NONFLAMMABLE REFRIGERANTS HAVING LOW GWP, AND SYSTEMS FOR AND METHODS OF PROVIDING REFRIGERATION
20230375230 · 2023-11-23
Assignee
Inventors
- Nilesh Purohit (Charlotte, NC, US)
- Kaimi Gao (Charlotte, NC, US)
- Ankit Sethi (Charlotte, NC, US)
- Ryan Hulse (Charlotte, NC, US)
Cpc classification
F25B7/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B9/006
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
F25B7/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Abstract
The present invention provides cascade refrigeration systems in which the low stage comprises a refrigerant with a GWP less than 150, and the high stage comprises a refrigerant that is either Class A1 or Class A2L and comprises at least about 75% by weight of HFO-1234ze(E).
Claims
1. A cascade refrigeration system, comprising: a. a low stage refrigeration circuit comprising: a low stage refrigerant having a GWP of about 150 or less; and a compressor; b. an inter-circuit heat exchanger in which said low stage refrigerant condenses; and c. a high stage refrigeration circuit comprising a high stage refrigerant which: (i) has either Class A1 or Class A2L flammability; (ii) evaporates at a temperature below said low stage refrigerant condensing temperature; and (iii) comprises at least about 77% by weight of HFO-1234ze(E), wherein said high stage refrigerant evaporates in said inter-circuit heat exchanger by absorbing heat from said refrigerant in said low stage refrigeration circuit.
2. The cascade refrigeration system of claim 1 wherein said high stage refrigerant has a Class A1 flammability.
3. The cascade refrigeration system of claim 1 wherein said high stage refrigerant comprises at least about 75% of HFO-1234ze(E).
4. The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of HFO-1234ze(E).
5. The cascade refrigeration system of claim 4 wherein said low stage refrigerant consists essentially of CO2.
6. The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of R471 A.
7. The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of R476 A.
8. The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of propane.
9. The cascade refrigeration system of claim 8 wherein said high stage refrigerant consists essentially of R471 A.
10. The cascade refrigeration system of claim 8 wherein said high stage refrigerant consists essentially of R476 A.
11. The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of HFO-1234yf.
12. The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of R454C.
13. The cascade refrigeration system of claim 13 wherein said high stage refrigerant consists essentially of R476 A.
14. The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of R455 A.
15. The cascade refrigeration system of claim 14 herein said high stage refrigerant consists essentially of R471 A.
16. The cascade refrigeration system of claim 14 wherein said high stage refrigerant consists essentially of R476 A.
17. The cascade refrigeration system of claim wherein said low stage refrigeration circuit comprises a plurality of low temperature refrigeration circuits.
18. The cascade refrigeration system of claim 1 wherein said low stage refrigeration circuit compressor comprises at least one compressor having a horsepower rating of about 2 horsepower or less.
19. A method for proving cooling in an extreme temperature air conditioning system comprising: a. providing an air conditioning system comprising a compressor, a condenser, an evaporator and a refrigerant, said refrigerant comprising: i. about 78.7% by weight of HFO-1234ze(E), ii. about 4.3% by weight of HFC-227ea; and iii. about 17% by weight of HFO-1336mzz(E); b. evaporating said refrigerant in said evaporator, and c. condensing said refrigerant at a temperature in the range of from about from about 55° C. to about 95° C.
20. A method for proving cooling in a high temperature heat pump comprising: a. providing a heat pump comprising a compressor, a condenser, an evaporator and a refrigerant, said refrigerant comprising: i. about 78.7% by weight of HFO-1234ze(E), ii. about 4.3% by weight of HFC-227ea; and iii. about 17% by weight of HFO-1336mzz(E); b. evaporating said refrigerant in said evaporator, and c. condensing said refrigerant at a temperature in the range of from about from about 55° C. to about 95° C.
Description
BRIEF DESCRIPTION OF THE FIGURES
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DESCRIPTION OF PREFERRED COMPOSITIONS
Definitions
[0218] As used herein, the terms “low stage” and “high stage” are used in a relative context to designate the relative evaporation temperatures of two or more cascaded refrigeration circuits. Thus, the term “low stage” in the context of a cascaded refrigeration system refers to the refrigeration circuit in which the refrigerant evaporators at temperature that is less than the evaporation temperature of the refrigerant in the “high stage.”
[0219] As used herein, the term “cascaded refrigeration” refers to a refrigeration system having a low stage refrigerant vapor is cooled, and preferably condensed, at least in part by rejecting heat to the high stage refrigerant.
[0220] The phrase “coefficient of performance” (hereinafter “COP”) is a universally accepted measure of refrigerant performance, especially useful in representing the relative thermodynamic efficiency of a refrigerant in a specific heating or cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration engineering, this term expresses the ratio of useful refrigeration or cooling capacity to the energy applied by the compressor in compressing the vapor and therefore expresses the capability of a given compressor to pump quantities of heat for a given volumetric flow rate of a heat transfer fluid, such as a refrigerant. In other words, given a specific compressor, a refrigerant with a higher COP will deliver more cooling or heating power. One means for estimating COP of a refrigerant at specific operating conditions is from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see for example, R.C. Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall, 1988 which is incorporated herein by reference in its entirety).
[0221] The phrase “Global Warming Potential” (hereinafter “GWP”) was developed to allow comparisons of the global warming impact of different gases. It compares the amount of heat trapped by a certain mass of a gas to the amount of heat trapped by a similar mass of carbon dioxide over a specific time period of time. Carbon dioxide was chosen by the Intergovernmental Panel on Climate Change (IPCC) as the reference gas and its GWP is taken as 1. The larger GWP, the more that a given gas warms the Earth compared to CO2 over that time period. As used herein, the term GWP means the value of GWP as measured in accordance with IPCC Fifth Assessment Report, 20141, referred to and abbreviated herein as AR5. Myhre, G., D. Shindell, F.-M. Breon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/pdf/assessmentreport/ar5/wg1/WG1AR5_Chapter08_FINAL.pdf (p. 73-79)
[0222] The term “non-flammable” refers to compounds or compositions which are determined to be nonflammable as determined in accordance with ASTM Standard E-681-2009 Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases) at conditions described in ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and described in Appendix B1 to ASHRAE Standard 34-2016 (as each standard exists as of the filing date of this application), which are incorporated herein by reference in its entirety (“Non-Flammability Test”). Flammability is defined as the ability of a composition to ignite and/or propagate a flame. Under this test, flammability is determined by measuring flame angles. A non-flammable substance would be classified as class “1” by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants (as each standard exists as of the filing date of this application).
[0223] As used herein, the term “evaporator glide” means the difference between the saturation temperature of the refrigerant at the entrance to the evaporator and the dew point of the refrigerant at the exit of the evaporator, assuming the pressure at the evaporator exit is the same as the pressure at the inlet. As used herein, the phrase “saturation temperature” means the temperature at which the liquid refrigerant boils into vapor at a given pressure.
[0224] The phrase “no or low toxicity” as used herein means the composition is classified as class “A” by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and described in Appendix B1 to ASHRAE Standard 34-2016 (as each standard exists as of the filing date of this application). A substance which is non-flammable and low toxicity would be classified as “A1” by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and described in Appendix B1 to ASHRAE Standard 34-2016 (as each standard exists as of the filing date of this application).
[0225] The term “degree of superheat” or simply “superheat” means the temperature rise of the refrigerant at the exit of the evaporator above the saturated vapor temperature (or dew temperature) of the refrigerant.
