High-Efficiency Air Conditioning System and Method

Abstract

This application relates to high-efficiency air conditioning systems and methods. The refrigeration system includes a heat source to be cooled and the radiator that can discharge heat from the radiator. The system has a capacity of about 2 to about 30 tons and contains a heat transfer composition containing a refrigerant. The refrigerant contains at least about 95% by weight of trans-1-chloro-3,3,3-trifluoropropene (trans-1233zd) or at least about 80% by weight of trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze).

Description

[0001] Cross - reference to related applications

[0002] This application is a divisional application of the patent application for invention titled "Efficient Air - conditioning System and Method" with the application date of January 6, 2017, application number 201780015459.0. This application claims the priority of U.S. Provisional Application No. 62 / 275,382 filed on January 6, 2016, the entire text of which is incorporated herein by reference. Technical Field

[0003] The present invention generally relates to air - conditioning systems, and more particularly to such systems that use a centrifugal compressor and have a cooling capacity of up to approximately 30 tons. Background Art

[0004] Certain halogenated olefins, including the compounds 1 - chloro - 3,3,3 - trifluoropropene (HFCO - 1233zd) and 1,3,3,3 - tetrafluoropropene (HFO - 1234ze), have been proposed for use in vapor - compression refrigeration systems. See US 7,833,433. The standard vapor - compression system is described in the '433 patent as including a compressor for compressing refrigerant vapor to produce a relatively elevated pressure and temperature vapor. An example of such a system is illustrated herein as Figure 1A . In such a system, the refrigerant is introduced via line 19A to the suction side of the compressor 11 at a relatively low pressure and the high - pressure refrigerant is discharged and conveyed via line 19B to the condenser 12. Heat is removed from this hot refrigerant vapor by condensing the refrigerant vapor in the condenser 12 to produce a relatively high - pressure liquid refrigerant, which enters line 15A. This relatively high - pressure liquid then undergoes a nominally isenthalpic pressure reduction in the expansion device 14 to produce a relatively low - temperature and low - pressure liquid, which is then vaporized by heat transferred from the object or fluid to be cooled in the evaporator 24. The resulting low - pressure vapor returns via line 19A to the suction side of the compressor, thereby completing the cycle.

[0005] The '433 patent generally suggests that the disclosed refrigerant compositions can be used in a variety of different cooling operations using vapor - compression systems, including chiller systems using centrifugal compressors. Generally, centrifugal chillers are large - capacity systems, i.e., systems having a capacity greater than 50 tons. Such systems most commonly have a cooling capacity of 50 to 150 tons, and some systems are as high as 8500 tons.

[0006] The Applicant has recognized that there are certain unexpected problems associated with the effort to use trans-HFCO-1233zd and / or trans-HFO-1234ze in small-capacity air conditioning systems using high-efficiency centrifugal compressors. As described in detail below, the Applicant has unexpectedly found that these problems can be overcome by using one or more special configurations in the air conditioning system, which allow the use of high-efficiency equipment, including high-efficiency compressors and evaporators, while overcoming the problems recognized by the Applicant when using trans-HFCO-1233zd and / or trans-HFO-1234ze in such systems. SUMMARY OF THE INVENTION

[0007] The Applicant has realized that it is highly desirable to provide low-capacity air conditioning systems using high-efficiency centrifugal compressors and high-efficiency evaporators in many applications. However, the Applicant has also realized that the use of refrigerant compositions containing a high percentage (e.g., higher than about 80 wt%) of HCFO-1233zd(E) or a high percentage (e.g., higher than about 80 wt%) of HFO-1234ze(E) can cause serious problems with the reliability and / or utility and / or efficiency of such systems.

[0008] For example, in certain air conditioning systems, it is highly desirable to use flooded evaporators because such heat exchange devices allow efficient heat transfer to the liquid refrigerant. This efficient operation is at least partially attributable to the fact that the heat transfer surface in such a device is substantially covered by the liquid refrigerant. However, due to the use of such high-efficiency equipment, the vapor leaving such an evaporator is substantially in a saturated state, i.e., having very little or no superheat. This is an advantage from an efficiency perspective, although in such cases it becomes particularly important to ensure that the vapor entering the compressor in a saturated state or near-saturated state does not condense. This is because the presence of such liquid refrigerant in the compressor has a negative impact on the efficiency and / or reliability of the compressor operation. Under typical operating conditions with other refrigerants, the use of saturated or near-saturated refrigerant vapor at the compressor suction port does not cause problems because heat is added to the refrigerant vapor during the nominal isentropic expansion process that occurs in a high-efficiency compressor and at least about 5° of superheat is generated when discharged from the compressor.

