JP2009062471A - Mixed working fluid and refrigerating cycle device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lowering of the coefficient of performance and lowering of the operation efficiency of a refrigerating cycle device when a fluid to be heated having a middle temperature of about ≥31°C is heated to a high temperature. <P>SOLUTION: A mixed working fluid contains carbon dioxide and difluoromethane, wherein the content of the carbon dioxide is substantially ≥80 wt.%. The refrigerating cycle device uses the mixed working fluid and is equipped with a compressor 11, a radiator 12, a pressure reducer 13 and an evaporator 14. The lowering of the coefficient of performance can be suppressed by the characteristics of the mixed working fluid when a fluid having a middle temperature is heated to a high temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mixed working fluid used as a refrigerant for a refrigeration cycle apparatus, for example, and a refrigeration cycle apparatus using the mixed working fluid.

  In general, the refrigeration cycle apparatus comprises a compressor, a four-way valve if necessary, a radiator (or a condenser), a decompressor such as a capillary tube or an expansion valve, an evaporator, etc., and constitutes a refrigeration cycle. Cooling or heating action is performed by circulating a refrigerant inside.

  As refrigerants in these refrigeration cycle apparatuses, halogenated hydrocarbons derived from methane or ethane called chlorofluorocarbons are known.

R22 (chlorodifluoromethane, CHClF ₂ , boiling point −40.8 ° C., critical temperature 96.2 ° C., critical pressure 4.99 MPa) and the like have been used as the refrigerant for the refrigeration cycle apparatus as described above. R22 is a fluorinated hydrocarbon (HCFC refrigerant) containing chlorine and hydrogen, and has the ability to destroy stratospheric ozone, so the usage and production regulations have already been determined by the Montreal Protocol.

  In recent years, in the field of heat pump water heaters, which is one of the heating devices using a refrigeration cycle, carbon dioxide (CO2, R744, boiling point-78.4 ° C., critical temperature 31.1 ° C., critical pressure as an alternative refrigerant for R22. 7.38 MPa) is drawing attention. In refrigeration cycle equipment using carbon dioxide, it can be a transcritical cycle that does not include a condensation process, and by using a supercritical region, it is suitable for use in heating a low-temperature fluid (eg, water) to a high temperature. In other words, it has been reported that the coefficient of performance (COP) when heating a low-temperature fluid to be heated to a high temperature is high (for example, see Non-Patent Document 1).

Carbon dioxide does not destroy stratospheric ozone even in global environmental problems, and has a global warming potential (hereinafter referred to as GWP) of 1 indicating the effect on global warming, which is much higher than the R22 GWP 1500. It is a small and excellent refrigerant.
Saikawa, Hashimoto, Johannes, "Proceedings of the 34th Japan Heat Transfer Symposium", 1997, p505

  However, since carbon dioxide has a low critical temperature of about 31 ° C., when a medium-temperature heated fluid of about 31 ° C. or higher is heated to a high temperature, the coefficient of performance decreases, and the operating efficiency of the refrigeration cycle apparatus decreases. There was a problem.

  In order to solve the above-described problems, the present invention can be applied to a case where a medium-temperature heated fluid is heated to a high temperature, a mixed working fluid with a small decrease in the coefficient of performance, and a case where a medium-temperature heated fluid is heated to a high temperature. It aims at providing the refrigerating-cycle apparatus with a small fall of the operating efficiency of a refrigerating-cycle apparatus.

In order to solve the above conventional problems, the present invention is a mixed working fluid containing carbon dioxide and difluoromethane, and the mixed working fluid is substantially 80% by weight or more of carbon dioxide. According to this, due to the characteristics of the mixed working fluid, it is possible to suppress a decrease in the coefficient of performance when heating the medium heated fluid to a high temperature.

  Further, the present invention is a mixed working fluid containing carbon dioxide and 1,1-difluoroethane, wherein the carbon dioxide is substantially 95% by weight or more. According to this, due to the characteristics of the mixed working fluid, it is possible to suppress a decrease in the coefficient of performance when heating the medium heated fluid to a high temperature.

