WO2024023986A1

WO2024023986A1 - Two-stage refrigeration device

Info

Publication number: WO2024023986A1
Application number: PCT/JP2022/029000
Authority: WO
Inventors: 智隆石川
Original assignee: 三菱電機株式会社
Priority date: 2022-07-27
Filing date: 2022-07-27
Publication date: 2024-02-01

Abstract

A two-stage refrigeration device (1000) comprises a first heat exchanger (12), a second heat exchanger (16), and a third heat exchanger (101). The first heat exchanger (12) exchanges heat between a first refrigerant and a second refrigerant. The second heat exchanger (16) exchanges heat between the first refrigerant and air inside a freezer. The third heat exchanger (101) exchanges heat between the second refrigerant and air outside the freezer. The two-stage refrigeration device (1000) additionally comprises an intermediate cooler (150) configured to cool the first refrigerant directed from a first compressor (10) toward the first heat exchanger (12).

Description

dual refrigeration equipment

The present disclosure relates to a dual refrigeration device.

A two-stage refrigeration cycle apparatus (two-stage refrigeration cycle apparatus) is used in a refrigeration system with a relatively low evaporation temperature used for refrigeration or freezing. For example, International Publication No. 2018/008129 (Patent Document 1) describes a binary system that performs heat exchange between a low-stage-side refrigerant and a high-stage-side refrigerant. An example of a refrigeration cycle device is disclosed.

International Publication No. 2018/008129

In the high-end cycle of a binary refrigeration cycle device, the degree of superheating of the refrigerant sucked into the compressor is appropriately controlled, and the system is operated so that the discharge temperature does not rise excessively.

However, when the refrigerant has a high specific heat ratio (=specific heat at constant pressure/specific heat at constant volume), the discharge temperature becomes high. For example, when a refrigerant with a high specific heat ratio such as R32 is applied to the high-temperature cycle, if the heat exchange amount of the cascade heat exchanger that exchanges heat between the two refrigerants in the binary refrigeration cycle increases, The temperature of the suction refrigerant also increases. For this reason, there is a possibility that the temperature of the discharged refrigerant on the high-end side exceeds the upper limit of heat resistance.

An object of the present disclosure is to provide a binary refrigeration system that can suppress the temperature of the refrigerant discharged from the compressor on the high side.

The present disclosure relates to a binary refrigeration system that cools the inside of a freezer using a first refrigerant and a second refrigerant having a lower specific heat ratio than the first refrigerant. The binary refrigeration system includes a first compressor, a first heat exchanger, a first expansion valve, a second heat exchanger, a second compressor, a third heat exchanger, and a second expansion valve. The first heat exchanger is configured to exchange heat between the first refrigerant and the second refrigerant. The second heat exchanger is configured to exchange heat between the first refrigerant and the air within the freezer. The third heat exchanger is configured to exchange heat between the second refrigerant and the air outside the freezer. The first compressor, the first heat exchanger, the first expansion valve, and the second heat exchanger constitute a first refrigerant circuit in which the first refrigerant circulates. The second compressor, the third heat exchanger, the second expansion valve, and the first heat exchanger constitute a second refrigerant circuit in which the second refrigerant circulates. The dual refrigeration system further includes a cooling device configured to cool the first refrigerant flowing from the first compressor to the first heat exchanger.

According to the dual refrigeration system of the present disclosure, since the cooling device is configured to cool the first refrigerant on the low source side, the temperature of the refrigerant discharged from the compressor on the high source side is suppressed to an appropriate temperature. can be kept.

FIG. 1 is a diagram showing the configuration of a binary refrigeration system 1000 according to the first embodiment. FIG. 3 is a diagram illustrating changes in refrigerant temperature when cascade heat exchangers exchange heat in a counterflow relationship. FIG. 3 is a diagram illustrating changes in refrigerant temperature when cascade heat exchangers exchange heat in a parallel flow relationship. It is a flow chart for explaining control of compressor 100 on the high side. It is a flowchart for explaining control of the expansion valve 102 on the high side. It is a flowchart for explaining the control of the compressor 10 on the low power side. It is a flowchart for explaining control of the expansion valve 15 on the low base side. 5 is a flowchart for explaining control of fan 150F of intercooler 150. FIG. FIG. 2 is a diagram showing the configuration of a binary refrigeration system 2000 according to a second embodiment. It is a flow chart for explaining control of expansion valve 302 of refrigerant circuit C3. It is a flow chart for explaining control of compressor 300 of refrigerant circuit C3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Although a plurality of embodiments will be described below, it has been planned from the beginning of the application to appropriately combine the configurations described in each embodiment. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a diagram showing the configuration of a binary refrigeration system 1000 according to the first embodiment. A binary refrigeration system 1000 shown in FIG. 1 includes an outdoor unit 1 installed outdoors and an indoor unit 2 installed inside a freezer.

