Patent Application
20250066654
Vapor-compression cycles have been used since as early as 1805. Various chemical compounds have been used as refrigerants in these cycles, including various chlorofluorocarbons (CFCs) such as dichlorodifluoromethane. Chlorofluorocarbons can deplete the ozone layer when they rise into the stratosphere and are decomposed by ultraviolet radiation. Alternatives to chlorofluorocarbons may not be optimized for high temperatures and, in addition, may pose occupational and environmental hazards.
High-temperature heat pump (HTHP) cycles are a specific subset of vapor-compression cycle which function by converting residual heat to high-grade heat to be used in industrial processes. High-temperature heat pump cycles represent a key decarbonizing technology as process heating, which usually requires burning of fuel, may be alternatively accomplished by upgrading low-temperature heat (i.e., “heat source”) and moving it to high-temperature units (i.e., “heat sink”). Conventional refrigerants are not well suited to the high temperatures of these high-temperature heat pumps as they often have limited temperature ranges, are incompatible with materials used in high-temperature heat pump compressors (e.g., lubricants), are greenhouse gases (e.g., hydrofluorocarbons) and thus have high global warming potential (GWP), or otherwise have other thermodynamic limitations leading to insufficient coefficient of performance (COP).
These drawings illustrate certain aspects of some of the examples of the present disclosure and should not be used to limit or define the invention.
It is to be understood that the present disclosure is not limited to particular composition or methods, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular examples only, and is not intended to be limiting. All numbers and ranges disclosed herein may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. Although individual examples are discussed herein, the invention covers all combinations of all those examples. As used herein, the singular forms “a”, “an”, and “the” include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not in a mandatory sense (i.e., must). The term “include,” and derivations thereof, mean “including, but not limited to.” The term “coupled” means directly or indirectly connected. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted for the purposes of understanding this invention.
Disclosed herein are various vapor-compression cycles using refrigerant as working fluid and, more particularly, disclosed are select refrigerants and their blends including hydrofluoroolefins (HFOs) to be used in various vapor-compression cycles. Advantages of the working fluids of the present disclosure may include improved thermal stability, low toxicity, low flammability, low cost, good compatibility with construction materials, high performance, high latent heat, low compression superheat, low throttling losses, high heat transfer properties, and improved compatibility with the environment.
Even more particularly, the present disclosure relates to C5 and/or C6 hydrofluoroolefins and C5 and/or C6 olefins and their compositions, structures, and material properties, and how they may be used, blended together, and optimized in single-stage or multiple-stage cycles. The C5 and/or C6 hydrofluoroolefins may be sterically hindered on both sides of the double bond. The C5 and/or C6 cis olefins are defined as any C5 and/or C6 cis olefin or its derivatives wherein any of the hydrogen or overcrowded substituent —CH3 groups of the C5 and/or C6 cis olefin may be replaced by any heteroatom group.
Without being limited by theory, it is believed that certain C5 and/or C6 hydrofluoroolefins and C5 and/or C6 cis olefins synergistically work together to exhibit favorable properties when used in certain vapor-compression cycles. The unique combinations of these compounds result in a working fluid which has a low flammability, high critical temperature, low critical pressure, low ozone-depletion potential, low global warming potential, good safety characteristics, thermal stability, as well as compatibility with construction materials, lubricants, and high temperature heat pumps.
Specifically, it is believed that the stereochemistry of C5 and/or C6 cis olefins, which are characterized by their symmetric and overcrowded substituent —CH3 groups or any heteroatom groups, interacts favorably with select C5 and/or C6 hydrofluoroolefins. For example, cis hex-2-ene and especially cis hex-3-ene have the highest critical temperature of the C6H12 with their crowded methyl (—CH3) substituent group attached symmetrically to the double bond. It is believed that refrigerants or working fluids having a critical temperature relatively close to the temperature of the heat source should reach the highest cycle efficiency.
Also, the dipole moment of certain cis or (Z) isomers such as those having polar substituents like —CF3 and —CH2CF3, may also contribute to the favorable properties of the working fluid due to their higher boiling point, higher critical temperature, and molecular weight. These synergistic properties allow them to be used in high temperature cycles safely, with good efficacy, and with minimal impact to the environment. The C5 and/or C6 cis olefin or cis olefin derivative has a higher boiling temperature and critical temperature due to its more crowded space around the double bond, i.e., the steric effect. The bulkier the substituent to a double bond is, the more pronounced the increase in boiling temperature and the increase in critical temperature will be. A trifluoromethyl group (—CF3) or a trifluoroethyl group (—CH2CF3) gives the cis isomer a synergistic dipole moment leading to a 16° C. higher boiling point and critical temperature as compared to the same molecules without these polar substituent groups, for example.