[0226] As used herein, the term “E-1,3,3,3-tetrafluoropropene” means the trans isomer of HFO-1234 ze and is abbreviated as HFO-1234ze (E).
[0227] As used herein, the term “E-1,1,1,4,4,4-hexafluorobut-2-ene” means the trans isomer of HFO-1336mzz and is abbreviated as HFO-1336mzz (E).
[0228] As used herein, the term “1,1,1,2,3,3,3-heptafluoropropane” is abbreviated as HFC-227 ea.
[0229] As used herein, the term “low temperature refrigeration” refers to a refrigeration system that operates under or within the following conditions: (a) condenser temperature from about 15° C. to about 50° C.; and (b) evaporator temperature from about −40° C. to about or less than about −15° C.
[0230] As used herein, the term “medium temperature refrigeration” refers to a refrigeration system that utilizes one or more compressors and operates under or within the following conditions: (a) a condenser temperature of from about 15° C. to about 60° C.; and (b) evaporator temperature of from about −15° C. to about 5° C.
[0231] As used herein the term “extreme temperature air conditioning system” means a vapor compression air conditioning system in which the condensing temperature of the refrigerant is from about 55° C. to about 95° C.
[0232] As used herein the term “high temperature heat pump system” means a vapor compression system operable in a heating mode in which the condensing temperature of the refrigerant is from about 55° C. to about 95° C.
[0233] As used herein, the term “R454C” means the refrigerant designated by ASHRAE as 454C and which consists of 21.5%+2/−2% of R-32 and 78.5 −+2/−2% of HFC-1234yf.
[0234] As used herein, the term “R455 A” means the refrigerant designated by ASHRAE as 455AC and which consists of 21.5%+2/−1% of R-32, 75.5 of HFC-1234yf+2/−2% and 3%+2/−1% of CO2.
[0235] As used herein, the term “R471 A” means the refrigerant designated by ASHRAE as 471 A and which consists of 78.7%+0.4/−1.5% of HFC-1234ze(E), 17%+1.5/−0.4% of HFC-1336mzz(E) and 4.3%+1.5/−0.4% of HFC-227ea.
[0236] As used herein, the term “R476 A” means the refrigerant designated by ASHRAE as 476 A and which consists of 78.7%+/−0.5/−2% of HFC-1234ze(E), 12%+2/−0.5% of HFC-1336mzz(E) and 10%+2/−0.51% of HFC-134a.
[0237] As used herein, the term “about” in relation to the amount expressed in weight percent means that the amount of the component can vary by an amount of +/−2% by weight.
[0238] Cascade Systems
[0239] The present invention includes cascade refrigeration systems, including each of Systems 1-7, in which said inter-circuit heat exchanger is a flooded heat exchanger in which said high stage refrigerant evaporates in said heat exchanger by absorbing heat from said low temperature refrigerant. As used herein, reference to a numbered system or group of numbered systems that have been defined herein means each of such numbered systems, including each system having a number within the group, including any suffixed numbered system. For example, reference to System 1 includes reference to each of Systems 1A, 1B and 1C.
[0240] As the term is used herein, “flooded heat exchanger” refers to a heat exchanger is which a liquid refrigerant is evaporated to produce refrigerant vapor with no substantial super heat. As the term is used herein, “no substantial super heat” means that the vapor exiting the evaporator is at a temperature that is not more than 1° C. above the boiling temperature of the liquid refrigerant in the heat exchanger.
[0241] The present invention also includes a cascade refrigeration system, including each of the Systems 1-7, in which the low stage refrigeration circuit comprises one or more of, and preferably a plurality of, low temperature refrigeration circuits.
[0242] The present invention also includes a cascade refrigeration system, including each of the Systems 1-7, in which the low stage refrigeration circuit comprises one or more of, and preferably a plurality of, low temperature refrigeration circuits and in which the high stage refrigeration circuit comprises one or more medium temperature refrigerant circuits.
[0243] In preferred embodiments, including in each of Systems 1-7, the high stage refrigeration circuit is located substantially completely outside of said low stage refrigeration unit(s). As used herein, the term “substantially completely outside” means that the components of the high stage are generally located remote from said components of the low stage refrigeration units, except that transport piping and the like which may be considered part of the high stage circuit can pass into or located near or among the low stage circuit in order to provide heat exchange between the refrigerant of the low stage and the refrigerant of the high stage via the inter-circuit heat exchanger.
[0244] In preferred embodiments, including in each of Systems 1-7, the low stage circuit comprises one or more “refrigeration units,” and preferably “low temperature refrigeration units.” As used herein, the term “refrigeration unit” means an at least partially closed and/or fully closable structure that is capable of providing cooling within at least a portion of that structure and which is structurally distinct from any structure enclosing or containing the high stage circuit.
[0245] In preferred embodiments, including in each of Systems 1-7, the high stage circuit comprises one or more “refrigeration units,” and preferably “medium temperature refrigeration units.”
[0246] The high stage circuit in the cascade systems of the present invention, including in each of Systems 1-7, may further comprise a fluid receiver for receiving high stage refrigerant from the condenser in the high stage circuit.
[0247] Each refrigeration unit including in each of Systems 1-7, may be located within a first area. The first area may be a shop floor. This means that each first refrigeration circuit (preferably low temperature refrigeration circuit) may also be located within a first area, such as a shop floor.
[0248] Each refrigeration unit, including in each of Systems 1-7, may comprise a space and/or objects contained within a space to be chilled, and preferably that space is within the refrigeration unit. Each evaporator in the low stage of such preferred refrigeration units may be located to chill its respective space/objects, preferably by cooling air within the space to be chilled.
[0249] As mentioned above, the high stage refrigeration circuit of the present invention, including in each of Systems 1-7, and preferably when the high stage circuit comprises a medium temperature refrigeration circuit, may have components thereof that extend between the first low stage circuit (preferably low temperature refrigeration unit) and at least a second area remote from said low stage circuit. The second area may be, for example, a machine room which houses a substantial portion of the components of the high stage circuit.
[0250] The high stage refrigeration circuit of the preset invention, including each of Systems 1-7, (preferably comprising medium temperature refrigeration circuits) may extend to a second and a third area. The third area may be an area outside of the building or buildings in which the low stage circuit is located. This allows for ambient cooling to be exploited.
[0251] Unless otherwise indicated herein for a particular embodiment, the refrigerant in the high stage circuit may be non-flammable, that is, classified as A1 under ASHRAE 34 (as measured by ASTM E681) or classified as A2L under ASHRAE 34 (as measured by ASTM E681). This may be desirable in those cases in which the high stage circuit includes long runs of piping that extend between different areas of a building: for example, between a shop floor (where low stage refrigeration units might be deployed) to a machine room. Consequently, it may be unsafe to have a flammable refrigerant in the high stage refrigeration circuit since both the risk of leaks and the severity of potential leaks is increased as the high stage circuit spans a greater area and therefore exposes more people and/or structures to risk of fire.
[0252] Each low stage refrigeration circuit, including in each of Systems 1-7, may comprise at least one fluid expansion device. The at least one fluid expansion device may be a capillary tube or an orifice tube. This means that simpler flow control devices, such as capillary and orifice tubes, can be and preferably are used to advantage in the low stage refrigeration circuit of the present invention, including each of Systems 1-7.