  Moreover, this invention is a refrigerating-cycle apparatus provided with the compressor, the heat radiator, the pressure reduction device, and the evaporator, and using the mixed working fluid in any one of the said this invention. According to this, due to the characteristics of the mixed working fluid, it is possible to suppress a decrease in the operating efficiency of the refrigeration cycle apparatus when the medium temperature heated fluid is heated to a high temperature.

  The mixed working fluid and the refrigeration cycle apparatus of the present invention can suppress a decrease in the coefficient of performance when the medium temperature heated fluid is heated to a high temperature.

  The first invention is a mixed working fluid containing carbon dioxide and difluoromethane, and the mixed working fluid in which carbon dioxide is substantially 80% by weight or more is a medium temperature heated fluid due to the characteristics of the mixed working fluid. It is possible to suppress a decrease in the coefficient of performance when heating the plate to a high temperature.

  The second invention is a mixed working fluid containing carbon dioxide and 1,1-difluoroethane, and the mixed working fluid in which carbon dioxide is substantially 95% by weight or more has an intermediate temperature due to the characteristics of the mixed working fluid. A decrease in the coefficient of performance when the fluid to be heated is heated to a high temperature can be suppressed.

  A third invention includes a compressor, a radiator, a decompressor, and an evaporator, and uses a mixed working fluid according to any one of the first and second inventions, so that the medium temperature is heated according to the characteristics of the mixed working fluid. A decrease in operating efficiency of the refrigeration cycle apparatus when the fluid is heated to a high temperature can be suppressed.

  According to a fourth aspect, in the third aspect, the medium working fluid is heated at a medium temperature while suppressing a decrease in the coefficient of performance by operating the mixed working fluid in the radiator at a pressure equal to or higher than the critical pressure of the mixed working fluid. Can be heated to a high temperature.

  5th invention WHEREIN: When the temperature of the to-be-heated fluid which flows into a heat radiator in 3rd or 4th invention is 31 degreeC or more, the fall of a coefficient of performance in the case of heating medium to-be-heated fluid to high temperature The effect which suppresses becomes remarkable.

  In a sixth aspect of the present invention, in any one of the third to fifth aspects, the floor warming panel is heated by directly or indirectly using the heat stored in the heated fluid heated by the radiator. By performing, the effect which suppresses the fall of a coefficient of performance at the time of heating the medium temperature to-be-heated fluid to high temperature becomes remarkable.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments. For example, in the following embodiment, a hot water heater will be described as an example. However, the present invention is not limited to the hot water heater, and may be an air conditioner capable of blowing hot air.

(Embodiment 1)
The mixed working fluid in the present embodiment includes carbon dioxide (CO ₂ , R 744, boiling point −78.4 ° C., critical temperature 31.1 ° C., critical pressure 7.38 MPa) and difluoromethane (CH ₂ F).
₂ and R32, a boiling point of −51.7 ° C., a critical temperature of 78.1 ° C., and a critical pressure of 5.78 MPa). The excellent characteristics when the mixed working fluid in the present embodiment is used as the refrigerant of the refrigeration cycle apparatus are shown below.

  Tables 1 and 2 show a two-component mixed working fluid composed of carbon dioxide (R744) and difluoromethane (R32) in which carbon dioxide (R744) is 80 wt% to 100 wt% (100 wt% is carbon dioxide ( R744) Comparison of heating performance of a single refrigerant).

  In Table 1, as conditions on the heated fluid (for example, water) side for heat exchange with the refrigerant in the radiator (or condenser), the radiator (or condenser) inlet temperature is 17 ° C., and the radiator (or condenser). The outlet temperature is 90 ° C., the conditions on the refrigerant side are such that the evaporation temperature of the evaporator is 8 ° C., and the minimum temperature difference between the fluid to be heated (for example, water) and the refrigerant in the radiator (or condenser) is 2K. And measured by controlling the high-pressure side pressure of the radiator (or condenser). In addition, this condition assumes the case where a low-temperature heated fluid (for example, water) of 17 ° C. is heated to 90 ° C. in a refrigeration cycle apparatus such as a heat pump water heater.

  Such a mixed working fluid is mixed with difluoromethane (R32) having a boiling point higher than that of a single carbon dioxide (R744) refrigerant. The pressure can be reduced and the coefficient of performance can be improved.