The outdoor unit 1 includes a compressor 10, an intercooler 150, a heat exchanger 12, a compressor 100, a heat exchanger 101, a fan 101F, an expansion valve 102,

pressure sensors

17 and 105, and a temperature It includes

sensors

18, 103, and 106 and a control device 200.

The indoor unit 2 includes an expansion valve 15, a heat exchanger 16, and a fan 16F.
The outdoor unit 1 includes a portion of a refrigerant circuit C1 that is a low-base refrigerant circuit, and a refrigerant circuit C2 that is a high-base refrigerant circuit. The indoor unit 2 includes the remainder of the refrigerant circuit C1. The refrigerant circuit C1 uses the first refrigerant. Refrigerant circuit C2 uses the second refrigerant. The first refrigerant has a lower boiling point than the second refrigerant at the same pressure. Further, the specific heat ratio of the second refrigerant is higher than that of the first refrigerant. As the second refrigerant, for example, R32 or a mixed refrigerant containing R32 can be used. As the first refrigerant, for example, CO ₂ or a mixed refrigerant containing CO ₂ can be used.

More specifically, the first refrigerant filled in the low-source refrigerant circuit C1 passes through an extension pipe that connects the indoor unit 2 and the outdoor unit 1. For this reason, it is preferable to select as the first refrigerant a refrigerant that is nonflammable, has a small temperature drop due to pressure loss, and has a low global warming potential (GWP) and whose main component is CO ₂ . Note that the first refrigerant may be a low boiling point refrigerant other than CO ₂ .

On the other hand, the second refrigerant filled in the refrigerant circuit C2 on the high side does not pass through the extension pipe, and even if it leaks, it will not be directly released into the freezer, which is frequently visited by users. For this reason, it is preferable to select a refrigerant (for example, R32, R290, R1234yf, R1234ze (E)) that has a high coefficient of performance (COP) of the refrigerant circuit and a relatively small GWP as the second refrigerant.

In addition, when a refrigerant with a higher boiling point than the first refrigerant on the low-source side is sealed in the high-source side refrigerant circuit C2, the refrigerant circuit C2 is designed to have a lower pressure resistance than the low-source side refrigerant circuit C1. Good too.

In FIG. 1, arrows indicate the flow of refrigerant during cooling operation of the binary refrigeration system.
In the low-source side refrigerant circuit C1, the first refrigerant circulates through the compressor 10, the intercooler 150, the heat exchanger 12, the expansion valve 15, and the heat exchanger 16 in this order and returns to the compressor 10. At this time, the heat exchanger 16 operates as an evaporator. Note that a liquid receiver may be disposed between the heat exchanger 12 and the expansion valve 15.

That is, during cooling operation, in the low-source side refrigerant circuit C1, the first refrigerant in the gas state compressed from the compressor 10 is cooled by the intercooler 150, and then flows into the heat exchanger 12, and the first refrigerant is Refrigerant condenses. The condensed first refrigerant is expanded in the expansion valve 15 . Thereafter, the first refrigerant exchanges heat with the air inside the refrigerator and evaporates in the heat exchanger 16 that functions as an evaporator. The evaporated first refrigerant then returns to the compressor 10. Note that the compressor 10 is configured so that the operating frequency f1 can be changed within a predetermined range by inverter control.

In the refrigerant circuit C2 on the high side, the second refrigerant circulates through the compressor 100, the heat exchanger 101, the expansion valve 102, and the heat exchanger 12 in this order and returns to the compressor 100. At this time, the heat exchanger 12 operates as an evaporator.

That is, during cooling operation, in the refrigerant circuit C2 on the high side, superheated steam compressed by the compressor 100 flows into the heat exchanger 101 functioning as a condenser, and the second refrigerant is condensed. The condensed second refrigerant expands in the expansion valve 102, exchanges heat with the heat exchanger 12, and evaporates. The evaporated second refrigerant returns to the compressor 100. Note that the compressor 100 is configured so that the operating frequency f2 can be changed within a predetermined range by inverter control.