[0253] One embodiment of a cascade refrigeration system according to the present invention is illustrated schematically in
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[0255] In this example, the refrigerant in each of the low stage refrigeration circuits 220a, 220b, 220c is a low GWP refrigerant such as CO2, propane, HFO-1234yf, R454C, R455 A or a combination of two or more of these. As the skilled person will appreciate, the refrigerants in each of the low stage circuits 220a, 220b, 220c may the same or different to the refrigerants in each other of the low stage refrigeration circuits 220a, 220b, 220c, but in a preferred embodiment each of the plurality of low stage circuits contains CO2, propane, HFO-1234yf, R454C, R455 A or a combination of two or more of these.
[0256] The refrigeration system 200 also has a high stage refrigeration circuit 210. The high stage circuit 210 has a compressor 211, a condenser 213 and a fluid receiver 214. The compressor 211, the condenser 213 and the fluid receiver 214 are connected in series and in the order given. While each of the compressors, condensers, fluid receivers, etc. in the high stage circuit are illustrated by a single icon, it will be appreciated that the compressor, the evaporator, the heat exchanger, expansion valve, etc. can each comprise a plurality of such units. The high stage refrigeration circuit 210 also has four parallel connected branches: three medium temperature cooling branches 217a, 217b and 217c, which are not in heat transfer communication with the low stage; and low stage cooling branch 216. The four parallel connected branches 217a, 217b, 217c and 216 are connected between the fluid receiver 214 and the compressor 211. Each of the medium temperature cooling branches 217a, 217b and 217c has an expansion valve 218a, 218b and 218c and an evaporator 219a, 219b and 219c, respectively. The expansion valve 218 and evaporator 219 are connected in series and in the order given between the fluid receiver 214 and the condenser 211. The high stage circuit 220, which in preferred embodiments comprises a low temperature cooling branch, 216 has an expansion valve 212 and an interface, in the form of inlet and outlet piping, conduits, valves and the like (represented collectively as 260a, 260b and 260c, respectively) which bring the high stage refrigerant liquid to and high stage refrigerant vapor from each of the inter-circuit heat exchangers 230a, 230b, 230c, which as shown in a preferred embodiment are located within the refrigeration unit 220. The low temperature cooling branch 216 interfaces each of the inter-circuit heat exchangers 230a, 230b, 230c at a respective circuit interface location 231a, 231b, 231c. Each circuit interface location 231a, 231b, 231c is arranged in series-parallel combination with each other of the circuit interface locations 231a, 231b, 231c.
[0257] The high stage refrigeration circuit 210 has components which extend between the sales floor 242, a machine room 241 and a roof 140. The cooling branch 216 and the medium temperature branches 218a, 218b, 218c of the medium temperature refrigeration circuit 210 are preferably located on the sales floor 242. The compressor 211 and the fluid receiver 214 are preferably located in the machine room 241. The condenser 213 is preferably located where it can be readily exposed to ambient conditions, such as on the roof 240.
[0258] In this example, the refrigerant in the high stage refrigeration circuit 210 comprises, consists essentially of, or consists of a refrigerant that comprises at least about 75% by weight of HFO-1234ze and has a Class A1 or A2L flammability. The present invention includes cascade systems in which the refrigerant in the high stage refrigeration circuit 210 comprises, consists essentially of, or consists of HFO-1234ze(E), R471 A and/or R476 A Further advantageously, the blend has a low GWP, making it an environmentally friendly solution, as well as excellent heat transfer performance properties, as illustrated below in the Examples hereof.
[0259] Use of the preferred embodiments as illustrated in
[0264] A number of beneficial results can be achieved using arrangements of the present invention of the type shown in
[0265] For example, installation and uninstallation of the refrigeration units and the overall cascaded refrigeration system 200 is simplified. This is because the refrigeration units, with their built-in, self-contained refrigeration circuits 220a, 220b, 220c, can be easily connected or disconnected with the high stage refrigeration circuit 210, with no modification to the refrigeration circuit 220, 220b, 220c required. In other words, the refrigeration units may simply be ‘plugged’ in to, or out of, the high stage refrigeration circuit 210.
[0266] Another advantage is that each refrigeration unit, including its respective first refrigeration circuit 220a, 220b, 220c, can be factory tested for defaults before being installed into a live refrigeration system 200. This mitigates the likelihood of faults, which can include leaks of potentially harmful refrigerants. Accordingly, a reduced leak rate can be achieved.
[0267] Another advantage in preferred embodiments is the provision of a flooded inter-circuit heat exchanger which in systems of the present invention, including each of Systems 1-7, results in improved heat transfer between the low stage and the high stage. Accordingly, the efficiency of the overall refrigeration system is improved.
[0268] In preferred embodiments, including each of Systems 1-7, the present invention also includes a cascaded refrigeration system, comprising: a plurality of low temperature refrigeration circuits, with each low temperature refrigeration circuit comprising a low temperature refrigerant having a GWP of about 150 or less and comprising at least about 50% by weight, or at least about 75% by weight by weight of R1234yf, including specifically R-454C and/or R455 A, and a compressor having a work output of about 3.5 kilowatts or less, an inter-circuit heat exchanger in which said low temperature refrigerant condenses in the range of temperatures of from about −5° C. to about −15° C.; and a medium temperature refrigeration circuit containing medium temperature refrigerant, wherein said medium temperature refrigerant comprises, consists essentially of, or consists of at least about 75% by weight of HFO-1234ze(E), including particularly R471 A and/or R476 A, and an evaporator in which said medium temperature refrigerant evaporates at a temperature below said low temperature refrigerant condensing temperature and in the range of about −5° C. to about −15° C., wherein said medium temperature refrigerant evaporates in said heat exchanger by absorbing heat from said low temperature refrigerant.
[0269] In preferred embodiments, including each of Systems 1-7, the present invention also includes a cascaded refrigeration system, comprising: a plurality of low temperature refrigeration circuits, with each low temperature refrigeration circuit comprising a low temperature refrigerant having a GWP of about 150 or less and comprising at least about 50% by weight, or at least about 75% by weight by weight of R1234yf, including specifically R-454C and R-455 A, and a compressor having a compressor rating of two horse power or less, an inter-circuit heat exchanger in which said low temperature refrigerant condenses in the range of temperatures of from about −5° C. to about −15° C.; and a medium temperature refrigeration circuit containing medium temperature refrigerant, wherein said medium temperature refrigerant comprises, consists essentially of, or consists of at least about 75% by weight of HFO-1234ze(E), including particularly R471 A and/or R476 A, and an evaporator in which said medium temperature refrigerant evaporates at a temperature below said low temperature refrigerant condensing temperature and in the range of about −5° C. to about −15° C., wherein said medium temperature refrigerant evaporates in said heat exchanger by absorbing heat from said low temperature refrigerant.
[0270] Cascade Refrigeration System—Alternatives
[0271] As the person skilled in the art will appreciate in view of the teachings contained here, there may be in accordance with the present invention, including each of Systems 1-7, any number of low stage refrigeration circuits 220. In particular, there may be as many low stage circuits 220 as there are refrigeration units to be cooled. Accordingly, the high stage refrigeration circuit 210 may be interfaced with any number of low stage refrigeration circuits 220, and visa-versa.
[0272] As will be clear to the skilled person in view of the teachings contained here, there may be in accordance with the present invention, including each of Systems 1-4, any number and arrangement of high stage circuit branches 217 and evaporators 218. In alternative arrangements in accordance with the present invention, including each of Systems 1-7, each low stage circuit 220 may be arranged fully in parallel with each other low stage circuit 220. An example of such an arrangement is shown in
[0273] Usefully, this means that a given portion of refrigerant from the high stage circuit 210 only passes through one inter-circuit heat exchanger 230 before it is returned to the compressor 211. This arrangement thus ensures that each of the heat exchangers 230 will receive high stage refrigerant at about the same temperature, since the arrangement prevents any of the heat exchangers from receiving a portion of the refrigerant that is pre-warmed as a result of passing through an upstream heat exchanger, as would be the case in a series arrangement.
