TECHNICAL FIELD

The present invention relates to a composition for a heat cycle system, and a heat cycle system employing the composition.

BACKGROUND ART

In this specification, abbreviated names of halogenated hydrocarbon compounds are described in brackets after the compound names, and in this specification, the abbreviated names are employed instead of the compound names as the case requires.

Heretofore, as a working fluid for a heat cycle system such as a refrigerant for a refrigerator, a refrigerant for an air-conditioning apparatus, a working fluid for power generation system (such as exhaust heat recovery power generation), a working fluid for a latent heat transport apparatus (such as a heat pipe) or a secondary cooling fluid, a chlorofluorocarbon (CFC) such as chlorotrifluoromethane or dichlorodifluoromethane or a hydrochlorofluorocarbon (HCFC) such as chlorodifluoromethane has been used. However, influences of CFCs and HCFCs over the ozone layer in the stratosphere have been pointed out, and their use is regulated at present.

Under the above conditions, as a working fluid for a heat cycle system, a hydrofluorocarbon (HFC) which has less influence over the ozone layer, such as difluoromethane (HFC-32), tetrafluoroethane or pentafluoroethane (HFC-125) has been used, instead of CFCs and HCFCs. For example, R410A (a pseudoazeotropic mixture fluid of HFC-32 and HFC-125 in a mass ratio of 1:1) is a refrigerant which has been widely used. However, it is pointed out that HFCs may cause global warming.

R410A has been widely used for a common air-conditioning apparatus such as a so-called package air-conditioner or room air-conditioner, due to its high refrigerating capacity. However, it has a global warming potential (GWP) of so high as 2,088, and accordingly development of a working fluid with low GWP has been desired. Further, development of a working fluid has been desired on the condition that R410A is simply replaced and existing apparatus will be used as they are.

In recent years, a hydrofluoroolefin (HFO) i.e. a HFC having a carbon-carbon double bond is expected, which is a working fluid having less influence over the ozone layer and having less influence over global warming, since the carbon-carbon double bond is likely to be decomposed by OH radicals in the air. In this specification, a saturated HFC will be referred to as a HFC and distinguished from a HFO unless otherwise specified. Further, a HFC may be referred to as a saturated hydrofluorocarbon in some cases.

As a working fluid employing a HFO, for example, Patent Document 1 discloses a technique relating to a working fluid using trifluoroethylene (HFO-1123) which has the above properties and with which excellent cycle performance will be obtained. Patent Document 1 also discloses an attempt to obtain a working fluid comprising HFO-1123 and various HFCs of HFOs in combination for the purpose of increasing the flame retardancy, cycle performance, etc. of the working fluid.

However, HFO-1123 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 under which compression and heating are repeatedly carried out in a heat cycle, it is inferior in the stability to a saturated hydrofluorocarbon or hydrochlorofluorocarbon such as a conventional HFC or HCFC.

Thus, a method for efficiently operating a heat cycle system employing HFO-1123 as a working fluid, with improved stability while excellent cycle performance of HFO-1123 is sufficiently made use of, has been desired.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: WO2012/157764

DISCLOSURE OF INVENTION

Technical Problem

The present invention has been made under these circumstances, and its object is to provide a composition for a heat cycle system comprising trifluoroethylene (HFO-1123), with more stabilized HFO-1123, while the low global warming potential and excellent cycle performance of HFO-1123 are sufficiently made use of, and a heat cycle system employing the composition, which has both less influence over global warming and high cycle performance, and with which the life of the working fluid for heat cycle is prolonged.

Solution to Problem

The present invention provides a working fluid for heat cycle, a composition for a heat cycle system and a heat cycle system of the following [1] to [15].

[1] A composition for a heat cycle system, which comprises a working fluid for heat cycle containing trifluoroethylene, and a stabilizer for preventing deterioration of the working fluid for heat cycle.

[2] The composition for a heat cycle system according to [1], wherein the stabilizer is at least one stabilizer selected from an oxidation resistance-improving agent, a heat resistance-improving agent and a metal deactivator.

[3] The composition for a heat cycle system according to [2], wherein the stabilizer is at least one compound selected from the group consisting of a phenol compound, an unsaturated hydrocarbon group-containing aromatic compound, an aromatic amine compound, an aromatic thiazine compound, a terpene compound, a quinone compound, a nitro compound, an epoxy compound, a lactone compound, an orthoester compound, a mono- or di-alkali metal salt compound of phthalic acid, and a thiodiphenyl ether hydroxide compound.
[4] The composition for a heat cycle system according to any one of [1] to [3], which contains the stabilizer in an amount of at least 1 mass ppm.
[5] The composition for a heat cycle system according to any one of [1] to [4], which further contains a refrigerant oil.
[6] The composition for a heat cycle system according to [5], wherein the refrigerant oil is at least one member selected from an ester refrigerant oil, an ether refrigerant oil, a polyglycol oil and a hydrocarbon refrigerant oil.
[7] The composition for a heat cycle system according to any one of [1] to [6], wherein the working fluid for heat cycle further contains at least one member selected from a saturated hydrofluorocarbon.
[8] The composition for a heat cycle system according to [7], wherein the saturated hydrofluorocarbon is at least one member selected from difluoromethane, 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane and pentafluoroethane.
[9] The composition for a heat cycle system according to any one of [1] to [8], wherein the working fluid for heat cycle further contains at least one member selected from a hydrofluorocarbon having a carbon-carbon double bond other than trifluoroethylene.
[10] The composition for a heat cycle system according to [9], wherein the hydrofluorocarbon having a carbon-carbon double bond is at least one member selected from 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene.
[11] The composition for a heat cycle system according to any one of [1] to [10], wherein the proportion of trifluoroethylene is at least 10 mass % based on the working fluid for heat cycle.
[12] The composition for a heat cycle system according to [11], wherein the proportion of trifluoroethylene is from 20 to 80 mass % based on the working fluid for heat cycle.
[13] The composition for a heat cycle system according to [11] or [12], wherein the working fluid for heat cycle further contains difluoromethane, and the proportion of difluoromethane is at least 20 mass % based on the working fluid for heat cycle.
[14] A heat cycle system, which employs the composition for a heat cycle system as defined in any one of [1] to [13].
[15] The heat cycle system according to [14], which is a refrigerating apparatus, an air-conditioning apparatus, a power generation system, a heat transport apparatus or a secondary cooling machine.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a composition for a heat cycle system comprising trifluoroethylene (HFO-1123), with a more stabilized working fluid for heat cycle containing HFO-1123, while the low global warming potential and excellent cycle performance of HFO-1123 are sufficiently made use of.

The heat cycle system of the present invention is a heat cycle system which has both less influence over global warming and high cycle performance, in which the working fluid for heat cycle is stabilized, and which is efficiently operated.

