JP7226623B2 - Working fluid for heat cycle, composition for heat cycle system, and heat cycle system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a working fluid for heat cycle, a composition for heat cycle system containing the same, and a heat cycle system using the composition.

Conventionally, refrigerants for refrigerators, refrigerants for air conditioners, working fluids for power generation systems (waste heat recovery power generation, etc.), working fluids for latent heat transport devices (heat pipes, etc.), working fluids for heat cycle systems such as secondary cooling media As such, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) have been used. However, it has been pointed out that CFCs and HCFCs have an impact on the ozone layer that exists in the stratosphere. CFCs in particular have a high ozone depletion potential (ODP). determined to be abolished.

Therefore, instead of CFCs and HCFCs, hydrofluorocarbons (HFCs), which have little effect on the ozone layer, have come to be used as working media for heat cycles. On the other hand, HFCs have a relatively high global warming potential (GWP) and are considered problematic.

For example, conventionally, trichlorofluoromethane (CFC-11) has been used as a working medium in centrifugal refrigerators used for cooling and heating of buildings, cold water production plants for industrial use, and the like. However, CFC-11, which has an ODP of 1 and a GWP of 4750, has already been completely abolished. Dichloro-2,2,2-trifluoroethane (HCFC-123) is used. As HFCs with a high GWP but an ODP of 0, 1,1,1,2-tetrafluoroethane (HFC-134a) with a GWP of 1430 and 1,1,1,3,3-tetrafluoroethane (HFC-134a) with a GWP of 1030 Pentafluoropropane (HFC-245fa) and the like are also used as substitutes for CFC-11.

On the other hand, hydrofluoroolefins (HFO), hydrochlorofluoroolefins (HCFO) and chlorofluoroolefins having a carbon-carbon double bond have recently been proposed as working media with less impact on the ozone layer and lower GWP. (CFO), etc. are expected. Since these working media have carbon-carbon double bonds, they are easily decomposed by OH radicals in the atmosphere. In this specification, saturated HFC is referred to as HFC unless otherwise specified, and is used to distinguish from HFO.

Among them, HCFO and CFO are compounds with suppressed flammability due to their high proportion of halogen in one molecule, and are being studied as working media with less environmental load and suppressed flammability. For example, Patent Document 1 describes a working medium using 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd).

WO2012/157763

The above working fluid using HCFO-1224yd has a low environmental load and good cycle performance. Such a working medium is required to maintain low flammability and to pose no problem in terms of safety.

Therefore, in the present invention, the ODP and GWP are sufficiently low, so that the impact on global warming is sufficiently suppressed, the cycle performance such as refrigerating capacity and coefficient of performance (COP) is good, and the combustibility is sufficiently high. An object of the present invention is to provide a working medium for thermal cycles that is suppressed and highly safe.

Another object of the present invention is to provide a composition for a heat cycle system containing such a working medium, and a heat cycle system using the composition.

The present invention has been made in view of the above, and provides a working fluid for heat cycle, a composition for heat cycle system, and a heat cycle system having the following configurations.

[1] A working fluid for thermal cycling containing 1-chloro-2,3,3,3-tetrafluoropropene and (E)-1,3,3,3-tetrafluoropropene, The total content of the 1-chloro-2,3,3,3-tetrafluoropropene and the 1,3,3,3-tetrafluoropropene contained in the medium is 50% by mass or more, and 1 -Chloro-2,3,3,3-tetrafluoropropene:(E)-1,3,3,3-tetrafluoropropene ratio is 20:80 to 99:1 on a mass basis A working medium for heat cycle characterized by:
[2] A thermal cycle working medium containing 1-chloro-2,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene, wherein The total content of the 1-chloro-2,3,3,3-tetrafluoropropene and the 2,3,3,3-tetrafluoropropene contained is 50% by mass or more, and 1-chloro- 2,3,3,3-tetrafluoropropene: A thermal cycle characterized in that the ratio represented by 2,3,3,3-tetrafluoropropene is 30:70 to 99:1 on a mass basis. Working medium for
[3] The 1-chloro-2,3,3,3-tetrafluoropropene is (E)-1-chloro-2,3,3,3-tetrafluoropropene: (Z)-1-chloro-2 , 3,3,3-tetrafluoropropene in a ratio of 50:50 to 0.01:99.99 on a mass basis.

[4] A composition for a heat cycle system comprising the working medium for heat cycle according to any one of [1] to [3].
[5] The composition for thermal cycle system according to [4], which contains lubricating oil.
[6] The composition for thermal cycle system according to [4] or [5], which contains a stabilizer that suppresses deterioration of the working medium for thermal cycle.

[7] A heat cycle system using the composition for heat cycle system according to any one of [4] to [6].
[8] The heat cycle system according to [7], wherein the heat cycle system is a freezer/refrigerator, an air conditioner, a power generation system, a heat transport device, or a secondary cooler.
[9] The heat cycle system according to [7] or [8], wherein the heat cycle system is a centrifugal refrigerator.
[10] The heat cycle system according to any one of [7] to [9], wherein the heat cycle system is a low-pressure centrifugal refrigerator.

According to the working medium for heat cycle and the composition for heat cycle system of the present invention, the working medium for heat cycle is excellent in cycle performance and sufficiently low in ODP and GWP to sufficiently suppress global warming. And a composition for a heat cycle system can be provided. Furthermore, the working medium for heat cycle and the composition for heat cycle system have sufficiently suppressed combustibility.

According to the heat cycle system of the present invention, since the composition for a heat cycle system of the present invention is used, the cycle performance is excellent, the environmental load can be reduced, and the combustibility is suppressed, so the safety is improved. It can be done.

1 is a schematic configuration diagram showing an example of a heat cycle system (refrigeration cycle system) of the present invention; FIG. FIG. 2 is a cycle diagram showing changes in state of a working medium for heat cycle on a pressure-enthalpy diagram in the heat cycle system of FIG. 1;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
In the present specification, with regard to halogenated hydrocarbons, abbreviations of the compounds are written in parentheses after the compound names, and the abbreviations are used in place of the compound names as necessary. In addition, (E) attached to the names and abbreviations of compounds having geometric isomers indicates the E-isomer (trans-isomer), and (Z) indicates the Z-isomer (cis-isomer). In the names and abbreviations of the compounds, if the E-isomer and Z-isomer are not specified, the names and abbreviations collectively include the E-isomer, the Z-isomer, and the mixture of the E-isomer and the Z-isomer.