[0274] As will be clear to the person skilled in the art in view of the teachings contained here, many other arrangements of the circuit interface locations 231a, 231b, 231c with respect to one and the high stage refrigeration circuit 210 can be achieved in accordance with the present invention, including each of Systems 1-7, and indeed are envisaged.
[0275] As will be clear to the person skilled in the art in view of the teachings contained here, by virtue of the preferred modular design of the low stage circuits of the preferred embodiments of the present invention, including each of Systems 1-7, allows use of non-flammable, low-pressure refrigerants with relatively low GWP.
[0276] Cascaded Refrigeration System with Flooded Evaporator
[0277] A preferred refrigeration system of the present invention is exemplified and will now be described with reference to
[0278] The receiver 414 is arranged to separate the gaseous and liquid refrigerant after it has passed through the expansion valve 418 such that the refrigerant allowed through to the medium 417 and low 416 temperature cooling branches—and therefore through to the evaporator 419 and heat exchangers 430a, 430b—is essentially 100% liquid. Another key feature of the refrigeration system 400 is the pump 442. The pump 442 drives the refrigerant to the medium 417 and low 416 temperature branches. In alternative system arrangements, the density difference between the liquid and gaseous phases of the refrigerant drives the system and no pump or fan is required.
[0279] In this example, the low stage refrigerant in refrigeration circuits 420a and 420b comprises, consists essentially of or consists of, a low GWP, non-flammable (Class A1) refrigerant, comprising at least about 50% by weight, or at least about 75% by weight by weight of R1234yf, including specifically R-454C and/or R455 A. As the skilled person will appreciate, the refrigerants in each of the refrigeration circuits 420a, 420b may be the same or different to the refrigerants in the other of the first refrigeration circuits 420a, 420b.
[0280] The refrigeration system 400 also has a high stage refrigeration circuit 410 which has a compressor branch 450 and an ambient cooling branch 451. The compressor branch 450 is connected in parallel with the ambient cooling branch 451. The compressor branch 450 has a compressor 411, a condenser 413, an expansion valve 418 and a receiver 414. The compressor 411, the condenser 413 and the expansion valve 418 are connected in series and in the order given. The receiver 414 is connected between the compressor 411 inlet and the expansion valve 418 outlet. The ambient cooling branch 451 has a chiller 452.
[0281] The compressor branch 450 and the ambient cooling branch 451 are connected in parallel by first 440 and second 441 controllable valves. The controllable valves 440, 441 are controllable such that the amount of refrigerant flowing in each of the compressor branch 450 and the ambient cooling branch 451 is controllable. The first control valve 440 is connected in series with a pump 442.
[0282] The high stage refrigeration circuit 410 also has two further branches which are connected in parallel with one another: a medium temperature cooling branch 417 and a low temperature cooling branch 416 which provides liquid refrigerant to the inter-circuit heat exchangers 431. The medium temperature cooling branch 417 and the branch 416 are connected between the pump 442 and the second controllable valve 441. The medium temperature cooling branch 417 has an evaporator 419. The low temperature cooling branch 416 interfaces each of the inter-circuit heat exchangers 430a, 430b of the first refrigeration circuits 420a, 420b at a respective circuit interface location 431a, 431b. Each of the circuit interface locations 431a, 431b is in series-parallel combination with the other circuit interface location 431a, 431b.
[0283] The cascade system 400 includes components that extend the high stage circuit and the low stage circuit between the sales floor 462, a machine room 461 and a roof 440. The branch 416 which brings high stage liquid refrigerant to the inter-circuit heat exchanger, and the medium temperature cooling branch 417, are preferably each located primarily on the sales floor 462. By primarily arranged on the sales floor 462, it is meant that the circuit locations 431a, 431b and the evaporator 419 are arranged on or very near the sales floor 462. The junction between the low 416 and medium 417 temperature cooling branches and some of the pipes of the low 416 and medium 417 branches may, however, be located in the machine room 461.
[0284] The compressor branch 450 in preferred embodiments includes components that extend the branch between the machine room 461 and the roof 460. More specifically, the compressor 411, the expansion valve 418 and the flooded receiver 414 are preferably located in the machine room 461. The condenser 413 is preferably located where ready access to ambient air is possible, such as on the roof 460.
[0285] The ambient cooling branch 450 preferably includes components that extend the branch between the machine room 461 and the roof 460. The chiller 452 is also located where ready access to ambient air is possible, such as on the roof 603.
[0286] The first and second controllable valves 440, 441 are preferably located in the machine room 461. The pump 442 is preferably located in the machine room 442.
[0287] In this example, the refrigerant in the high stage circuit 410 preferably comprises, consists essentially of, or consists of at least about 75% by weight of HFO-1234ze(E), including particularly R471 A.
[0288] Though structurally different, in use, the refrigeration system 400 operates in a similar manner to refrigeration system 200 with the following key differences. Firstly, the receiver in the high stage refrigeration circuit 410 in the refrigeration system 400 results in inter-circuit heat exchangers 430a and 430b being flooded evaporators for the high stage circuit, and the medium temperature evaporator 419 is also a flooded evaporator.
[0289] As the skilled person will appreciate based on the disclosure and teaching contained herein, there are several advantages associated with using a refrigeration arrangement in accordance with the present invention, including each of Cascade Systems 1-7, which uses a flooded evaporator, as disclosed for example in system 400.
[0290] Applicants have found that one such advantage is an unexpected improvement in the coefficient of performance (COP). Without necessarily being bound to any particular theory, it is believed that this advantage, which is unexpected, arises in part because less compressor 411 work is required and the cooling capacity of the second refrigeration circuit 410 is improved because the system allows operation with superheating the refrigerant before it enters the compressor.
[0291] A second difference in the way the refrigeration system 400 operates compared to the refrigeration system 200 lies in the provision of the ambient cooling branch 451 and controllable valves 440, 441. The ambient cooling branch 451 allows the compressor branch 450 to be bypassed when the ambient temperature is sufficiently low to chill the refrigerant. This is achieved by routing the ambient cooling branch 451 to the roof 460 to provide maximum exposure of the refrigerant to the ambient air temperature. This is sometimes called winter operation. Usefully, this provides essentially free chilling of the refrigerant in the second refrigeration circuit 410. Clearly this is advantageous both from a cost and environmental perspective as energy consumption is greatly reduced as compared to running the compressor branch 450.
[0292] For the purposes of convenience, the term “flooded system,” “flooded cascade system,” and the like refer to systems of the present disclosure in which at least one and preferably all of the heat exchangers in the low stage refrigeration circuit (preferably low temperature circuit) for condensing the low stage refrigerant (preferably medium temperature refrigerant) are flooded evaporators for the high stage refrigerant (preferably the medium temperature refrigerant). In preferred embodiments in accordance with the present invention, including each of Systems 1-7, the medium temperature evaporator is also a flooded evaporator. The potential advantages described in reference to the cascaded refrigeration system apply equally well to the flooded cascaded refrigeration system: the terms used to describe the flooded and non-flooded cascaded refrigeration system being comparable.
[0293] Further advantages of the flooded cascaded refrigeration system in accordance with the present invention, including each of Systems 1-7, can include: reduced energy consumption due to exploitation of the ambient cooling branch (winter operation); improved heat transfer performance in the heat exchangers and evaporators due to their flooded operation; no thermostatic expansion valves are required due to the provision of a pump in the circuit; and low cost materials can be used to manufacture the second refrigeration circuit due to it being suitable for low pressure refrigerant.
