JP2019504985A - Multi-stage low GWP air conditioning system - Google Patents

Abstract

Preferably, a first heat transfer circuit comprising a first heat transfer fluid in a steam / compression circulation loop disposed at least substantially outside the living space, and at least substantially disposed inside the living space. Air and / or articles disposed in a living space used by a human or other animal, comprising a second heat transfer circuit comprising a second heat transfer fluid different from the first heat transfer fluid being Disclosed is a cooling system for adjusting. In a preferred embodiment, the second heat transfer circuit does not include a steam compressor, but the system includes at least one intermediate heat exchanger, whereby the first heat transfer fluid and the second heat transfer fluid are between. Heat exchange, transferring heat to the first heat transfer fluid, preferably thereby evaporating the first heat transfer fluid and transferring from the second heat transfer fluid, thereby Two heat transfer fluids are condensed. Preferably, the intermediate heat exchanger is arranged outside the living space. The first heat transfer fluid includes a refrigerant having a GWP of about 500 or less, and the second heat transfer fluid also has a GWP of less than 500, low flammability and low toxicity, and even more preferably the first A refrigerant having a flammability substantially lower than the flammability of the refrigerant in the heat transfer fluid and / or a toxicity substantially lower than the toxicity of the refrigerant in the first heat transfer fluid.
[Selection] Figure 1

Description

This application claims priority to US Provisional Application No. 62 / 295,731, filed Feb. 16, 2016, the entire contents of which are incorporated herein by reference.
The present invention relates to safe, effective, high efficiency, low global warming potential (low GWP) air conditioning and related cooling systems and methods.

  In typical air conditioning and refrigerant systems, a compressor is used to compress heat transfer steam from a lower pressure to a higher pressure, thereby adding heat to the steam. This added heat is typically dissipated in a heat exchanger commonly referred to as a condenser. In the condenser, at least a majority of the vapor is condensed to produce a relatively high pressure liquid heat transfer fluid. Typically, a condenser uses a fluid that is available in large quantities in an ambient environment, such as ambient ambient air, as a heat sink. Once condensed, the high pressure heat transfer fluid is subjected to substantially isenthalpy expansion, such as by passing it through an expansion device or valve, where it expands to a lower pressure, thereby causing the fluid to cool. The lower pressure and lower temperature heat transfer fluid from the expansion operation is then typically sent to the evaporator where it absorbs heat and thereby evaporates. This evaporation process provides cooling of the fluid or object that is intended to be subsequently cooled. In normal air conditioning applications, the fluid to be cooled is indoor air in a living space that is air conditioned. In a cooling system, cooling may include cooling the air inside the cold container or storage unit. After the heat transfer fluid has evaporated at low pressure in the evaporator, it is returned to the compressor where the cycle begins again.

  The formation of an efficient, effective and safe air conditioning system that is simultaneously environmentally friendly, i.e., having both a low GWP effect and a low ozone depletion (ODP) effect, is a complex and interrelated factor and requirement A combination is involved. With regard to efficiency and effectiveness, it is important to operate the heat transfer fluid in an air conditioning system with a high level of efficiency and high capacity. At the same time, it is important that the fluid has a low value for both GWP and ODP since heat transfer fluid can leak into the atmosphere over time.

  Applicants believe that some fluids can achieve both high levels of efficiency and effectiveness, and at the same time achieve both low levels of GWP and ODP, but this combination of multiple requirements. It has been recognized that many satisfactory fluids have the disadvantage of having deficiencies with regard to safety. For example, fluids that may otherwise be acceptable may be undesirable for use due to combustion characteristics and / or toxicity issues. Applicants believe that such flammable and / or toxic fluids are unintentionally released into the cooling (or heating in the case of heat pump applications) unintentionally, thereby making the user unsafe. It has been recognized that the use of fluids having such properties is particularly undesirable in normal air conditioning systems because they are exposed to or can be exposed to conditions.

  In accordance with one aspect of the present invention, a refrigerant system is provided for conditioning air and / or articles disposed within a living space for use by a human or other animal. A preferred embodiment of such a system includes at least a first heat transfer circuit, preferably including a first heat transfer fluid in the vapor / compression circulation loop and disposed substantially outside the living space. This first circuit is sometimes referred to as an “outdoor loop” in the present invention for convenience. The outdoor loop preferably includes a compressor, preferably a heat exchanger that serves to condense the heat transfer fluid in the outdoor loop by heat exchange with outdoor ambient air, and an expansion device. The preferred system also includes a second heat transfer fluid that is different from the first heat transfer fluid and includes at least a second heat transfer circuit disposed substantially inside the living space. This second circuit is sometimes referred to as an “indoor loop” in the present invention for convenience. Preferably, the indoor loop includes an evaporator heat exchanger that serves to evaporate the second heat transfer fluid in the indoor loop, preferably by heat exchange with indoor air. In a preferred embodiment, the second heat transfer circuit does not include a steam compressor.

  Preferred systems preferably include at least one intermediate heat exchanger, thereby allowing heat exchange between the first heat transfer fluid and the second heat transfer fluid to transfer heat to the first heat transfer fluid. Preferably, thereby evaporating the first heat transfer fluid and transferring from the second heat transfer fluid, thereby condensing the second heat transfer fluid. Preferably, the intermediate heat exchanger is arranged outside the living space or outside the area to be conditioned.

  An important feature of the preferred system is that the first heat transfer fluid includes a refrigerant having a GWP of about 500 or less, more preferably about 400 or less, and even more preferably about 150 or less, the second heat transfer fluid being Also has a GWP of less than about 500, more preferably less than about 400, even more preferably less than 150, and is substantially less than the flammability of the refrigerant in the first heat transfer fluid, with low flammability and low toxicity. A refrigerant having low flammability and / or substantially lower toxicity than that of the refrigerant in the first heat transfer fluid.

  In a preferred embodiment, the first heat transfer fluid includes a refrigerant having a GWP of about 500 or less, and the second heat transfer fluid also has a GWP of about 500 or less in the first heat transfer fluid. A refrigerant having a flammability substantially lower than the flammability of the refrigerant and / or a toxicity substantially lower than that of the refrigerant in the first heat transfer fluid.