As used herein, the term "thermal cycle system" refers to an operating system in which a thermal cycle working medium (hereinafter also simply referred to as a working medium) is introduced into the thermal cycle system to enable the thermal cycle to be performed. A system comprising a medium and a system for thermal cycling. "Heat cycle system" means a heat cycle designed to allow heat exchange (heat cycle) between the working medium and other substances other than the working medium by circulating the working medium in the system. system for

<Working medium for heat cycle>
As described above, the working medium for heat cycle use, which is an embodiment of the present invention, is obtained by mixing a specific working medium at a predetermined ratio. Specifically, the following two working media are mentioned.

<First heat cycle working medium>
The first thermal cycle working fluid of the present embodiment is 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd) and (E)-1,3,3,3-tetrafluoropropene. (HFO-1234ze (E)), the total content of HCFO-1224yd and HFO-1234ze (E) contained in the working medium is 50% by mass or more, and HCFO-1224yd: HFO-1234ze ( The ratio represented by E) is 20:80 to 99:1 on a mass basis.

<Second Working Medium for Heat Cycle>
The second thermal cycle working fluid of the present embodiment is 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd) and 2,3,3,3-tetrafluoropropene (HFO-1234yf). ), the total content of HCFO-1224yd and HFO-1234yf contained in the working medium is 50% by mass or more, and the ratio represented by HCFO-1224yd:HFO-1234yf is, on a mass basis, 30:70 to 99:1.

The working media of these embodiments are used in combination with a thermal cycling system. Further, these working mediums may be combined with compounds other than the working medium and used in the heat cycle system as a composition for heat cycle system containing these working mediums.

Next, each component contained in the working medium described above will be described.
(HCFO-1224yd)
HCFO-1224yd has in its molecule a halogen that suppresses combustibility and a carbon-carbon double bond that is easily decomposed by OH radicals in the atmosphere. It is an essential component also contained in the working medium.

This HCFO-1224yd has geometric isomers of HCFO-1224yd (Z) and HCFO-1224yd (E), the boiling point of HCFO-1224yd (Z) is 15 ° C., and the boiling point of HCFO-1224yd (E) is 19°C. GWP is <1 for both HCFO-1224yd(Z) and HCFO-1224yd(E). The ODP is 0 for both HCFO-1224yd(Z) and HCFO-1224yd(E). HCFO-1224yd(Z) has higher chemical stability than HCFO-1224yd(E).

In this specification, the notation "HCFO-1224yd" includes HCFO-1224yd(Z) alone, HCFO-1224yd(E) alone, a mixture of HCFO-1224yd(Z) and HCFO-1224yd(E), are interpreted as including any of
In the present embodiment, HCFO-1224yd preferably has a ratio of HCFO-1224yd (E):HCFO-1224yd (Z) of 50:50 to 0:100 on a mass basis. In terms of cost, it is more preferably 50:50 to 0.001:99.999, even more preferably 50:50 to 0.01:99.99, and 20:80 to 0.01. : 99.99 is particularly preferred.

(HFO-1234ze (E))
HFO-1234ze (E) has a carbon-carbon double bond in its molecule that is easily decomposed by OH radicals in the atmosphere. It is possible to obtain a working medium for heat cycle with good cycle performance while maintaining the above. This HFO-1234ze(E) has a boiling point of −15° C., a GWP of <1 and an ODP of 0.

(HFO-1234yf)
HFO-1234yf has a carbon-carbon double bond in its molecule that is easily decomposed by OH radicals in the atmosphere. , can be used as a working medium for thermal cycling with good cycle performance. This HFO-1234yf has a boiling point of −29.4° C., a GWP of <1 and an ODP of 0.

Table 1 shows the properties of HCFO-1224yd, HFO-1234ze(E), and HFO-1234yf, which are contained in the working fluid for heat cycle of the present embodiment, as the working fluid. Specifically, the properties shown here are compared with those of HCFO-1224yd(Z) alone in terms of boiling point, cycle performance, and environmental load.

(cycle performance)
Cycle performance includes, for example, the coefficient of performance and refrigeration capacity evaluated in the heat cycle system (refrigeration cycle system) shown in FIG. The coefficient of performance and refrigerating capacity of HCFO-1224yd (Z), HFO-1234ze (E) and HFO-1234yf are relative coefficients of performance and relative refrigerating capacity based on HCFO-1224yd (Z) alone (1.00). as shown in Table 1. A relative coefficient of performance and a relative refrigerating capacity greater than 1 indicate that the working medium has better cycle performance than HCFO-1224yd(Z).

(Environmental load)
Environmental impact is assessed by ODP and GWP. ODP is a value indicated by or measured according to the Ozone Layer Protection Law. GWP is the 100-year value given in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (2007) or measured according to the method of that report. In this specification, GWP refers to this value unless otherwise specified. The GWP of the working medium, which is a mixture, is a weighted average based on the composition mass of each component.

From Table 1, HFO-1234ze (E) is much superior in refrigerating capacity as a working medium compared to HCFO-1224yd (Z) alone, has the same coefficient of performance, and has environmental load such as GWP. is small.

In addition, HFO-1234yf, as compared with HCFO-1224yd(Z) alone, has a very excellent refrigerating capacity as a working medium, almost the same coefficient of performance, and a small environmental load such as GWP.

The working fluid for heat cycle of the present embodiment contains HCFO-1224yd (Z) and HFO-1234ze (E) or HFO-1234yf in an arbitrary ratio, thereby further improving cycle performance and improving combustibility. It is a working medium with good safety that sufficiently suppresses In other words, the working fluid for heat cycle of this embodiment is a working fluid for heat cycle with further improved functions compared to conventionally used HCFO-1224yd(Z).

Here, when the working medium is a mixture containing a plurality of compounds as described above, it is necessary to consider the temperature gradient. The temperature gradient is an index that measures the difference in composition between the liquid phase and the gas phase in the working medium of the mixture. shown. The temperature gradient is 0 in the compound alone and in the azeotrope, and the temperature gradient is extremely close to 0 in the pseudo-azeotrope, which exhibits a behavior close to that of the azeotrope (small change in gas-liquid composition) during evaporation.

If the temperature gradient is large, for example, the temperature at the inlet of the evaporator drops, which increases the possibility of frost formation, which is a problem. Furthermore, in the heat cycle system, in order to improve the heat exchange efficiency, it is common to make the working medium flowing through the heat exchanger and the heat source fluid such as water or air flow countercurrently, and this is the case in a stable operating state. Due to the small temperature difference of the heat source fluid, it is difficult to obtain an energy efficient thermal cycling system for non-azeotropic mixtures with large temperature gradients. Therefore, when a mixture is used as a working medium, a working medium having an appropriate temperature gradient is desired.

