KR20060064344A - Refrigeration apparatus using carbon dioxide mixed refrigerant - Google Patents

Abstract

The present invention relates to a refrigerating apparatus using a carbon dioxide mixed refrigerant, and relatively comprising an intermediate cooler separating the mixed refrigerant passed through the compressor and the condenser into an auxiliary refrigerant and a carbon dioxide refrigerant, and liquefying the carbon dioxide refrigerant using the separated auxiliary refrigerant. It is an object of the present invention to provide a refrigeration apparatus that can achieve a low temperature freezing effect of below 50 ° C by using a low compression ratio compressor.

In order to achieve the above object, a refrigeration apparatus using a carbon dioxide mixed refrigerant according to the present invention is a refrigeration apparatus including a compressor, a condenser, an expansion valve, and an evaporator, and is provided between the condenser and the expansion valve, The mixed refrigerant in which carbon dioxide and auxiliary refrigerant are mixed is separated into gaseous carbon dioxide and mainly liquid state auxiliary refrigerant using the difference in specific gravity, and the separated carbon dioxide is liquefied using the separated auxiliary refrigerant to form the expansion valve. It includes an intermediate cooler to supply.

Refrigeration Units, Intercoolers, Carbon Dioxide, HCFCs, R-141b, Steam Compression Refrigeration Cycles

Description

Refrigerator using mixed refrigerant with carbon dioxide             

1 is a schematic diagram showing a first embodiment of the present invention having an intermediate cooler.

Figure 2 is a schematic diagram showing a second embodiment of the present invention having two intermediate coolers arranged in series.

3 is a temperature-pressure state diagram of carbon dioxide.

Fig. 4 is a schematic Molier diagram showing a refrigeration cycle according to the second embodiment.

Figure 5 is a schematic diagram showing a conventional single refrigerant circulation refrigeration apparatus.

Figure 6 is a schematic diagram showing a conventional binary refrigeration apparatus.

10,11,12: intermediate chiller 20,21,22: mixed refrigerant separator

30, 31, 32: intermediate heat exchanger 40, 41, 42: auxiliary expansion valve

201,211,221: Upper refrigerant pipe 204,214,224: Lower refrigerant pipe

202, 212, 222: refrigerant delivery pipe 300, 310, 320: evaporation unit

The present invention relates to a refrigerating apparatus using a carbon dioxide mixed refrigerant, and more particularly, an intermediate cooler for separating a mixed refrigerant passed through a compressor and a condenser into an auxiliary refrigerant and a carbon dioxide refrigerant, and liquefying the carbon dioxide refrigerant using the separated auxiliary refrigerant. The present invention relates to a refrigerating device that can obtain a low temperature freezing effect of below 50 ° C by using a compressor having a relatively low compression ratio.

Generally, a refrigerating device refers to a device that performs mechanical work or absorbs heat to freeze the temperature in a closed container below the temperature around it.

A working fluid that transfers heat to a high temperature surrounding in an airtight container of a low temperature freezing device, and a heat transfer fluid is called a refrigerant. Freon has been used as a refrigerant until recently, but the development of substitutes has been made due to the ozone depletion problem, and some of them have already been used. The principle of the refrigerating device is to use a phenomenon in which these easy-to-vaporize refrigerants are used as liquids and take away the heat of vaporization from the surroundings when they vaporize.

The most widely used freezer is a vapor compression freezer, which is composed of a compressor, a condenser, an expansion valve, and an evaporator, as shown in FIG. The compressor is operated by an electric motor to compress a gaseous refrigerant and send it to a condenser, which is cooled by liquefied water or air outside the refrigerator. When the liquid refrigerant is decompressed while being injected into the evaporator while the flow rate is adjusted in the expansion valve, it expands and vaporizes, absorbs heat from the vicinity of the evaporator, and cools the inside of the container. The gaseous refrigerant is then returned to the compressor and compressed to a liquid state. This repeated four-step change of compression, condensation, expansion, and vaporization is called the refrigeration cycle.

However, there are various problems in obtaining a low temperature freezing effect of about -50 ° C to -60 ° C with a general vapor compression freezer.

As shown in FIG. 5, when a single refrigerant circulation cycle is used, the refrigerant pressure in the high pressure portion is excessively high, which leads to many constraints on the manufacture of parts, and the compression ratio of the refrigerant in the compressor must be very large. A device using a two-stage compressor has been proposed to increase the compression ratio, but in addition to the need for two compressors, there is a problem in that energy consumption is high.