  In a preferred embodiment, the first heat transfer fluid includes a refrigerant having a GWP of about 400 or less, and the second heat transfer fluid also has a GWP of about 400 or less in the first heat transfer fluid. A refrigerant having a flammability substantially lower than the flammability of the refrigerant and / or a toxicity substantially lower than that of the refrigerant in the first heat transfer fluid.

  In a preferred embodiment, the first heat transfer fluid includes a refrigerant having a GWP of about 150 or less, and the second heat transfer fluid also has a GWP of about 150 or less in the first heat transfer fluid. A refrigerant having a flammability substantially lower than the flammability of the refrigerant and / or a toxicity substantially lower than that of the refrigerant in the first heat transfer fluid.

  In a preferred embodiment, the second refrigerant comprises trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), more preferably at least about 50% by weight, even more preferably Comprising at least about 75% by weight of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), wherein the first refrigerant is higher than the flammability of HCFO-1233zd (E). , Preferably having substantially high flammability.

  In a preferred embodiment, the second refrigerant comprises trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), more preferably at least about 75% by weight, even more preferably. Comprising at least about 80% by weight of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), wherein the first refrigerant is higher than the flammability of HCFO-1233zd (E). , Preferably having substantially high flammability.

FIG. 1 is a generalized process flow diagram of one preferred embodiment of an air conditioning system according to the present invention. FIG. 2 is a generalized process flow diagram of another preferred embodiment of an air conditioning system according to the present invention. FIG. 3 is a generalized process flow diagram of another preferred embodiment of an air conditioning system according to the present invention. FIG. 4 is a schematic diagram of a heat exchanger according to an aspect of the present invention. FIG. 5 is a generalized process flow diagram of another preferred embodiment of an air conditioning system that can operate with both cooling and heating in accordance with the present invention.

  In each of the aspects described herein, the system includes a first heat transfer composition that includes a first refrigerant and preferably a lubricant for the compressor, and a second that includes a second refrigerant. A heat transfer composition. Preferably, at least about 50 wt%, more preferably at least about 80 wt% of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), or at least about 75 wt%, and more Preferably, the second refrigerant comprising at least about 80% by weight of trans-1,3,3,3-tetrafluoropropene (HFO-1234ze (E)) is preferably class A toxic according to ASHRAE standard 34, And a low-flammability and low-toxic refrigerant having Class 1 or Class 2 or Class 2L flammability. In highly preferred embodiments, the second refrigerant comprises at least about 95% by weight HFCO-1233zd (E), and in some embodiments consists essentially of or consists of it.

  In a highly preferred embodiment, the second refrigerant comprises about 95% to about 99% by weight of one or more of a five carbon saturated hydrocarbon, preferably isopentane, n-pentane, or neopentane, a preferred form of such embodiment. In, the combination of HFCO-1233zd (E) and such pentane is in the form of an azeotropic composition.

  In a highly preferred embodiment, the second refrigerant comprises from about 85 wt% to about 90 wt% trans-1,3,3,3-tetrafluoropropene (HFO-1234ze (E)) and from about 10 wt% to About 15% by weight of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), even more preferably in some embodiments about 88% by weight of trans-1,3,3 3,3-tetrafluoropropene (HFO-1234ze (E)) and about 12% by weight of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).

  In a highly preferred embodiment, the second refrigerant comprises greater than about 50 wt.% And up to about 67.5 wt.% Trans-1,3,3,3-tetrafluoropropene (HFO-1234ze (E)) and about 9.7% by weight to less than about 50% by weight HFCO-1233zd (E)), even more preferably in some embodiments about 67% by weight trans-1,3,3,3-tetrafluoropropene. (HFO-1234ze (E)) and about 33% by weight HFCO-1233zd (E). In accordance with ASHRAE Standard 34 (measures initial steam flammability from the fraction of the mixture that would occur in the event of a refrigerant leak), Applicants unexpectedly anticipated such a preferred embodiment. It has been found that a second refrigerant can be provided that is non-flammable and that produces a pressure above about 1 bar in the indoor loop of the cooling system.

  One skilled in the art, in view of the disclosure contained herein, some aspects of the present invention are relatively safe (low toxicity and low flammability) and low GWP (thus these are air conditioning applications). It will be appreciated that it provides the advantage of using only refrigerants (which are highly preferred for use in close proximity to people or other animals using the living space normally encountered in).

  Preferably, in a preferred embodiment, the first refrigerant may include one or more components that make such refrigerant substantially less desirable than the second refrigerant from a toxic and / or flammable standard. All such first refrigerants are included within the scope of the present invention. For example, the first refrigerant may include HFC-32 (preferably in an amount of about 0% to about 22% by weight), HFO-1234ze (preferably in an amount of about 0% to about 78% by weight), HFO-1234yf. (Preferably in an amount of about 0% to 78% by weight), and one or more blends including one or more of propane can be included. In contrast to the first heat transfer composition, the second heat transfer composition of the present invention is generally free of lubricant because the fluid does not need to pass through the compressor.

  The first heat transfer composition is also generally a lubricant, generally in an amount of about 30 to about 50% by weight of the heat transfer composition, based on the total weight of refrigerant and other optional components present in the system. Including. Other optional ingredients include compatibilizers such as propane for the purpose of promoting the compatibility and / or solubility of the lubricant. When present, such compatibilizers such as propane, butanes, and pentanes are preferably present in an amount of about 0.5 to about 5% by weight of the composition. Also, as disclosed by US Pat. No. 6,516,837, the disclosure of which is incorporated herein by reference, a combination of surfactant and solubilizer is added to the composition to make it oil soluble. Can also be promoted. Commonly used such as polyol esters (POE) and polyalkylene glycols (PAG), silicone oils, mineral oils, alkylbenzenes (AB), and poly (α-olefins) (PAO) used in chillers with hydrofluorocarbon (HFC) refrigerants The resulting cooling lubricant can be used with the refrigerant composition of the present invention. A preferred lubricant is POE.

A type of embodiment shown in FIG.
In the following description, components or members of a system that are generally the same or similar in different aspects, or may be, are indicated using the same numbers or symbols.

