JP2011191032A - Compression refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce compression work done by a compressor and inexpensively improve efficiency of an refrigerating cycle. <P>SOLUTION: This compression refrigerating cycle is constituted by interconnecting an evaporator 1, the compressor 2, a condenser 3 and an expansion valve 4 via refrigerant piping 5. A cold taking-out pipe 6 is connected to the evaporator 1 to take out cold by evaporation latent heat in the evaporator 1. First and second adsorbers 8, 9 filled with an adsorbent are connected to a portion in the middle of the refrigerant piping 5 interconnecting the compressor 2 to the condenser 3, via a four-way change-over valve 7 as a switching means. Hot water piping 10 is connected to the first and second adsorbers 8, 9 and adsorbed refrigerant gas is desorbed by heating. Thus, refrigerant gas compressed by the compressor 2 is adsorbed by the first adsorber 8 and the pressure of the refrigerant gas on the outlet side of the compressor 2 is reduced. In the second adsorber 9, the adsorbed refrigerant gas is heated for desorption and is supplied to the condenser 3. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention includes an evaporator for evaporating a refrigerant liquid, a compressor for compressing a refrigerant gas evaporated by the evaporator, a condenser for condensing and liquefying the refrigerant gas compressed by the compressor, and the condenser. A low-temperature and low-pressure mechanism that lowers the temperature of the liquefied refrigerant liquid at low temperatures and low pressures. The present invention relates to a compression refrigeration cycle configured to take out cold heat due to latent heat of vaporization in a vessel.

  Conventionally, this type of compression refrigeration cycle is configured by connecting a heat source side heat exchanger functioning as a compressor and a condenser, a decompression mechanism, and a use side heat exchanger functioning as an evaporator through a flow path. Yes. Then, the high-temperature / high-pressure refrigerant vapor compressed by the compressor is introduced into the heat source side heat exchanger (condenser), where it is converted into a liquid refrigerant, and the liquid refrigerant is depressurized by the decompression mechanism, The refrigerant is introduced into a use side heat exchanger (evaporator), where it evaporates into a low-temperature / low-pressure refrigerant vapor, which is then sucked into the compressor to form a compression refrigeration cycle.

In addition, an absorption refrigeration system evaporator was interposed in the flow path connecting the condenser and the decompression mechanism, and liquid refrigerant introduced into the use side heat exchanger (evaporator) was generated in the absorption refrigeration system. Supercooled with cold heat.
The absorption refrigeration system includes a generator, a condenser, an evaporator, an absorber, a solution pump, and a solution heat exchanger.
This absorption refrigeration system is configured by a heat drive system that is driven by heating a generator. (See Patent Document 1 and FIG. 1).

Japanese Patent Laid-Open No. 11-223412

According to the above-described conventional example, it is possible to increase the refrigeration capacity and improve the efficiency of the refrigeration cycle by supercooling the condensed liquid refrigerant than in the case of the normal compression refrigeration cycle.
That is, the compression process (A → B), the condensation process (B → C), the adiabatic expansion process (C → D), and the evaporation process (D → A) shown in the normal compression refrigeration cycle diagram of FIG. ), The condensing step is increased by (C → C ′) (B → C ′) as shown in the compression refrigeration cycle diagram in FIG. You can increase your ability.

However, in the above-described conventional example, a separate new refrigeration system is required to obtain cold heat for cooling the refrigerant in the compression refrigeration cycle. In the absorption refrigeration system, a generator, a condenser, an evaporator, and an absorber In addition, a solution pump, a solution heat exchanger, and the like are required, the structure of the entire apparatus constituting the compression refrigeration cycle is complicated, and there is a disadvantage that the cost is higher than the effect of improving the efficiency of the refrigeration cycle.
In addition, an adsorption refrigeration system may be used to obtain cold heat for cooling the refrigerant in the compression refrigeration cycle. However, as in the case of the absorption refrigeration system, the structure of the entire equipment constituting the compression refrigeration cycle is complicated. Therefore, there is a disadvantage that the cost is higher than the effect of improving the efficiency of the refrigeration cycle.

