exchanger. Since it can cool, the temperature of the carbon dioxide refrigerant of a 1st freezing cycle can be made lower than ambient temperature, and COP of the 1st freezing cycle using a carbon dioxide refrigerant can be raised. Further, since the temperature immediately before the first expansion device of the carbon dioxide refrigerant can be stabilized by the heat exchanger regardless of the ambient temperature, a high COP can be stably obtained even in the summer when the ambient temperature is high. Can do.

FIG. 1 is an overall configuration diagram of a refrigeration apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a general refrigeration apparatus conventionally used.

  Hereinafter, preferred embodiments of a refrigeration apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of a refrigeration apparatus 10 according to an embodiment of the present invention. The refrigeration apparatus 10 includes a first refrigeration cycle (first system) 12 that uses carbon dioxide as a refrigerant, and a second refrigeration cycle that uses a refrigerant other than carbon dioxide (hereinafter also referred to as “second refrigerant”) as a refrigerant ( This is a system that includes two refrigeration cycles (second system) 14 and that heat-exchanges one carbon dioxide refrigerant and the other second refrigerant with a heat exchanger 16.

The first refrigeration cycle 12 includes a first compressor 18, a first radiator (first condenser, intermediate radiator) 20 connected to the discharge side of the first compressor 18, and an outlet of the first radiator 20. A second compressor 22 connected to the side, a second radiator (second condenser) 24 connected to the discharge side of the second compressor 22, and the outlet connected to the outlet side of the second radiator 24. A heat exchanger 16, an expansion device (first expansion device, expansion valve) 26 connected to the outlet side of the heat exchanger 16, and a heat absorber (evaporator) 28 connected to the outlet side of the expansion device 26 A refrigeration cycle is configured by connecting these components with a pipe (refrigerant pipe) 30 as a main component device. As described above, the first refrigeration cycle 12 uses carbon dioxide (carbon dioxide, CO ₂ ) as a refrigerant.

  In the first refrigeration cycle 12, the fan whose pressure is increased by the first compressor 18 to increase the enthalpy and the temperature is higher than the ambient temperature is supplied to the first radiator 20 by a fan attached to the first radiator 20. (Blower) Cools with air at an ambient temperature sent from 32 to lower the enthalpy and bring the temperature to the vicinity of the ambient temperature. Subsequently, the refrigerant is boosted to a predetermined pressure by the second compressor 22. The refrigerant that has been pressurized by the second compressor 22 to become high enthalpy, high temperature, and high pressure is cooled by the air at the ambient temperature sent from the fan (blower device) 34 by the second radiator 24 to become low enthalpy, Near ambient temperature. The refrigerant that has exited the second radiator 24 passes through the flow path 16a of the heat exchanger 16 and is cooled. Then, the refrigerant is adiabatically expanded by the expansion device 26 to become a low pressure, and becomes a target temperature lower than the ambient temperature. After flowing into the heat absorber 28 and absorbing heat from the outside to become high enthalpy, the refrigeration cycle is formed by returning to the first compressor 18. The cold temperature (cold heat) generated in the heat absorber 28 is used for cooling a showcase, for example.

  On the other hand, the second refrigeration cycle 14 includes a compressor 36, a radiator (condenser) 38 connected to the discharge side of the compressor 36, and an expansion device (second expansion device) connected to the outlet side of the radiator 38. , An expansion valve) 40 and the heat exchanger 16 connected to the outlet side of the expansion device 40 are main components, and a pipe (refrigerant pipe) 42 is connected between them to constitute a refrigeration cycle. ing. As described above, the second refrigeration cycle 14 uses the second refrigerant other than carbon dioxide as the refrigerant. In the present embodiment, a configuration using CFC-based R134a is exemplified as the second refrigerant, but the second refrigerant is not particularly limited as long as it is a refrigerant other than a commonly used carbon dioxide refrigerant. For example, ammonia And natural refrigerants such as HC (hydrocarbon) and various chlorofluorocarbon refrigerants.

  In the second refrigeration cycle 14, the second refrigerant whose enthalpy is increased by the pressure by the compressor 36 and the temperature becomes higher than the ambient temperature is supplied to the fan (blower) attached to the radiator 38 by the radiator 38. The enthalpy is lowered by cooling with air at an ambient temperature sent from 43, and the temperature is brought to the ambient temperature. Subsequently, the second refrigerant is adiabatically expanded by the expansion device 40 and flows into the heat exchanger 16 in a low-pressure and low-temperature state, and flows through the flow path 16a when passing through the flow path 16b. After absorbing heat from the carbon dioxide refrigerant to become high enthalpy, returning to the compressor 36 forms a refrigeration cycle.

  Thus, the refrigeration apparatus 10 is provided with the heat exchanger 16 that exchanges heat between the carbon dioxide refrigerant of the first refrigeration cycle 12 and the second refrigerant of the second refrigeration cycle 14.