  One preferred air conditioning system, generally indicated at 10, is shown in FIG. Here, the broken line represents an approximate boundary between the indoor loop and the outdoor loop. The compressor 11, the condenser 12, the intermediate heat exchanger 13, and the expansion valve 14 are located outdoors along with any associated conduits 15 and 16 and other connection devices and associated devices (not shown). The The outdoor loop (sometimes also referred to herein as a “high temperature refrigerant circuit”) preferably comprises a first heat transfer composition, preferably in accordance with one or more of the preferred embodiments described above, which is the first refrigerant. And a lubricant for the compressor, at least a first refrigerant circulates in the circuit by conduits 15 and 16 and other related conduits and devices.

  The indoor loop (also sometimes referred to as a “cold refrigerant circuit” in the present invention) preferably comprises at least a second heat transfer composition comprising at least a second refrigerant, the second refrigerant comprising a first refrigerant It has at least one safety characteristic, such as flammability and toxicity, that is superior to the corresponding safety characteristic of the refrigerant. In a highly preferred embodiment, the second refrigerant is preferably sufficiently toxic to be expressed as Class A according to ASHRAE Standard 34, and preferably has a flammability rating of Class 1 or 2L. It is sufficiently low in flammability to have. In a highly preferred embodiment, the second refrigerant comprises HFCO-1233zd, even more preferably trans-HFCO-1233zd, preferably consisting essentially of it, and in some embodiments consisting thereof. In other highly preferred embodiments, the second refrigerant comprises HFO-1234ze (E) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), preferably these And in some embodiments from these. In view of the disclosure contained herein, one of ordinary skill in the art would consider such an aspect of the present invention to identify a human or animal that is or may be present in a living space or a regulated space. Of HFCO-1233zd (E) and HFO-1234ze (E) / HFC-227ea in a location close to a human or other animal that uses the living space or enters the conditioned space while being separated from one refrigerant It will be appreciated that such a relatively safe (low toxicity and low flammability) and low GWP refrigerant provides the advantage of using only. Thus, depending on the preferred equipment configuration and refrigerant selection, it has many desirable properties such as capacity, efficiency, low GWP and low ODP, while at the same time making them very disadvantageous and / or To provide a system that benefits from the use of refrigerants having one or more properties that make it impossible to use them in close proximity to humans or other animals in a restricted and / or closed location Can do. Such a combination provides a very good advantage in terms of all desirable properties for such a refrigerant system.

  In a preferred embodiment, the first refrigerant includes, for example, HFC-32 (preferably in an amount of about 0 wt% to about 22 wt%), HFO-1234ze (preferably in an amount of about 0 wt% to about 78 wt%). ), HFO-1234yf (preferably in an amount of from about 0% to 78% by weight), and one or more blends of propane.

  The heat transfer fluid in the outdoor circuit generally and preferably includes a lubricant for the compressor, generally in an amount of about 30 to about 50% by weight of the heat transfer fluid, with the remainder being a refrigerant, and others that can be present. Of optional ingredients. Other optional ingredients include compatibilizers such as propane for the purpose of promoting the compatibility and / or solubility of the lubricant. When present, such compatibilizers such as propane, butanes, and pentanes are preferably present in an amount of about 0.5 to about 5% by weight of the composition. Also, a combination of surfactant and solubilizer is added to the composition as disclosed in US Pat. No. 6,516,837, the disclosure of which is incorporated herein by reference. It can also promote solubility. Commonly used such as polyol esters (POE) and polyalkylene glycols (PAG), silicone oils, mineral oils, alkylbenzenes (AB), and poly (α-olefins) (PAO) used in chillers with hydrofluorocarbon (HFC) refrigerants The resulting cooling lubricant can be used with the refrigerant composition of the present invention. A preferred lubricant is POE.

  In operation, the second refrigerant according to the present invention is circulated through the circuit by flowing it through the intermediate heat exchanger 13, where the heat is transferred to the first refrigerant and thereby the second refrigerant. At least a portion, preferably substantially all, of the refrigerant is condensed into liquid form and discharged from the intermediate heat exchanger through conduit 17. In a preferred embodiment, the second refrigerant discharged from the intermediate heat exchanger is introduced into the receiver 18 to provide a liquid reservoir for the second refrigerant. Although the receptacle 18 is shown in the figure as being located indoors, the container can also be located outdoors and, if present, it is also preferred to place the pump 20 outdoors. There is a case. The liquid refrigerant from the separation container is sent to the evaporator through the conduit 21. In the example shown in FIG. 1, the liquid pump 20 is shown to assist in sending liquid refrigerant to the evaporator 24 through conduits 21, 22 and valve 23. However, in other aspects, the second refrigerant liquid can be delivered from the receiver using other means or techniques that can be used alone or in combination with a liquid pump. For example, in some embodiments, the transfer of liquid refrigerant can be performed by using gravity feed to the liquid evaporator, while in other embodiments, the thermosiphon configuration is used to Liquid refrigerant can be sent to the evaporator 24 and from the evaporator to the intermediate heat exchanger 13.

  In a preferred embodiment, wherein the refrigerant comprises at least about 90% by weight of either HCFO-1233zd (E) or HFO-1234ze (E), and preferably consists essentially of it, preferably the operating conditions comprise Corresponds to the values listed in the table below.

A type of embodiment shown in FIG.
Another preferred embodiment of the present invention is shown in FIG. The compressor 11, the condenser 12, the intermediate heat exchanger 13, the expansion valve 14, and the suction line heat exchanger 30 are optional associated conduits 15A, 15B, 16A, and 16B, as well as other connection devices and associated devices. (Not shown) and placed outdoors. The outdoor loop (sometimes also referred to in the present invention as a “high temperature refrigerant circuit”) preferably includes a first heat transfer composition comprising a first refrigerant and a lubricant for the compressor, at least the refrigerant being in conduit 17. 19, 21, and 22, and other related conduits and devices circulate in the circuit.

  The indoor loop is constructed in substantially the same manner as described above with respect to the indoor loop of FIG. 1, and the first and second heat transfer compositions are also preferably as shown elsewhere herein. It is.