A mixture of HCFO-1224yd(Z) and HFO-1234ze(E) and a mixture of HCFO-1224yd(Z) and HFO-1234yf do not azeotrope at any mixture ratio. That is, these mixtures are non-azeotropic mixtures at any mixing ratio.

Therefore, in the working medium for heat cycle of the present embodiment, when the above mixture is used, it is preferable to set the composition in consideration of the temperature gradient. The temperature gradient is, for example, preferably 14° C. or less, more preferably 13° C. or less, and even more preferably 12° C. or less.

In addition, since there is almost no change in the environmental load such as GWP due to the composition change in the above mixture, the mixture of HCFO-1224yd (Z) and HFO-1234ze (E), A preferred composition may be selected mainly by considering the balance between cycle performance and temperature gradient.

In addition, as a preferred composition of the mixture of HCFO-1224yd (Z) and HFO-1234ze (E) in the working fluid for heat cycle of the present embodiment, considering the balance between combustibility, cycle performance and temperature gradient, HCFO A composition in which the ratio of HCFO-1224yd (Z) is 20 to 99% by mass and the ratio of HFO-1234ze (E) is 80 to 1% by mass with respect to the total amount of -1224yd (Z) and HFO-1234ze (E) mentioned. If the composition of HCFO-1224yd (Z) and HFO-1234ze (E) in the working medium is within the above range, it is possible to sufficiently suppress combustibility while improving cycle performance.

The composition preferably has a ratio of HCFO-1224yd(Z) of 40 to 99% by mass, a ratio of HFO-1234ze(E) of 60 to 1% by mass, and a ratio of HCFO-1224yd(Z) of 70 to 99% by mass. Particularly preferred is 99% by mass and a proportion of HFO-1234ze(E) of 30 to 1% by mass.

A preferred composition of the mixture of HCFO-1224yd(Z) and HFO-1234yf in the working fluid for heat cycle of the present embodiment is HCFO-1224yd(Z) in consideration of the balance between combustibility, cycle performance and temperature gradient. and HFO-1234yf, the ratio of HCFO-1224yd(Z) is 30 to 99% by mass and the ratio of HFO-1234yf is 70 to 1% by mass. If the composition of HCFO-1224yd(Z) and HFO-1234yf in the working medium is within the above range, it is possible to sufficiently suppress combustibility while improving cycle performance.

The composition preferably has a proportion of HCFO-1224yd(Z) of 50 to 99% by mass, a proportion of HFO-1234yf of 50 to 1% by mass, and a proportion of HCFO-1224yd(Z) of 80 to 99% by mass. , HFO-1234yf in a proportion of 20 to 1% by weight is particularly preferred.

In these mixtures, the total content of HCFO-1224yd(Z) and HFO-1234ze(E) or the total content of HCFO-1224yd(Z) and HFO-1234yf is 50% by mass or more relative to the total amount of the working medium. The total content is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 100% by mass with respect to the total amount of the working medium.

If the total content of HCFO-1224yd(Z) and HFO-1234ze(E) or the total content of HCFO-1224yd(Z) and HFO-1234yf is within the above range, the cycle performance of the working fluid is improved, Combustibility can be sufficiently suppressed. These working media furthermore serve as working media for thermal cycling, which have favorable features such as less load on the environment and almost no problem of temperature gradients.

From the viewpoint of further improving the cycle performance of the working medium, the working medium for thermal cycling of the present embodiment preferably contains HCFO-1224yd(Z), HFO-1234ze(E), and HFO-1234yf. In this case, the ratio of HCFO-1224yd (Z) to the total amount of HCFO-1224yd (Z), HFO-1234ze (E) and HFO-1234yf is 10 to 50% by mass, and the ratio of HFO-1234ze (E) is 40 to It is preferable that the ratio of HFO-1234yf is 80% by mass and 10 to 50% by mass.

(Evaluation method for cycle performance, combustibility and temperature gradient)
The cycle performance (refrigerating capacity (Q), coefficient of performance (COP)), combustibility and temperature gradient of the working medium for thermal cycle can be evaluated using, for example, a refrigeration cycle system whose schematic diagram is shown in FIG.

The refrigerating cycle system 10 shown in FIG. 1 includes a compressor 11 that compresses a working medium vapor A into a high-temperature and high-pressure working medium vapor B, and cools and liquefies the working medium vapor B discharged from the compressor 11. A condenser 12 as a low-temperature and high-pressure working medium C, an expansion valve 13 for expanding the working medium C discharged from the condenser 12 into a low-temperature and low-pressure working medium D, and a working medium D discharged from the expansion valve 13. is heated to form a high-temperature and low-pressure working medium vapor A, a pump 15 that supplies a load fluid E to the evaporator 14, and a pump 16 that supplies a fluid F to the condenser 12. It is a system that

In the refrigeration cycle system 10, the following cycles (i) to (iv) are repeated.
(i) The working medium vapor A discharged from the evaporator 14 is compressed by the compressor 11 into a high-temperature, high-pressure working medium vapor B (hereinafter referred to as "AB process").
(ii) The working medium vapor B discharged from the compressor 11 is cooled by the fluid F in the condenser 12 and liquefied to form a low-temperature, high-pressure working medium C. At this time, the fluid F is heated to become a fluid F' and discharged from the condenser 12 (hereinafter referred to as "BC process").
(iii) The working medium C discharged from the condenser 12 is expanded by the expansion valve 13 to form a low-temperature, low-pressure working medium D (hereinafter referred to as "CD process").
(iv) The working medium D discharged from the expansion valve 13 is heated by the load fluid E in the evaporator 14 to produce a high-temperature, low-pressure working medium vapor A. At this time, the load fluid E is cooled to become a load fluid E' and discharged from the evaporator 14 (hereinafter referred to as "DA process").

The refrigeration cycle system 10 is a cycle system including adiabatic/isentropic change, isenthalpy change, and isobaric change. If the state change of the working medium is described on the pressure-enthalpy line (curve) diagram shown in FIG. 2, it can be represented as a trapezoid with A, B, C, and D as vertices.

The AB process is a process in which adiabatic compression is performed in the compressor 11 to convert the high-temperature, low-pressure working medium vapor A into the high-temperature, high-pressure working medium vapor B, and is indicated by line AB in FIG. As will be described later, the working medium vapor A is introduced into the compressor 11 in a superheated state, and the resulting working medium vapor B is also in a superheated state.