In order to improve the energy efficiency of the low temperature freezer, a binary freezer is used, the schematic configuration of which is shown in FIG. The binary refrigeration apparatus includes a heat exchanger configured as a first refrigerant having excellent high temperature characteristics and a second refrigerant having excellent low temperature characteristics, and serving as an evaporator of the first refrigerant circuit and a condenser of the second refrigerant circuit. That is, it has a structure which takes away heat from a 2nd refrigerant | coolant and condenses as a 1st refrigerant | vaporizes. The dual refrigeration unit can reduce the energy consumption in the compressor through this configuration, but there is a problem such as a two-stage compression refrigeration unit in that two compressors are required, and the configuration of the apparatus is complicated.

In addition, since it has been found that Freon (CFC) gas, which has conventionally been mainly used as a refrigerant such as a refrigerator, is a substance that destroys the ozone layer, regulations on this have been gradually tightened. The Montreal Protocol on Substances that Deplete the Ozone Layer in September 1987 froze production and consumption as of 1986, and reduced 20 percent in one year from July 1993 to 1986. It also supplemented the Montreal Protocol in London in 1990 to reduce 50% by 1995, 85% by 1997, and completely ban production by 2000. In addition, CCl ₃ CH _{3, which} has low destructive power, will be eliminated by 2005, and HCFC, which is a substitute, will be eliminated by 2040.

Therefore, the development of a refrigeration apparatus that can use natural refrigerants such as carbon dioxide, hydrocarbons, ammonia, water and air is required to prevent the ozone layer destruction and to satisfy environmental regulations. Among the natural refrigerants, carbon dioxide has received the most attention as a refrigerant for a low temperature freezer. However, when the carbon dioxide refrigerant is used in the existing refrigerating device, the pressure difference between the low pressure side and the high pressure side is increased, and a high compression ratio is required, and the high pressure side pressure is excessively high.

The use of a dual freezer can overcome the problems caused by pressure, but as mentioned above, the problem of complicated and enlarged devices is inevitable. Therefore, there is a need for a refrigeration apparatus that can be operated at a relatively low compression ratio through a one-way refrigeration cycle while enabling low temperature refrigeration using a carbon dioxide refrigerant.

In order to solve the above problems, the present invention provides a relatively low compression ratio by separating the mixed refrigerant passing through the compressor and the condenser into an auxiliary refrigerant and a carbon dioxide refrigerant, and an intermediate cooler for liquefying the carbon dioxide refrigerant using the separated auxiliary refrigerant. It is an object of the present invention to provide a refrigeration apparatus that can achieve a low temperature freezing effect of below 50 ° C by using a compressor.

In order to achieve the object of the present invention, a refrigeration apparatus using a carbon dioxide mixed refrigerant according to the present invention comprises a refrigerant circuit including a compressor, a condenser, an expansion valve, and an evaporator, and is provided between the condenser and the expansion valve. The mixed refrigerant in which carbon dioxide and auxiliary refrigerant are mixed is separated into a carbon dioxide mainly in a gas state and an auxiliary refrigerant mainly in a liquid state by using a difference in specific gravity, and the separated carbon dioxide is liquefied by using the separated auxiliary refrigerant. An intermediate cooler for supplying the expansion valve.

The auxiliary refrigerant is liquefied at the same temperature as the surroundings of the condenser with respect to the pressure condition of the condenser outlet, and can be cooled to a temperature at which the carbon dioxide is liquefied in the intermediate cooler as the liquid pressure is lowered. It may be selected from HCFC series refrigerants such as R-141b, R-142b, HCFC-124, and HFC series refrigerants such as HFC-125. However, if the ozone layer destruction or environmental problems are not taken into consideration, it may be selected from among CFC (freon) series refrigerants.

The refrigeration apparatus according to the present invention may ideally have one intermediate cooler, or may have a structure in which two or more intermediate coolers are connected in series.