  In operation, the first refrigerant according to the present invention is discharged from the compressor 11 as a relatively high pressure refrigerant vapor (which may contain entrained lubricant), which is then the condenser. 12 where heat is preferably transferred to ambient air and at least partially condensed. The refrigerant effluent from condenser 12 is sent through conduit 15A to suction line heat exchanger 30 where further heat is taken into the effluent from intermediate heat exchanger 13. The effluent stream from the suction / liquid line heat exchanger 30 is then routed through conduit 15B to the expansion valve 14 where it reduces the refrigerant pressure and thereby reduces the refrigerant temperature. The relatively cool liquid refrigerant from the expansion valve is then introduced into the intermediate heat exchanger 13 where it obtains heat from the second refrigerant vapor discharged from the evaporator 24 in the indoor loop. The first refrigerant effluent from the intermediate heat exchanger then passes through conduit 16A to suction / liquid line heat exchanger 30 where it obtains heat from the condenser effluent from conduit 15A and the higher temperature second. Two refrigerant vapors are generated and sent to the inlet of the compressor 11 by conduit 16B.

  The evaporator effluent is sent to the intermediate heat exchanger 13 through the receiver conduit 19, where heat is taken up by the effluent from the suction line heat exchanger which is sent to the intermediate heat exchanger through the conduit 15B, and the second A relatively cool flow of refrigerant is generated. This cold stream of the second refrigerant discharged from the intermediate heat exchanger 13 is sent to a receiver tank 18 which provides a reservoir for the cold liquid refrigerant, from the tank through a conduit 21 and then through a control valve 23. To be fed into the evaporator 24. In some embodiments, a pump 20 is provided to provide liquid flow to the control valve 23. The cooled ambient air takes heat in the evaporator 24 to a cold liquid refrigerant, thereby vaporizing the liquid refrigerant, producing a refrigerant vapor with little or no overheating, this The steam is then returned to the intermediate heat exchanger 13.

  In a preferred embodiment, wherein the refrigerant comprises at least about 90% by weight of either HCFO-1233zd (E) or HFO-1234ze (E), and preferably consists essentially of it, preferably the operating conditions comprise Corresponds to the values listed in the table below.

A mode of the type shown in FIG.
Another preferred embodiment of the present invention is shown in FIG. The two-stage compressor 11, the condenser 12, the intermediate heat exchanger 13, the expansion valve 14, and the steam injection heat exchanger 40 (including the associated intermediate expansion valve 41) include any associated conduits 15A-15 and other Placed outdoors with connecting devices and associated devices (not shown and / or not labeled). The outdoor loop (sometimes also referred to in the present invention as a “high temperature refrigerant circuit”) preferably includes a first heat transfer composition comprising a first refrigerant and a lubricant for the compressor, at least the refrigerant being in conduit 15. And 16 and other related conduits and devices circulate in the circuit.

  The indoor loop is constructed in substantially the same manner as described above with respect to the indoor loop of FIG. 1, and the first and second heat transfer compositions are also preferably as shown elsewhere herein. It is.

  In operation, the first refrigerant according to the present invention (which may contain entrained lubricant) is used as a relatively high pressure refrigerant vapor (which may contain entrained lubricant) as a compressor. 11 and is then introduced into a condenser 12 where heat is preferably transferred to ambient air to at least partially condense. The refrigerant effluent from the condenser 12 contains at least partially, preferably practically fully condensed refrigerant. The refrigerant effluent from the condenser 12 is sent through the conduit 15A, a part of the refrigerant effluent is sent through the conduit 15B to the intermediate expansion device 41, and the other part of the effluent, preferably the remainder of the effluent, is steam injection heat. Send to exchanger 40.

  The intermediate expansion device 41 preferably reduces the pressure of the outflow to substantially the same enthalpy to approximately the pressure of the second stage suction of the compressor 11, or the heat exchanger 41 and associated conduits, equipment, etc. Considering the pressure loss through the pressure, the pressure is sufficiently higher than the pressure. As a result of the pressure drop across the expansion device 41, the pressure of the refrigerant flowing through the heat exchanger 40 is lower than the temperature of the high-pressure refrigerant flowing through the heat exchanger 40. Within the heat exchanger 40, heat moves from the high pressure flow to the flow that has passed through the expansion valve 41. As a result, the temperature of the intermediate pressure stream exhausted from the heat exchanger 40 is higher than the temperature of the inlet stream, thereby producing a superheated steam stream, which is routed to the second stage of the compressor 11 through conduit 19C. send.

  As the higher pressure stream sent by conduit 15A is sent through heat exchanger 40, it is taken up by the lower pressure stream discharged from expansion device 41 and discharged from the heat exchanger through conduit 15C. It then flows to the expansion device 14 and is then sent to an intermediate heat exchanger where it gets heat and is sent to the first stage of the compressor suction.

  In a preferred embodiment, wherein the refrigerant comprises at least about 90% by weight of either HCFO-1233zd (E) or HFO-1234ze (E), and preferably consists essentially of it, preferably the operating conditions comprise Corresponds to the values listed in the table below.

A type of embodiment shown in FIG.
In the following description, components or members of a system that are generally the same or similar in different aspects, or may be, are indicated using the same numbers or symbols.

The embodiment disclosed in FIG. 5 is similar to the embodiment of FIG. 1 except that the system is equipped with a reversible valve so that it can be operated in heating mode as described below.
One preferred air conditioning system that can be operated in both cooling and heating modes is indicated generally at 10 in FIG. 1, and the line shown represents a rough boundary between the indoor and outdoor loops, and compressor 11 , Outdoor coil 12, intermediate heat exchanger 13, expansion valve 14, and reversible valve 500 are placed outdoors along with any associated conduits 15 and 16, and other connecting devices and associated devices (not shown). Is done. The outdoor loop preferably comprises a first heat transfer composition comprising a first refrigerant preferably according to one or more of the preferred embodiments described above and a lubricant for the compressor, wherein at least the first refrigerant is Circulation in the circuit by conduits 15 and 16 and other related conduits and devices.

  The indoor loop preferably includes a second heat transfer composition comprising at least a second refrigerant, the second refrigerant being flammable and toxic that is superior to the corresponding safety characteristics of the first refrigerant. Having at least one safety characteristic. In a highly preferred embodiment, the second refrigerant is preferably sufficiently toxic to be expressed as Class A according to ASHRAE Standard 34, and preferably has a flammability rating of Class 1 or 2L. It is sufficiently low in flammability to have. In a highly preferred embodiment, the second refrigerant comprises HFCO-1233zd, even more preferably trans-HFCO-1233zd, preferably consisting essentially of it, and in some embodiments consisting thereof. In other highly preferred embodiments, the second refrigerant comprises HFO-1234ze (E) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), preferably these And in some embodiments from these. In view of the disclosure contained herein, one of ordinary skill in the art would consider such an aspect of the present invention to identify a human or animal that is or may be present in a living space or a regulated space. Of HFCO-1233zd (E) and HFO-1234ze (E) / HFC-227ea in a location close to a human or other animal that uses the living space or enters the conditioned space while being separated from one refrigerant It will be appreciated that such a relatively safe (low toxicity and low flammability) and low GWP refrigerant provides the advantage of using only. Thus, depending on the preferred equipment configuration and refrigerant selection, it has many desirable properties such as capacity, efficiency, low GWP and low ODP, while at the same time making them very disadvantageous and / or To provide a system that benefits from the use of refrigerants having one or more properties that make it impossible to use them in close proximity to humans or other animals in a restricted and / or closed location Can do. Such a combination provides a very good advantage in terms of all desirable properties for such a refrigerant system.