Table 2 shows that the condition of the heated fluid (for example, water) side for heat exchange with the refrigerant in the radiator (or condenser) is 35 ° C. at the inlet temperature of the radiator (or condenser), and the radiator (or condenser). The outlet temperature is 90 ° C, and the conditions on the refrigerant side are 8 ° C for the evaporation temperature of the evaporator,
Alternatively, the pressure is measured by controlling the high-pressure side pressure of the radiator (or the condenser) so that the minimum temperature difference between the fluid to be heated (for example, water) and the refrigerant in the condenser is 2K. This condition assumes a case where a medium fluid to be heated (for example, water) at 35 ° C. is heated to 90 ° C. in a refrigeration cycle apparatus such as a heat pump water heater.

  In Table 2 in the case of heating a medium fluid to be heated at 35 ° C., the ratio of improvement in the coefficient of performance for carbon dioxide (R744) single refrigerant is higher than in Table 1 in the case of heating a fluid to be heated at a low temperature of 17 ° C. large. That is, such a mixed working fluid has a carbon dioxide (R744) single refrigerant as much as a single refrigerant of carbon dioxide (R744) even when a medium temperature heated fluid higher than the critical temperature (about 31 ° C.) of the single refrigerant (R744) is heated to a high temperature. The coefficient of performance does not decrease. This is because the critical temperature of the mixed working fluid is increased as shown in Table 3 by mixing difluoromethane (R32) having a higher critical temperature than that of a single refrigerant of carbon dioxide (R744).

  In the two-component system of carbon dioxide (R744) and difluoromethane (R32), an azeotrope-like mixture is not constituted, and a non-azeotropic mixture having an evaporation temperature gradient is formed. However, in a mixture in which 80% by weight or more of carbon dioxide (R744) is mixed, the evaporation temperature gradient is approximately 5K or less, and the non-azeotropic property is small. For this reason, when used in a refrigeration cycle apparatus, carbon dioxide (R744) is desirably 80% by weight or more in terms of an easy-to-handle refrigerant that does not easily cause problems such as frost adhesion to the evaporator.

  Furthermore, these mixtures have no effect on the stratospheric ozone layer, and as shown in Table 3, the GWP is as small as 150 or less, and the burden on global warming is small.

  In addition to the main components of carbon dioxide (R744) and difluoromethane (R32), there is no problem even if some other components are contained.

(Embodiment 2)
The mixed working fluid in the present embodiment includes carbon dioxide (CO ₂ , R 744, boiling point −78.4 ° C., critical temperature 31.1 ° C., critical pressure 7.38 MPa), 1,1-difluoroethane (CHF ₂ CH ₃ R152a, boiling point -24.0 ° C, critical temperature 113.3 ° C, critical pressure 4.52 MPa). The excellent characteristics when the mixed working fluid in the present embodiment is used as the refrigerant of the refrigeration cycle apparatus are shown below.

  Tables 4 and 5 show a two-component mixed working fluid composed of carbon dioxide (R744) and 1,1-difluoroethane (R152a) in which carbon dioxide (R744) is 80 wt% to 100 wt% (100 wt% is The heating performance of carbon dioxide (R744) single refrigerant) is compared.

  The test conditions in Table 4 are the same as in Table 1, and the test conditions in Table 5 are the same as in Table 2. From Table 4, such a mixed working fluid is compared with carbon dioxide (R744) single refrigerant by mixing 1,1-difluoroethane (R152a), which has a higher boiling point than carbon dioxide (R744) single refrigerant. The high pressure side pressure and the low pressure side pressure can be reduced. Under the conditions in Table 4, the coefficient of performance is almost equivalent.

  Further, in Table 5 in the case of heating the medium heated fluid at 35 ° C., the coefficient of performance for the single refrigerant of carbon dioxide (R744) is improved as compared with Table 4 in the case of heating the heated fluid at a low temperature of 17 ° C. The ratio is large. That is, such a mixed working fluid has a carbon dioxide (R744) single refrigerant as much as a single refrigerant of carbon dioxide (R744) even when a medium temperature heated fluid higher than the critical temperature (about 31 ° C.) of the single refrigerant (R744) is heated to a high temperature. The coefficient of performance does not decrease. This is because the critical temperature of the mixed working fluid rises as shown in Table 6 by mixing 1,1-difluoroethane (R152a), which has a higher critical temperature than carbon dioxide (R744) single refrigerant.