The intermediate cooler takes advantage of the fact that the carbon dioxide mixed refrigerant is discharged from the compressor at a high temperature and high pressure, and the auxiliary refrigerant is first liquefied at room temperature while passing through the condenser. First, the liquefied auxiliary refrigerant is separated by using the specific gravity difference, and the carbon dioxide is cooled and liquefied on the principle of taking the heat of evaporation from the carbon dioxide by spraying it around the carbon dioxide refrigerant delivery pipe in a reduced pressure state through an expansion valve. In the case where the two intermediate coolers are connected in series, the carbon dioxide mixture refrigerant separated and cooled first is secondarily separated to increase the purity of carbon dioxide, and the second pure refrigerant is cooled again to liquefy by cooling the high purity carbon dioxide refrigerant. do.

When the liquefied refrigerant takes heat from the surroundings of the evaporator through an expansion valve and an evaporator and vaporizes again, the refrigerant is returned to the intermediate cooler and mixed with the auxiliary refrigerant vaporized in the intermediate cooler to be sucked into the compressor. At this time, the carbon dioxide gas vaporized in the evaporator is a gas close to a low temperature saturated state, and the temperature is increased while exchanging heat with the carbon dioxide refrigerant delivery pipe in the intermediate cooler, and thus is sucked into the compressor in a state where the pressure is raised to some extent. It is possible to lower the compression ratio of the required compressor.

The intermediate cooler receives the mixed refrigerant in a predetermined space insulated, separates and discharges relatively small specific carbon dioxide from the upper side of the space by using the difference in specific gravity of the supplied mixed refrigerant, and has a relatively high specific gravity from the lower side of the space. A mixed refrigerant separator for separating and discharging a large auxiliary refrigerant; And an intermediate heat exchanger that cools and discharges the carbon dioxide by adiabatic expansion of the auxiliary refrigerant in an evaporation unit that surrounds the refrigerant transport pipe through which the separated carbon dioxide is transferred and is insulated from the outside.

In addition, the intermediate heat exchanger may allow the carbon dioxide returned through the expansion valve and the evaporator in the evaporator to be mixed with the auxiliary refrigerant vaporized in the evaporator again and then sucked into the compressor.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

1 is a schematic diagram showing a first embodiment of the present invention having an intermediate cooler. As shown in the figure, this embodiment includes a compressor, a condenser, an expansion valve and an evaporator, and an intermediate cooler connected in series between an outlet side 203 of the condenser and an inlet side 223 of the expansion valve ( 10).

The intermediate cooler 10 includes a mixed refrigerant separator 20, an intermediate heat exchanger 30, and an auxiliary expansion valve 40, respectively. The mixed refrigerant separator 20 includes an upper refrigerant pipe 201 and a lower refrigerant pipe 204 respectively connected to the upper and lower portions of an empty container, and the lower refrigerant pipe in which liquid auxiliary refrigerant is separated and discharged. On the downstream side of 204, an auxiliary expansion valve 40 for lowering the liquid pressure of the auxiliary refrigerant is provided. An intermediate heat exchanger 30 is provided downstream of the upper refrigerant pipe 201 through which carbon dioxide, which is mainly gaseous, is discharged. The intermediate heat exchanger 30 is an insulated sealed container, and a refrigerant transport pipe 202 passing therein. Is connected to the upper refrigerant pipe 201 to pass the carbon dioxide mainly gaseous state.

Inside the intermediate heat exchanger is provided with an evaporator 300 which passes through the auxiliary expansion valve and the auxiliary refrigerant with a reduced liquid pressure is injected to take evaporation heat while evaporating around the refrigerant transport pipe. In addition, the evaporator 300 of the intermediate heat exchanger 30 is provided with a return refrigerant inlet 301 through which the refrigerant gas returned through the evaporator is introduced, thereby allowing the returned refrigerant to evaporate from the evaporator 300. A return refrigerant outlet 302 is provided, through which the auxiliary refrigerant gas is mixed and discharged again.

Referring to the operation of the refrigerator according to the flow of the refrigerant according to the present invention. The mixed refrigerant in which carbon dioxide and auxiliary refrigerant are mixed is compressed in a compressor to be in a high temperature and high pressure state, and radiates through a condenser. At this time, as the temperature of the mixed refrigerant becomes similar to the temperature around the condenser, the auxiliary refrigerant having a relatively high boiling point is liquefied first, and carbon dioxide is maintained as it is. In the mixed refrigerant separator 20, an auxiliary refrigerant mainly in a liquid state and having a high specific gravity is discharged to the lower refrigerant pipe 204, and carbon dioxide mainly in a gaseous state and a small specific gravity is separated and discharged into the upper refrigerant pipe 201.