[0009] However, the Applicant has realized that problems will arise when using the preferred refrigerant compositions of the present invention under the conditions of the type preferably used in systems with high-efficiency centrifugal compressors. More specifically, the Applicant has found that the preferred refrigerant compositions of the present invention do not produce a normal or expected amount of superheat during the high-efficiency compression process under typical conditions. In fact, the Applicant has found that for the operation of a high-efficiency centrifugal compressor, in the absence of one or more of the solutions provided herein, "wet vapor" is discharged from the compressor. As used herein, the term "wet vapor" refers to a vapor in which condensate is entrained. As is well known to those skilled in the art, the presence of such a vapor in a compressor can be very detrimental to the efficient and / or reliable operation of a centrifugal compressor. Accordingly, the Applicant has found that in the absence of this solution, the use of the refrigerant according to the preferred aspect of the present invention in the operation of a high-efficiency centrifugal compressor, especially in applications that also use a high-efficiency, low-superheat or no-superheat evaporator, can cause unexpected problems. However, the Applicant has also realized that it is highly desirable to operate such a system with the preferred heat transfer composition of the present invention because such operation can provide environmentally beneficial operation.

[0010] To overcome the problems and difficulties that the Applicant has recognized, one aspect of the present invention provides a refrigeration system of the type having a heat source to be cooled and a heat sink that can discharge heat from the radiator, the system preferably having a capacity of about 2 to about 30 tons and comprising:

[0011] (a) A heat transfer composition containing a refrigerant, the refrigerant comprising at least about 80% by weight of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)) or at least about 80% by weight of trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)),

[0012] (b) A centrifugal compressor having: (i) a refrigerant suction port for receiving relatively low-pressure refrigerant vapor at a pressure of about 40 to about 350 kPa and (ii) a discharge port for discharging relatively high-pressure refrigerant vapor at a discharge:suction pressure ratio of at least about 2:1;

[0013] (c) A condenser fluidly connected to the refrigerant discharge port of the compressor, which is used to receive at least a portion of the refrigerant vapor discharged by the compressor and to condense at least most of the refrigerant vapor, preferably substantially all of the refrigerant vapor, by heat transfer with the radiator to produce relatively high-pressure refrigerant liquid at a temperature of about 10°C to about 60°C;

[0014] (d) An expander fluidly connected to the condenser, which is configured to reduce the pressure of the high-pressure refrigerant liquid with substantially constant enthalpy to produce a low-pressure refrigerant liquid at a pressure of about 40 to about 350 kPa;

[0015] (e) A highly efficient evaporator, preferably a flooded evaporator, fluidly connected to the expander, which is configured to receive the low-pressure refrigerant liquid from the expander and evaporate the low-pressure refrigerant liquid by absorbing heat from the source to be cooled to produce a relatively low-pressure refrigerant vapor at a pressure of about 40 to about 350 kPa. The refrigerant vapor leaving the evaporator preferably has substantially no superheat;

[0016] (f) At least one heat exchanger fluidly connected between the evaporator and the refrigerant suction inlet of the compressor. The at least one heat exchanger receives at least a portion of the low-pressure refrigerant vapor from the evaporator and heats the low-pressure refrigerant vapor to produce a low-pressure refrigerant vapor having a temperature that is at least about 5 °C higher than the temperature of the vapor entering the at least one heat exchanger. The high-temperature refrigerant vapor from the at least one heat exchanger is fluidly connected to the compressor suction inlet to supply low-pressure refrigerant vapor to the compressor.

[0017] As used herein, the term "capacity" defined in "tons" refers to the heat transfer rate equivalent to the heat required to melt 1 ton (2000 lb; 907 kg) of ice at 0 °C (32 °F) in 24 hours and is typically equivalent to about 12,000 BTU / hour.

[0018] Other embodiments and aspects of the present invention are disclosed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A is an illustrative diagram of a prior art heat transfer system.

[0020] Figure 1B is a generalized process flow diagram of a preferred embodiment of an air conditioning system according to the present invention.

[0021] Figure 2 is a generalized process flow diagram of another preferred embodiment of an air conditioning system according to the present invention.

[0022] Figure 3 is a generalized process flow diagram of another preferred embodiment of an air conditioning system according to the present invention.

[0023] Figure 4A is a generalized process flow diagram of another preferred embodiment of an air conditioning system according to the present invention.

[0024] Figure 4BIt is a more specific process flow diagram of a preferred embodiment of an air conditioning system with flame retardant characteristics according to an aspect of the present invention. Detailed Description

[0025] Preferred heat transfer composition

[0026] In the various embodiments described herein, the system includes a heat transfer composition comprising a refrigerant and preferably but not necessarily a compressor lubricant. The refrigerant preferably comprises at least about 70 wt% or at least about 80 wt% of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)) or trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), and is a non-flammable and low-toxic refrigerant, preferably having a Class A toxicity according to ASHRAE Standard 2013 and a Class 1 or Class 2 or Class 2L flammability according to ASHRAE Standard 34-2013 and described in Appendix B1 of ASHRAE Standard 34-2013.