When the first refrigerant and the second refrigerant are circulating normally in this way, the heat exchanger 12 functions as a cascade condenser that exchanges heat between the first refrigerant and the second refrigerant.

The control device 200 controls the pressure sensor 105 and temperature sensor 106 arranged between the evaporation side outlet of the heat exchanger 12 and the suction section of the compressor 100 in order to bring the degree of superheat of the refrigerant sucked into the compressor 100 to a target value. The expansion valve 102 is configured to control the expansion valve 102 based on the output.

The control device 200 also controls the operating frequency f1 of the compressor 10 based on the output of the pressure sensor 17 provided in the suction section of the compressor 10 in order to set the evaporation temperature of the refrigerant circuit C1 to a target value. It is composed of

Further, the control device 200 controls the expansion valve 15 based on the output of the temperature sensor 18 provided in the suction section of the compressor 10 in order to bring the degree of superheat of the refrigerant sucked into the compressor 10 to a target value. configured.

Further, the control device 200 controls the operating frequency f2 of the compressor 100 based on the output of the pressure sensor 105 provided at the discharge part of the compressor 100 in order to set the condensing temperature of the refrigerant circuit C1 to a target value. It is composed of

In addition, the control device 200 controls the heat exchanger based on the output of a pressure sensor (not shown) disposed between the compressor 100 and the heat exchanger 101 in order to set the condensation temperature of the refrigerant circuit C2 to a target value. 101, the fan 101F is controlled.

By performing the above-described control, the control device 200 can maintain the refrigerant circuits C1 and C2 in a desired state.

The control device 200 includes a CPU (Central Processing Unit) 201, a memory 202 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown), and the like. The CPU 201 expands a program stored in the ROM to a RAM or the like and executes the program. The program stored in the ROM is a program in which the processing procedure of the control device 200 is written. The control device 200 executes control of each device in the binary refrigeration system according to these programs. This control is not limited to processing by software, but can also be performed by dedicated hardware (electronic circuit).

Note that the control device 200 may be distributed in the indoor unit 2 and the outdoor unit 1, and may be connected through communication.

As shown in FIG. 1, the binary refrigeration system 1000 of this embodiment includes a cooling device for cooling the first refrigerant between the compressor 10 and the heat exchanger 12 in the low-source refrigerant circuit C1. ing. Specifically, an intercooler 150, which is an air-cooled heat exchanger, is disposed as a cooling device to radiate heat from the first refrigerant in a superheated gas state. By providing the intercooler 150 and the fan 150F, a portion of the condensed heat on the low source side can be radiated to the atmosphere. Therefore, the amount of heat that needs to be processed in the refrigerant circuit C2 on the high-end side can be reduced, so the sizes of the compressor 100, heat exchanger 101, and heat exchanger 12 can be reduced, and power consumption can also be reduced. can.

Furthermore, the intercooler 150 may be a heat exchanger in which the heat exchanger 101 and the fin portion are integrated.

The control device 200 controls the fan 150F of the intercooler 150 based on the output of the temperature sensor 103 disposed between the compressor 100 and the heat exchanger 101 in order to set the discharge refrigerant temperature of the refrigerant circuit C2 to the target value. configured to control.

Furthermore, the heat exchanger 12 is configured so that the first refrigerant and the second refrigerant exchange heat in a parallel flow relationship. This suppresses an increase in the degree of superheating of the refrigerant sucked into the compressor 100, thereby suppressing an increase in the temperature of the refrigerant discharged. The difference in refrigerant temperature between counterflow and parallel flow will be explained below.

FIG. 2 is a diagram illustrating changes in refrigerant temperature when the cascade heat exchanger exchanges heat in a counterflow relationship. In FIG. 2, temperature T1 indicates the temperature of the first refrigerant on the low-temperature side, and temperature T2 indicates the temperature of the second refrigerant on the high-temperature side. Further, the vertical axis indicates the refrigerant temperature T, and the horizontal axis indicates the distance from the refrigerant inlet to the heat exchange position when considering the second refrigerant in the heat exchanger.

When the cascade heat exchanger has a counterflow relationship, the first refrigerant flows in the opposite direction to the second refrigerant, as shown by the arrows in FIG. Therefore, since the temperature difference Tw1 can be ensured regardless of the heat exchange position, counterflow generally has better heat exchange performance. However, since the first refrigerant on the low source side exchanges heat with the outlet section of the second refrigerant on the high source side when the temperature is high (at the refrigerant inlet), the degree of superheating SH2 of the suction refrigerant on the high source side increases. It ends up.