[0294] Particularly in view of the advantages described herein, the present invention including each of Systems 1-7, includes a cascaded refrigeration system, comprising: a plurality of low stage refrigeration circuits, with each low stage refrigeration circuit comprising a first refrigerant comprises, consists essentially of or consists of, a low GWP, non-flammable (Class A1) refrigerant, comprising at least about 50% by weight, or at least about 75% by weight by weight of R1234yf, including specifically R-454C and/or R455 A, a compressor having a horse power rating of about 2 horse power or less, and an inter-circuit heat exchanger in which said low stage refrigerant condenses; and a high stage refrigeration circuit containing a high stage refrigerant which comprises, consists essentially of, or consists of at least about 75% by weight of HFO-1234ze(E), including particularly R471 A and/or R476 A, and a flooded evaporator in which said high stage refrigerant evaporates at a temperature below said low stage refrigerant condensing temperature wherein said high stage refrigerant evaporates in said inter-circuit heat exchanger by absorbing heat from said first refrigerant.
[0295] Flooded Cascade Refrigeration System—Alternatives
[0296] The alternatives described above in reference to the cascaded refrigeration system apply equally well to the flooded cascaded refrigeration system. Other alternatives include removal of the ambient cooling branch 451 and/or reversion of the flooded system to a direct expansion system. A yet further alteration of the system 400, including each of Systems 1-7, which is envisaged is that the ambient cooling branch 451 may be shortened and simplified such that it only bypasses the compressor 411, rather than the entire compressor branch.
[0297] Advantageously, the use of a shortened ambient chilling branch, that is, one in which the branch routes liquid refrigerant from receiver outlet to the condenser inlet results in: first, a simplified circuit as the chiller and first controllable valve at the inlet of the receiver pump are no longer required; and second, a lower cost circuit, since the amount of extra piping for the ambient chilling branch and the number of components is reduced, therefore reducing material costs.
[0298] Suction Line Heat Exchanger
[0299] A further possible alteration of any of the systems forming part of this disclosure including each of Systems 1-7, is that any number of the self-contained refrigeration circuits may include a suction line heat exchanger (SLHX). More specifically, any of the low stage refrigeration circuits 220a, 220b, 220c in system 200, including each of Systems 1-7, may include an SLHX; and any of the low stage refrigeration circuits 420a, 420b may include an SLHX. For comparison,
[0300] The circuit 700 in
[0301] The circuit 750 in
[0302] Secondly, disadvantageously, on the vapor line side—that is, the low-pressure side—the refrigerant exiting the evaporator 740 receives extra heat from the liquid line, which effectively increases the superheating. This results in a higher suction line temperature. As a result of the higher suction line temperature to the compressor 710, the enthalpy difference of the compression process increases. This increases the compressor power required to compress the refrigerant. Accordingly, this has a detrimental effect on the system performance.
[0303] In summary, both the first and second effects of improved evaporator capacity and improved compressor power requirements need to be considered in order to determine whether or not introducing a SLHX results in an overall beneficial effect. Generally, the use of a SLHX in accordance with the present invention, including each of Systems 1-7 and in particular such systems 200 and 300 herein, leads to an overall positive and unexpectedly beneficial effect.
[0304] The high stage refrigeration circuit, including in each of Systems 1-4, may comprise a second evaporator. The second evaporator may be coupled in parallel with the circuit interface locations.
[0305] Each of the circuit interface locations, including in each of Systems 1-4, may be coupled in series-parallel combination with each other of the circuit interface locations. Usefully, this means that if one of the circuit interface locations, first refrigeration circuits, or first refrigeration units has a fault or blockage detected, the location, circuit or unit at fault can be isolated and/or bypassed by the second refrigeration circuit so that faults do not propagate through the system.
[0306] Each of the circuit interface locations, including in each of Systems 1-7, may be coupled in series with at least one other circuit interface location.
[0307] Each of the circuit interface locations, including in each of Systems 1-7, may be coupled in series with each other of the circuit interface locations.
[0308] Each of the circuit interface locations, including in each of Systems 1-7, may be coupled in parallel with at least one other circuit interface location.
[0309] Each of the circuit interface locations, including in each of Systems 1-7, may be coupled in parallel with each other of the circuit interface locations.
[0310] Refrigerant Compositions
[0311] HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea
[0312] The present invention provides a refrigerant which may comprise, consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E), and HFC-227ea, and such a refrigerant is particularly useful as the high stage refrigerant of the preferred cascade systems of the present invention, including particularly Systems 1-7.
[0313] The present invention also provides a refrigerant which may comprise, consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E), and HFC-227ea, and such a refrigerant is particularly useful in heat transfer methods, including particularly Heat Transfer Methods Systems 1-3.
[0314] The refrigerant may comprise: (a) from about 74.6% by weight to about 78.6% by weight of HFO-1234ze(E); (b) from about 17% by weight to about 21% by weight of HFO-1336mzz (E); and (c) from greater than 0% to about 4.4% by weight of HFC-227ea. Preferably, the refrigerant comprises (a) 74.6% by weight to about 78.6% by weight of HFO-1234ze(E); (b) from about 17% by weight to about 19% by weight of HFO-1336mzz (E); and (c) about 4.4% by weight of HFC-227ea. For example, the refrigerant may comprise HFC-227ea in an amount of about 4.4% by weight. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1A.
[0315] The refrigerant may comprise (a) about 78.6% by weight of HFO-1234ze(E); (b) about 17% by weight of HFO-1336mzz (E); and (c) about 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1B.
[0316] The refrigerant may comprise: (a) about 76.6% by weight of HFO-1234ze(E); (b) about 19% by weight of HFO-1336mzz (E); and (c) about 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1C.
[0317] The refrigerant may comprise: (a) about 74.6% by weight of HFO-1234ze(E); (b) about 21% by weight of HFO-1336mzz (E); and (c) about 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1D.
[0318] The refrigerant may comprise: (a) 78.6%+0.5%/−2.0% by weight of HFO-1234ze(E); (b) 17%+2.0%/−0.5% by weight of HFO-1336mzz (E); and (c) 4.4%+2.0%/−0.5% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1E.
[0319] The refrigerant may comprise: (a) 76.6%+0.5%/−2.0% by weight of HFO-1234ze(E); (b) 19%+2.0%/−0.5% by weight of HFO-1336mzz (E); and (c) 4.4%+2.0%/−0.5% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1F.
[0320] The refrigerant may comprise: (a) 74.6%+0.5%/−2.0% by weight of HFO-1234ze(E); (b) 21%+2.0%/−0.5% by weight of HFO-1336mzz (E); and (c) 4.4%+2.0%/−0.5% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1G.
[0321] The refrigerant may comprise: (a) 78.6% by weight of HFO-1234ze(E); (b) 17% by weight of HFO-1336mzz (E); and (c) 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1H.
[0322] The refrigerant may comprise: (a) 76.6% by weight of HFO-1234ze(E); (b) 19% by weight of HFO-1336mzz (E); and (c) 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1I.
[0323] The refrigerant may comprise: (a) 74.6% by weight of HFO-1234ze(E); (b) 21% by weight of HFO-1336mzz (E); and (c) 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometimes referred to for convenience as Refrigerant 1J.