  In a preferred embodiment, the first refrigerant includes, for example, HFC-32 (preferably in an amount of about 0 wt% to about 22 wt%), HFO-1234ze (preferably in an amount of about 0 wt% to about 78 wt%). ), HFO-1234yf (preferably in an amount of from about 0% to 78% by weight), and one or more blends of propane.

  The heat transfer fluid in the outdoor circuit generally and preferably includes a lubricant for the compressor, generally in an amount of about 30 to about 50% by weight of the heat transfer fluid, with the remainder being a refrigerant, and others that can be present. Of optional ingredients. Other optional ingredients include compatibilizers such as propane for the purpose of promoting the compatibility and / or solubility of the lubricant. When present, such compatibilizers such as propane, butanes, and pentanes are preferably present in an amount of about 0.5 to about 5% by weight of the composition. Also, as disclosed by US Pat. No. 6,516,837, the disclosure of which is incorporated herein by reference, a combination of surfactant and solubilizer is added to the composition to make it oil soluble. Can also be promoted. Commonly used such as polyol esters (POE) and polyalkylene glycols (PAG), silicone oils, mineral oils, alkylbenzenes (AB), and poly (α-olefins) (PAO) used in chillers with hydrofluorocarbon (HFC) refrigerants The resulting cooling lubricant can be used with the refrigerant composition of the present invention. A preferred lubricant is POE.

  In operation, a second refrigerant according to the heating mode embodiment of FIG. 5 of the present invention is circulated through the circuit by flowing through the intermediate heat exchanger 13, whereby in the intermediate heat exchanger, from the first refrigerant. Heat is recovered, whereby at least a portion, preferably substantially all, of the second refrigerant is vaporized into vapor form and discharged from the intermediate heat exchanger through conduit 17. The vaporous refrigerant is sent through a conduit 21 to a condenser where it is condensed while discharging heat into the living space. In the example shown in FIG. 1, the liquid pump 20 is shown to help route liquid refrigerant through the conduits 21, 22 and valve 23 to the condenser 24. In addition, the indoor loop also includes a reversible valve 501, which allows the system to operate in both heating and cooling modes.

  In a preferred embodiment, the refrigerant comprises at least about 90% by weight of HCFO-1233zd (E) and HFO-1234ze (E), preferably consisting essentially of, preferably consisting of.

Comparative Example 1:
An air conditioning system according to a normal configuration using R-410A as the refrigerant was operated according to the following parameters.

Operating conditions-R410A basic cycle:
1. Condensation temperature = 45 ° C .; corresponding outdoor ambient temperature = 35 ° C .;
2. Condensation temperature-ambient temperature = 10 ° C .;
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 7 ° C; corresponding indoor room temperature = 27 ° C;
5). Evaporator overheating = 5.0 ° C;
6). Isentropic efficiency = 72%;
7). Volumetric efficiency = 100%.

The capacity and COP of this system were determined and used as reference values for determining relative capacity and COP in the following examples.
Example 1A:
Operating conditions of Example 1A (FIG. 1):
The system configured as shown in FIG. 1 was operated with a series of different first (outdoor) and second (indoor) refrigerants according to the following operating parameters.

1. Condensation temperature = 45 ° C .; corresponding outdoor ambient temperature = 35 ° C .;
2. Condensation temperature-ambient temperature = 10 ° C .;
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 7 ° C; corresponding indoor room temperature = 27 ° C;
5). Evaporator overheating = 0.0 ° C (full liquid);
6). Intermediate heat exchanger overheat = 5.0 ° C .;
7). Isentropic efficiency = 72%;
8). Volumetric efficiency = 100%;
9. Difference of saturation temperatures intermediate heat exchanger = 5 ° C.

  The results are given in Table 1A below (percentages for blends are given in weight%).

  As can be seen from the above results, each of the air conditioning systems according to the present invention is capable of just comparable to a conventional R410A air conditioning system operated as shown, and in all cases at least 85 relative to such a conventional system. % COP (efficiency) could be given. Significantly, in all cases, the system uses refrigerants each having a GWP of less than 150 (approximately 10 times improvement over cooling systems based on R-410A). The ability to achieve this combination of properties is very beneficial but is an unexpected result.

Operating conditions of Example 1B (FIG. 1):
The system configured as shown in FIG. 1 is subject to the same operating parameters except that the condensation temperature was adjusted for each blend to obtain an efficiency substantially comparable to that achieved according to Comparative Example 1. A series of different first (outdoor) and second (indoor) refrigerants were operated. The results are given in Table 1B below.

  The above results showed that it is possible to achieve a system according to the invention that produces an efficiency substantially comparable to that of a system based on R-410A with only a relatively small change in condenser temperature. . Alternatively, the efficiency according to the present invention can be achieved by increasing the heat transfer area in the condenser slightly compared to the amount of heat transfer area in the condenser used for the comparative R-410A system. Is preferably increased without lowering or changing. Furthermore, the system according to FIG. 2 using a suction line heat exchanger shows an advantageous improvement in efficiency compared to the configuration of the present invention without the heat exchanger reported in Example 1A.

Example 1C (FIG. 1) —Change of ambient conditions:
A system configured as shown in FIG. 1 is a series of different firsts according to the same operating parameters as Example 1A, except that the ambient temperature was adjusted to 35 ° C., 45 ° C., and 55 ° C. for each blend. It was operated using outdoor) and second (indoor) refrigerants. The results are given in Table 1C below.

  The above results showed that, according to some aspects of the present invention, superior performance can be provided as compared to the R-410A system as ambient temperature increases above 35 ° C.