FIG. 3 is a diagram illustrating changes in refrigerant temperature when cascade heat exchangers exchange heat in a parallel flow relationship. In FIG. 3, temperature T1 indicates the temperature of the first refrigerant on the low-temperature side, and temperature T2 indicates the temperature of the second refrigerant on the high-temperature side. Further, the vertical axis indicates the refrigerant temperature T, and the horizontal axis indicates the distance from the refrigerant inlet to the heat exchange position when considering the second refrigerant in the heat exchanger.

When the cascade heat exchanger is in a parallel flow relationship, the first refrigerant flows in the same direction as the second refrigerant, as shown by the arrows in FIG. Therefore, the amount of heat exchanged is large at the inlet section where the temperature difference Tw2 is large, but the amount of heat exchanged is small at the outlet section because the temperature difference is small, so generally parallel flow has better heat exchange performance than counterflow. becomes worse.

However, in this embodiment, the heat exchanger 12 is configured to exchange heat in parallel flow. In the case of parallel flow, the first refrigerant on the low-temperature side exchanges heat with the outlet of the second refrigerant on the high-temperature side when the temperature is low (at the outlet of the refrigerant). The degree of superheating SH2 of the suction refrigerant on the high side is smaller than the degree of superheating SH2 in the case of counterflow shown in FIG.

Next, details of the control executed by the control device 200 in the first embodiment will be described.
FIG. 4 is a flowchart for explaining control of the compressor 100 on the high end side.

First, in step S11, the control device 200 uses the pressure sensor 105 to detect the pressure Ps2 of the low pressure section of the high-side refrigerant circuit C2. Subsequently, in step S12, the control device 200 compares the pressure Ps2 and the target pressure value Ps2*. If Ps2>Ps2* holds true (YES in S12), control device 200 reduces operating frequency f2 of compressor 100 in step S13. On the other hand, if Ps2>Ps2* does not hold (NO in S12), control device 200 increases operating frequency f2 of compressor 100 in step S14. By repeatedly performing this process at regular intervals, the pressure Ps2 in the low pressure section of the high-side refrigerant circuit C2 is maintained near the target value Ps2*.

FIG. 5 is a flowchart for explaining control of the expansion valve 102 on the high side.
First, in step S21, the control device 200 uses the pressure sensor 105 and the temperature sensor 106 to detect the degree of superheat SH2 of the refrigerant sucked into the high-end refrigerant circuit C2. For example, the saturation temperature corresponding to the pressure detected by the pressure sensor 105 is determined by referring to a saturation temperature table stored in advance, and the degree of superheating SH2 is obtained by calculating the difference between the temperature detected by the temperature sensor 106 and the saturation temperature. be able to.

Subsequently, in step S22, the control device 200 compares the degree of superheat SH2 and the target degree of superheat SH2*. If SH2>SH2* holds true (YES in S22), the control device 200 increases the opening degree of the expansion valve 102 in step S23. On the other hand, if SH2>SH2* does not hold (NO in S22), the control device 200 decreases the opening degree of the expansion valve 102 in step S24. By repeatedly performing this process at regular intervals, the degree of superheat SH2 of the refrigerant sucked into the high-end refrigerant circuit C2 is maintained near the target degree of superheat SH2*.

FIG. 6 is a flowchart for explaining the control of the compressor 10 on the low-power side.
First, in step S31, the control device 200 uses the pressure sensor 17 to detect the pressure Ps1 of the low pressure section of the low-source side refrigerant circuit C1. Subsequently, in step S32, the control device 200 compares the pressure Ps1 and the target pressure value Ps1*. If Ps1>Ps1* holds true (YES in S32), control device 200 reduces operating frequency f1 of compressor 100 in step S33. On the other hand, if Ps1>Ps1* does not hold (NO in S32), the control device 200 increases the operating frequency f1 of the compressor 100 in step S34. By repeatedly performing this process at regular intervals, the pressure Ps1 of the low pressure section of the low source side refrigerant circuit C1 is maintained near the target value Ps1*.