[0324] The refrigerant may comprise: (a) from about 78.6% by weight to about 80.6% by weight of HFO-1234ze(E); (b) from about 15% by weight to about 17% by weight of HFO-1336mzz (E); and (c) about 4.4% by weight of HFC-227ea. It will be appreciated that the refrigerant may consist essentially of, or consist of HFO-1234ze(E), HFO-1336mzz (E) and HFC-227ea in the above amounts. Refrigerants as described in this paragraph are sometime referred to for convenience as Refrigerant 1K.
[0325] The refrigerant, including each of Refrigerants 1A-1K, has a GWP of less than about 150. As used here, the term “Refrigerants 1A-1K” means separately and independently each of the Refrigerants 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1 I, 1J and 1K. The refrigerant, including each of Refrigerants 1A-1K has no or low toxicity. In other words, the refrigerant is a class A refrigerant.
[0326] The refrigerant, including each of Refrigerants 1A-1K, preferably has a glide of less than 4.5, more preferably less than about 3° C., and even more preferably of less than about 2° C.
[0327] It will be appreciated that the refrigerant, including each of Refrigerants 1A-1I, in preferred embodiments has a combination of one or more of, and most preferably all of, the above properties.
[0328] Heat Transfer Compositions:
[0329] The refrigerants of the invention may be provided in a heat transfer composition.
[0330] The heat transfer compositions of the present invention can comprise a refrigerant of the present invention, including any of the preferred refrigerant compositions disclosed herein and in particular each of Refrigerants 1A-1K. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 1.
[0331] The present invention also relates to a heat transfer composition which comprises the refrigerant, including each of Refrigerants 1A-1K, in an amount of at least about 80% by weight of the heat transfer composition, or at least about 90% by weight of the heat transfer composition, or at least about 97% by weight of the heat transfer composition, or at least about 99% by weight of the heat transfer composition. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 2.
[0332] The heat transfer composition may consist essentially of or consist of the refrigerant. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 3.
[0333] Lubricants:
[0334] Preferably, the heat transfer composition may additionally comprise a lubricant. The lubricant lubricates the refrigeration compressor using the refrigerant. Preferably the lubricant is present in the heat transfer composition in amounts of from about 1% to about 50% by weight of heat transfer composition, more preferably in amounts of from about 10% to about 50% by weight of the heat transfer composition, and most preferably about 30% to about 50% by weight of the heat transfer composition. Useful lubricants include, alkyl benzenes, esters, polyol esters (“POEs”), poly alkylene glycols (“PAGs”), polyvinyl ethers (“PVEs”), poly(alpha-olefin) (“PAOs”), and combinations thereof. Commercially available alkyl benzene lubricants include Zerol 150 (registered trademark). PAGs are available as GM Goodwrench Refrigeration Oil and MOPAR-56. Other useful esters include phosphate esters, dibasic acid esters, and fluoroesters.
[0335] Commercially available POEs include neopentyl glycol dipelargonate which is available as Emery 2917 (registered trademark) and Hatcol 2370 (registered trademark) and pentaerythritol derivatives including those sold under the trade designations Emkarate RL32-3MAF and Emkarate RL68H by CPI Fluid Engineering. Emkarate RL32-3MAF and Emkarate RL68H have the properties identified in the following table:
TABLE-US-00001 Property RL32-3MAF RL68H Viscosity @ 40° C. (ASTM D445), cSt about 31 about 67 Viscosity @ 100° C. (ASTM D445), cSt about 5.6 about 9.4 Pour Point (ASTM D97), ° C. about −40 about −40
[0336] Commercially available PVE's include the polyvinylethers FVC-32D (registered trademark) and FVC-68D (registered trademark) by Idemitsu.
[0337] Preferred lubricants include POEs and PVEs, more preferably POEs. Of course, different mixtures of different types of lubricants may be used.
[0338] The heat transfer composition of the present invention may consist essentially of or consist of a refrigerant, including each of Refrigerants 1A-1K, and lubricant, including in particular each of the preferred lubricants as described above. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 4.
[0339] A preferred heat transfer composition of the invention comprises any one of the Refrigerants 1A-1K and POE lubricant. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 5.
[0340] A preferred heat transfer composition of the invention comprises any one of the Refrigerants 1A-1K and PAG lubricant. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 6.
[0341] A preferred heat transfer composition of the invention comprises any one of the Refrigerants 1A-1K and PVE lubricant. Heat transfer compositions as described in this paragraph are sometimes referred to for convenience as Heat Transfer Composition 7.
[0342] The present invention also includes, and provides particular advantage in connection with, high temperature heat pump systems that include refrigerants of the present invention, including each of Refrigerants 1A-1K, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 1.
[0343] The present invention also includes, and provides particular advantage in connection with, medium temperature refrigeration systems with two-stage vapor injected compression that include refrigerants of the present invention, including each of Refrigerants 1A-1K, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 2.
[0344] The present invention also includes, and provides particular advantage in connection with, vending machines, including with suction line/liquid line heat exchanger, that include refrigerants of the present invention, including each of Refrigerants 1A-1K, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 3.
[0345] The present invention also includes, and provides particular advantage in connection with, air-source heat pump water heaters, including with suction line/liquid line heat exchanger, that include refrigerants of the present invention, including each of Refrigerants 1A-1K, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 4.
[0346] The present invention also includes, and provides particular advantage in connection with, air conditioning systems, including mobile, residential and commercial air conditioning systems, that include refrigerants of the present invention, including each of Refrigerants 1A-1B, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 5.
[0347] The present invention also includes, and provides particular advantage in connection with, secondary fluid refrigeration systems that include refrigerants of the present invention, including each of Refrigerants 1A-1K, and/or that include heat transfer compositions of the invention, including each of Heat Transfer Compositions 1-7, and/or that operate in accordance with Heat Transfer Methods 1-3. Heat transfer systems as described in this paragraph are sometimes referred to for convenience as Heat Transfer System 6.
EXAMPLES
[0348] In the examples which follow, the refrigerant compositions which are the subject of one or more examples are identified in the example. Each of the refrigerants was subjected to thermodynamic analysis to determine its ability to match the operating characteristics of R-404 A in various refrigeration systems. The analysis was performed using experimental data collected for properties of various binary and ternary pairs of components used in the refrigerant. The composition of each pair was varied over a series of relative percentages in the experimental evaluation and the mixture parameters for each pair were regressed to the experimentally obtained data. Known vapor/liquid equilibrium behavior data available in the National Institute of Science and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties Database software (Refprop 9.1 NIST Standard Database 23 from April 2016) was used for the Examples. The parameters selected for conducting the analysis were: same compressor displacement for all refrigerants, same operating conditions for all refrigerants, same compressor isentropic and volumetric efficiency for all refrigerants. In each Example, simulations were conducted using the measured vapor liquid equilibrium data. The simulation results are reported for each Example.
Example 1: Performance in Cascade Refrigeration System
[0349] Cascade systems are generally used in applications where there is a large temperature difference (e.g., about 50-80° C., such as about 60-70° C.) between the ambient temperature and the box temperature (e.g., the difference in temperature between the air-side of the condenser in the high stage, and the air-side of the evaporator in the low stage). For example, a cascade system may be used for freezing products in a supermarket. In the following Examples the baseline cascade system uses CO2 in the low stage and R134a in the high stage, and the refrigerant combinations of the present invention involve the low stage of the cascade refrigeration system being CO2 or propane or HFO-1234yf or R454C or 455 A and the refrigerant used in the high-stage of the system being 1234ze(E), or R471 A, or R476 A.