  The present invention has been made in view of such circumstances, and the invention according to claim 1 is to reduce the compression work of the compressor and to improve the efficiency of the refrigeration cycle at a low cost. Therefore, the invention according to claim 2 aims to make it possible to efficiently reduce the compression work of the compressor, and the invention according to claim 3 makes it possible to further reduce the compression work of the compressor. Accordingly, an object of the present invention is to improve the efficiency of the refrigeration cycle at a lower cost.

In order to achieve the above-described object, the invention according to claim 1
An evaporator for evaporating the refrigerant liquid;
A compressor for compressing the refrigerant gas vaporized in the evaporator;
A condenser for condensing and liquefying the refrigerant gas compressed by the compressor;
A low-temperature and low-pressure mechanism for reducing the temperature and pressure of the refrigerant liquid liquefied by the condenser,
The evaporator, the compressor, the condenser, and the low-temperature and low-pressure mechanism are connected via a refrigerant pipe so that the refrigerant flows in that order, and the cooling heat due to latent heat of evaporation in the evaporator is taken out. In the compression refrigeration cycle, the refrigerant pipe connecting the compressor and the condenser receives the high-temperature and high-pressure refrigerant gas compressed by the compressor by adsorption or absorption, and the pressure of the refrigerant gas on the outlet side of the compressor A pressure reducing means for reducing the pressure is provided.

(Action / Effect)
According to the configuration of the compression refrigeration cycle of the invention according to claim 1, the pressure reducing means accepts the high-temperature and high-pressure refrigerant gas compressed by the compressor by adsorption or absorption, and the refrigerant gas pressure on the outlet side of the compressor Can be reduced.
Therefore, it is possible to reduce the compression work of the compressor by reducing the pressure of the refrigerant gas on the outlet side of the compressor while only providing a pressure reducing means for receiving the refrigerant gas by adsorption or absorption. Compressed refrigeration compared to the case where an absorption refrigeration system that requires generators, condensers, evaporators, absorbers, solution pumps, solution heat exchangers, etc. is provided to obtain cold heat that supercools the liquid refrigerant. The structure of the entire equipment constituting the cycle can be simplified, and the efficiency of the refrigeration cycle can be reduced and improved.

In order to achieve the above-described object, the invention according to claim 2
In the compression refrigeration cycle according to claim 1,
Pressure drop means,
A plurality of containers containing pressure reducing agents for reducing the pressure of the refrigerant gas are connected in parallel to the refrigerant pipe, and the state is switched between accepting the refrigerant gas from the compressor and discharging the accepted refrigerant gas to the condenser side. It comprises a switching means.

(Action / Effect)
According to the configuration of the compression refrigeration cycle of the invention according to claim 2, while the refrigerant gas from the compressor is received by one pressure reducing means, the refrigerant gas received by the other pressure reducing means is transferred to the condenser side. The refrigerant gas can be discharged and the pressure of the refrigerant gas on the outlet side of the compressor can be continuously reduced.
Therefore, the compression work of the compressor can be efficiently reduced and the efficiency of the refrigeration cycle can be further improved as compared with the case where the refrigerant gas is received into the pressure reduction means and the refrigerant gas is discharged from the pressure reduction means intermittently. Can be improved.

In order to achieve the above-described object, the invention according to claim 3
In the compression refrigeration cycle according to claim 1 or 2,
A cooling means for cooling the heat generated when the refrigerant gas is received is attached to the pressure lowering means.

(Action / Effect)
According to the configuration of the compression refrigeration cycle of the invention according to claim 3, it is possible to cool the heat generated by the pressure reducing means and enhance the pressure reducing performance of the pressure reducing means.
Therefore, since the pressure of the refrigerant gas at the outlet side of the compressor can be reduced more favorably, the compression work of the compressor can be further reduced, and the efficiency of the refrigeration cycle can be further improved.

In order to achieve the above-described object, the invention according to claim 4
In the compression refrigeration cycle according to any one of claims 1, 2, and 3,
With an engine that drives the compressor,
When the refrigerant gas is discharged, the pressure lowering means is provided with a heating means for heating with exhaust heat from the engine.

(Action / Effect)
According to the configuration of the compression refrigeration cycle of the invention according to claim 4, the refrigerant gas can be discharged from the pressure reducing means by the exhaust heat from the engine that drives the compressor.
Therefore, since the exhaust heat from the engine that drives the compressor is used for the discharge of the refrigerant gas from the pressure reducing means, it is not necessary to provide another heat source for heating, and the efficiency of the refrigeration cycle is further improved at a lower cost. it can.