The discharge pressure is the pressure (Px) in the state of B in FIG. 2, which is the maximum pressure in the refrigeration cycle. Further, the temperature (Tx) in the state of B in FIG. 2 is the discharge temperature, which is the maximum temperature in the refrigeration cycle. As will be explained below, since the BC process is isobaric cooling, the discharge pressure shows the same value as the condensation pressure. Therefore, in FIG. 2, the condensing pressure is indicated as Px for convenience.

The BC process is a process in which isobaric cooling is performed in the condenser 12 to convert the high-temperature, high-pressure working medium vapor B into the low-temperature, high-pressure working medium C, and is indicated by the BC line in FIG. The pressure at this time is the condensation pressure. Among the intersection points of the pressure-enthalpy line and the BC line, the intersection point _T1 on the high enthalpy side is the condensation temperature, and the intersection point _T2 on the low enthalpy side is the condensation boiling temperature. Here, the temperature gradient when the working medium is a non-azeotropic mixed medium is shown as the difference between _T1 and _T2 .

The CD process is a process in which the expansion valve 13 performs isenthalpic expansion to convert the low-temperature, high-pressure working medium C into a low-temperature, low-pressure working medium D, and is indicated by line CD in FIG. If the temperature of the low-temperature, high-pressure working medium C is denoted by T ₃ , T ₂ -T ₃ is the degree of supercooling (SC) of the working medium in the cycles (i) to (iv).

The DA process is a process in which isobaric heating is performed in the evaporator 14 and the low-temperature, low-pressure working medium D is returned to the high-temperature, low-pressure working medium vapor A, and is indicated by the DA line in FIG. The pressure at this time is the evaporation pressure. Among the intersection points of the pressure-enthalpy line and the DA line, the intersection point _T6 on the high enthalpy side is the evaporation temperature. Denoting the temperature of the working medium vapor A by T ₇ , T ₇ -T ₆ is the superheat (SH) of the working medium in cycles (i) to (iv). Note that _T4 indicates the temperature of the working medium D.

The refrigerating capacity (Q) and coefficient of performance (COP) of the working medium are A (after evaporation, high temperature and low pressure), B (after compression, high temperature and high pressure), C (after condensation, low temperature and high pressure), D (after expansion , low temperature and low pressure), each enthalpy, h _A , h _B , h _C , and h _D in each state are obtained from the following equations (A) and (B), respectively. At this time, it is assumed that there is no loss due to equipment efficiency and no pressure loss in piping and heat exchangers.

The thermodynamic properties necessary for calculating the cycle performance of the working medium can be calculated based on the generalized equation of state (Soave-Redlich-Kwong equation) based on the corresponding state principle and thermodynamic relational expressions. If the characteristic values are not available, calculations are made using the estimation method based on the atomic group contribution method.

Q= _hA - _hD (A)
COP=Q/compression work=(h _A −h _D )/(h _B −h _A ) (B)

Q indicated by (h _A - h _D ) above corresponds to the output (kW) of the refrigeration cycle, and the compression work indicated by (h _B - h _A ), for example, required to operate the compressor The amount of electric power corresponds to the consumed power (kW). Also, Q means the ability to refrigerate the load fluid, and the higher the Q, the more work can be done in the same system. In other words, a large Q indicates that the desired performance can be obtained with a small amount of working medium, and the system can be miniaturized.

The numerical values in Table 1 are also based on the above calculation method, but the temperature conditions of the refrigeration cycle at this time are based on the numerical values when the following temperatures are used for evaluation.

Evaporation temperature; 5°C (average temperature of evaporation start temperature and evaporation completion temperature)
Condensation completion temperature; 40°C (average temperature of condensation start temperature and condensation completion temperature)
Degree of supercooling (SC); 5°C
Degree of superheat (SH); 0°C
Compressor efficiency: 0.8

(Optional component)
In addition to HCFO-1224yd and HFO-1234ze(E) or HCFO-1224yd and HFO-1234yf, the working medium for heat cycle of the present embodiment contains a known compound used as a working medium for the total amount of the working medium for heat cycle. may optionally be contained at a rate of 50% by mass or less. When such a compound (optional component) is contained, the ratio of this compound (optional component) to the total amount of the working medium is more preferably 30% by mass or less, further preferably 20% by mass or less, and particularly 10% by mass or less. Preferably, 5% by mass or less is most preferable.

Examples of optional components include HFCs, HFOs other than HFO-1234ze(E) and HFO-1234yf (hereinafter also referred to as "other HFOs"), HCFOs other than HCFO-1224yd (hereinafter also referred to as "other HCFOs"). ) and trans-1,2-dichloroethylene.

When the optional component is combined with a mixture of HCFO-1224yd and HFO-1234ze (E) or a mixture of HCFO-1224yd and HFO-1234yf to form a working medium, it has the effect of further increasing cycle performance, while increasing GWP and the like. It is preferable to select from the viewpoint of keeping the load on the environment within an allowable range and sufficiently ensuring safety such as not improving combustibility.

(HFC)
HFC is known to have a higher GWP than HCFO-1224yd, HFO-1234ze(E) and HFO-1234yf. Therefore, as an HFC combined with a mixture of HCFO-1224yd and HFO-1234ze(E) or a mixture of HCFO-1224yd and HFO-1234yf, when used as a working medium, the environmental load such as GWP in particular should be within the allowable range. It is preferable to select it appropriately while keeping in mind that it should be kept.

Specifically, HFCs having 1 to 5 carbon atoms are preferable as HFCs having a low environmental load such as GWP. HFCs may be linear, branched, or cyclic.

HFCs include difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, heptafluorocyclopentane and the like.

Among these, 1,1,2,2-tetrafluoroethane, HFC-134a, HFC-245fa, and 1,1,1,3,3-pentafluorobutane (HFC-365mfc) are more preferred, and HFC-134a , HFC-245fa and HFC-365mfc are more preferred. HFC may be used individually by 1 type, and may be used in combination of 2 or more type.

(HFO)
Even HFOs other than HFO-1234ze(E) and HFO-1234yf have an order of magnitude lower GWP than HFCs. Therefore, other HFOs are preferably selected as appropriate, taking into account that safety can be ensured without improving cycle performance as a working medium and combustibility, rather than considering GWP.