The working fluid of the present disclosure includes one or more C5 and/or C6 hydrofluoroolefins and at least one C5 and/or C6 cis or (Z) olefin. Typically, components of the working fluid are selected such that the working fluid presents the favorable properties mentioned above. As will be discussed in greater detail below, suitability of the working fluid for a particular vapor-compression cycle is judged based on critical temperature, critical pressure, anticipated flammability, and safety classifications, as well as their chlorine and bromine content. For example, mixing the C5 and/or C6 hydrofluoroolefins with the C5 and/or C6 cis olefins is guided by raising the critical temperature while staying within the boundary of the A2L (mild flammability, low toxicity, and low global warming potential) or A1 (lowest flammability with no flame propagation, lowest toxicity, and lowest global warming potential).
As mentioned above, the working fluid of the present disclosure includes one or more C5 and/or C6 cis or (Z) hydrofluoroolefins. Suitable C5 hydrofluoroolefins may include (Z)-1,1,1,4,4,4-hexafluoro-2-methyl-2-butene, 2-(difluoromethyl)-1,1,4,4-tetrafluorobut-2-ene, 1,1,1,4,4,4-hexafluoro-2-(trifluoromethyl)-2-butene, (E)-1,1,1,4,4,4-hexafluoro-2-methyl-2-butene, (E)-1,1,1,2,4,4,4-heptafluoro-3-methylbut-2-ene, (Z)-1,1,1,2,4,4,4-heptafluoro-3-methylbut-2-ene, (E)-1,1,1,3,5,5,5-heptafluoro-2-pentene, (Z)-1,1,1,3,5,5,5-heptafluoro-2-pentene, or any combinations thereof, for example. Without being limited by theory, it is believed that both the high molecular weight and steric bulk of these compounds (i.e., as represented by their A-values) contribute to the higher boiling and critical temperatures of the working fluid.
Alternative or additional C5 hydrofluoroolefins to those provided above may include one or more monofluoromethyl-, difluoromethyl-, and/or trifluoromethyl-substituted C5 olefins, for example. A C5 hydrofluoroolefins may be linear or branched. Non-limiting examples of branched C5 olefins which may be substituted with one or more mono, di, or trifluoromethyl groups to form C5 hydrofluoroolefins may include 1-pentene, trans-2-pentene, cis-2-pentene, cis-piperylene, trans-piperylene, 2-methyl-1-butene, 2-methyl-2-butene, isoprene, trans-1,3-pentadiene, cis-1,3-pentadiene, 2-methyl-2-butene, and any combinations thereof.
Example C6 cis or (Z) hydrofluoroolefins may include (Z)-1,1,1,4,4,4-hexafluoro-2,3-dimethyl-2-butene, (Z)-1,1,1-Trifluoro-3-trifluoromethyl-pent-2-ene, (Z)-1,1,4,4-Tetrafluoro-2-methyl-3-difluoromethyl-but-2-ene, (Z)-1,1,1,4,4,4-Hexafluoro-2-fluoromethyl-3-methyl-but-2-ene, (Z)-1,1,1,2,4,4,4-Heptafluoro-pent-2-ene, (E)-1,1,1,3,5,5,5-Heptafluoro-2-methyl-pent-2-ene, 1,1,1,4,4,4-Hexafluoro-2-trifluoromethyl-3-methyl-but-2-ene, (Z)-1,1,4,4-Tetrafluoro-2,3-dimethyl-but-2-ene.
Alternative or additional C6 cis or (Z) hydrofluoroolefins to those provided above may include, for example, one or more monofluoromethyl-, difluoromethyl-, and/or trifluoromethyl-substituted C6 olefins. A C6 hydrofluoroolefins may be linear or branched. Non-limiting examples of branched C6 olefins which may be substituted with one or more mono, di, or trifluoromethyl groups to form C6 hydrofluoroolefins may include cis-2-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, and any combinations thereof.