As the pressure lowering means applied in the present invention, a configuration for adsorbing refrigerant gas using an adsorbent as a pressure reducing agent and a configuration for absorbing refrigerant gas using an absorbent as a pressure lowering agent can be adopted.
As the adsorbent, any one of activated carbon, synthetic zeolite, silica gel, or a combination thereof can be used, and as the absorbent, either tetraethylene glycol dimethyl ether or water can be used.

Further, as the refrigerant used in the compression refrigeration cycle of the present invention, any of hydrofluorocarbon (HFC), ammonia (NH ₃ ), hydrofluoroolefin (HFO), carbon dioxide (CO ₂ ), and isobutane can be used (invoice) Item 6).

According to the compression refrigeration cycle of the first aspect of the invention, the pressure reducing means accepts the high-temperature and high-pressure refrigerant gas compressed by the compressor by adsorption or absorption, and reduces the pressure of the refrigerant gas on the outlet side of the compressor. can do.
Therefore, it is possible to reduce the compression work of the compressor by reducing the pressure of the refrigerant gas on the outlet side of the compressor while only providing a pressure reducing means for receiving the refrigerant gas by adsorption or absorption. Compressed refrigeration compared to the case where an absorption refrigeration system that requires generators, condensers, evaporators, absorbers, solution pumps, solution heat exchangers, etc. is provided to obtain cold heat that supercools the liquid refrigerant. The structure of the entire equipment constituting the cycle can be simplified, and the efficiency of the refrigeration cycle can be reduced and improved.

It is a whole schematic block diagram which shows Example 1 of the compression refrigeration cycle which concerns on this invention. It is a compression refrigeration cycle diagram of the present invention. It is a whole schematic block diagram which shows Example 2 of the compression refrigeration cycle which concerns on this invention. It is a whole schematic block diagram which shows Example 3 of the compression refrigeration cycle which concerns on this invention. (A) is a normal compression refrigeration cycle figure, (b) is a compression refrigeration cycle figure which performs the supercooling of a prior art example.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an overall schematic configuration diagram showing a first embodiment of a compression refrigeration cycle according to the present invention, in which hydrofluorocarbon (HFC) is used as a refrigerant, and an evaporator 1 that evaporates and evaporates a refrigerant liquid. The compressor 2 that compresses the refrigerant gas, the condenser 3 that condenses and liquefies the refrigerant gas compressed by the compressor 2, and the expansion as a low-temperature and low-pressure mechanism that lowers the temperature of the refrigerant liquid liquefied by the condenser 3 The evaporator 1, the compressor 2, the condenser 3, and the expansion valve 4 are connected via a refrigerant pipe 5 so that the refrigerant flows in that order, thereby forming a compression refrigeration cycle.
As the low temperature / low pressure mechanism, a capillary tube or the like may be used instead of the expansion valve 4.
The evaporator 1 is connected to a cold heat extraction pipe 6, and is configured to extract cold heat for cooling, refrigeration, freezing, and the like by latent heat of vaporization in the evaporator 1.

First and second adsorbers 8 and 9 are connected in parallel through a four-way switching valve 7 as a switching means at a midpoint of the refrigerant pipe 5 that connects the compressor 2 and the condenser 3.
Each of the first and second adsorbers 8 and 9 is configured by filling activated carbon as an adsorbent in a container.
The first and second adsorbers 8 and 9 utilize engine exhaust heat (exhaust heat from engine cooling water or secondary use heat from combustion exhaust gas), solar heat, combustion exhaust heat from a waste disposal device, and the like. A hot water pipe 10 for supplying the hot water obtained in this way is connected, and the refrigerant gas adsorbed by the first and second adsorbers 8 and 9 is desorbed by heating.