[0027] In highly preferred embodiments, including embodiments of the type disclosed herein that provide flame retardant characteristics for the system and method, the refrigerant comprises at least about 95 wt% HFCO-1233zd(E), and in some embodiments consists essentially of or consists of it.

[0028] In some other highly preferred embodiments, the refrigerant comprises about 1 wt% to about 5 wt% of a five-carbon saturated hydrocarbon, preferably one or more of isopentane, n-pentane, or neopentane, and in a preferred aspect of such embodiments the combination of the HFCO-1233zd(E) and the pentane is in the form of an azeotropic composition. Such azeotropic and zeotropic-like compositions are disclosed in U.S. Patent 8,802,874, U.S. Patent 8,163,196, and U.S. Patent 8,703,006, each of which is hereby incorporated by reference herein. The heat transfer composition of the present invention comprising a refrigerant composition as described in this paragraph preferably comprises a lubricant comprising POE and / or mineral oil and / or alkylbenzene or consisting of it.

[0029] In highly preferred embodiments, including those of the type disclosed herein that provide flame retardant characteristics for the system and method, the 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 wt% 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), and even more preferably in some embodiments about 88% trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and about 12 wt% 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea). The heat transfer compositions of the present invention comprising a refrigerant composition as described in this paragraph preferably comprise a lubricant, which comprises or consists of POE.

[0030] Those skilled in the art will recognize, based on the disclosure contained herein, that such embodiments of the present invention offer the advantage of utilizing only relatively safe (low toxicity and low flammability) low GWP refrigerants, making them highly preferred for locations proximate to humans or other animals residing in a dwelling, as is often encountered in air conditioning applications.

[0031] The heat transfer compositions of the present invention generally comprise a lubricant. However, embodiments of the present invention include systems and methods that use compressors that do not require a lubricant and / or do not require the combination of a lubricant with the refrigerant. However, for those preferred embodiments where the lubricant and the refrigerant are included together as a mixture at one or more locations in the system, the lubricant is preferably present in the system in an amount of from about 30 to about 50 wt% of the heat transfer composition based on the total weight of the refrigerant in the system and the total weight of the lubricant in the system, and other optional components as described below may also be present. In a preferred embodiment, it is contemplated that the heat transfer compositions of the present invention, particularly in the form of carry-over vapor from the compressor and in the form of liquid from the condenser and entering the evaporator, comprise from about 97 wt% to about 99.5 wt% of the refrigerant of the present invention and from about 0.5 to about 3 wt% of a lubricant, such lubricant preferably being a POE lubricant and / or a mineral oil lubricant.

[0032] Other optional components include compatibilizers such as propane to assist in the compatibility and / or solubility of the lubricant. When present, such compatibilizers, including propane, butane, and pentane, are preferably present in an amount of from about 0.5 to about 5 weight percent of the composition. A combination of surfactants and solubilizers can also be added to the present composition to assist in oil solubility, as disclosed in U.S. Patent 6,516,837, the disclosure of which is incorporated herein by reference. Conventional refrigeration lubricants used in refrigeration machinery with hydrofluorocarbon (HFC) refrigerants, such as polyol esters (POE), polyalkylene glycols (PAG), silicone oils, mineral oils, alkyl benzenes (AB), and poly(alpha-olefins) (PAO), can be used with the refrigerant compositions of the present invention. Preferred lubricants of the present invention are selected from POE, mineral oil, and alkyl benzene.

[0033] system

[0034] The present refrigeration system and method are particularly applicable to low-capacity air conditioning systems, i.e., systems having a capacity of 30 tons or less, particularly residential air conditioning, particularly residential air conditioning having a capacity of from about 2 to about 5 tons, and particularly commercial packaged rooftop air conditioning units having a capacity of from about 5 to about 30 tons.