[0350] Operating conditions were: [0351] Condensing temperature=45° C. [0352] High-stage Condensing Temperature—Ambient Temperature=10° C. [0353] High-stage condenser sub-cooling=0.0° C. (system with receiver) [0354] Evaporating temperature=−30° C., Corresponding box temperature=−18° C. [0355] Low-stage Evaporator Superheat=3.3° C. [0356] High-stage and Low-stage Compressor Isentropic Efficiency=65% [0357] Volumetric Efficiency=100% [0358] Temperature Rise in Suction Line Low Stage=15° C. [0359] Temperature Rise in Suction Line High Stage=10° C. [0360] Intermediate Heat Exchanger CO2 Condensing Temperature=0C, 5° C. and 10° C. [0361] Intermediate Heat Exchanger Superheat=3.3° C. [0362] Difference in Temperature in Intermediate Heat Exchanger=8° C.
[0363] The results are reported in Table E1 below.
TABLE-US-00002 TABLE E1 Performance in Cascade Refrigeration System Refrigerant Efficiency @ Efficiency @ Efficiency @ Example Low Stage high Stage Tcond = 0° C. Tcond = 5° C. Tcond = 10° C. Comparative CO2 R134a 100% 100% 100% Ex. 1A CO2 R1234ze(E) ~100% 100% 100% Ex. 1B CO2 R476A ~100% 100% 100% Ex. 1C Propane R1234ze(E) 107% 110% 114% Ex. 1D Propane R471A 107% 110% 114% Ex. 1E Propane R476A 107% 110% 114% Ex. 1F R1234yf R1234ze(E) 106% 108% 112% Ex. 1G R1234yf R471A 106% 108% 112% Ex. 1H R1234yf R476A 106% 108% 112% Ex. 1I R454C R1234ze(E) 106% 109% 113% Ex. 1J R454C R471A 106% 109% 113% Ex. 1K R454C R476A 106% 109% 113% Ex. 1L R455A R1234ze(E) 105% 108% 112% Ex. 1M R455A R471A 105% 108% 112% Ex. 1N R455A R476A 105% 108% 112%
[0364] As can be seen by the results reported in Table E1 above, in every case the combination of refrigerants of the present invention, including as defined in Systems 1-7, produced an efficiency that is as high as or higher than the base-line efficiency.
Example 2: Micro-Cascade Refrigeration System
[0365] A micro-cascade system combines a traditional medium temperature DX refrigeration system, with or without suction line liquid line heat exchanger (SLHX), which operates with the same refrigerant pairs as identified in Table 1 above. As used herein, the term “medium temperature DX refrigeration system” refers to a medium temperature system in which the evaporator is a dry evaporator.
[0366] A useful micro-cascade system is disclosed in our pending U.S. Ser. No. 16/014,863 filed Jun. 21, 2018, and U.S. Ser. No. 16/015,145 filed Jun. 21, 2018, claiming priority to U.S. Ser. 62/522,386 filed Jun. 21, 2017, U.S. Ser. 62/522,846 filed Jun. 21, 2017, 62/522,851 filed Jun. 21, 2017, and Ser. 62/522,860 filed Jun. 21, 2017, all incorporated herein by reference in their entireties.
[0367] Operating conditions:
[0368] Baseline R404 A combined MT and LT system [0369] Refrigeration Capacity [0370] Low Temperature: 33,000 W [0371] Medium Temperature: 67,000 W [0372] Volumetric efficiency: 95% for both MT ad LT [0373] Compressor Isentropic efficiency [0374] Medium Temperature=70% and Low Temperature=67% [0375] Condensing temperature: 105° F. [0376] Medium Temperature evaporation temperature: 20° F. [0377] Low Temperature evaporation temperature: −20° F. [0378] Evaporator superheat: 10° F. (both Medium and Low Temperature) [0379] Suction line temperature rise (due to heat transfer to surroundings) [0380] Baseline: Medium Temperature: 25° F.; Low Temperature: 50° F. [0381] Cascade/self-contained without SLHX: Medium Temperature: 10° F.; Low Temperature: 25° F. [0382] Cascade/self-contained with SLHX: Medium Temperature: 10° F.; Low Temperature: 15° F.
[0383] SLHX efficiency when used: 65%
[0384] The results are reported in Table E2 below.
TABLE-US-00003 TABLE E2 Micro-Cascade Performance Compared to R404A Refrigerant Efficiency relative Example Low Stage High Stage to R404A Comparative R404A R404A 100% Ex. 1A CO2 R1234ze(E) ~122% Ex. 1B CO2 R471A ~122% Ex. 1C CO2 R476A ~122% Ex. 1D Propane R1234ze(E) ~127% Ex. 1E Propane R471A ~127% Ex. 1F Propane R476A ~127% Ex. 1G R1234yf R1234ze(E) ~126% Ex. 1H R1234yf R476A ~126% Ex. 1I R454C R1234ze(E) ~126% Ex. 1J R454C R471A ~126% Ex. 1K R454C R476A ~126% Ex. 1L R455A R1234ze(E) ~126% Ex. 1M R455A R476A ~126%
[0385] As can be seen by the results reported in Table E2 above, in every case the combination of refrigerants of the present invention, including as defined in Systems 1-7, produced an efficiency that is about 122% or higher than the base-line case while achieving a capacity that is similar to the baseline. This is an important and unexpected advantage.
Example 3: Performance in Extreme Temperature Air Conditioning Systems
[0386] Refrigerant R471 A was performance tested in a stationary air conditioning system under various condenser temperature conditions within the extreme temperature range. The analysis was carried out to assess the efficiency of R471 A in this system, which is generally representative of Refrigerants 1A-1K, using R134a as the baseline refrigerant. The results are reported in Tables 3A and 3B below, based on the following operating conditions: [0387] Condensing temperature=55° C. to 95° C. [0388] Condenser sub-cooling=5.0° C. [0389] Evaporating temperature=10° C., corresponding indoor room temperature=35° C. [0390] Evaporator Superheat=5.0° C. [0391] Compressor Isentropic Efficiency=65% [0392] Volumetric Efficiency=100%
TABLE-US-00004 TABLE 3A Performance in Extreme Temperature AC systems Refrig- Condensing 55° C. Condensing 75° C. Condensing 95° C. erant Efficiency Efficiency Efficiency R404A 100% 100% 100% R471A 100% ~100% ~99%
[0393] R471 A shows efficiency similar to R134a over range of condensing temperatures which correspond to different ambient temperatures within the extreme temperature air conditioning range. In addition, additional performance parameters are provided below for the case in which the condensing temperature is 75° C.
TABLE-US-00005 TABLE 3B Performance in Extreme Temperature Air Conditioning Systems Refrigerant Efficiency Capacity Evaporator Glide, ° C. R134a 100% 100% 0 R471A ~100% 65% 1.9
[0394] In view of the results reported in this example, this refrigerant shows exceptional performance when all relevant performance factors are considered.
Example 4: Performance in High Temperature Heat Pump Systems
[0395] Refrigerant R471 A was performance tested in a high temperature heat pump under various condenser temperature conditions within the range typically encountered for high temperature heat pumps. The analysis was carried out to assess the efficiency of R471 A in this system, which is generally representative of Refrigerants 1A-1K, using R134a as the baseline refrigerant, under the conditions below.