With the above configuration, the four-way switching valve 7 is switched, and the first adsorber 8 is connected to the compressor 2 side and the second adsorber 9 is connected to the condenser 3 side, as indicated by the solid line. The refrigerant gas compressed in step 1 is adsorbed by the first adsorber 8 to reduce the pressure of the refrigerant gas on the outlet side of the compressor 2, while in the second adsorber 9, the refrigerant adsorbed there The gas is heated and desorbed, and can be supplied to the condenser 3.
For example, after a predetermined time such as 2 to 3 minutes set by a timer or the like has elapsed, the four-way switching valve 7 is switched, and the first adsorber 8 is placed on the condenser 3 side as shown by the broken line, and the second adsorption is performed. The compressor 9 is connected to the compressor 2 side, and the refrigerant gas compressed by the compressor 2 is adsorbed by the second adsorber 9 to reduce the pressure of the refrigerant gas on the outlet side of the compressor 2. In the first adsorber 8, the refrigerant gas adsorbed thereon can be heated and desorbed and supplied to the condenser 3. By alternately repeating the above operation, the refrigerant gas can be continuously adsorbed and desorbed.

  As a result of the above processing, the refrigerant gas compressed by the compressor 2 is adsorbed by the first adsorber 8 or the second adsorber 9 as shown in the compression refrigeration cycle diagram of the present invention in FIG. The pressure of the refrigerant gas at the outlet side of the machine 2 is reduced, the compression work of the compressor 2 is reduced (the reduced work is indicated by W), and the efficiency of the refrigeration cycle can be improved.

FIG. 3 is an overall schematic configuration diagram showing a second embodiment of the compression refrigeration cycle according to the present invention. The differences from the first embodiment are as follows.
That is, an engine 11 is linked and connected to the compressor 2, and a cooling water supply is provided to the engine 11 through a heat-dissipating heat exchanger 12 and a cooling water pump 13 for cooling the water flowing inside through heat exchange with the outside air. A pipe 14 is connected, and a cooling water discharge pipe 15 for taking out high-temperature cooling water after engine cooling is connected.

A cooling water discharge pipe 15 is connected to one end of each hot water pipe 10 of each of the first and second adsorbers 8 and 9 via a two-way valve 16 and a first intermediate pipe 17. A cooling water supply pipe 14 is connected to the other end side via a second intermediate pipe 18.
The two-way valve 16 and the four-way switching valve 7 supply high-temperature cooling water after engine cooling to the adsorber (the second adsorber 9 in FIG. 3) on the side where the refrigerant gas from the compressor 2 is not supplied. It is configured to be switched in conjunction with the supply.

With the above configuration, the first adsorber is configured to supply the high-temperature cooling water after engine cooling to either the first adsorber 8 or the second adsorber 9, that is, using engine exhaust heat. The refrigerant gas adsorbed by the 8 or the second adsorber 9 can be desorbed. Other configurations are the same as those of the first embodiment, and the description thereof is omitted by giving the same numbers.
One end side of the hot water pipe 10 for supplying the engine exhaust heat described above to either the first adsorber 8 or the second adsorber 9 is provided via a two-way valve 16 and a first intermediate pipe 17. The cooling water discharge pipe 15 is connected and the cooling water supply pipe 14 is connected to the other end side of the hot water pipe 10 via the second intermediate pipe 18 and is referred to as a heating means.

FIG. 4 is an overall schematic configuration diagram showing a third embodiment of the compression refrigeration cycle according to the present invention. The differences from the second embodiment are as follows.
That is, the adsorbent side heat-dissipating heat exchanger 21 is provided so as to cool using the cool air from the cooling fan 3a of the condenser 3, and the adsorbent-side heat dissipating heat exchanger 21 is provided with one of the adsorbent side heat dissipating heat exchangers 21. An adsorbent cooling water supply pipe 23 having a water pump 22 interposed therebetween is connected to the other adsorbent cooling water return pipe 24.

The first intermediate pipes 17, 17 are connected to the cooling water discharge pipe 15 and the adsorbent cooling water return pipe 24 via the first four-way switching valve 25, and the second intermediate pipes 18, 18 are cooled. The water supply pipe 14 and the adsorbent coolant supply pipe 23 are connected via a second four-way switching valve 26.
The four-way switching valve 7 and the first and second four-way switching valves 25 and 26 are adsorbers on the side to which the refrigerant gas is supplied from the compressor 2 (the first adsorber 8 in FIG. 4). The adsorber on the side to which the refrigerant gas from the compressor 2 is not supplied while the cooling water cooled by the adsorbent side heat radiating heat exchanger 21 (with a temperature of about 40 ° C., for example) is supplied to In FIG. 4, the second adsorber 9) is configured to be switched in conjunction so as to supply the high-temperature cooling water after engine cooling. Other configurations are the same as those of the second embodiment, and the description thereof is omitted by assigning the same numbers.