FIG. 7 is a flowchart for explaining control of the expansion valve 15 on the low base side.
First, in step S41, the control device 200 uses the pressure sensor 17 and the temperature sensor 18 to detect the degree of superheat SH1 of the refrigerant sucked into the low-source refrigerant circuit C1. For example, the saturation temperature corresponding to the pressure detected by the pressure sensor 17 is determined by referring to a saturation temperature table stored in advance, and the degree of superheating SH1 is obtained by calculating the difference between the temperature detected by the temperature sensor 18 and the saturation temperature. be able to.

Subsequently, in step S42, the control device 200 compares the degree of superheat SH1 and the target degree of superheat SH1*. If SH1>SH1* holds true (YES in S42), the control device 200 increases the opening degree of the expansion valve 15 in step S43. On the other hand, if SH1>SH1* does not hold (NO in S42), the control device 200 reduces the opening degree of the expansion valve 15 in step S44. By repeatedly performing this process at regular intervals, the degree of superheat SH1 of the refrigerant sucked into the low-source side refrigerant circuit C1 is maintained near the target degree of superheat SH1*.

FIG. 8 is a flowchart for explaining control of fan 150F of intercooler 150.

First, in step S51, the control device 200 uses the temperature sensor 103 to detect the discharge temperature Td2 of the refrigerant in the high-end refrigerant circuit C2. Subsequently, in step S52, the control device 200 compares the discharge temperature Td2 and the target discharge temperature Td2*. If Td2>Td2* holds true (YES in S52), control device 200 increases the rotational speed of fan 150F of intercooler 150 in step S53. This increases the amount of cooling of the first refrigerant in the intercooler 150. On the other hand, if Td2>Td2* does not hold (NO in S52), control device 200 reduces the rotation speed of fan 150F of intercooler 150 in step S54. By repeatedly performing this process at regular intervals, the discharge temperature Td2 of the refrigerant in the high-end refrigerant circuit C2 is maintained near the target discharge temperature Td2*.

As explained above, according to the binary refrigeration system 1000 of the first embodiment, the intercooler 150 is used as a cooling device. Therefore, part of the condensation heat on the low-source side can be radiated to the atmosphere. For this reason, it is possible to prevent the refrigerant temperature in the high-end refrigerant circuit C2 from increasing, so that the discharge temperature Td2 of the compressor 100 can be set around the target temperature Td2*, which is below the heat-resistant temperature. In addition, since the amount of heat that needs to be processed in the refrigerant circuit C2 on the high-end side can be reduced, the sizes of the compressor 100, heat exchanger 101, and heat exchanger 12 can be reduced, and power consumption can also be reduced. can.

Furthermore, since the heat exchanger 12, which is a cascade heat exchanger, is configured to exchange heat in parallel flow, it is possible to suppress an increase in the degree of superheat SH2 of the suction refrigerant.

Embodiment 2.
FIG. 9 is a diagram showing the configuration of a binary refrigeration system 2000 according to the second embodiment. A binary refrigeration system 2000 shown in FIG. 9 includes an outdoor unit 2001 installed outdoors and an indoor unit 2 installed inside the freezer. The indoor unit 2 is the same as in Embodiment 1, so the description will not be repeated.

Outdoor unit 2001 includes a refrigerant circuit C3 in place of intercooler 150 and fan 150F in the configuration of outdoor unit 1 in FIG. The other configuration of outdoor unit 2001 is the same as outdoor unit 1.

Refrigerant circuit C3 includes a compressor 300, a heat exchanger 301, a fan 301F, an expansion valve 302, a heat exchanger 312,

temperature sensors

303 and 306, and a pressure sensor 305.

Refrigerant circuit C3 uses the third refrigerant. The specific heat ratio of the second refrigerant is higher than the specific heat ratio of the first refrigerant. Further, the specific heat ratio of the third refrigerant is lower than the specific heat ratio of the second refrigerant circulating in the refrigerant circuit C2. As the first refrigerant, for example, CO ₂ or a mixed refrigerant containing CO ₂ can be used. As the second refrigerant circulating in the refrigerant circuit C2, for example, R32 or a mixed refrigerant containing R32 can be used. As the third refrigerant circulating in the refrigerant circuit C3, for example, a refrigerant containing any one of R32, R1234yf, R1234ze(E), R134a, and R290 can be used.

In the first embodiment, the intercooler 150 and the fan 150F cooled the first refrigerant circulating in the lower-side refrigerant circuit C1. In the third embodiment, the first refrigerant is cooled by a refrigerant circuit C3, which is a refrigeration cycle different from the high base cycle and the low base cycle, as a cooling device.