Other HFOs include HFO-1336mzz (Z), HFO-1336mzz (E), 1,2-difluoroethylene (HFO-1132), 2-fluoropropene (HFO-1261yf), 1,1,2-trifluoro Propene (HFO-1243yc), (E)-1,2,3,3,3-pentafluoropropene (HFO-1225ye (E)), (Z)-1,2,3,3,3-pentafluoropropene (HFO-1225ye (Z)), (Z)-1,3,3,3-tetrafluoropropene (HFO-1234ze (Z)), 3,3,3-trifluoropropene (HFO-1243zf) .

Preferred other HFOs are HFO-1234ze(Z) and HFO-1243zf. Other HFOs may be used singly or in combination of two or more. Incidentally, HFO-1234ze(Z) has a boiling point of 9.7° C., a GWP of <1, and an ODP of 0.

(HCFO)
HCFOs include 1-chloro-2,2-difluoroethylene (HCFO-1122), 1,2-dichlorofluoroethylene (HCFO-1121), 1-chloro-2-fluoroethylene (HCFO-1131), 2-chloro -3,3,3-trifluoropropene (HCFO-1233xf), 1-chloro-2,3,3-trifluoro-1-propene (HCFO-1233yd) and 1-chloro-3,3,3-tetrafluoro Propene (HCFO-1233zd) may be mentioned.

As another HCFO, HCFO-1233zd is preferable because it has a high critical temperature and is excellent in durability and coefficient of performance. Other HCFOs may be used singly or in combination of two or more.

(Other optional ingredients)
The working medium used in the heat cycle system of the present embodiment may contain carbon dioxide, hydrocarbons, chlorofluoroolefins (CFO), etc., in addition to the above components. Other optional components are preferably components that have little impact on the ozone layer and have little impact on global warming.

Hydrocarbons include propane, propylene, cyclopropane, butane, isobutane, pentane, isopentane, and the like. One type of hydrocarbon may be used alone, or two or more types may be used in combination. Containing hydrocarbons improves the solubility of the mineral lubricating oil in the working medium.
When the working medium contains hydrocarbons, the content of hydrocarbons is preferably 10% by mass or less, more preferably 5% by mass or less, relative to 100% by mass of the working medium, from the viewpoint of combustibility. .

CFOs include chlorofluoropropene, chlorofluoroethylene, and the like. From the point that it is easy to suppress the combustibility of the working medium without significantly reducing the cycle performance of the working medium, as the CFO, 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya), 1 ,3-dichloro-1,2,3,3-tetrafluoropropene (CFO-1214yb) and 1,2-dichloro-1,2-difluoroethylene (CFO-1112) are preferred. One type of CFO may be used alone, or two or more types may be used in combination.

When the working medium contains the above optional components, the content of each optional component is 50% by mass or less, preferably 30% by mass or less, and further 20% by mass or less, relative to 100% by mass of the working medium. Preferably, 10% by mass or less is particularly preferable. When a plurality of optional components are contained, the total content of the optional components in the working medium is 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, relative to 100% by mass of the working medium, 10% by mass or less is particularly preferred.

<Composition for heat cycle system>
The working medium of the present embodiment can be used as the composition for the heat cycle system of the present embodiment, including the working medium, when applied to the heat cycle system. The composition for a heat cycle system of the present embodiment usually contains lubricating oil in addition to the working medium of the present embodiment described above. In addition, the composition for thermal cycle system of the present embodiment may contain known additives such as stabilizers and leak detection substances. These lubricating oils and additives can also be used in combination.

(Lubricant)
As the lubricating oil, known lubricating oils conventionally used in working medium compositions can be employed without particular limitation, together with working mediums comprising halogenated hydrocarbons. Specific examples of lubricating oils include oxygen-containing synthetic oils (ester-based lubricating oils, ether-based lubricating oils, etc.), fluorine-based lubricating oils, mineral-based lubricating oils, hydrocarbon-based synthetic oils, and the like.

Examples of ester-based lubricating oils include dibasic acid ester oils, polyol ester oils, complex ester oils, and polyol carbonate ester oils.

Ether lubricating oils include polyvinyl ether oils and polyoxyalkylene oils such as polyglycol oils.

Examples of fluorine-based lubricating oils include synthetic oils (mineral oils, poly-α-olefins, alkylbenzenes, alkylnaphthalenes, etc. described later) in which hydrogen atoms are substituted with fluorine atoms, perfluoropolyether oils, fluorinated silicone oils, and the like. be done.

As mineral lubricating oils, the lubricating oil fraction obtained by atmospheric distillation or vacuum distillation of crude oil is subjected to refining treatment (solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrogenation refining, clay treatment, etc.), and refined paraffinic mineral oils, naphthenic mineral oils, and the like.

Examples of hydrocarbon-based synthetic oils include poly-α-olefins, alkylbenzenes, alkylnaphthalenes, and the like.

Lubricating oils may be used alone or in combination of two or more.
As the lubricating oil, one or more selected from polyol ester oil, polyvinyl ether oil and polyglycol oil are preferable from the viewpoint of compatibility with the working medium.

The amount of lubricating oil to be added may be within a range that does not significantly reduce the effects of the present invention, and is preferably 10 to 100 parts by mass, more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the working medium.

(stabilizer)
Stabilizers are components that improve the stability of the working medium against heat and oxidation. As the stabilizer, known stabilizers conventionally used in thermal cycle systems, such as oxidation resistance improvers, heat resistance improvers, metal deactivators, etc., can be used together with a working medium comprising a halogenated hydrocarbon without particular limitation. can be adopted.

Examples of oxidation resistance improvers and heat resistance improvers include N,N'-diphenylphenylenediamine, p-octyldiphenylamine, p,p'-dioctyldiphenylamine, N-phenyl-1-naphthylamine, and N-phenyl-2-naphthylamine. , N-(p-dodecyl)phenyl-2-naphthylamine, di-1-naphthylamine, di-2-naphthylamine, N-alkylphenothiazine, 6-(t-butyl)phenol, 2,6-di-(t-butyl ) phenol, 4-methyl-2,6-di-(t-butyl)phenol, 4,4′-methylenebis(2,6-di-t-butylphenol) and the like. The oxidation resistance improver and the heat resistance improver may be used singly or in combination of two or more.

Metal deactivators include imidazole, benzimidazole, 2-mercaptobenzthiazole, 2,5-dimethylcaptothiadiazole, salicyridin-propylenediamine, pyrazole, benzotriazole, toltriazole, 2-methylbenzamidazole, 3,5- Dimethylpyrazole, methylenebis-benzotriazole, organic acids or their esters, primary, secondary or tertiary aliphatic amines, amine salts of organic or inorganic acids, heterocyclic nitrogen-containing compounds, alkyl acid phosphates amine salts or derivatives thereof.