  In a two-component system of carbon dioxide (R744) and 1,1-difluoroethane (R152a), an azeotrope-like mixture is not formed, and a non-azeotropic mixture having an evaporation temperature gradient is formed. However, in a mixture in which 95% by weight or more of carbon dioxide (R744) is mixed, the evaporation temperature gradient is about 5K or less, and the non-azeotropic property is small. For this reason, when used in a refrigeration cycle apparatus, carbon dioxide (R744) is desirably 95% by weight or more from the viewpoint of an easy-to-handle refrigerant that does not easily cause problems such as frost adhesion to the evaporator.

  Furthermore, these mixtures have no effect on the stratospheric ozone layer, and as shown in Table 6, the GWP is as small as 150 or less, and the burden on global warming is also small.

In addition to the main components of carbon dioxide (R744) and 1,1-difluoroethane (R152a), there is no problem even if some other components are contained.

(Embodiment 3)
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to the present embodiment, and particularly shows an example applied to a water heater. As shown in FIG. 1, the refrigeration cycle apparatus 100 mainly includes a refrigerant circuit A, a hot water storage circuit B, and a floor warming circuit C. The refrigerant circuit A includes a compressor 11 that compresses the refrigerant, a radiator 12 that cools the refrigerant compressed by the compressor 11, a decompressor 13 that decompresses the refrigerant cooled by the radiator 12, and a decompressor 13. And an evaporator 14 for evaporating the decompressed refrigerant. The compressor 11, the radiator 12, the decompressor 13, and the evaporator 14 are connected to each other by refrigerant piping so that the refrigerant circulates in this order.

  The compressor 11 may employ a positive displacement fluid mechanism such as a scroll type, a reciprocating type, or a rotary type. The radiator 12 is a water heat exchanger including a refrigerant channel 12a and a water channel 12b. The evaporator 14 is an air heat exchanger represented by a fin tube type heat exchanger. A fan 17 is provided adjacent to the evaporator 14. The fan 17 supplies air (cooled fluid) to be heat exchanged with the refrigerant in the evaporator 14 to the evaporator 14. The amount of air flowing through the evaporator 14 changes according to the rotational speed of the fan 17. When the refrigeration cycle apparatus 100 is used as an air conditioner, the radiator 12 is also composed of an air heat exchanger, and the fluid to be heated becomes indoor or outdoor air.

  The refrigerant circuit A is composed of carbon dioxide (R744) and difluoromethane (R32), and the carbon dioxide (R744) is filled with a mixed working fluid containing approximately 80% by weight or more of carbon dioxide (R744) as a refrigerant. Yes. In FIG. 1, the solid line arrow has shown the flow direction of the refrigerant | coolant.

  In the hot water storage circuit B, the first circulation pump 15, the fluid flow path 12 b of the radiator 12, and the hot water supply tank 16 are connected to each other by a water pipe so that water or hot water that is a heated fluid in the hot water storage tank 16 circulates. Has been. Furthermore, the hot water storage tank 16, the floor warming heat exchanger 20, and the second circulation pump 21 are connected to each other by a water pipe so that water or hot water in the hot water storage tank 16 circulates.

  A first circulation pump 15 is provided in the water flow path between the radiator 12 and the hot water storage tank 16. The first circulation pump 15 sends water to the radiator 12 for heat exchange with the refrigerant by the radiator 12. The amount of water flowing through the radiator 12 changes according to the rotation speed of the first circulation pump 15. The water heated by the radiator 12 becomes hot water and is stored in the hot water storage tank 16. The hot water stored in the hot water storage tank 16 passes through the hot water outlet pipe 18 and is adjusted to an appropriate temperature by a mixing valve (not shown) or the like, and then discharged from a faucet such as a kitchen or a bath. When the hot water is discharged from the hot water storage tank 16, low temperature water is supplied from the city water to the hot water storage tank 16 through the water supply pipe 19. In FIG. 1, broken line arrows indicate the flow direction of water (or hot water).