Example 2A
Operating conditions of Example 2A (FIG. 2):
The system configured as shown in FIG. 2 was operated with a series of different first (outdoor) and second (indoor) refrigerants according to the following operating parameters.

1. Condensation temperature = 45 ° C .; corresponding outdoor ambient temperature = 35 ° C .;
2. Condensation temperature-ambient temperature = 10 ° C .;
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 7 ° C; corresponding indoor room temperature = 27 ° C;
5). Evaporator overheating = 0.0 ° C (full liquid);
6). Intermediate heat exchanger overheat = 5.0 ° C .;
7). Isentropic efficiency = 72%;
8). Volumetric efficiency = 100%;
9. Intermediate heat exchanger saturation temperature difference = 5 ° C.

  The results are shown in Table 2A below (percent of blends are given in weight%).

  As can be seen from the above results, each of the air conditioning systems according to the present invention is capable of just comparable to a conventional R410A air conditioning system operated as shown, and in all cases at least 90 relative to such a conventional system. % COP (efficiency) could be given. Significantly, in all cases, the system uses refrigerants each having a GWP of less than 150 (approximately 10 times improvement over cooling systems based on R-410A). The ability to achieve this combination of properties is very beneficial but is an unexpected result.

Example 2B:
Example 2B (FIG. 2)-Changing the condenser temperature:
The system configured as shown in FIG. 2 operates the same as Example 2A, except that the condensation temperature was adjusted for each blend to obtain an efficiency substantially comparable to that achieved according to Comparative Example 1. According to the parameters, it was operated with a series of different first (outdoor) and second (indoor) refrigerants. The results are given in Table 2B below.

  The above results show that it is possible to achieve a system according to the invention that produces an efficiency substantially comparable to that of a system based on R-410A with only a relatively small change in condenser temperature. Yes. Alternatively, the efficiency of the method can be achieved by increasing the heat transfer area in the condenser slightly by comparing it to the amount of heat transfer area in the condenser used for the comparative R-410A system. Is preferably increased without lowering or changing.

Example 2C (FIG. 2) —Modification of Ambient Conditions A system configured as shown in FIG. 2 was compared to Example 2A except that the ambient temperature was adjusted to 35 ° C., 45 ° C., and 55 ° C. for each blend. A series of different first (outdoor) and second (indoor) refrigerants were operated according to the same operating parameters. The results are given in Table 2C below.

  The above results showed that, according to some aspects of the present invention, superior performance can be provided as compared to the R-410A system as ambient temperature increases above 35 ° C.

Example 3A:
Operating conditions of Example 3A (FIG. 3):
The system configured as shown in FIG. 3 was operated using 100% trans-HFCO-1233zd as a series of different first (outdoor) refrigerants and indoor refrigerants according to the following operating parameters.

1. Condensation temperature = 45 ° C .; corresponding outdoor ambient temperature = 35 ° C .;
2. Condensation temperature-ambient temperature = 10 ° C .;
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 7 ° C; corresponding indoor room temperature = 27 ° C;
5). Evaporator overheating = 0.0 ° C (full liquid);
6). Intermediate heat exchanger overheat = 5.0 ° C .;
7). Isentropic efficiency for both stages = 72%;
8). Volumetric efficiency = 100%;
9. Saturation temperature difference in the intermediate heat exchanger = 5 ° C .;
10. Steam jet heat exchanger effectiveness = 35%, 55%, 75%, 85%.

  The results are shown in Table 3A below (percentages for blends are given in weight%).

  As can be seen from the above results, each of the air conditioning systems according to the present invention is capable of just comparable to a conventional R410A air conditioning system operated as shown, and in all cases at least 90 relative to such a conventional system. % COP (efficiency) could be given. Significantly, in all cases, the system uses refrigerants each having a GWP of less than 150 (approximately 10 times improvement over cooling systems based on R-410A). The ability to achieve this combination of properties is very beneficial but is an unexpected result.

Example 3B:
Example 3B (FIG. 3)-Changing condenser temperature:
The system configured as shown in FIG. 3 operates the same as Example 3A, except that the condensation temperature was adjusted for each blend to obtain an efficiency substantially comparable to that achieved according to Comparative Example 1. According to the parameters, it was operated with a series of different first (outdoor) refrigerants and 100% trans-HFCO-1233zd as the indoor refrigerant. The results are given in Table 3B below.

  The above results show that it is possible to achieve a system according to the invention that produces an efficiency substantially comparable to that of a system based on R-410A with only a relatively small change in condenser temperature. Yes. Alternatively, the efficiency of the method can be achieved by increasing the heat transfer area in the condenser slightly by comparing it to the amount of heat transfer area in the condenser used for the comparative R-410A system. Is preferably increased without lowering or changing.

Example 3C (FIG. 3) —Modification of Ambient Conditions A system configured as shown in FIG. 3 was compared to Example 2A except that the ambient temperature was adjusted to 35 ° C., 45 ° C., and 55 ° C. for each blend. A series of different first (outdoor) and second (indoor) refrigerants were operated according to the same operating parameters. The results are given in Table 3C below.

  The above results showed that, according to some aspects of the present invention, superior performance can be provided as compared to the R-410A system as ambient temperature increases above 35 ° C.

Example 4:
The air conditioning system of Example 1 uses an indoor refrigerant containing various binary mixtures of trans-HCFO-1233zd and trans-HFO-1234ze, and generally encompasses the condenser temperature used in many critical air conditioning systems. It was operated using an evaporator temperature in the range of about -1 ° C to about 10 ° C. The results of the test are reported in Table 4A below.

  Applicants have found that compositions in which the amount of trans-HFO-1234ze is at least about 50% by weight allows operating indoor circuits under pressures greater than 1 atmosphere, as shown in Table 4 above. This avoids the need for a purge system, while at the same time allowing the use of relatively low cost containers and conduits and / or sufficient to advantageously avoid refrigerant leakage that would otherwise occur in high pressure systems. Has been found to be given a low system pressure. In addition, Applicants tested the flammability of trans-HFO-1234ze / trans-HCFO-1233zd, i.e., the blend was fractionated flammability (refrigerant combustion in case of leakage from the system). The results of this study are reported in Table 4B below.