The stabilizer may be added in an amount that does not significantly reduce the effects of the present invention.

(leak detection substance)
Leak detection materials include ultraviolet fluorescent dyes, odorous gases, and odor masking agents.
As the ultraviolet fluorescent dye, U.S. Pat. known ultraviolet fluorescent dyes conventionally used in thermal cycling systems together with working media comprising halogenated hydrocarbons.

As the odor masking agent, there are known perfumes used in heat cycle systems together with a working medium comprising a halogenated hydrocarbon, such as those described in Japanese Patent Application Publication No. 2008-500437 and Japanese Patent Application Publication No. 2008-531836. mentioned.

When a leak detection substance is used, a solubilizer that improves the solubility of the leak detection substance in the working medium may be used.

Examples of the solubilizer include those described in JP-A-2007-511645, JP-A-2008-500437 and JP-A-2008-531836.

The amount of the leakage detection substance to be added may be within a range that does not significantly reduce the effects of the present invention, and is preferably 2 parts by mass or less, more preferably 0.5 parts by mass or less with respect to 100 parts by mass of the working medium.

<Heat cycle system>
The heat cycle system of the present embodiment is obtained by applying the composition for a heat cycle system containing the above working medium to a heat cycle device or device. The heat cycle system includes a heat cycle system including heat exchangers such as compressors, condensers, and evaporators.

The heat cycle system of the present embodiment may be a heat pump system using hot heat obtained by a condenser, or a refrigeration cycle system using cold heat obtained by an evaporator. The heat cycle system of this embodiment may be of a flooded evaporator type or a direct expansion type. In the heat cycle system of the present embodiment, the substance other than the working medium that exchanges heat with the working medium is preferably water or air.

Specific examples of the heat cycle system of the present embodiment include freezer/refrigerator equipment, air conditioners, power generation systems, heat transport equipment, secondary coolers, and the like. In particular, the heat cycle system of this embodiment is preferably used as an air conditioner, which is often installed outdoors, because it can stably exhibit cycle performance even in a higher temperature operating environment. Moreover, the heat cycle system of this embodiment is preferably used as a freezer/refrigerator.

As the power generation system, a power generation system based on a Rankine cycle system is preferable. Specifically, as a power generation system, the working medium is heated by geothermal energy, solar heat, waste heat in a medium to high temperature range of about 50 to 200 ° C, etc. in an evaporator, and the working medium that has become high-temperature and high-pressure steam is expanded. A system in which adiabatic expansion is performed in a machine and the work generated by the adiabatic expansion drives a generator to generate power is exemplified.

Further, the heat cycle system of this embodiment may be a heat transport device. A latent heat transport device is preferable as the heat transport device. Examples of latent heat transport devices include heat pipes and two-phase closed thermosiphon devices that transport latent heat using phenomena such as evaporation, boiling, and condensation of a working medium enclosed in the device. A heat pipe is applied to a relatively small cooling device such as a cooling device for a heat-generating part of a semiconductor element or an electronic device. Since the two-phase closed thermosiphon does not require a wig and has a simple structure, it is widely used for gas-gas heat exchangers, promotion of snow melting on roads, and prevention of freezing.

Specific examples of freezing/refrigerating equipment include showcases (built-in showcases, separate showcases, etc.), commercial freezers/refrigerators, vending machines, ice machines, and the like.

Specific examples of air conditioning equipment include room air conditioners, package air conditioners (store package air conditioners, building package air conditioners, facility package air conditioners, etc.), heat source equipment chilling units, gas engine heat pumps, air conditioners for trains, and air conditioners for automobiles. etc.

Examples of the chilling unit for the heat source equipment include volumetric compression refrigerators and centrifugal refrigerators. Centrifugal refrigerators, which will be described below, have a large amount of working medium filled, so the effects of the present embodiment are more pronounced. It is preferable to be able to obtain

Here, the centrifugal refrigerator is a refrigerator using a centrifugal compressor. A centrifugal refrigerator is a type of vapor compression refrigerator, and is usually called a turbo refrigerator. A centrifugal compressor has an impeller, and compresses the working medium by discharging the working medium to the outer periphery with the rotating impeller. Centrifugal refrigerators are used in office buildings, district cooling and heating, cooling and heating in hospitals, semiconductor factories, cold water production plants in the petrochemical industry, and the like.

The centrifugal refrigerator may be either a low-pressure type or a high-pressure type, but a low-pressure centrifugal refrigerator is preferable. In addition, the low-pressure type refers to, for example, CFC-11, HCFC-123, HFC-245fa, etc., which are not subject to the application of the High Pressure Gas Safety Law, that is, "at normal temperature, the pressure becomes 0.2 MPa or more Liquefied gas with a pressure of 0.2 MPa or higher, or a centrifugal refrigerator that uses a working medium that does not fall under "liquefied gas whose temperature is 35°C or lower when the pressure is 0.2 MPa or higher." .

In addition, when the heat cycle system is operated, it is preferable to provide a means for suppressing the mixing of moisture and non-condensable gas such as oxygen in order to avoid the occurrence of problems caused by the mixing of these gases.

Moisture entrapment in thermal cycling systems can cause problems, especially when used at low temperatures. For example, problems such as freezing in the capillary tube, hydrolysis of the working medium and refrigerating machine oil, deterioration of materials due to acid components generated in the cycle, generation of contaminants, and the like occur. In particular, when the refrigerating machine oil is polyalkylene glycol, polyol ester, or the like, it has extremely high hygroscopicity and is likely to undergo a hydrolysis reaction. cause. Therefore, in order to suppress hydrolysis of the refrigerating machine oil, it is necessary to control the moisture concentration in the heat cycle system.

As a method for controlling the moisture concentration in the heat cycle system, there is a method using moisture removing means such as a desiccant (silica gel, activated alumina, zeolite, etc.). From the viewpoint of dehydration efficiency, the desiccant is preferably brought into contact with the liquid composition for a heat cycle system. For example, it is preferable to place a desiccant at the outlet of the condenser or the inlet of the evaporator to contact the thermal cycle system composition.

As the desiccant, a zeolite-based desiccant is preferable from the viewpoint of the chemical reactivity between the desiccant and the composition for a heat cycle system and the ability of the desiccant to absorb moisture.