  The floor warming circuit C includes a floor warming heat exchanger 20, a circulation pipe 23 disposed in the floor warming panel 22, and a third circulation pump 24, which is different from the water in the hot water storage tank 16. Are connected to each other by water piping so that they circulate. The hot water in the upper part of the hot water storage tank 16 is supplied to the floor warming heat exchanger 20 by the second circulation pump 21 and exchanges heat with the floor warming circulating water, and then returns to the lower or middle part of the hot water storage tank 16. On the other hand, the floor warming circulating water is supplied to the floor warming heat exchanger 20 by the third circulation pump 24, heated by the floor warming heat exchanger 20, and then flows into the circulation pipe 23. The warm floor panel 22 is warmed by hot water flowing through the circulation pipe 23 to perform floor heating. Hot water that has flowed out of the circulation pipe 23 is sucked into the third circulation pump 24.

In such a refrigeration cycle apparatus, hot water stored in the hot water storage tank 16 is not discharged and left for a long time, or floor heating is performed, and hot water of about 50 ° C. is heated from the floor warming heat exchanger 20. May return to the lower part or the middle part of the hot water storage tank 16, the temperature of the water in the lower part of the hot water storage tank 16 may rise to about 31 ° C. or more. When such medium-temperature water is caused to flow into the radiator 12 by the first circulation pump 15 and is heated again to hot water by the radiator 12, it is refrigerated compared to the case where low-temperature hot water is heated to high temperature. The operating efficiency of the cycle device may be reduced. However, in this embodiment, carbon dioxide (R744) and difluoromethane (R32) are used as refrigerants, and carbon dioxide (R744) uses a mixed working fluid containing approximately 80% by weight or more of carbon dioxide (R744). Therefore, compared with the refrigerating-cycle apparatus using the carbon dioxide (R744) single refrigerant | coolant as a refrigerant | coolant, the fall of operation efficiency is small. Therefore, even when a medium-temperature heated fluid of about 31 ° C. or higher is heated to a high temperature, the problem that the operation efficiency of the refrigeration cycle apparatus is reduced can be solved.

  In the present embodiment, the floor warming circulating water different from the hot water in the hot water storage tank 16 circulates in the circulation pipe 23 of the floor warming panel 22. In other words, the present embodiment is configured to perform floor heating by indirectly using the amount of heat stored in the heated fluid in the hot water storage tank 16. In addition to such a configuration, the hot water in the hot water storage tank 16 directly circulates to the circulation pipe 23 of the warm floor panel 22 or the hot water that has flowed out of the radiator 12 directly to the circulation pipe 23 of the warm floor panel 22. It may be configured to circulate, that is, to perform floor heating by directly using the amount of heat stored in the fluid to be heated.

  As described above, the mixed working fluid of the present invention and the refrigeration cycle apparatus using the same are a hot water heater that heats the fluid to be heated flowing into the radiator at a temperature of about 31 ° C. or higher to a temperature higher than the temperature of flowing in, Applicable to applications such as air conditioners.

Configuration diagram of a refrigeration cycle apparatus according to Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Compressor 12 Radiator 13 Decompressor 14 Evaporator 15 1st circulation pump 16 Hot water storage tank 17 Fan 18 Hot water outlet pipe 19 Water supply pipe 20 Heater for floor warming 21 Second circulation pump 22 Floor warming panel 23 Circulation pipe 24 3rd Circulation pump
100 Refrigeration cycle equipment

Claims (6)

A mixed working fluid comprising carbon dioxide and difluoromethane, wherein the carbon dioxide is substantially 80% by weight or more. A mixed working fluid comprising carbon dioxide and 1,1-difluoroethane, wherein the carbon dioxide is substantially 95% by weight or more. A refrigeration cycle apparatus comprising a compressor, a radiator, a decompressor, and an evaporator, wherein the mixed working fluid according to claim 1 is used. The refrigeration cycle apparatus according to claim 3, wherein the pressure of the mixed working fluid in the radiator is operated at a critical pressure or higher of the mixed working fluid. The refrigeration cycle apparatus according to claim 3 or 4, wherein the temperature of the heated fluid flowing into the radiator is 31 ° C or higher. The refrigeration cycle apparatus according to any one of claims 3 to 5, wherein the floor warming panel is heated by heat stored in a fluid to be heated heated by a radiator to perform floor heating.

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