In this description, abbreviated names of halogenated hydrocarbon compounds are described in brackets after the compound names, and in this description, the abbreviated names are employed in place of the compound names as necessary.
Conventionally, as a working medium for a heat cycle system such as a refrigerant for a refrigerator, a refrigerant for an air-conditioning apparatus, a working medium for a power generation system (such as an exhaust heat recovery power generation), a working medium for a latent heat transport apparatus (such as a heat pipe), or a secondary cooling medium, chlorofluorocarbon (CFC) such as chlorotrifluoromethane or dichlorodifluoromethane, and hydrochlorofluorocarbon (HCFC) such as chlorodifluoromethane have been used. However, effects of CFC and HCFC on the ozone layer in the stratosphere have been pointed out, and they are subjected to regulation at present.
Under such circumstances, as a working medium for heat cycle, hydrofluorocarbons (HFC) having less effect on the ozone layer, such as difluoromethane (HFC-32), tetrafluoroethane, and pentafluoroethane (HFC-125), have been used in place of CFC and HCFC. For example, R410A (a pseudoazeotropic mixed refrigerant of HFC-32 and HFC-125 at a mass ratio of 1:1) or the like is a refrigerant that has been widely used conventionally. However, it has been pointed out that HFCs may cause global warming.
For example, 1,1,1,2-tetrafluoroethane (HFC-134a) used as a refrigerant for an automobile air conditioner has a global warming potential so high as 1430 (100 years). Further, in an automobile air conditioner, the refrigerant is highly likely to leak out to the air from a connection hose, a bearing, or the like.
As a refrigerant to be used in place of HFC-134a, carbon dioxide and 1,1-difluoroethane (HFC-152a) having a global warming potential of 124 (100 years) that is lower as compared with HFC-134a, have been under consideration.
However, with carbon dioxide, the equipment pressure tends to be extremely high as compared with HFC-134a, and therefore, there are many problems that should be solved in applying carbon dioxide to all automobiles. HFC-152a has a combustion range, and has a problem for securing the safety
Further, HFC-134a has been used as a working medium of a centrifugal refrigerator (to be also called a turbo refrigerator). The centrifugal refrigerator is to be used for cooling and heating of buildings and in plants of producing industrial cold-water, and the like. As the working medium of the centrifugal refrigerator, flon such as CFC-11 has been used, but, in relation to the recent ozone layer destruction problem, production and use of flon have been regulated internationally, and therefore, flon is being converted to a working medium using hydrogen-containing flon not containing chlorine such as, for example, tetrafluoroethane (HFC-134a) or pentafluoropropane (HFC-245fa).
Here, HFC-134a has a global warming potential of 1430 (100 years), which is large. Further, HFC-245fa has a global warming potential of 1030 (100 years), but is highly toxic. In the centrifugal refrigerator, an amount of the working medium to be filled is larger as compared with another refrigerator and a heat pump. In a centrifugal refrigerator having a 500-refrigeration ton class capacity, for example, about 700 to 800 kg of a working medium is filled. The centrifugal refrigerator is often installed in a machine room of a building, and even if leakage of the working medium occurs due to an accident, or the like, there is a possibility that the working medium in large amounts is to be released into the air. As above, the working medium to be used for the centrifugal refrigerator is strongly required to have not only a small global warming potential environmentally, but also high safety, namely low toxicity or low flammability particular.
In recent years, expectations are concentrated on compounds having a carbon-carbon double bond such as hydrofluoroolefin (HFO), hydrochlorofluoroolefin (HCFO), and chlorofluoroolefin (CFO), which are a working medium having less effect on the ozone layer and less effect on global warming because the carbon-carbon double bond is likely to be decomposed by OH radicals in the air. In this description, saturated HFC is called HFC and discriminated from HFO unless otherwise stated. Further, HFC may be clearly described as saturated hydrofluorocarbon in some cases.
Among HFO, HCFO, and CFO each having the carbon-carbon double bond described above, HCFO and CFO are compounds having suppressed flammability because they are high in proportion of halogen in one molecule. Therefore, as a working medium having less effect on the ozone layer and less effect on global warming and further having suppressed flammability, using HCFO and CFO has been considered. As such a working medium, a working medium using 1-chloro-2,3,3,3-tetrafluoropropene (to be referred to as “HCFO-1224yd” hereinafter) (for example, see Patent Document WO 2012/157763 A1), which is, for example, hydrochlorofluoropropene, has been known.
However, HCFO-1224yd is a compound having an unsaturated bond in its molecule and is a compound having a very short life in the air, and accordingly, under conditions that compression and heating are repeatedly performed in a heat cycle, it has a problem of being inferior in stability to saturated hydrofluorocarbon or hydrochlorofluorocarbon such as conventional HFC or HCFC.
Thus, there has been desired a method capable of efficiently operating a heat cycle system using HCFO-1224yd as a working medium, with improved stability while sufficiently taking advantage of cycle performance of HCFO-1224yd.
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