As mentioned above, the working fluids of the present disclosure may include at least one C5 and/or C6 cis olefin. The cis olefins of this disclosure may not be well suited as stand-alone refrigerants or working fluids due to their high flammability. However, as alluded to previously, certain hydrofluoroolefins may serve to temper the high flammability of these cis olefins while imparting favorable properties to the working fluids and exhibiting synergy with the cis olefins. For example, mixing select C5 hydrofluoroolefins with select cis olefins allows for a higher critical temperature while staying within an A1 or A2L classification. Examples of cis olefins according to the present disclosure include 2-methyl-2-butene, 2,3-dimethyl-2 butene, or both.
The C5 and/or C6 cis or (Z) olefins and C5 and/or C6 hydrofluoroolefins of the present disclosure may be enantiomerically pure or essentially enantiomerically pure. In some examples, the C5 and/or C6 cis olefins and C5 and/or C6 hydrofluoroolefins may be diastereomerically pure or essentially diastereomerically pure. In some examples, the C5 and/or C6 cis olefins and C5 and/or C6 hydrofluoroolefins may be free or essentially free of trans-olefins. As used herein, the terms “essentially pure” and “essentially free of” refer to a composition with only negligible or trace amounts of the impurities, e.g., in an amount less than about 0.1 wt. %, less than about 0.01 wt. %, or less than about 0.001 wt. %.
Table 1 is a reference table showing example C5 cis or (Z) hydrofluoroolefins and cis olefins, as well as corresponding data, in accordance with some examples of the present disclosure. The data includes critical temperatures, critical pressures, global warming potential (GWP), ozone depletion potential (ODP), Norm Π, and safety classification (SC).
The ozone depletion potential (ODP) is determined based on the amount of chlorine or bromine present in the compound.
The safety classification is a safety classification for refrigerants or working fluids provided by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) according to toxicity (A and B) and flammability (1, 2, and 3) classes.
The normalized flammability index (Norm. Π or Πnorm) ranges from −100 to +100. Πnorm=0 represents the 1/2L boundary and Πnorm=100 estimates high flammability. The boundary between 2/2L is taken as Πnorm=40. Negative values represent class 1 (nonflammable). Example working fluids may have a high fluorine content, i.e., fluorine to (fluorine+hydrogen) ratio or F/(F+H), to make the working fluid less flammable. For all refrigerants ranging from alkanes/alkenes to fully fluorinated alkanes/alkenes, F/(F+H) can range from 0 to 1. For hydrofluoroolefins, the ratio above 0.66, a ratio above 0.7, a ratio above 0.8, or a ratio above 0.9 may be considered high.
Olefins (OLE) A and B (or OLE A & B), shown in Table 1A, may be produced from fractionation of petroleum or dehydrogenation of a corresponding alkane. Examples of C6 hydrofluoroolefins include name and chemical structure are given in Table 1B.
Tables 2A-2D show various refrigerants listed in Table 1A as well as the predicted properties of each working fluid. The working fluid may comprise any of the working fluids shown in Tables 2A-2D. While certain amounts of each compound are shown in Tables 2A-2D, it should be understood that the working fluid of the present disclosure may comprise any of the disclosed compounds in any amount, including any mixtures or combinations thereof. Table 2A gives mole fractions and properties for the pure components and the blends from mixing HFO D or C with Olefin A or B (OLE A or OLE B) to make nonflammable (A1) working fluids. Similarly, Table 2B gives mole fractions and properties for the pure components and the blends from mixing HFO D or C with OLE A or B to make mildly flammable (A2L) working fluids. Table 2C gives mole fractions and properties for the pure components and the blends from mixing HFO A or B with HFO D or C to make nonflammable (A1) working fluids. Table 2D gives mole fractions and properties for the pure components and the blends from mixing HFO A or B with OLE A or B to make mildly flammable (A2L) working fluids.
Table 2E gives mole fractions and properties for the pure components and the blends from mixing HFO E or G with OLE A or B to make nonflammable (A1) working fluids.
In one or more examples, any C5 and/or C6 cis olefin or any derivatives or combination thereof, may be individually or collectively present in a working fluid in an amount from about 0.001 wt. % to about 100 wt. %. Alternatively, from about 0.001 wt. % to about 5 wt. %, about 5 wt. % to about 15 wt. %, about 15 wt. % to about 25 wt. %, about 25 wt. % to about 40 wt. %, about 40 wt. % to about 65 wt. %, about 65 wt. % to about 80 wt. %, about 80 wt. % to about 90 wt. %, about 90 wt. % to about 95 wt. %, about 95 wt. % to about 99 wt. %, or any ranges therebetween.