As the zeolite-based desiccant, when using a refrigerating machine oil having a higher hygroscopicity than a conventional mineral refrigerating machine oil, the compound represented by the following formula (C) is the main component because of its excellent hygroscopic ability. Zeolitic desiccants are preferred.

_{M2 /nO.Al2O3.xSiO2.yH2O ( C )}

However, M is a Group 1 element such as Na or K or a Group 2 element such as Ca, n is the valence of M, and x and y are values determined by the crystal structure. By changing M, the pore size can be adjusted.

Pore size and breaking strength are important in selecting a desiccant. When using a desiccant having a pore diameter larger than the molecular diameter of various components such as a working medium contained in the composition for a heat cycle system (hereinafter referred to as "working medium, etc."), the working medium, etc. is adsorbed in the desiccant. As a result, a chemical reaction occurs between the working medium and the desiccant, resulting in undesirable phenomena such as the generation of non-condensable gas, a decrease in the strength of the desiccant, and a decrease in adsorption capacity.

Therefore, it is preferable to use a zeolite-based desiccant with a small pore size as the desiccant. In particular, a sodium-potassium A-type synthetic zeolite having a pore size of 3.5 angstroms or less is preferable. By applying a sodium-potassium A-type synthetic zeolite having a pore diameter smaller than the molecular diameter of the working medium, etc., it is possible to selectively adsorb and remove only moisture in the heat cycle system without adsorbing the working medium. In other words, since adsorption to a desiccant such as a working medium is unlikely to occur, thermal decomposition is unlikely to occur, and as a result, deterioration of materials constituting the thermal cycle system and generation of contaminants can be suppressed.

If the size of the zeolite-based desiccant is too small, it may cause clogging in the valves and piping details of the heat cycle system, and if it is too large, the drying capacity will decrease. . The shape is preferably granular or cylindrical.

The zeolite-based desiccant can be made into any shape by solidifying powdered zeolite with a binder (bentonite, etc.). Other desiccants (silica gel, activated alumina, etc.) may be used in combination as long as the zeolite desiccant is the main component.

Furthermore, if a noncondensable gas enters the heat cycle system, it will have adverse effects such as poor heat transfer in the condenser and evaporator and an increase in operating pressure, so it is necessary to suppress the entry as much as possible. In particular, oxygen, which is one of the noncondensable gases, reacts with the working medium and refrigerating machine oil to promote decomposition.

The concentration of the noncondensable gas in the gas phase portion of the working medium is preferably 1.5% by volume or less, particularly preferably 0.5% by volume or less, in terms of volume ratio to the working medium.

Although the heat cycle system of this embodiment has been described above, the heat cycle system of this embodiment is not limited to the above. These embodiments may be modified or varied without departing from the spirit and scope of the invention.

The heat cycle system of the present embodiment uses a predetermined composition for heat cycle system containing the working medium of the present embodiment. Therefore, a heat cycle system using the composition for a heat cycle system containing this working medium has good cycle performance as described above, and has sufficiently low ODP and GWP to suppress the impact on global warming. It is an excellent one that exhibits the characteristics of a working medium that is suppressed in combustibility and has high safety. In particular, since the combustibility of the working medium is suppressed, dangers such as fire and explosion can be avoided even if some trouble occurs in the thermal cycle system.

[EXAMPLES] Hereafter, although an Example demonstrates this invention in detail, this invention is not limited to a following Example.

[Examples 1-1 to 1-9]
A working medium was prepared by mixing HCFO-1224yd (Z) and HFO-1234ze (E) in the proportions shown in Table 2, and the temperature gradient and refrigeration cycle performance (refrigeration capacity Q and coefficient of performance COP) were measured by the following method. bottom.

<Measurement of temperature gradient and refrigeration cycle performance>
The temperature gradient and the refrigeration cycle performance (refrigeration capacity and coefficient of performance) are measured by applying a working medium to the refrigeration cycle system 10 shown in FIG. , isobaric cooling by the condenser 12 in the BC process, isenthalpic expansion by the expansion valve 13 in the CD process, and isobaric heating by the evaporator 14 in the DA process.

The measurement conditions were that the evaporation temperature of the working medium in the evaporator 14 (average temperature of the evaporation start temperature and the evaporation completion temperature) was 5°C, the condensation completion temperature of the working medium in the condenser 12 (the average temperature of the condensation start temperature and the condensation completion temperature ) was performed at 40°C, the degree of supercooling (SC) of the working medium in the condenser 12 was 5°C, and the degree of superheating (SH) of the working medium in the evaporator 14 was 0°C. In addition, it is assumed that the compressor efficiency is 0.8 and that there is no pressure loss in piping and heat exchangers.

The refrigerating capacity and coefficient of performance are determined by the enthalpy of each state of the working medium A (high temperature and low pressure after evaporation), B (high temperature and high pressure after compression), C (low temperature and high pressure after condensation), and D (low temperature and low pressure after expansion). It was obtained from the above formulas (A) and (B) using h.

The thermodynamic properties required for calculating the refrigeration cycle performance were calculated based on the generalized equation of state (Soave-Redlich-Kwong equation) based on the corresponding state principle and thermodynamic relational expressions. When characteristic values were not available, calculations were made using an estimation method based on the atomic group contribution method.

The refrigerating capacity and the coefficient of performance were obtained as relative ratios when the refrigerating capacity and the coefficient of performance of HCFC-1224yd(Z) measured in the same manner as above were assumed to be 1.00, respectively. The temperature gradient was determined as the difference between _T1 and _T2 in FIG. Also, the GWP of the working medium was obtained as a weighted average by composition mass based on the GWP of each compound shown in Table 1. That is, the GWP of the working medium was obtained by dividing the sum of the product of the mass % of each compound constituting the working medium and the GWP by 100. The working media of Examples 1-1 to 1-9 all have an ODP of 0.

[Examples 2-1 to 2-8]
A working medium was prepared by mixing HCFO-1224yd(Z) and HFO-1234yf in the proportions shown in Table 3, and the temperature gradient and refrigeration cycle performance (refrigeration capacity Q and coefficient of performance COP) were measured in the same manner as in Example 1 above. It was measured. The ODP of the working fluids of Examples 2-1 to 2-8 is 0.

[Examples 3-1 to 3-15]
A working medium was prepared by mixing HCFO-1224yd (Z), HFO-1234ze (E) and HFO-1234yf in the proportions shown in Table 4, and the temperature gradient and refrigeration cycle performance (refrigeration capacity Q and coefficient of performance (COP) were measured. The working media of Examples 3-1 to 3-15 all have an ODP of 0.