  The heat exchanger 16 has a flow path 16a through which the carbon dioxide refrigerant in the first refrigeration cycle 12 flows by connecting the pipe 30 and a flow through which the second refrigerant in the second refrigeration cycle 14 flows by connecting the pipe 42. The counter flow type heat exchanger includes a channel 16b and uses a carbon dioxide refrigerant in the channel 16a and a second refrigerant in the channel 16b as counterflows.

  Therefore, in the heat exchanger 16, the temperature between the second carbon dioxide refrigerant flowing through the flow path 16a at a temperature near the ambient temperature in the second radiator 24 and the second refrigerant having a temperature lower than the ambient temperature in the expansion device 40. By the heat exchange at, heat is transferred from the high-temperature side carbon dioxide refrigerant toward the low-temperature side second refrigerant, and the temperature of the carbon dioxide refrigerant can be made lower than the ambient temperature. In addition, since the heat exchanger 16 is configured as a counter-flow type, the temperature of the carbon dioxide refrigerant flowing out of the heat exchanger 16 can be lowered to near the temperature of the second refrigerant flowing into the heat exchanger 16. is there.

  The refrigeration apparatus 10 is further provided with a temperature sensor 44 that measures the temperature of the carbon dioxide refrigerant on the outlet side of the heat exchanger 16 of the first refrigeration cycle 12, and the detection result of the temperature sensor 44 is sent to the controller 46. The controller 46 is a control device that controls the operation state of the second refrigeration cycle, more specifically, the operation of the compressor 36 based on the temperature detected by the temperature sensor 44. Of course, the controller 46 may be configured to perform control on the first refrigeration cycle 12 side, or may be used as a control device that comprehensively controls the refrigeration apparatus 10 as a whole.

  In the refrigeration apparatus 10 configured as described above, for example, the expansion device 26 and the heat absorber 28 on the first refrigeration cycle 12 side are installed at a use site such as a showcase or an indoor unit for air conditioning, It is assembled as a unit and installed outdoors.

  Next, the operation of the refrigeration apparatus 10 according to this embodiment will be described.

  During the operation of the refrigeration apparatus 10, as described above, the carbon dioxide refrigerant is circulated in the first refrigeration cycle 12, and the second refrigerant is circulated in the second refrigeration cycle 14, thereby forming a refrigeration cycle. As a result, when the refrigeration apparatus 10 is used as a refrigeration / cooling apparatus, a product or the like is refrigerated by a heat absorber 28 installed inside a device such as a showcase installed indoors, for example.・ Cooling can be performed.

  At this time, the refrigeration apparatus 10 is provided with a heat exchanger 16 that exchanges heat between the carbon dioxide refrigerant of the first refrigeration cycle 12 and the second refrigerant of the second refrigeration cycle 14, and more specifically, heat exchange. The cooler 16 has a carbon dioxide refrigerant flowing between the second radiator 24 and the expansion device 26 on the first refrigeration cycle 12 side, and a second flow between the expansion device 40 and the compressor 36 on the second refrigeration cycle 14 side. 2 Exchange heat with refrigerant. As a result, the carbon dioxide refrigerant that has been cooled by the second radiator 24 on the first refrigeration cycle 12 side to become low enthalpy and has a temperature close to the ambient temperature is adiabatically expanded by the expansion device 40 on the second refrigeration cycle 14 side. Since the temperature is lower than the ambient temperature by the endothermic action due to the evaporation of the second refrigerant, which has become low pressure and low temperature, the temperature becomes about the temperature of the second refrigerant flowing into the heat exchanger 16, so the COP of the first refrigeration cycle 12 Will improve. That is, the heat exchanger 16 has a function as a heat absorber (evaporator) in the second refrigeration cycle 14 and a function as a third-stage radiator (condenser) in the first refrigeration cycle 12.

  During the operation of the refrigeration apparatus 10, under the control of the controller 46, the second refrigeration is performed based on the detected temperature of the carbon dioxide refrigerant on the outlet side of the second radiator 24 (inlet side of the expansion device 26) by the temperature sensor 44. The operation control of the compressor 36 in the cycle 14 is performed. For example, the operation of the compressor 36 is stopped or the control for decreasing or increasing the rotational speed of the compressor 36 is performed as necessary. As a result, the temperature of the carbon dioxide refrigerant exiting the heat exchanger 16 can be stabilized regardless of the ambient temperature, the efficiency of the first refrigeration cycle 12 is improved, and the operation of the compressor 36 controls the second refrigeration. The efficiency of the cycle 14 is also improved.

  As described above, according to the refrigeration apparatus 10 according to the present embodiment, the heat exchanger 16 that exchanges heat between the carbon dioxide refrigerant of the first refrigeration cycle 12 and the second refrigerant of the second refrigeration cycle 14 is provided with the first On the refrigeration cycle 12 side, it is provided between the second radiator 24 and the expansion device 26, and on the second refrigeration cycle 14 side, it is provided between the expansion device 40 and the compressor 36.