In one or more examples, any C5 and/or C6 cis or (Z) hydrofluoroolefin (HFO) or any derivatives or combination thereof, may be individually or collectively present in a working fluid in an amount from about 0.001 wt. % to about 100 wt. %. Alternatively, from about 0.001 wt. % to about 5 wt. %, about 5 wt. % to about 15 wt. %, about 15 wt. % to about 25 wt. %, about 25 wt. % to about 40 wt. %, about 40 wt. % to about 65 wt. %, about 65 wt. % to about 80 wt. %, about 80 wt. % to about 90 wt. %, about 90 wt. % to about 95 wt. %, about 95 wt. % to about 99 wt. %, or any ranges therebetween.
The C5 cis or (Z) hydrofluoroolefin may be selected from the group comprising HFO A, HFO B, HFO C, HFO E, HFO F, HFO G, HFO H, HFO I, or any derivatives or combination thereof, for example. In some examples, Olefin A and/or Olefin B may be combined with any C5 hydrofluoroolefin (HFO) selected from the group consisting of HFO A, HFO B, HFO C, HFO D, HFO E, HFO F, HFO G, HFO H, HFO I, and any combination thereof. Mole fractions of one or more components of the working fluid may be adjusted to suit a particular application.
The working fluid disclosed herein may be used in various refrigeration cycles as well as heat pump cycles including high temperature heat pump cycles. Carnot efficiency of a high temperature heat pump cycle may be improved by up to 6% by virtue of employing a higher temperature sink (e.g., 199° C.) while maintaining low flammability and little to no ozone depletion potential or global warming potential. In addition, the higher sink temperatures may meet various process heating needs in the range of about 150° C. to about 200° C., such as processes in the food, paper, metal, and chemical industries, etc., to use non-limiting examples.
The working fluid disclosed herein may be used to upgrade low-grade waste heat (<100° C.) to a higher temperature (100-200° C.) to be used in a Steam Rankine Cycle (SRC) or an Organic Rankine cycle (ORC) to generate power, for example. The Rankine cycles are vapor/liquid 2-phase cycles as opposed to the Brayton cycles that are single-phase gas cycles. The low temperature heat sources may include geothermal heat, solar thermal energy, biomass thermal energy, waste heat from power plants such as any industrial exhaust gases, or any combination thereof.
The organic Rankine cycle is effective at recovering heat from low-temperature sources and may be applied at smaller scales compared to water/steam Rankine cycle systems. In embodiments, the organic Rankine cycle uses a high-molecular weight organic compound compared to water as the working fluid for steam Rankine cycle. In embodiments, the high-molecular weight organic compound may be a hydrocarbon (HC), a hydrofluorocarbon (HFC), a hydrofluoroolefin (HFO), or any combination thereof. The high-molecular weight organic compound of the present disclosure acts as organic heat carrier. The high-molecular weight organic compound of the present disclosure has a lower boiling point and a lower vapor pressure compared to water. Therefore, the high-molecular weight organic compound of the present disclosure is better able to vaporize at low temperatures to run the turbines. The higher the molecular weight of the organic compound of the present disclosure and/or the higher its vapor density, the more energy (work) can be transmitted to the generator at the same turbine rotation speed. The high-molecular weight organic compounds of the present disclosure with their higher critical temperatures will give increased efficiency and also lead to higher expansion ratios.
In geothermal applications, binary organic Rankine cycle plants may use the low-temperature heat from the low temperature geothermal fluid to heat up and vaporize a secondary organic fluid, i.e., the high-molecular weight organic compound of the present disclosure, that drives a turbine that generates electric power, for example. Thus, the original heat source fluid remains within a closed loop of piping without passing through the turbine without any harmful emissions into the atmosphere. The heat that is not converted into electricity can be delivered to a thermal user. The low-temperature organic Rankine cycle systems may use the hydrofluoroolefins (HFOs) disclosed above as working fluid, which have zero global warming potential (GWP), zero Ozone Depletion Potential (ODP), and low flammability (A1/A2L). Therefore, the disclosed new refrigerants of the present disclosure can also serve as the working fluid in an organic Rankine cycle power cycle operated at medium temperatures (e.g., turbine inlet from about 120° C. to about 190° C.).