  The adsorbent side heat radiation heat exchanger 21, the adsorbent cooling water pump 22, and the adsorbent cooling water supply pipe 23 for cooling the adsorber on the side supplied with the refrigerant gas from the compressor 2 described above. The adsorbent coolant return pipe 24 and the first and second four-way switching valves 25 and 26 are referred to as cooling means.

Next, the effect | action by the said structure is demonstrated, using an example of a specific numerical value.
Cold heat is extracted using the latent heat of vaporization of the refrigerant in the evaporator 1, and refrigerant gas (temperature 5 ° C., pressure 0.9 MPa) evaporated in the evaporator 1 is sucked into the compressor 2.
The refrigerant gas is adiabatically compressed by the compressor 2 to become a high-pressure gas having a temperature of about 70 ° C. and a pressure of 2.8 MPa. The refrigerant gas from the compressor 2 is supplied to the first adsorber 8 and is adsorbed by the adsorbent. At this time, the adsorbent generates heat, but is cooled by the cooling water cooled by the adsorbent-side heat-dissipating heat exchanger 21, so that the adsorbent adsorbs the refrigerant gas until it reaches a specific equilibrium pressure and equilibrium temperature. In Example 3, the equilibrium pressure is 2 MPa and the equilibrium temperature is about 50 ° C.

When the refrigerant gas is adsorbed and the refrigerant gas adsorption capacity is reduced, the four-way switching valve 7 and the first and second four-way switching valves 25 and 26 are switched, and the first adsorber 8 is switched to the condenser 3. In addition to being connected, engine cooling water (temperature of about 80 ° C.) after engine cooling is supplied to the first adsorber 8, the adsorbent of the first adsorber 8 is heated, and the adsorbed refrigerant gas is desorbed Is done. At this time, the second adsorber 9 is switched to the adsorbing state, and the refrigerant gas from the compressor 2 is adsorbed by the adsorbent of the second adsorber 9.
Switching between the four-way switching valve 7 and the first and second four-way switching valves 25 and 26 is performed approximately every 2 to 3 minutes.
The refrigerant gas (temperature about 60 ° C., pressure 2.8 MPa) desorbed by the first adsorber 8 is condensed and liquefied by the condenser 3 to become a refrigerant liquid having a temperature of 45 ° C. and a pressure of 2.8 MPa.

  With the above configuration, since the adsorbent of the first adsorber 8 or the second adsorber 9 adsorbs the refrigerant gas from the compressor 2, the pressure of the refrigerant gas at the outlet of the compressor 2 can be reduced. The compression work of the compressor 2 can be reduced and the efficiency of the compression refrigeration cycle can be improved.

In the above embodiment, two adsorbers are provided. For example, a partition is provided at the center of one container, adsorbents are filled on both sides of the partition, and the adsorption position and desorption regeneration are performed by rotation. A so-called desiccant type may be used which is alternately changed to the position.
Further, it may be configured with three or more absorbers. The adsorber has the largest adsorption amount at the start of adsorption, and the adsorption amount gradually decreases as the adsorption progresses. There exists an advantage which can improve the pressure fall performance of the refrigerant gas in 2 exits.

  Moreover, in the said Example, although comprised so that the refrigerant gas from the compressor 2 may be adsorbed using the 1st and 2nd adsorbers 8 and 9 which filled the container with the adsorbent, You may use the accommodated absorber, and it has the structure which adsorb | sucks or absorbs the refrigerant gas from those compressors 2, and is named a pressure reduction means generically.