Next, details of the control executed by the control device 200 in the second embodiment will be described. Note that each control of the compressor 100 and expansion valve 102 on the high-end side and the compressor 10 and expansion valve 15 on the low-end side shown in FIGS. 4 to 7 is the same in the second embodiment, so the explanation will not be repeated. do not have.

FIG. 10 is a flowchart for explaining control of the expansion valve 302 of the refrigerant circuit C3.

First, in step S111, the control device 200 uses the pressure sensor 305 and the temperature sensor 306 to detect the degree of superheat SH3 of the refrigerant sucked into the refrigerant circuit C3. For example, the saturation temperature corresponding to the pressure detected by the pressure sensor 305 is determined by referring to a saturation temperature table stored in advance, and the degree of superheating SH3 is obtained by calculating the difference between the temperature detected by the temperature sensor 306 and the saturation temperature. be able to.

Subsequently, in step S112, the control device 200 compares the degree of superheat SH3 and the target degree of superheat SH3*. If SH3>SH3* holds true (YES in S112), control device 200 increases the opening degree of expansion valve 302 in step S113. On the other hand, if SH3>SH3* does not hold (NO in S112), the control device 200 decreases the opening degree of the expansion valve 302 in step S114. By repeatedly performing this process at regular intervals, the degree of superheat SH3 of the refrigerant sucked into the refrigerant circuit C3 is maintained near the target degree of superheat SH3*.

FIG. 11 is a flowchart for explaining the control of the compressor 300 of the refrigerant circuit C3.

First, in step S121, the control device 200 uses the temperature sensor 103 to detect the discharge temperature Td2 of the refrigerant in the high-side refrigerant circuit C2. Subsequently, in step S122, the control device 200 compares the discharge temperature Td2 and the target discharge temperature Td2*. If Td2>Td2* holds true (YES in S122), control device 200 increases operating frequency f3 of compressor 300 in step S123. This increases the amount of cooling of the first refrigerant in the heat exchanger 312 of the refrigerant circuit C3. On the other hand, if Td2>Td2* does not hold (NO in S122), control device 200 decreases operating frequency f3 of compressor 300 in step S124. By repeatedly performing this process at regular intervals, the discharge temperature Td2 of the refrigerant in the high-end refrigerant circuit C2 is maintained near the target discharge temperature Td2*.

As explained above, according to the binary refrigeration system 1000 of the second embodiment, the refrigerant circuit C3, which is a separate refrigeration cycle, is used as a cooling device. Therefore, a part of the condensed heat amount on the low-source side can be radiated to the atmosphere through the third refrigerant. Therefore, the amount of heat exchanged in the heat exchanger 12 can be reduced, and an increase in the refrigerant temperature in the high-end refrigerant circuit C2 can be prevented. The temperature can be set to an appropriate temperature around Td2*. In addition, since the amount of heat that needs to be processed in the refrigerant circuit C2 on the high-end side can be reduced, the sizes of the compressor 100, heat exchanger 101, and heat exchanger 12 can be reduced, and power consumption can also be reduced. can.

Furthermore, since the heat exchanger 12, which is a cascade heat exchanger, is configured to exchange heat in parallel flow, it is possible to suppress an increase in the degree of superheating SH2 of the suction refrigerant.

In Embodiment 3, the heat exchanger 312, which is a similar cascade heat exchanger, may also exchange heat in parallel flows, but the heat exchange efficiency is higher than that in counter-flows as shown in FIG. is more preferable because it increases.

(summary)
The present embodiment will be summarized below with reference to the drawings again.

(1) The present disclosure relates to a binary refrigeration system that cools the inside of a freezer using a first refrigerant and a second refrigerant having a lower specific heat ratio than the first refrigerant. The

binary refrigeration apparatuses

1000, 2000 shown in FIGS. 1 and 9 include a first compressor 10, a first heat exchanger 12, a first expansion valve 15, a second heat exchanger 16, a second compressor 100, a third A heat exchanger 101 and a second expansion valve 102 are provided. The first heat exchanger 12 is configured to exchange heat between the first refrigerant and the second refrigerant. The second heat exchanger 16 is configured to exchange heat between the first refrigerant and the air within the freezer. The third heat exchanger 101 is configured to exchange heat between the second refrigerant and the air outside the freezer. The first compressor 10, the first heat exchanger 12, the first expansion valve 15, and the second heat exchanger 16 constitute a first refrigerant circuit C1 in which the first refrigerant circulates. The second compressor 100, the third heat exchanger 101, the second expansion valve 102, and the first heat exchanger 12 constitute a second refrigerant circuit C2 in which the second refrigerant circulates. The

binary refrigeration apparatuses

1000 and 2000 further include a cooling device (intercooler 150 or refrigerant circuit C3) configured to cool the first refrigerant flowing from the first compressor 10 to the first heat exchanger 12.