[0035] Figure 1B embodiments of the type illustrated

[0036] In Figure 1BThe figure illustrates a preferred air conditioning system generally designated as 10. Such a preferred air conditioning system includes a compressor 11, a condenser 12, an evaporator 24 (preferably a flooded evaporator), an expansion valve 14, and a suction line heat exchanger 30, as well as any associated piping 15A, 15B, 16A, and 16B and other connections and associated equipment (not shown). In operation, the refrigerant according to the present invention is discharged from the compressor 11 as a relatively high-pressure refrigerant vapor, which may contain entrained lubricant, and is then conveyed via line 19C to the condenser 12. In the condenser 12, the refrigerant vapor transfers a portion of its heat, preferably via a phase change and preferably to ambient air, and produces an effluent stream containing at least a portion, preferably substantially completely condensed, refrigerant. The refrigerant effluent from the condenser 12 is conveyed via line 15A to the suction line heat exchanger 30, where, as more fully explained below, it loses additional heat to the effluent from the evaporator 24. The effluent from the suction / liquid line heat exchanger 30 is then conveyed via line 15B to the expansion valve 14, where the pressure of the refrigerant is reduced, preferably by a substantially isenthalpic reduction, which in turn reduces the temperature of the refrigerant. The relatively cold liquid refrigerant from the expansion valve 14 flows to a receiver tank 18, which provides a reserve of cold liquid refrigerant, which is fed via a control valve (not shown) in line 19A to the evaporator 24, where it absorbs heat from the object or fluid being cooled, preferably the ambient air within a dwelling or other space being cooled. The refrigerant effluent vapor from the evaporator 24 (which is preferably a substantially saturated refrigerant vapor having substantially no superheat (e.g., the superheat of the vapor leaving the evaporator is less than about 1 °C, more preferably less than about 0.5 °C, and even more preferably less than about 0.1 °C)) is then conveyed via line 19A to the suction / liquid line heat exchanger 30, where it obtains heat from the condenser effluent from line 15A and produces a refrigerant vapor at a higher temperature, which is conveyed via line 16B to the inlet of the compressor 11. In a preferred embodiment, the vapor leaving the suction line heat exchanger has a temperature that is at least about 5 °C, and even more preferably at least about 7 °C, higher than the substantially saturated vapor entering the suction line heat exchanger. The high-temperature refrigerant vapor is then conveyed to the suction inlet of the compressor 11, where it is compressed as described above.

[0037] In a preferred embodiment where the refrigerant comprises at least about 90 wt% HCFO-1233zd(E), preferably consists essentially of, and more preferably consists of, the operating conditions correspond to the values described in the following table:

[0038]

[0039] In a preferred embodiment where the refrigerant comprises at least about 80 wt% HFO-1234ze(E), even more preferably 88 wt% HFO-1234ze(E) and 12 wt% HFC-227ea, the operating conditions correspond to the values described in the following table:

[0040] Figure 2 An embodiment of the type illustrated in the figure

[0041] In Figure 2 Another preferred air conditioning system generally designated as 10 is illustrated. Such a preferred air conditioning system includes a multi-stage compressor shown as a two-stage compressor 11, a condenser 12, an evaporator 24 (which is preferably a flooded evaporator in some embodiments), an expansion valve 14, and a vapor injection heat exchanger 40, which includes an associated intermediate expansion valve 41, and any associated pipes 15A–15C and 19A–19D and other connections and associated equipment (not shown and / or not labeled). In operation, the refrigerant according to the present invention is discharged from the compressor 11 as a relatively high-pressure refrigerant vapor, which may contain entrained lubricant, and is then conveyed via the pipe 19D to the condenser 12. In the condenser 12, the refrigerant vapor transfers a portion of its heat, preferably via a phase change and preferably to ambient air, and produces an effluent stream containing at least a portion, preferably substantially completely condensed, refrigerant. The refrigerant effluent from the condenser 12 is conveyed via the pipe 15A, and a portion of the refrigerant effluent is conveyed via the pipe 15B to the intermediate expansion device 41, and another portion of the effluent, preferably the remaining effluent, is conveyed to the vapor injection heat exchanger 40.

[0042] In operation, the intermediate expansion device 41 reduces the pressure of the effluent stream, preferably a substantially isenthalpic reduction to about the pressure at the second stage suction of the compressor 11 or sufficiently higher than such a pressure to account for the pressure drop across the heat exchanger 41 and associated pipes, fixtures, etc. Due to the pressure drop across the expansion device 41, the temperature of the refrigerant flowing to the heat exchanger 40 is reduced relative to the temperature of the high-pressure refrigerant flowing to the heat exchanger 40. Heat is transferred from the high-pressure stream to the stream passing through the expansion valve 41 in the heat exchanger 40. Thus, the temperature of the intermediate pressure stream leaving the heat exchanger 40 is higher than the temperature of the inlet stream, preferably at least about 5 °C higher, thereby producing a superheated vapor stream, which is conveyed via the pipe 19C to the second stage of the compressor 11.

[0043] As the higher pressure stream conveyed through line 15A passes through heat exchanger 40, it loses heat to the lower pressure stream exiting expansion device 41 and exits the heat exchanger via line 15C and then flows to receiving tank 18, which provides a reserve of cold liquid refrigerant that is fed via a control valve (not shown) in line 19A to evaporator 24. The ambient air to be cooled loses heat to this cold liquid refrigerant in the evaporator, which in turn vaporizes the liquid refrigerant and produces refrigerant vapor with little or no superheat, which then flows to the first stage of compressor 11.