In the above embodiment, hydrofluorocarbon (HFC) is used as the refrigerant and activated carbon is used as the adsorbent of the adsorber, but various refrigerants, adsorbents and absorbents can be used. And it lists about each combination of a refrigerant | coolant and an absorber. When there are a plurality of adsorbents and absorbents, they are listed in order of performance.
(A) Combination example of refrigerant and adsorbent A1. Refrigerant: Hydrofluorocarbon (HFC)
Adsorbent: Activated carbon
: Honeycomb activated carbon
: Carbon dioxide treated activated carbon
: Activated carbon treated with steam
: Carbon gel fine particles
: Mesoporous silica A2. Refrigerant: Ammonia (NH ₃ )
Adsorbent: Synthetic zeolite
: Activated carbon
: Silica gel A3. Refrigerant: Hydrofluoroolefin, Hypozinc fluoric acid (HFO)
Adsorbent: Activated carbon
: Honeycomb activated carbon
: Carbon dioxide treated activated carbon
: Activated carbon treated with steam
: Carbon gel fine particles
: Mesoporous silica A4. Refrigerant: Carbon dioxide (CO ₂ )
Adsorbent: Activated carbon
: Synthetic zeolite
: Silica gel A5. Refrigerant: Isobutane Adsorbent: Activated carbon
: Synthetic zeolite
: Example of combination of silica gel (B) refrigerant and absorbent B1. Refrigerant: Hydrofluorocarbon (HFC)
Absorbent: Tetraethylene glycol dimethyl ether
: Dimethylformamide
: Dibutyl phthalate ester B2. Refrigerant: Ammonia (NH ₃ )
Absorbent: Water B3. Refrigerant: Hydrofluoroolefin, Hypozinc fluoric acid (HFO)
Absorbent: Tetraethylene glycol dimethyl ether B4. Refrigerant: Carbon dioxide (CO ₂ )
Absorbent: water

1 ... Evaporator
2 ... Compressor
3 ... Condenser
4. Expansion valve (low temperature and low pressure mechanism)
5 ... Refrigerant piping
7. Four-way switching valve (switching means)
8: First adsorber (pressure reduction means)
9: Second adsorber (pressure reduction means)
11 ... Engine 16 ... Two-way valve (heating means)
17 ... 1st middle (heating means)
18 ... second intermediate (heating means)
21 ... Adsorbent side heat dissipation heat exchanger (cooling means)
22 ... Cooling water pump for adsorbent (cooling means)
23 ... Adsorbent cooling water supply pipe (cooling means)
24 ... Coolant return pipe for adsorbent (cooling means)
25. First four-way switching valve (cooling means)
26: Second four-way switching valve (cooling means)

Claims (6)

An evaporator for evaporating the refrigerant liquid;
A compressor for compressing the refrigerant gas vaporized in the evaporator;
A condenser for condensing and liquefying the refrigerant gas compressed by the compressor;
A low-temperature and low-pressure mechanism for reducing the temperature and pressure of the refrigerant liquid liquefied by the condenser,
The evaporator, the compressor, the condenser, and the low-temperature and low-pressure mechanism are connected via a refrigerant pipe so that the refrigerant flows in that order, and the cooling heat due to latent heat of evaporation in the evaporator is taken out. In the compression refrigeration cycle, the refrigerant pipe connecting the compressor and the condenser receives the high-temperature and high-pressure refrigerant gas compressed by the compressor by adsorption or absorption, and the pressure of the refrigerant gas on the outlet side of the compressor A compression refrigeration cycle, characterized in that pressure reducing means for reducing the pressure is provided. In the compression refrigeration cycle according to claim 1,
Pressure drop means
A plurality of containers containing pressure reducing agents for reducing the pressure of the refrigerant gas are connected in parallel to the refrigerant pipe, and the state is switched between accepting the refrigerant gas from the compressor and discharging the accepted refrigerant gas to the condenser side. A compression refrigeration cycle comprising switching means. In the compression refrigeration cycle according to claim 1 or 2,
A compression refrigeration cycle in which a cooling means for cooling heat generated upon reception of refrigerant gas is attached to the pressure lowering means. In the compression refrigeration cycle according to any one of claims 1, 2, and 3,
With an engine that drives the compressor,
A compression refrigeration cycle in which heating means for heating with exhaust heat from the engine is attached to the pressure lowering means when the refrigerant gas is discharged. In the compression refrigeration cycle according to any one of claims 1, 2, 3, and 4,
A compression refrigeration cycle in which the pressure reducing agent is one of activated carbon, synthetic zeolite, silica gel, tetraethylene glycol dimethyl ether, water, or a plurality thereof. In the compression refrigeration cycle according to any one of claims 1, 2, 3, 4, and 5,
A compression refrigeration cycle in which the refrigerant is any one of hydrofluorocarbon (HFC), ammonia (NH ₃ ), hydrofluoroolefin (HFO), carbon dioxide (CO ₂ ), and isobutane.

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