[Examples 4-1 to 4-9]
A working medium was prepared by mixing HCFO-1224yd (Z) and HFO-1234ze (Z) at the ratios shown in Table 5, and the temperature gradient and refrigeration cycle performance (refrigeration capacity Q and coefficient of performance) were evaluated in the same manner as in Example 1 above. COP) was measured. The working media of Examples 4-1 to 4-9 all have an ODP of 0.

As can be seen from Tables 2 to 5, the working fluids of Examples 1-1 to 1-9, Examples 2-1 to 2-8 and Examples 3-1 to 3-15 are all HCFO-1224yd (Z) Compared to Examples 4-1 to 4-9 using a single working medium or a mixed working medium of HCFO-1224yd (Z) and HFO-1234ze (Z), the refrigerating capacity is excellent, and the coefficient of performance is It is a working fluid for thermal cycling that is substantially equivalent, has sufficient cycle performance, and has sufficiently low ODP and GWP to sufficiently suppress the impact on global warming.

<Combustibility test>
Next, a working medium for heat cycle consisting of the mixtures obtained in Examples 1-6 to 1-9 and Examples 2-6 to 2-8, and further HCFO-1224yd (Z) at 10% by mass and HFO-1234ze A working medium for thermal cycling comprising a mixture containing 90% by mass of (E) (Example 1-10), and a working medium for thermal cycling comprising a mixture comprising 20% by mass of HCFO-1224yd (Z) and 80% by mass of HFO-1234yf. For (Example 2-9), each working medium was mixed with air at a ratio of 10 to 90 mass % every 1 mass % to air, and combustibility was evaluated when an equilibrium state was reached.

Evaluation of combustibility was carried out as follows using equipment specified in ASTM E-681. After evacuating the inside of a flask with an internal volume of 12 liters installed in a constant temperature bath controlled at 58.0 to 59.0° C., each working medium mixed with air at the above ratio was sealed up to atmospheric pressure. . After that, the gas phase near the center of the flask was ignited by electric discharge at 15 kV and 30 mA for 0.4 seconds, and the spread of the flame was visually confirmed. It was judged that there was combustibility when the angle of upward flame spread was 90 degrees or more, and that there was no combustibility when it was less than 90 degrees. The results are shown in Tables 6 and 7.

Tables 2 and 3 summarize the constituent compounds of the working medium used here. The working fluids shown in Tables 2 and 3 are working fluids in a non-flammable range, and evaluations of refrigeration cycle performance and global warming potential (GWP) of the working fluids are also shown.

From the above results, the working medium for heat cycle consisting of a mixture of HCFO-1224yd (Z) and HFO-1234ze (E) has sufficient combustibility if it contains 20% by mass or more of HCFO-1224yd (Z). , and it was found that the working medium can be highly safe.

In addition, if the working medium for heat cycle consisting of a mixture of HCFO-1224yd(Z) and HFO-1234yf contains 30% by mass or more of HCFO-1224yd(Z), the combustibility is sufficiently suppressed, and the working medium It was found to be highly safe as

The working medium of the present embodiment, the composition for a heat cycle system containing the same, and the heat cycle system using the composition are freezer/refrigerator equipment (built-in showcase, separate showcase, commercial freezer/refrigerator, vending machines, ice machines, etc.), air conditioners (room air conditioners, packaged air conditioners for stores, packaged air conditioners for buildings, packaged air conditioners for facilities, chilling units for heat source equipment, gas engine heat pumps, air conditioners for trains, air conditioners for automobiles, etc.) , power generation systems (waste heat recovery power generation, etc.), heat transport devices (heat pipes, etc.), and secondary coolers.

DESCRIPTION OF SYMBOLS 10... Refrigeration cycle system, 11... Compressor, 12... Condenser, 13... Expansion valve, 14... Evaporator, 15, 16... Pump.

Claims (10)

A working medium for thermal cycling comprising (Z)-1-chloro-2,3,3,3-tetrafluoropropene and (E)-1,3,3,3-tetrafluoropropene,
The sum of (Z)-1-chloro-2,3,3,3-tetrafluoropropene and (E)-1,3,3,3-tetrafluoropropene contained in the working medium for thermal cycling The content is 50% by mass or more, and (Z)-1-chloro-2,3,3,3-tetrafluoropropene: represented by (E)-1,3,3,3-tetrafluoropropene The ratio of the × 100: (excluding (70/95.5) × 100),
In combustibility evaluation when the ratio of the working medium for heat cycle and air is changed between 10 and 90% by mass and an equilibrium state is reached, discharge ignition is performed for 0.4 seconds at 15 kV and 30 mA. A working medium for thermal cycling, wherein the angle of upward flame spread is less than 90 degrees. A working medium for thermal cycling comprising (Z)-1-chloro-2,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene,
The total content of the (Z)-1-chloro-2,3,3,3-tetrafluoropropene and the 2,3,3,3-tetrafluoropropene contained in the working medium for heat cycle is 50 % by mass or more, and the ratio represented by (Z)-1-chloro-2,3,3,3-tetrafluoropropene:2,3,3,3-tetrafluoropropene is, on a mass basis, 30:70 to 50:50 (however, (42.5/92.5) x 100: (50/92.5) x 100 and (25.5/95.5) x 100: (70/95.5) 5) excluding × 100) and
In combustibility evaluation when the ratio of the working medium for heat cycle and air is changed between 10 and 90% by mass and an equilibrium state is reached, discharge ignition is performed for 0.4 seconds at 15 kV and 30 mA. A working medium for thermal cycling, wherein the angle of upward flame spread is less than 90 degrees. 3. The working fluid for heat cycle according to claim 1, further comprising (E)-1-chloro-2,3,3,3-tetrafluoropropene. A composition for a heat cycle system comprising the working medium for heat cycle according to any one of claims 1 to 3. 5. The composition for a thermal cycle system according to claim 4, comprising lubricating oil. 6. The composition for thermal cycle system according to claim 4, further comprising a stabilizer that suppresses deterioration of the working medium for thermal cycle. A heat cycle system using the composition for a heat cycle system according to any one of claims 4 to 6. 8. The heat cycle system according to claim 7, wherein the heat cycle system is a freezer/refrigerator, an air conditioner, a power generation system, a heat transport device, or a secondary cooler. The heat cycle system according to claim 7 or 8, wherein the heat cycle system is a centrifugal refrigerator. The heat cycle system according to any one of claims 7 to 9, wherein the heat cycle system is a low-pressure centrifugal refrigerator.

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