The carbon dioxide separated by the upper refrigerant pipe 201 passes through the inside of the intermediate heat exchanger 30 along the refrigerant transfer pipe 202, and the auxiliary refrigerant separated by the lower refrigerant pipe 204 from the auxiliary expansion valve 40. After the adiabatic expansion process, the pressure and the temperature are dropped to the evaporator 300 of the intermediate heat exchanger 30. In the evaporator 300, the auxiliary liquid in the liquid state is evaporated by evaporating heat from the refrigerant transport pipe 202, whereby the carbon dioxide in the transport pipe is liquefied under a relatively low pressure.

The liquefied carbon dioxide is injected into the evaporator after the liquid pressure and temperature drop through the expansion valve, and vaporizes by absorbing the heat of evaporation from around the evaporator. The vaporized carbon dioxide is returned to the return refrigerant inlet 301 of the intermediate heat exchanger 30, mixed with the auxiliary refrigerant gas evaporated in the evaporator 300, and then again returned through the return refrigerant outlet 302. Is inhaled. However, when the refrigerating device reaches a steady state, the returned carbon dioxide refrigerant is relatively low temperature (approximately -55 ° C), low pressure, but in a state in which temperature and pressure are increased while exchanging heat with the refrigerant transfer pipe 202. Since it is sucked into the compressor, the compression ratio of the compressor can be reduced. At this time, the carbon dioxide refrigerant in the refrigerant transport pipe 202 is further cooled by heat exchange with the return refrigerant can be easily liquefied.

Referring to the temperature-pressure state diagram of carbon dioxide shown in FIG. 3, a high pressure of about 6 MPa (about 60 atm) is required to condense carbon dioxide in a condenser operated at about 25 ° C. at room temperature. When a cooler is provided, it can be liquefied by cooling to about -25 ° C at a relatively low pressure of about 1.5 MPa (about 15 atm).

The auxiliary refrigerant is a refrigerant that can be liquefied at a temperature around the condenser when the pressure of about 1.5MPa is suitable, it is preferable that the latent heat of evaporation compared to carbon dioxide can take away a lot of heat in a small amount. In addition, it is desirable to have a material that meets environmental standards due to low ozone layer destruction. Therefore, the auxiliary refrigerant is preferably selected in consideration of the operating temperature and pressure conditions of the refrigerating device from the refrigerant of the HFC series or HCFC series developed to replace the refrigerant of the CFC series.

The mixing ratio of carbon dioxide and auxiliary refrigerant may vary slightly depending on the operating temperature and pressure conditions of the refrigerating device and the type of auxiliary refrigerant. Carbon dioxide predominates, and the auxiliary refrigerant is negative. If the ratio of the auxiliary refrigerant is too high, the secondary refrigerant is condensed in the condenser and the pressure of the carbon dioxide remaining in the gas state is lowered, which may cause a problem that the temperature required for liquefaction is too low. If the ratio of the auxiliary coolant is too low, a problem may occur that the carbon dioxide in the gaseous state cannot be sufficiently cooled with the auxiliary coolant first liquefied. Therefore, the mixing ratio of the refrigerant should be determined in consideration of the temperature and pressure at which the device is operated and the latent heat of evaporation of the auxiliary refrigerant material.

Fig. 2 is a schematic diagram showing a second embodiment of the present invention having two intermediate coolers arranged in series. The overall configuration is the same as that of the first embodiment described above, and there is a difference in that the two intermediate coolers 10 and 11 are arranged in succession. The carbon dioxide mixed refrigerant primarily separated from the first mixed refrigerant separator 21 of the first intermediate cooler 11 is passed through the first refrigerant transfer pipe 212 in the first intermediate heat exchanger 31 by the liquefied auxiliary refrigerant. Is cooled. At this time, the inside of the first refrigerant transport pipe 212 is a state that does not reach a low temperature enough to liquefy carbon dioxide.

As described above, the carbon dioxide mixed refrigerant cooled and separated first from the first intermediate cooler flows into the inlet 213 of the second mixed refrigerant separator 22 of the second intermediate cooler 12 and repeats the above process again. The refrigerant separated from the second mixed refrigerant separator 22 and passing through the second refrigerant conveying pipe 222 in the second intermediate heat exchanger 32 is liquefied by capturing evaporative heat to the auxiliary refrigerant liquefied as carbon dioxide of high purity and expanding the expansion valve. Inlet to the (223).