  As a result, the carbon dioxide refrigerant immediately before flowing into the expansion device 26 on the first refrigeration cycle 12 side can be cooled by the endothermic action due to evaporation of the second refrigerant on the second refrigeration cycle 14 side. The temperature of the 12 carbon dioxide refrigerant can be made lower than the ambient temperature, and the COP of the first refrigeration cycle 12 using the carbon dioxide refrigerant can be increased. At this time, since a refrigerant capable of obtaining a COP higher than carbon dioxide, such as R134a, can be used for the second refrigeration cycle 14, for example, a configuration in which a carbon dioxide refrigerant is shunted and used for cooling as in Patent Document 1 above. The COP of the entire system can be increased compared to Moreover, since the heat exchanger 16 is provided, the temperature immediately before the carbon dioxide refrigerant expansion device 26 can be stabilized regardless of the ambient temperature, so that a high COP can be stabilized even in the summer when the ambient temperature is high. Can be obtained.

  In this case, all of the second refrigeration cycle 14 can be manufactured in the factory, and assembly work at the installation site such as a showcase is not necessary. Therefore, leakage of the refrigerant from the second refrigeration cycle 14 can be prevented. Therefore, a refrigerant having a higher COP than carbon dioxide, such as a general chlorofluorocarbon refrigerant or a natural refrigerant, can be selected for the second refrigeration cycle 14, and the COP of the entire system can be further improved. In addition, the second refrigeration cycle 14 can generate a refrigeration capacity that only cools the carbon dioxide refrigerant cooled to the ambient temperature by the first radiator 20 and the second radiator 24 on the first refrigeration cycle 12 side. Therefore, the second refrigeration cycle 14 can be downsized, and the length of the pipe 42 can be shortened. As a result, the amount of the second refrigerant used in the second refrigeration cycle 14 can also be reduced.

  In the refrigeration apparatus 10, as described above, it is also effective to include the controller 46 that controls the operation state of the second refrigeration cycle 14 based on the refrigerant temperature in the first refrigeration cycle 12. Thereby, based on the temperature of the carbon dioxide refrigerant in the first refrigeration cycle 12, the second refrigeration cycle 14 can be stopped or an operation with reduced output can be performed, thereby further improving the efficiency of the entire system. Can do.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be freely changed without departing from the gist of the present invention.

  For example, in the above embodiment, the first refrigeration cycle 12 includes the first compressor 18 and the second compressor 22, and the first radiator 20 is provided between them. The compressor 18 and the second compressor 22 may be replaced by a single two-stage compression compressor. In this case, a radiator similar to the first radiator 20 is provided between the two-stage compression units. Are preferably connected. On the other hand, in addition to the first compressor 18 and the second compressor 22, a third stage compressor may be added. In this case, the second compressor 22 and the third stage compressor may be In addition, it is preferable to connect a heatsink as necessary, and the same applies to a compression system having three or more stages.

  In the above embodiment, a configuration example of a refrigeration circuit mainly provided with a compressor, a radiator, an expansion device, and a heat absorber has been shown, but this refrigeration circuit includes other components such as various valve mechanisms and accumulators, Of course, a heat insulating material or the like may be provided.

DESCRIPTION OF SYMBOLS 10, 100 Refrigeration apparatus 12 1st refrigeration cycle 14 2nd refrigeration cycle 16 Heat exchanger 16a, 16b Flow path 18 1st compressor 20 1st radiator 22 2nd compressor 24 2nd radiator 26, 40 Expansion apparatus 28 Heat absorber 30, 42 Piping 36 Compressor 38 Radiator 44 Temperature sensor 46 Controller

Claims (5)

A first compressor; a first radiator connected to a discharge side of the first compressor; a second compressor connected to an outlet side of the first radiator; and a discharge side of the second compressor A second radiator connected to the heat exchanger, a heat exchanger connected to the outlet side of the second radiator, a first expansion device connected to the outlet side of the heat exchanger, and the first expansion device A first refrigeration cycle having a heat absorber connected to the outlet side and using carbon dioxide as a refrigerant;
A compressor, a radiator connected to the discharge side of the compressor, and a second expansion device connected to the outlet side of the radiator, the outlet side of the second expansion device and the compressor A second refrigeration cycle in which the heat exchanger is connected between,
With
The refrigeration apparatus, wherein the heat exchanger is capable of exchanging heat between the refrigerant of the first refrigeration cycle and the refrigerant of the second refrigeration cycle. The refrigeration apparatus according to claim 1, wherein
The refrigeration apparatus, wherein the heat exchanger is a counterflow heat exchanger in which the refrigerant of the first refrigeration cycle and the refrigerant of the second refrigeration cycle are counterflowed. The refrigeration apparatus according to claim 1 or 2,
A refrigerant other than carbon dioxide is used in the second refrigeration cycle. The refrigeration apparatus according to any one of claims 1 to 3,
A refrigeration apparatus comprising: a control device that controls an operating state of the second refrigeration cycle based on a refrigerant temperature in the first refrigeration cycle. The refrigeration apparatus according to claim 4,
The control device detects the refrigerant temperature at the outlet of the heat exchanger in the first refrigeration cycle, and controls the operating state of the compressor in the second refrigeration cycle based on the detected refrigerant temperature. Refrigeration equipment characterized.

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