The working fluid may be azeotropic or non-azeotropic. The working fluid may have a boiling point from about 28° C. to about 75° C., or any ranges therebetween. The working fluid may have an average critical temperature between about 160° C. and about 255° C., or any ranges therebetween. The working fluid may have an average critical pressure from about 25 bar to about 35 bar, or any ranges therebetween. Concentrations of the various components, which may be present in the working fluid, may be adjusted to suit a particular application. Concentrations of the components may be modified to adjust any of boiling point, critical temperature, critical pressure, molecular weight, global warming potential (GWP), Ozone Depletion Potential (ODP), and/or Safety Classification as mentioned above.
The working fluid may have an American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) toxicity rating of A. In addition, the working fluid may have an ASHRAE flammability rating of 1, 2L, or 2. The working fluid may have an ASHRAE safety classification of A1, A2L or A2. The working fluid may also have an Ozone Depletion Potential rating of 0 or about 0. The working fluid may have a global warming potential of 0 or about 0. The working fluid may have a total equivalent warming impact (TEWI) of zero or about 0.
Depending upon the operating temperatures and the choice of the working fluid, a heat pump using the working fluid may have a Carnot efficiency in the range from about 0.3 to about 0.7. Alternatively, from about 0.3 to about 0.4, about 0.4 to about 0.5, about 0.5 to about 0.7, or any ranges therebetween.
The working fluid of the present disclosure may allow for a temperature difference between a heat source and a heat sink from about 40° C. to about 95° C., or any ranges therebetween.
The working fluid may comprise (Z)-1,1,1,4,4,4,-hexafluoro-2-methyl-but-2-ene, having the formula as follows.
The working fluid may comprise 1,1,4,4-tetrafluoro-2-(difluoromethyl)-but-2-ene, having the formula as follows.
The working fluid may comprise 1,1,1,4,4,4-hexafluoro-2-(trifluoromethyl)-but-2-ene, having the formula as follows.
The working fluid may comprise (Z)-1,1,1,4,4,4-hexafluoro-but-2-ene, having the formula as follows.
The working fluid may comprise (E)-1,1,1,2,4,4,4-heptafluoro-3-methyl-but-2-ene, (HFO E, cis), having the formula as follows.
The working fluid may comprise (Z)-1,1,1,2,4,4,4-heptafluoro-3-methyl-but-2-ene, (HFO F, trans), having the formula as follows.
The working fluid may comprise (E)-1,1,1,3,5,5,5-heptafluoropent-2-ene, (HFO G, cis), having the formula as follows.
The working fluid may comprise (Z)-1,1,1,3,5,5,5-heptafluoro-pent-2-ene, (HFO H, trans), having the formula as follows.
The working fluid may comprise (E)-1,1,1,4,4,4-hexafluoro-2-methyl-but-2-ene (HFO I, trans), having the formula as follows.
The working fluid may comprise 2-methyl-but-2-ene, having the formula as follows.
The working fluid may comprise 2,3-dimethyl-but-2-ene, having the formula as follows.
The working fluid may comprise 1,1,1,4,4,4-hexafluoro-2,3-dimethyl-but-2-ene, having the formula as follows.
1,1,1,4,4,4-hexafluoro-2,3-dimethyl-but-2-ene possesses 2 dipole moment structures and therefore has a strong polarity and is sterically hindered on both sides of the double bond.
Table 3 shows various high temperature heat pump cycle configurations including 1-stage and 2-stage high temperature heat pumps with various ejector, economizer, flash, evaporator, condenser, and internal heat exchanger (IHX) configurations. The working fluid of the present disclosure may be used in these and other vapor-compression cycle configurations.
Working fluids having a critical temperature relatively close to the temperature of the heat source should reach the highest cycle efficiency. The C5 and C6 hydrofluoroolefins and C5 and C6 cis-olefin have critical temperatures close to the temperature of the heat source. In
The process flowsheet 1600 used for the Aspen Plus® modeling with the high pressure heat pump with an internal heat exchanger (IHX) of
Although specific examples have been described above, these examples are not intended to limit the scope of the present disclosure, even where only a single example is described with respect to a particular feature. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise. The above description is intended to cover such alternatives, modifications, and equivalents as would be apparent to a person skilled in the art having the benefit of this disclosure.
The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Various advantages of the present disclosure have been described herein, but examples may provide some, all, or none of such advantages, or may provide other advantages.
This application claims the priority of U.S. Provisional Patent Application No. 63/534,457, filed Aug. 24, 2023, which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63534457 | Aug 2023 | US |