(2) In (1), the cooling device (intercooler 150) in FIG. 1 is configured to exchange heat between the air outside the freezer and the first refrigerant.

(3) In (1), the cooling device (refrigerant circuit C3) in FIG. a fourth heat exchanger 301 configured to exchange heat between and a fifth heat exchanger 312 configured to perform heat exchange between the third refrigerant and the first refrigerant.

(4) In (3), the specific heat ratio of the third refrigerant is lower than the specific heat ratio of the first refrigerant.
(5) In (4), the third refrigerant is a refrigerant containing any one of R32, R1234yf, R1234ze(E), R134a, and R290.

(6) In any one of (1) to (5), the first heat exchanger 12 is a cascade heat exchanger configured so that the first refrigerant and the second refrigerant pass in a parallel flow relationship. It is.

(7) In any one of (1) to (5), the first refrigerant is a refrigerant containing CO2.

(8) In any one of (1) to (5), the second refrigerant is a refrigerant containing R32.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments described above, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1,2001 Outdoor unit, 2 Indoor unit, 10,100,300 Compressor, 12,16,101,301,312 Heat exchanger, 15,102,302 Expansion valve, 16F, 101F, 150F, 301F Fan, 17, 105,305 Pressure sensor, 18,103,106,303,306 Temperature sensor, 150 Intercooler, 200 Control device, 201 CPU, 202 Memory, 1000,2000 Binary refrigeration system, C1, C2, C3 Refrigerant circuit.

Claims

A binary refrigeration device that cools the inside of a freezer using a first refrigerant and a second refrigerant having a lower specific heat ratio than the first refrigerant,
comprising a first compressor, a first heat exchanger, a first expansion valve, a second heat exchanger, a second compressor, a third heat exchanger, and a second expansion valve,
The first heat exchanger is configured to exchange heat between the first refrigerant and the second refrigerant,
The second heat exchanger is configured to exchange heat between the first refrigerant and air in the freezer,
The third heat exchanger is configured to exchange heat between the second refrigerant and air outside the freezer,
The first compressor, the first heat exchanger, the first expansion valve, and the second heat exchanger constitute a first refrigerant circuit in which the first refrigerant circulates,
The second compressor, the third heat exchanger, the second expansion valve, and the first heat exchanger constitute a second refrigerant circuit in which the second refrigerant circulates,
The dual refrigeration device includes:
A dual refrigeration system further comprising a cooling device configured to cool the first refrigerant flowing from the first compressor to the first heat exchanger.
The binary refrigeration device according to claim 1, wherein the cooling device is configured to exchange heat between air outside the freezer and the first refrigerant.
The cooling device includes:
a third compressor that compresses a third refrigerant;
a fourth heat exchanger configured to exchange heat between the third refrigerant discharged from the third compressor and air outside the freezer;
a third expansion valve that reduces the pressure of the third refrigerant that has passed through the fourth heat exchanger;
The binary refrigeration system according to claim 1, further comprising a fifth heat exchanger configured to perform heat exchange between the third refrigerant and the first refrigerant that have passed through the third expansion valve. .
The binary refrigeration system according to claim 3, wherein the specific heat ratio of the third refrigerant is lower than the specific heat ratio of the first refrigerant.
The binary refrigeration system according to claim 4, wherein the third refrigerant is a refrigerant containing any one of R32, R1234yf, R1234ze(E), R134a, and R290.
The first heat exchanger is a cascade heat exchanger configured so that the first refrigerant and the second refrigerant pass in parallel flow relationship, according to any one of claims 1 to 5. dual refrigeration equipment.
The binary refrigeration apparatus according to any one of claims 1 to 5, wherein the first refrigerant is a refrigerant containing CO 2 .
The binary refrigeration apparatus according to any one of claims 1 to 5, wherein the second refrigerant is a refrigerant containing R32.