  Based on the results reported in Table 4B above, Applicants have found that liquid blends with more than 67% by weight trans-HFO-1234ze are flammable as measured according to fractionation tests conducted according to ASTM-34. Yes, according to the results in Table 4A, it has been found that an amount of less than about 50% by weight trans-HFO-1234ze (ie greater than 50% trans-HFCO-1233zd) creates the possibility of negative system pressure. It was.

Example 5-Compatibility with plastics useful in low pressure systems:
Applicants have immersed samples of various plastics in trans-HFCO-1233zd under atmospheric pressure at room temperature (about 24 ° C. to 25 ° C.) for 2 weeks, and then removed the samples from trans-HFCO-1233zd. The stability of various plastic material amounts when exposed to trans-HFCO-1233zd was tested by degassing for 24 hours. The results are reported in Table 5 below.

As shown by the results in Table 5 above, the average volume change (%) for each of the tested plastic materials was less than 5%.
Example 6:
The air conditioning system of Example 1 includes an ASHRAE 34 that includes any preferred low-temperature refrigerant of the present invention, such as a high-temperature refrigerant that is an A2L refrigerant, such as HFO-1234ze (E), HFCO-1233zd (E), and combinations thereof. Therefore, it was operated under conditions where there was unintentional leakage into the low temperature non-flammable refrigerant. In such a case, if unintentional leakage occurs inside the intermediate heat exchanger, A2L (weakly flammable) refrigerant is mixed with nonflammable low-temperature refrigerant. The mixture of the low-temperature refrigerant (for example, R1233zd (E)) and the A2L refrigerant that is formed may eventually leak into the room. However, in many cases it is non-flammable material that leaks into the room. In some embodiments, the accumulator is used in conjunction with a suitable control device to ensure that an appropriate fill ratio is maintained between the high side and the low side (non-flammable). Can be ensured. There is also the possibility of introducing one or more devices into the system that can detect the leakage of flammable refrigerant into the indoor loop and release all such refrigerant to the outside of the residence. is there. One such leak detection system is described in US application 15 / 400,891 filed Jan. 6, 2017 (see particularly FIGS. 4A and 4B) and provisional application 62 / 275,382 filed Jan. 6, 2016 ( Each of which is incorporated herein by reference).

  Table 6 shows the filling ratio that can prevent dangerous situations from occurring inside the living space in the event of a leak.

Comparative Example 2:
A reversible heat pump system according to a conventional prior art configuration using R-410A as the refrigerant was operated in heating mode according to the following parameters.

Operating conditions-R410A basic cycle:
1. Condensation temperature = 40 ° C .; corresponding indoor room temperature = 21.1 ° C .;
2. Condensation temperature-ambient temperature = 19 ° C .:
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 0 ° C; corresponding outdoor ambient temperature = 8.3 ° C;
5). Evaporator overheating = 5.0 ° C;
6). Isentropic efficiency = 72%;
7). Volumetric efficiency = 100%.

The capacity and COP of this system were determined and used as reference values for determining relative capacity and COP in the following Examples 7A and 7B according to the present invention.
Example 7A:
The system configured as shown in FIG. 6 was operated with a series of different first (outdoor) and second (indoor) refrigerants according to the following operating parameters.

1. Condensation temperature = 40 ° C .; corresponding indoor room temperature = 21.1 ° C .;
2. Condensation temperature-ambient temperature = 19 ° C .:
3. Expansion device supercooling = 5.0 ° C .;
4). Evaporation temperature = 0 ° C; corresponding outdoor ambient temperature = 8.3 ° C;
5). Evaporator overheating = 0.0 ° C (full liquid);
6). Intermediate heat exchanger overheat = 5.0 ° C .;
7). Isentropic efficiency = 72%;
8). Volumetric efficiency = 100%;
9. Intermediate heat exchanger saturation temperature difference = 5 ° C.

  The results are given in Table 1A below (percentages for blends are given in weight%)

  As can be seen from the above results, each of the air conditioning systems according to the present invention is capable of just comparable to a conventional R410A air conditioning system operated as shown, and in all cases at least 90 relative to such a conventional system. % COP (efficiency) could be given. Significantly, in all cases, the system uses refrigerants each having a GWP of less than 150 (approximately 10 times improvement over cooling systems based on R-410A). The ability to achieve this combination of properties is very beneficial but is an unexpected result.

Operating conditions of Example 7B (FIG. 5):
A system configured as shown in FIG. 5 is subject to the same operating parameters except that the condensation temperature was adjusted for each blend to obtain an efficiency substantially comparable to that achieved according to Comparative Example 2. A series of different first (outdoor) and second (indoor) refrigerants were operated. The results are given in Table 7B below.

  The above results showed that it is possible to achieve a system according to the invention that produces an efficiency substantially comparable to that of a system based on R-410A with only a relatively small change in condenser temperature. . Alternatively, the efficiency of the method can be achieved by increasing the heat transfer area in the condenser slightly by comparing it to the amount of heat transfer area in the condenser used for the comparative R-410A system. Is preferably increased without lowering or changing.

Claims (11)