[0044] In a preferred embodiment in which the refrigerant comprises at least about 90 wt% HCFO-1233zd(E), preferably consists essentially of it, and more preferably consists of it, the operating conditions correspond to the values described in the following table:

[0045]

[0046] In a preferred embodiment in which the refrigerant comprises at least about 80 wt% HFO-1234ze(E), even more preferably 88 wt% HFO-1234ze(E) and 12 wt% HFC-227ea, the operating conditions correspond to the values described in the following table:

[0047] Figure 3 embodiments of the type illustrated

[0048] In Figure 3The figure illustrates another preferred air conditioning system generally designated as 10. Such a preferred air conditioning system includes a compressor 11 (which may be a multi-stage compressor of the type described herein, but is shown as a single-stage compressor in the illustrated embodiment), a condenser 12, an evaporator 24 (which is preferably a flooded evaporator in some embodiments), an expansion valve 14, a flash gas separator 18, and any associated pipes 15A–15C and 19A–19C and other connections and associated equipment (not shown and / or not labeled). In operation, the refrigerant according to the present invention is discharged from the compressor 11 as a relatively high-pressure refrigerant vapor, which may contain entrained lubricant, and is then conveyed via pipe 19C to the condenser 12. In the condenser 12, the refrigerant vapor transfers a portion of its heat, preferably via a phase change and preferably to the ambient outside air, and produces an effluent stream containing at least a portion, preferably substantially completely condensed, refrigerant. The refrigerant effluent from the condenser 12 is conveyed via pipe 15A to the expansion device 14. The lower-pressure stream leaving the expander 14 flows via pipe 15B to the flash gas separator 18, which provides a reservoir of cold liquid refrigerant that is fed via a control valve (not shown) in pipe 15C to the evaporator 24. The ambient air to be cooled loses heat to this cold liquid refrigerant in the evaporator 24, which in turn vaporizes the liquid refrigerant and produces refrigerant vapor with little or no superheat, which then flows to the first stage of the compressor 11. The flash gas generated during the pressure drop in the expansion device 14 then flows via pipe 19B to the suction side of the compressor 11.

[0049] In a preferred embodiment in which the refrigerant comprises at least about 90 wt% HCFO-1233zd(E), preferably consists essentially of it, and preferably consists of it, the operating conditions correspond to the values described in the following table:

[0050]

[0051] In a preferred embodiment in which the refrigerant comprises at least about 80 wt% HFO-1234zd(E), even more preferably 88 wt% HFO-1234ze(E) and 12 wt% HFC-227ea, the operating conditions correspond to the values described in the following table:

[0052] Figure 4A An embodiment of the type illustrated in

[0053] In Figure 4AThe figure illustrates another preferred air conditioning system generally designated as 10. Such a preferred air conditioning system includes a compressor 11 (which can be a multi-stage compressor of the type described herein), a condenser 12, an evaporator 24 (which is preferably a flooded evaporator in some embodiments), an expansion valve 14, a high-pressure receiver, and any associated pipes 15A–15C and 19A–19B and other connections and associated equipment (not shown and / or not labeled). In operation, the refrigerant according to the present invention is discharged from the compressor 11 as a relatively high-pressure refrigerant vapor, which may contain entrained lubricant, and is then conveyed via pipe 19B to the condenser 12. In the condenser 12, the refrigerant vapor transfers a portion of its heat, preferably via a phase change and preferably to ambient outside air, and produces an effluent stream containing at least a portion, preferably substantially completely condensed, refrigerant. The refrigerant effluent from the condenser 12 is conveyed via pipe 15A to the high-pressure receiver 50, which provides a reserve of liquid refrigerant. A sensor-activated safety valve 60 is connected to pipe 15A via a port or other form of connection. The sensor-activated safety valve includes a sensor that monitors for flame, smoke, combustible gas concentration, or other indication of the presence of flame or a higher likelihood of ignition and / or is in communication therewith, and the sensor is located near a portion of the refrigeration system, preferably within a residence or other area being cooled. Since the preferred refrigerant of the present invention has flame-retardant properties, if the sensor detects flame and / or smoke (or other indication of the presence or increased likelihood of ignition), the sensor-activated safety valve will open and release the refrigerant into the area in which it is located, thereby assisting in suppressing and / or extinguishing a fire. The use of the high-pressure receiver ensures that a relatively large reserve of high-pressure liquid refrigerant is available in such an emergency situation. The remainder of the refrigeration system may operate according to any one or more of the embodiments described herein.

[0054] Examples

[0055] Example 1 - 1233zd, without suction line heat exchanger

[0056] An air conditioning system according to a typical arrangement shown in the figures labeled as prior art uses a refrigerant composed of HCFO-1233zd(E) according to the following parameters:

[0057] Operating conditions

[0058] 1 - Evaporation temperature: 7 °C

[0059] 2 - Condensation temperature: varying from 20 °C to 60 °C

[0060] 3 - Isentropic efficiency: varying from 0.7 to 0.8

[0061] 4 - No subcooling or superheating. Since the system of this embodiment has no superheating in the vapor leaving the evaporator (which is the case for a flooded evaporator, for example), saturated vapor enters the suction side of the centrifugal compressor. During normal operation with many other refrigerants, isentropic or near - isentropic expansion of the refrigerant vapor results in a discharge gas having a temperature representative of at least about 5 °C of superheat at the discharge pressure. This degree of superheat is generally considered necessary to ensure safe and reliable operation of the compressor to ensure that "wet vapor" does not exist in the compressor. For the system of this embodiment, operation at several near - isentropic compression levels was evaluated to determine if safe and reliable operation is achieved using HCFO - 1233zd(E). These results are reported in Table 1 below:

[0062] Table 1

[0063]

[0064] From the results reported in Table 1 above, it can be seen that when using the most efficient compressor (isentropic efficiency = 1), the vapor leaving the compressor contains at least a certain proportion of liquid, resulting in wet - vapor discharge, which as described above has serious negative implications for efficient and / or reliable operation. When the compressor efficiency is reduced to 0.8, the required superheat level is not achieved for any of the tested condenser temperatures. Even when the compressor efficiency is reduced to 0.75 and 0.7 (which are not preferred options in themselves), the desired superheat level is not achieved for the entire range of condenser temperature conditions.

[0065] Example 2A - 1233zd, using a suction line heat exchanger

[0066] An air - conditioning system according to the present invention using a suction line heat exchanger (SLHX) as illustrated and a refrigerant composed of HCFO - 1233zd(E) was tested according to the same operating parameters of the single - stage compressor for operation at 80% isentropic efficiency as in Figure 1B Example 1. Several heat exchanger efficiency levels of the suction line heat exchanger were examined, and the results are reported in Table 2A below:

[0067] Table 2A

[0068]

[0069] It can be seen from the results reported above that operation according to the embodiment of the present invention as illustrated in Figure 1B produces at least about 5 °C of superheat at the compressor outlet over the entire range of tested condensation temperatures.

[0070] Example 2B has an azeotrope of R1233zd

[0071] Repeat Example 2A, except that a series of azeotropic refrigerant blends based on HCFO-1233zd(E) as described in Table 2B below are used in place of the refrigerant consisting only of 1233zd(E) used in Example 2A. Acceptable operation is achieved.

[0072] In addition, the transport properties of these additional refrigerants, as well as those of the refrigerant consisting of HCFO-1233zd(E), are tested and reported in Table 2B below.

[0073] Table 2B

[0074]

[0075] Example 3A - 1233zd, using a suction line heat exchanger

[0076] Tested according to the same operating parameters of Example 1 using a suction line heat exchanger (SLHX) with SLHX efficiencies of 0.5 and 0.7 and an air conditioning system according to the present invention using a refrigerant consisting of HCFO-1233zd(E) as Figure 1B illustrated. This test provides a comparison of the relative efficiency of such systems with the system described in Example 1 without using an SLHX (both systems use a compressor efficiency of 80%), and this comparison is reported in Table 3A below:

[0077] Table 3A

[0078]

[0079] As can be seen from the results reported in Table 3A above, in addition to overcoming the wet vapor problem, the system according to the Figure 1B configuration produces an improvement in the overall system efficiency (COP) under all test conditions.

[0080] Example 4A - 1233zd, using a multistage compressor

[0081] Tested at a series of condensing temperatures from 30°C to 60°C using a two-stage compressor according to the system configuration as Figure 2 illustrated and an air conditioning system according to the present invention using a refrigerant consisting of HCFO-1233zd(E). The operating conditions of the compressor at an isentropic efficiency of 80% and an evaporator temperature of 7°C for each condenser temperature are reported in Table 4A1:

[0082] Table 4A1

[0083] Condensing temperature [°C] Compressor inlet temperature [kPa] Intermediate pressure [kPa] Discharge pressure [kPa] 30° 64.6 100 155 35° 64.6 109 183 40° 64.6 118 216 45° 64.6 128 252 50° 64.6 138 293 55° 64.6 148 340 60° 64.6 159 390 .

[0084] Tested using as Figure 2The multi-stage compressor arrangement illustrated in the figure and the same air conditioning using the refrigerant composed of HCFO-1233zd(E) are compared with the operation of a single-stage compressor configured according to Example 1. In addition, the same set of comparative tests are run on the refrigerant composed of R11. The results of these comparative tests are reported in Table 4A2 below:

[0085] Table 4A2

[0086]

[0087] As can be seen from the results reported above, the configuration of the present invention using an embodiment of the type illustrated in Figure 2 achieves a significant improvement in system efficiency (COP) due to the use of 2- and 3-stage compression, with an improvement of up to 115% in quantity. In addition, the test results reported above show that the use of HCFO-1233zd(E) in two-stage and three-stage compressor operation results in significantly better efficiency (COP) improvement compared to the improvement achieved using R-11 in the same system.

[0088] Example 5 - 1233zd and 1233zd blend, using a flash gas separator

[0089] The same operating parameters for a single-stage compressor operating at 80% isentropic efficiency according to Example 1 are tested using a flash gas separator as illustrated in Figure 3 and an air conditioning system arranged according to the present invention using a refrigerant composed of HCFO-1233zd(E) and a blend. The evaporator operates in a flooded configuration and results in a reduced pressure drop across the evaporator and thus a higher suction pressure in the compressor. In addition, due to the relatively low pressure in this system caused by the use of the refrigerant composed of HCFO-1233zd(E) and a blend, a compact heat exchanger made of low-cost materials can be used. For example, round tube fins and / or microchannel heat exchangers can be made of aluminum instead of copper. This configuration provides excellent heat transfer performance, low weight, and a compact heat transfer system.