Thereafter, the carbon dioxide refrigerant in the liquid state, which is decompressed in a state of being insulated from the expansion valve, is further evaporated by absorbing the surrounding heat in the evaporator, and maintains the temperature around the evaporator at about -55 ° C. The triple point temperature of carbon dioxide is -56.56 ° C. At lower temperatures, the carbon dioxide may solidify into dry ice particles and obstruct the flow of the refrigerant. Therefore, it is preferable to operate near the triple point temperature.

In this embodiment, R-141b of HCFC series is used as the auxiliary refrigerant. R-141b (CH ₃ CCl ₂ F) has a boiling point of 32 ° C and freezing point of -103.5 ° C under one atmosphere of pressure, according to its Material Stability Data Sheet (MSDS). The ODP (Ozone Depletion Index Based on CFC-11) value is 0.07 to 0.1, and is a substance that can replace CFC (freon) in applications such as refrigerants, foaming agents, and cleaning agents in semiconductor processes.

In this embodiment, the mixing ratio of R-141b is preferably 4w% to 10w%. As described above, if the mass ratio of the R-141b is less than 4%, the separated carbon dioxide gas cannot be sufficiently cooled until the liquefied carbon dioxide gas. If the mass ratio is greater than 10%, the auxiliary refrigerant R-141b is liquefied and the pressure of the mixed refrigerant is increased. Since the pressure becomes as small as the partial pressure, there is a problem of cooling to a lower temperature in order to liquefy the separated carbon dioxide gas.

Examples of auxiliary refrigerants that can replace R-141b include HFC-125 having a boiling point of 49 ° C, HCFC-124 having a boiling point of -12 ° C, R-142b having a HCFC series and a boiling point of -92 ° C, and the like. In addition, it will be apparent to those skilled in the art that materials having similar physical properties in addition to those mentioned herein may be used as auxiliary refrigerants.

Fig. 4 is a schematic Molier diagram showing a refrigeration cycle according to the second embodiment. This represents the state of carbon dioxide in the mixed refrigerant. a is the state at the outlet of the compressor. Thereafter, the high temperature and high pressure mixed refrigerant is separated into carbon dioxide and an auxiliary refrigerant R-141b through the condenser and the first mixed refrigerant separator, and the carbon dioxide is first cooled in the first intermediate heat exchanger to reach a state b, and the second intermediate The liquid is liquefied through the cooler to reach the c state. In the above high pressure section, when the pressure is approximately 1.5 to 2.1 MPa and the pressure in the second intermediate heat exchanger is 1.5 MPa, the liquefaction of carbon dioxide proceeds at a temperature of approximately -25 ° C.

Liquefied carbon dioxide refrigerant is adiabatic expansion through the expansion valve in the c ~ d section, and absorbs heat passing through the evaporator in the pressure and temperature is lowered to reach the e state. In the evaporation section of the second and first intermediate heat exchanger, the heat is exchanged with the refrigerant transport pipe, mixed with the R-141b gas again, and the temperature and the pressure are raised to the f state, and then suctioned into the compressor.

Through such a process, the refrigerating device according to the second embodiment of the present invention can cool the temperature around the evaporator to about -55 ° C.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common knowledge in the field of the present invention that various substitutions and modifications and changes can be made without departing from the technical spirit of the present invention. Will be evident to those who have

Accordingly, the refrigeration apparatus using the carbon dioxide mixed refrigerant according to the present invention is relatively provided by separating the mixed refrigerant passing through the compressor and the condenser into an auxiliary refrigerant and a carbon dioxide refrigerant, and having an intermediate cooler for liquefying the carbon dioxide refrigerant using the separated auxiliary refrigerant. By using a low compression ratio compressor, there is an effect of obtaining a low temperature freezing effect of below 50 ° C.