[0396] Operating conditions: [0397] Condensing temperature=55° C. to 95° C. [0398] Condenser sub-cooling=5.0° C. [0399] Evaporating temperature=30° C. [0400] Evaporator Superheat=5.0° C. [0401] Compressor Isentropic Efficiency=65% [0402] Volumetric Efficiency=100%
TABLE-US-00006 TABLE 4 Performance in High Temperature Heat Pump Systems Refrig- Condensing 55° C. Condensing 75° C. Condensing 95° C. erant Efficiency Efficiency Efficiency R134a 100% 100% 100% R471A 101 101 102
[0403] Refrigerant R471 A shows efficiency similar to R134a over range of condensing temperatures which correspond to the range typically present in high temperature heat pump applications, with R471 A showing exceptional performance in when all relevant performance factors are considered.
Comparative Example 1-Centralized Distributed Direct Expansion Super Market Refrigeration System
[0404] A centralized distributed supermarket refrigeration system according to process flow as illustrated in
[0405] The system is operated with R404 A and R448 A as the refrigerant at a series of ambient conditions ranging from about −13° C. to about 45° C. under the following conditions.
TABLE-US-00007 Example Designation Description Unit C1A (I) C1B (II) Refrigerant R404A R448a Global Warming [—] 3943 1273 Potential (AR5) Refrigerant Charge [kg] 1450 750 Leak Rate [%] 15% 10% MT Evaporation [° C.] −6.7 −6.7 Temperature LT Evaporation [° C.] −28.9 −28.9 Temperature LT/MT Cooling Load [kW] 87/138 87/138 Evaporator Superheat [° C.] 5.5 5.5 MT/LT Suction Superheat LT [° C.] 27.7 22.2 Suction Superheat MT [° C.] 13.8 8.3 Isentropic [—] 0.67 0.67 Efficiency LT Isentropic [—] 0.7 0.7 Efficiency MT Approach Temp. [K] — — Cascade HX Approach Temp. [K] 5.5 5.5 Condenser Minimum [° C.] 21 21 Condensing Temp.
[0406] The results of the system operation (using R404 A in the centralized system of Comparative Example 1 as a baseline for the COP values) are shown in
Comparative Example 2—Direct Expansion Cascade Super Market Refrigeration System
[0407] A direct expansion cascade supermarket refrigeration system according to process flow as illustrated in
[0408] The system is operated, at a series of ambient conditions ranging from about −13° C. to about 45° C., with three different refrigerants (R134a, R515B and R471 A) in the high side (MT system) and R744 in the low side (LT system) under the following conditions.
TABLE-US-00008 Example Designation Description Unit C2A C2B C2C (III) Refrigerant R134a/R744 R515B/R744 R471A/R744 Global Warming [—] <150 <300 <150 Potential (AR5) Refrigerant Charge [kg] 1450 1450 1450 Leak Rate [%] 15% 15% 15% MT Evaporation [° C.] −6.7 −6.7 −6.7 Temperature LT Evaporation [° C.] −28.9 −28.9 −28.9 Temperature LT/MT Cooling [kW] 87/138 87/138 87/138 Load Evaporator [° C.] 5.5 5.5 5.5 Superheat MT/LT Suction Superheat [° C.] 27.7 27.7 27.7 LT Suction Superheat [° C.] 13.8 13.8 13.8 MT Isentropic [—] 0.6 0.6 0.6 Efficiency LT Isentropic [—] 0.7 0.7 0.7 Efficiency MT Approach Temp. [K] 5.5 5.5 5.5 Cascade HX Approach Temp. [K] 5.5 5.5 5.5 Condenser Minimum [° C.] 21 21 21 Condensing Temp.
[0409] The results of the system operation (using R404 A in the centralized system of Comparative Example 1 as a baseline for the COP) are shown in
Comparative Example 3—CO2 Booster Super Market Refrigeration System
[0410] A CO.sub.2 booster system using a parallel compression system and mechanical subcooler in a supermarket refrigeration system according to process flow as illustrated in
[0411] The system is operated, at a series of ambient conditions ranging from about −13° C. to about 45° C., with R744 and CO2 booster under the following conditions.
TABLE-US-00009 Example Designation Description Unit C3 (V) Refrigerant R744/CO2 Global Warming [—] 1 Potential (AR5) Refrigerant Charge [kg] 1000 Leak Rate [%] 15% MT Evaporation [° C.] −6.1 Temperature LT Evaporation [° C.] −28.3 Temperature LT/MT Cooling [kW] 87/138 Load Evaporator [° C.] 5.5 Superheat MT/LT Suction Superheat LT [° C.] 22.2 Suction Superheat MT [° C.] 8.3 Isentropic [—] 0.67 Efficiency LT Isentropic [—] 0.7 Efficiency MT Approach Temp. [K] — Cascade HX Approach Temp. [K] 5.5 SC, Condenser 2.5 TC Minimum [° C.] 10 Condensing Temp.
[0412] The results of the system operation (using R404 A in the centralized system of Comparative Example 1 as a baseline for the COP values) are shown in
Comparative Example 4—R290 Water-Cooled Super Market Refrigeration System
[0413] An R290 water cooled supermarket refrigeration system is provided and is operated at a series of ambient conditions ranging from about −13° C. to about 45° C., with R744 and CO2 booster under the following conditions.
TABLE-US-00010 Example Designation Description Unit C4 (VI) Refrigerant R290 Global Warming [—] 3 Potential (AR5) Refrigerant Charge [kg] 750 Leak Rate [%] 10% MT Evaporation [° C.] −5.5 Temperature LT Evaporation [° C.] −27.8 Temperature LT/MT Cooling [kW] 87/138 Load Evaporator [° C.] 5.5 Superheat MT/LT Suction Superheat LT [° C.] 5.5 Suction Superheat MT [° C.] 5.5 Isentropic [—] 0.52 Efficiency LT Isentropic [—] 0.55 Efficiency MT Approach Temp. [K] 5.5 Cascade HX Approach Temp. [K] 5.5 Condenser Minimum [° C.] 15.5 Condensing Temp.
[0414] The results of the system operation (using R404 A in the centralized system of Comparative Example 1 as a baseline for the COP) are shown in
Example 5—Micro Cascade Super Market Refrigeration System
[0415] A micro cascade supermarket refrigeration system according to process flow as illustrated in
TABLE-US-00011 Example Designation Description Unit 5A 5B 5C (IV) Refrigerant R471A/ R471A/ R471A/ R744 R1234yf R455A Global Warming [—] <150 <300 <150 Potential (AR5) Refrigerant Charge [kg] 750 750 750 Leak Rate [%] 10% 10% 10% MT Evaporation [° C.] −6.7 −6.7 −6.7 Temperature LT Evaporation [° C.] −27.8 −27.8 −27.8 Temperature LT/MT Cooling [kW] 87/138 87/138 87/138 Load Evaporator [° C.] 5.5 5.5 5.5 Superheat MT/LT Suction Superheat [° C.] 5.5 5.5 5.5 LT Suction Superheat [° C.] 13.8 13.8 13.8 MT Isentropic [—] 0.6 0.6 0.6 Efficiency LT Isentropic [—] 0.7 0.7 0.7 Efficiency MT Approach Temp. [K] 5.5 5.5 5.5 Cascade HX Approach Temp. [K] 5.5 5.5 5.5 Condenser Minimum [° C.] 15.5 15.5 15.5 Condensing Temp.
[0416] The results of the system operation (using R404 A in the centralized system of Comparative Example 1 as a baseline for the COP values) are shown in
[0417] The results of this Example in terms of Life Cycle Performance Analysis (Equivalent Emissions and Weighted COP) are shown in
Direct Emissions=Refrigerant Charge (kg)×((Annual Leak×Lifetime)+End of Life Losses)×GWP
Indirect Emissions=Annual Energy Consumption×Lifetime×Emission Factor
[0418] As can be seen from