[0090] Example 6 - 1233zd(E) and 1233zd(E) blend, using a sensor-activated safety valve Test using as Figure 4A and 4BThe sensor-activated safety valve illustrated in the figure and the air conditioning system according to the present invention using a refrigerant composed of HCFO-1233zd(E) and each refrigerant disclosed in Table 2B. The sensor-activated safety valve is preferably a solenoid-type valve. The sensor used measures the natural gas concentration in a residential furnace unit. In the case of a fuel leak in the burner device of the furnace, such as a natural gas leak, the sensor can detect an elevated gas concentration, for example 1000 ppm, to activate the solenoid valve. The activated valve will open and release R1233zd(E) into such a combustible natural gas atmosphere. Due to the flame-retardant property of R1233zd(E), the fire likelihood can be reduced by suppressing and / or eliminating the fire conditions near the safety valve located near the sensed combustible atmosphere. Therefore, the sensor detects a fire condition or a condition indicating an increased fire likelihood and the safety valve opens to suppress and / or eliminate the fire conditions near the safety valve located near the sensed flame and / or sensed condition.

[0091] Example 7A - 1234ze(E) blend, no suction line heat exchanger

[0092] An air conditioning system according to a typical arrangement shown in the figures marked as prior art uses a refrigerant composed of approximately 88 wt% HFO-1234ze(E) and approximately 12 wt% R227ea according to the following parameters:

[0093] Operating conditions – prior art

[0094] 1 - Evaporation temperature: 7 °C

[0095] 2 - Condensing temperature: varying from 20 °C to 60 °C

[0096] 3 - Isentropic efficiency: 0.7 - 0.8

[0097] 4 - No subcooling or superheating Since the system of this embodiment has no superheating in the vapor leaving the evaporator (which is the case for a flooded evaporator, for example), saturated vapor enters the suction side of the centrifugal compressor. In normal operation using many other refrigerants, the isentropic or near-isentropic expansion of the refrigerant vapor produces a discharge gas having a temperature representative of at least approximately 5 °C of superheat at the discharge pressure. This degree of superheat is generally considered necessary to ensure the safe and reliable operation of the compressor to ensure the absence of "wet vapor" in the compressor. For the system of this embodiment, the operation at several near-isentropic compression levels was evaluated to determine whether the above blend of HFO-1234ze(E) and R-227ea achieves safe and reliable operation. These results are reported in Table 7A below:

[0098] Table 7A

[0099]

[0100] As can be seen from the results reported in Table 7A above, all of the tested conditions except for five did not produce the minimum level of 5°C superheat in the compressor discharge, and the conditions that produced greater than this minimum superheat used an undesirably low isentropic efficiency of 0.7 at high condenser temperatures.

[0101] Example 7B - 1234ze blend, using a suction line heat exchanger

[0102] Tested according to the same operating parameters of the single - stage compressor for operation at 80% isentropic efficiency using a suction line heat exchanger (SLHX) as illustrated in Figure 1B and an air - conditioning system according to the arrangement of the present invention using a refrigerant composed of approximately 88 wt% HFO - 1234ze(E) and approximately 12 wt% R227ea. Several heat exchanger efficiency levels of the suction line heat exchanger were examined, and the results are reported in Table 7B below:

[0103] Table 7B

[0104]

[0105] It can be seen from the results reported in Table 7B above that, according to Figure 1B the embodiments of the present invention as illustrated in, operation produces at least approximately 5°C of superheat at the compressor outlet over the entire range of tested condensing temperatures.

[0106] Example 7C – 1234ze blend, using a suction line heat exchanger

[0107] Tested according to the same operating parameters of Example 7A using a suction line heat exchanger (SLHX) with SLHX efficiencies of 0.5 and 0.7 and an air - conditioning system according to the present invention as illustrated in Figure 1B using a refrigerant composed of approximately 88 wt% HFO - 1234ze(E) and approximately 12 wt% R227ea. This test provides a comparison of the relative efficiency of such systems with the system described in Example 7A without using an SLHX (both systems use a compressor efficiency of 80%), and this comparison is reported in Table 7C below:

[0108] Table 7C

[0109]

[0110] As can be seen from the results reported in Table 7C above, in addition to overcoming the wet - vapor problem, the systems configured according to Figure 1B produce an improvement in the overall system efficiency (COP) under all tested conditions.