Claims (13)

A refrigeration apparatus composed of a refrigerant circuit including a compressor, a condenser, an expansion valve, and an evaporator, The refrigerant is provided between the condenser and the expansion valve, and the mixed refrigerant mixed with carbon dioxide and the auxiliary refrigerant is separated into gaseous carbon dioxide and mainly liquid auxiliary refrigerant using the specific gravity difference, and the separated auxiliary refrigerant is used. And an intermediate cooler for liquefying the separated carbon dioxide to supply liquid carbon dioxide refrigerant to the expansion valve. Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 1, The auxiliary refrigerant, Liquefied at the same temperature as the surrounding of the condenser with respect to the pressure condition of the condenser outlet, and cooled to a temperature at which the carbon dioxide is liquefied in the intermediate cooler as the liquid pressure is lowered, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 2, The auxiliary refrigerant is a refrigerant selected from a refrigerant group of HCFC series or HFC series, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 3, The auxiliary refrigerant is R-141b, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 1, The refrigerating device, At least two or more intermediate coolers connected in series between the condenser and the expansion valve; To separate and cool the carbon dioxide refrigerant primarily separated from the first intermediate cooler and cooled in the second intermediate cooler, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method according to claim 1 or 5, The intermediate cooler, The mixed refrigerant is supplied to the predetermined space insulated, and the carbon dioxide having a relatively small specific gravity is separated and discharged from the upper side of the space by using the difference in specific gravity of the supplied mixed refrigerant, and the auxiliary refrigerant having a relatively large specific gravity is discharged from the lower side of the space. A mixed refrigerant separator for separating and discharging; And And an intermediate heat exchanger surrounding the pipe through which the separated carbon dioxide is transported, and cooling and discharging the carbon dioxide by evaporating an auxiliary refrigerant in an evaporator that is insulated from the outside. Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 6, The intermediate heat exchanger, In the evaporator, the carbon dioxide and the auxiliary refrigerant returned through the expansion valve and the evaporator are mixed again to be sucked into the compressor. Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 1, The mixed refrigerant, Carbon dioxide is 90% to 96% by mass, the rest consisting of R-141b, Refrigeration apparatus using a carbon dioxide mixed refrigerant. A refrigeration apparatus composed of a refrigerant circuit including a compressor, a condenser, an expansion valve, and an evaporator, A refrigerant having a mixture of carbon dioxide and R-141b mixed with the condenser outlet, and supplied with a mixture of carbon dioxide and R-141b, and separating and discharging a component having a relatively low specific gravity from an upper side of the space by using a specific gravity difference of the supplied mixed refrigerant. A first mixed refrigerant separator having a first upper refrigerant pipe and a first lower refrigerant pipe separating and discharging a component having a relatively high specific gravity from a lower side of the space; A first intermediate heat exchanger which further cools and discharges the refrigerant separated through the first upper refrigerant pipe by evaporating the refrigerant separated through the first lower discharge pipe in an evaporator which surrounds the first upper refrigerant pipe and is insulated from the outside; ; A second upper refrigerant pipe receiving the refrigerant discharged from the first intermediate heat exchanger and separating and discharging a component having a relatively low specific gravity from an upper side of the space by using a difference in specific gravity of the supplied mixed refrigerant; and a lower side of the space A second mixed refrigerant separator having a second lower refrigerant pipe separating and discharging a component having a relatively high specific gravity therefrom; And A second intermediate heat exchanger for further cooling and discharging the refrigerant separated through the second upper refrigerant pipe by adiabatic expansion of the refrigerant separated through the second lower discharge pipe in the evaporator which surrounds the second upper refrigerant pipe and is insulated from the outside; Including a flag, The refrigerant vapor returned from the second upper refrigerant pipe through the expansion valve and the evaporator is mixed with the refrigerant expanded in the evaporation unit of the first and second intermediate heat exchangers to be sucked into the compressor. Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 9, The compressor and condenser, At the condenser outlet at room temperature, R-141b of the mixed refrigerant mainly exists in the liquid state, and carbon dioxide satisfies the pressure conditions that exist mainly in the gaseous state. Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 10, The compressor, Discharge pressure is 1.5MPa to 2.1MPa, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 9, The second intermediate heat exchanger has its evaporator connected to the outlet of the evaporator, and the refrigerant vapor returned through the evaporator is mixed with the expanded refrigerant in the evaporator of the second intermediate heat exchanger, The evaporator of the second intermediate heat exchanger is connected to the evaporator of the first intermediate heat exchanger, and the mixed refrigerant introduced from the second intermediate heat exchanger is mixed again with the refrigerant expanded in the evaporator of the first intermediate heat exchanger. To be sucked into the compressor, Refrigeration apparatus using a carbon dioxide mixed refrigerant. The method of claim 9, The mixed refrigerant, Carbon dioxide is 90% to 96% by mass, the rest consisting of R-141b, Refrigeration apparatus using a carbon dioxide mixed refrigerant.

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