A cooling system for cooling or heating air in a space used by humans, or for cooling or heating articles disposed in a space used by humans using air in the space used by humans. ,
(A) (i) an outdoor refrigerant having a GWP of less than about 500, wherein the outdoor circuit flows through at least a portion of the outdoor circuit and either exhausts heat from the system or absorbs heat into the system, wherein the outdoor circuit At least the part through which the outdoor refrigerant flows is not located in the space used by humans);
(Ii) a phase change heat exchanger;
(Iii) a compressor that provides a vapor stream of outdoor refrigerant; and (iv) an intermediate heat exchanger that absorbs or discharges heat by at least a portion of the outdoor refrigerant stream;
And (b) (i) an indoor refrigerant that flows through at least a portion of the indoor circuit and absorbs heat from or expells heat from the space used by humans (wherein indoor At least a portion of the circuit through which the indoor refrigerant flows is disposed in a space for human use, the indoor refrigerant comprising at least about 50 wt% HCFO-1233zd (E), and (1) ASHRAE Non-flammable according to Standard 34; (2) has an occupational exposure limit (OEL) higher than 400, classified as Class A by ASHRAE Standard 34; and (3) has a GWP less than about 500); And (ii) an intermediate heat exchanger of the outdoor refrigerant circuit that absorbs heat from or exhausts heat to the indoor refrigerant by the outdoor refrigerant flow;
Indoor refrigerant circuit including:
Including the above system. A cooling system for cooling air in a space used by a human or for cooling an article disposed in a space used by a human using air in the space used by a human,
(A) (i) a high temperature refrigerant having a GWP of less than about 500 that flows through at least a portion of the high temperature circuit and exhausts heat from the system, where the high temperature refrigerant flows through at least the high temperature circuit; The part is not located in the space used by humans);
(Ii) a condenser providing at least a first condenser effluent stream comprising a liquid hot refrigerant stream at a first temperature;
(Iii) an expansion valve fluidly connected to the liquid hot refrigerant stream from the condenser and providing a hot refrigerant stream at a second temperature lower than the first temperature;
(Iv) a compressor that supplies a vapor stream containing at least a portion of the refrigerant to the condenser; and (v) generating a vapor flow containing the high temperature refrigerant by absorbing heat by at least a portion of the high temperature refrigerant flow from the expansion valve. Intermediate heat exchanger (vapor flow from the intermediate heat exchanger is in fluid communication with the compressor inlet);
(B) (i) a low-temperature refrigerant that flows through at least a portion of the low-pressure circuit and absorbs heat from the space used by humans, where the low-temperature circuit passes through at least it The portion through which the cryogenic refrigerant flows is located in a space for human use, and the cryogenic refrigerant comprises at least about 50% by weight HCFO-1233zd (E) and is (1) non-flammable according to ASHRAE Standard 34. Yes; (2) have an occupational exposure limit (OEL) higher than 400, classified as Class A by ASHRAE Standard 34; and (3) have a GWP less than about 500);
(Ii) an accumulator comprising at least a portion of a low-temperature refrigerant in a liquid state;
(Iii) an evaporator fluidly connected to the accumulator that receives liquid cryogen from the accumulator and then generates a vaporized cryogen stream; and (iv) an evaporator by the hot refrigerant stream from the expansion valve The intermediate heat exchanger of the high-temperature refrigerant circuit that absorbs heat from the low-temperature refrigerant vapor from the intermediate heat exchanger (the intermediate heat exchanger generates a liquid outflow containing the low-temperature refrigerant, and the low-temperature liquid outflow from the intermediate heat exchanger is In fluid communication);
Low temperature refrigerant circuit including:
Including the above system.   The cooling system of claim 2, wherein at least a portion of the liquid from the accumulator is sent to the evaporator inlet by a thermosiphon effect.   The cooling system of claim 2, wherein the high temperature refrigerant comprises about 22 wt% or less of R-32.   The cooling system of claim 2, wherein the high temperature refrigerant comprises no more than about 78 wt% R-1234ze or no more than about 78 wt% R-1234yf.   The cooling system of claim 2, wherein the high temperature refrigerant comprises about 10 wt% to about 100 wt% propane.   The cooling system of claim 2, wherein the condenser is operated at a temperature in the range of about 35 ° C. to about 70 ° C. A cooling system for cooling air in a space used by a human or for cooling an article disposed in a space used by a human using air in the space used by a human,
(A) (i) A high-temperature refrigerant that flows through at least a portion of the high-pressure circuit and exhausts heat from the system (here, at least a portion of the high-temperature circuit through which the high-temperature refrigerant flows is a space used by humans) Is not located within);
(Ii) a condenser providing at least a first condenser effluent stream comprising a liquid hot refrigerant stream at a first temperature;
(Iii) an expansion valve fluidly connected to the liquid hot refrigerant stream from the condenser and providing a hot refrigerant stream at a second temperature lower than the first temperature;
(Iv) a compressor that supplies a vapor stream comprising at least a portion of the refrigerant to the condenser;
(V) an intermediate heat exchanger that absorbs heat by at least a portion of the hot refrigerant stream from the expansion valve and produces a hot effluent stream containing hot refrigerant at a temperature higher than the temperature of the flow from the expansion valve; (Vi) connected between the condenser and the expansion valve and between the intermediate heat exchanger and the compressor inlet; (1) the suction line heat exchanger removes at least a portion of the liquid hot refrigerant stream from the condenser; And heat is expelled from the liquid hot refrigerant stream before the liquid hot refrigerant stream is introduced into the expansion valve; and (2) the suction line heat exchanger is from the intermediate heat exchanger A suction line heat exchanger that receives at least a portion of the discharged hot refrigerant and absorbs heat from the liquid hot refrigerant stream from the condenser (where the flow after absorbing heat is compressed) In fluid communication with the machine inlet);
(B) (i) a low-temperature refrigerant that flows through at least a portion of the low-pressure circuit and absorbs heat from the space used by humans, where the low-temperature circuit passes through at least it The portion through which the cryogenic refrigerant flows is located in a space for human use, and the cryogenic refrigerant comprises at least about 50% by weight HCFO-1233zd (E) and is (1) non-flammable according to ASHRAE Standard 34. Yes; (2) have an occupational exposure limit (OEL) higher than 400, classified as Class A by ASHRAE Standard 34; and (3) have a GWP less than about 500);
(Ii) an accumulator comprising at least a portion of a low-temperature refrigerant in a liquid state;
(Iii) an evaporator fluidly connected to the accumulator that receives liquid cryogen from the accumulator and then generates a vaporized cryogen stream; and (iv) an evaporator by the hot refrigerant stream from the expansion valve The intermediate heat exchanger of the high-temperature refrigerant circuit that absorbs heat from the low-temperature refrigerant vapor from the intermediate heat exchanger (the intermediate heat exchanger generates a liquid outflow containing the low-temperature refrigerant, and the low-temperature liquid outflow from the intermediate heat exchanger In fluid communication with the inlet);
Low temperature refrigerant circuit including:
Including the above system.   The cooling system of claim 8, wherein the high temperature refrigerant comprises one or more of R-32, R-1234ze, R-1234yf, and propane.   The cooling system of claim 8, wherein the condenser is operated at a temperature in the range of about 35 ° C. to about 70 ° C.   A sensor that detects leakage of high temperature refrigerant into the low temperature refrigerant, and filling the low temperature cooling circuit with an additional amount of low temperature refrigerant in response to the sensor to ensure that the low temperature refrigerant is maintained as an incombustible refrigerant. The cooling system of claim 2 further comprising a low temperature refrigerant charge controller.

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