[0111] Example 8A - 1234ze Blend, Using a Multistage Compressor

[0112] The tests were conducted using two - stage and three - stage compressors configured according to the system illustrated as Figure 2 and an air - conditioning system according to the present invention using a refrigerant composed of approximately 88 wt% HFO - 1234ze(E) and approximately 12 wt% R227ea and compared with the operation of a single - stage compressor configured as in Example 1. Additionally, the same set of comparative tests were run on a refrigerant composed of R134a. The results of these comparative tests are reported in Table 8A below:

[0113] Table 8A

[0114]

[0115] As can be seen from the results reported above, the configuration of the present invention using an embodiment of the type illustrated as Figure 2 achieves a significant improvement in system efficiency (COP) due to the use of 2 - and 3 - stage compression, with an improvement of up to 115% in magnitude. Additionally, the test results reported above show that the use of the HFO - 1234ze(E) / 227ea blend in two - stage and three - stage compressor operation results in significantly better efficiency (COP) improvements compared to those achieved using R134a in the same system.

[0116] Example 9

[0117] In each of the above embodiments, the system includes plastic components that come into contact with the refrigerant during operation. These materials from which these components are made are compatible and / or stable. The applicant has tested the stability of various plastic materials when exposed to trans - HFCO - 1233zd. The tests included immersing samples of various plastics in trans - HFCO - 1233zd at room temperature (about 24°C - 25°C) under ambient pressure conditions for two (2) weeks, after which the samples were removed from the trans - HFCO - 1233zd and allowed to outgas for 24 hours. The results are reported in Table 9 below:

[0118] Table 9

[0119]

[0120] As illustrated by the results in Table 5 above, the average percentage change in volume of each of the plastic materials tested was less than 5%.

Claims

1. A refrigeration method for cooling a heat source using an air conditioning system having a capacity of 2 to 30 tons, the method comprising: (a) A heat transfer composition containing a refrigerant, the refrigerant comprising 85 wt% to 90 wt% of trans-1,3,3,3-tetrafluoropropene and 10 wt% to 15 wt% of 1,1,1,2,3,3,3-heptafluoropropane; (b) A centrifugal compressor having a refrigerant suction port for receiving low-pressure refrigerant vapor and a discharge port for discharging high-pressure refrigerant vapor, the compressor having an efficiency of at least 0.65; (c) A condenser fluidly connected to the refrigerant discharge port of the compressor, the condenser for receiving the high-pressure refrigerant vapor and condensing at least most of the refrigerant vapor by heat transfer with a radiator to produce high-pressure refrigerant liquid at a temperature of 10°C to 60°C; (d) An expander fluidly connected to the condenser, which substantially isenthalpically reduces the pressure of the high-pressure refrigerant liquid to produce low-pressure refrigerant liquid; (e) An evaporator fluidly connected to the expander, which receives the low-pressure refrigerant liquid and evaporates the low-pressure refrigerant liquid by absorbing heat from the source to be cooled to produce low-pressure refrigerant vapor; and (f) At least one heat exchanger fluidly connected between the evaporator and the refrigerant suction port of the compressor, wherein the at least one heat exchanger receives at least a portion of the low-pressure refrigerant vapor from the evaporator and heats the low-pressure refrigerant vapor to produce low-pressure refrigerant vapor having a temperature at least 5°C higher than the temperature of the vapor entering the at least one heat exchanger, and the high-temperature refrigerant vapor from the at least one heat exchanger is fluidly connected to the compressor suction port to supply low-pressure refrigerant vapor to the compressor.

2. The refrigeration method of claim 1, wherein the refrigerant comprises 88 wt% of trans-1,3,3,3-tetrafluoropropene and 12 wt% of 1,1,1,2,3,3,3-heptafluoropropane.

3. The refrigeration method of claim 1, wherein the centrifugal compressor has a refrigerant suction port for receiving low-pressure refrigerant vapor at a pressure of 210 to 310 kPa and a discharge port for discharging high-pressure refrigerant vapor at a pressure of 420 to 1600 kPa.

4. The refrigeration method of claim 1, wherein the expander fluidly connected to the condenser substantially isenthalpically reduces the pressure of the high-pressure refrigerant liquid to produce low-pressure refrigerant liquid at a pressure of 210 to 310 kPa.

5. The refrigeration method of claim 1, wherein the evaporator fluidly connected to the expander receives the low-pressure refrigerant liquid and evaporates the low-pressure refrigerant liquid by absorbing heat from the source to be cooled to produce low-pressure refrigerant vapor at a pressure of 210 to 310 kPa.

6. The refrigeration method of any of the preceding claims, wherein the heat transfer composition contains a lubricant selected from polyol esters, polyalkylene glycols, silicone oils, mineral oils, alkylbenzenes, and poly(α-olefins).

7. The refrigeration method according to claim 6, wherein the lubricant is selected from polyol esters, mineral oils, and combinations thereof.

8. The refrigeration method according to claim 6, wherein based on the total weight of the refrigerant and the total weight of the lubricant in the refrigeration system, the amount of the lubricant present is 30-50% by weight.

Images