Method for predicting group contributions in CO2 binary mixed working fluid gas-liquid phase equilibrium

Abstract

The application discloses a group contribution prediction method for gas-liquid phase equilibrium of CO2 binary mixed working medium, and the method comprises the following steps: obtaining CO2 binary mixed working medium; for a given temperature interval and a liquid phase molar composition interval of CO2, each temperature value in the temperature interval is traversed, and the current traversed temperature value is kept unchanged; based on a cubic state equation and a group contribution prediction model, the pressure of the mixed working medium and the gas phase molar composition of CO2 are calculated under each liquid phase molar composition in the liquid phase molar composition interval of CO2; when the temperature values in the temperature interval are completely traversed, the pressure of the mixed working medium and the gas phase molar composition of CO2 under each temperature value in the temperature interval are obtained. The application overcomes the defect that a correlation model needs to depend on a large amount of experimental data, reduces the experimental workload, and has high prediction precision.

Description

Technical Field

[0001] This invention relates to the field of refrigerant mixing calculation technology, specifically to a method for predicting the group contribution of a CO2 binary mixed refrigerant gas-liquid phase equilibrium. Background Technology

[0002] Carbon dioxide (CO2) is a natural working fluid. Due to its high thermal stability, safety, environmental friendliness, and ability to achieve high energy density and miniaturization of components, CO2 power cycles have broad application prospects in next-generation heat-to-work conversion cycles, waste heat from internal combustion engines, medium- and low-temperature thermal energy, thermal power, nuclear power, and solar energy utilization. At the same time, using CO2 as a circulation medium is also a direct way to utilize CO2 resources. However, pure CO2 circulation operates at high pressure, posing safety hazards in applications, and its low critical temperature requires a high-performance cooling source.

[0003] While HC (hydrocarbons), HFC (hydrofluorocarbons), and HFO (hydrofluoroolefins) refrigerants can improve energy efficiency, some refrigerants, such as HC, are flammable and explosive, resulting in poor safety; others, such as HFC, have high gas per vaporization power (GWP), failing to meet the requirements of the Kigali Amendment to the Montreal Protocol; and still others, such as HFO, have low latent heat of vaporization and poor thermal performance. Therefore, it is difficult to find a pure refrigerant that is high in performance, thermal stability, and environmentally friendly and safe.

[0004] CO2 binary mixed working fluid power cycle, through different component ratios, can have advantages such as improving energy utilization efficiency, being environmentally friendly, eliminating flammability, reducing the risk of flammability and explosion, reducing GWP value, and improving the thermodynamic performance of the working fluid.

[0005] The gas-liquid phase equilibrium of a mixed working fluid is the basis for calculating enthalpy and entropy, which are crucial for thermodynamic cycle performance analysis. Therefore, the gas-liquid phase equilibrium of a CO2 binary mixed working fluid is one of the most fundamental physical properties of the mixed working fluid and the basis for mixed working fluid cycle calculations. It reflects the pressure and temperature in the mixture system and the interrelationships between the gas and liquid phase components when the mixture is in gas-liquid equilibrium.

[0006] Currently, regarding the gas-liquid phase equilibrium of CO2 binary working fluids, the paper "Comparative Study and Prediction of Mixing Rules for Gas-Liquid Phase Equilibrium of CO2 Working Fluids," by Wu Zirui et al., *Journal of Chemical Industry and Engineering (Engineering Technology Series I), Vol. 73, No. 4, January 2022*, proposes to improve the calculation accuracy of CO2 mixed working fluid gas-liquid phase equilibrium data by using the PR equation of state combined with three mixing rules to calculate the gas-liquid phase equilibrium properties of seven CO2+HFCs / HFOs and four CO2+HCs mixed working fluids. It also proposes using a difference model to predict the gas-liquid phase equilibrium properties of CO2 mixed working fluids. However, the calculation of the gas-liquid phase equilibrium of mixed working fluids still requires a large amount of experimental data on gas-liquid phase equilibrium, which, under current conditions, consumes a significant amount of time and effort.

[0007] The paper, "A Group Contribution Method for the Gas-Liquid Equilibrium of Non-azeotropic Working Fluids," by Che Chunwen et al., *Journal of Engineering Thermophysics*, Engineering Technology II, Vol. 42, No. 12, December 2021, proposes a fugacity coefficient model based on group contributions to address the insufficient accuracy of conventional models in predicting the gas-liquid equilibrium of non-azeotropic refrigerant mixtures. This model can predict the properties of a large number of multi-component mixtures using only a few common group parameters. However, the prediction method proposed in this paper does not show high accuracy in predicting the gas-liquid equilibrium of CO2 and mixtures of hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins, and is not well-suited for CO2 working fluids. Summary of the Invention

[0008] The technical problem to be solved by this invention is how to achieve high prediction accuracy of CO2 binary mixed working fluid gas-liquid phase equilibrium prediction while reducing the amount of experimental work.

[0009] The present invention solves the above-mentioned technical problems through the following technical means:

[0010] This invention proposes a method for predicting the functional group contribution in the gas-liquid phase equilibrium of a CO2 binary working fluid, the method comprising the following steps:

[0011] Obtain a binary working fluid containing CO2;

[0012] For a given temperature range and a liquid phase molar composition range of CO2, iterate through each temperature value within the temperature range, keeping the currently traversed temperature value unchanged, and calculate the pressure of the mixed working fluid and the gas phase molar composition of CO2 under each liquid phase molar composition within the liquid phase molar composition range of CO2 based on the cubic equation of state and the group contribution prediction model.

[0013] When all temperature values ​​within the temperature range have been traversed, the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value within the temperature range are obtained.

[0014] This invention employs a group contribution prediction method, which overcomes the shortcomings of correlation models that rely on a large amount of experimental data through the interaction between groups. It eliminates the need for extensive experimental data to fit interaction parameters, thus simplifying the experimental workload and improving prediction accuracy. Under certain temperatures and any liquid phase molar fraction, it can calculate the corresponding pressure and gas phase molar composition, thereby achieving the prediction of gas-liquid phase equilibrium. Furthermore, the prediction results can be widely used for the analysis and calculation of saturated liquid pressure of CO2 mixed working fluid in thermodynamic cycles.

[0015] Furthermore, the formula for the group contribution prediction model is expressed as follows:

[0016]

[0017]

[0018] In the formula: a m b m These are the gravitational term and co-volume term of the mixed working fluid, respectively; a i b i These are the gravitational term and co-volume term of the working fluid, respectively; a ij C represents the interaction term between component i and component j of the mixed working fluid; HV C WS G represents the parameters of the cubic equation of state. E R is the excess Helmholtz free energy under infinite pressure; T is the universal gas constant; k is the temperature. ij x represents the interaction parameters of the mixed working fluid; i x is the molar composition of component i; j Let J be the molar composition of component j; C be the parameters related to the equation of state, for the PR equation C = -0.62323.

[0019] Furthermore, the formula for the interaction parameters of the mixed working fluid is expressed as follows:

[0020]

[0021] In the formula: x, y are fitting parameters; M is the refrigerant mixed with CO2; This is the critical pressure of CO2; The eccentricity factor for CO2; This represents the number of fluorine atoms in the refrigerant. ω is the critical pressure of the refrigerant; M The eccentricity factor of the refrigerant; T is the critical temperature of CO2. c,M This is the critical temperature of the refrigerant.

[0022] Furthermore, in the CO2 binary working fluid, the refrigerant mixed with CO2 includes hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins.

[0023] Furthermore, the hydrocarbon includes at least one of ethane, propane, butane, isobutane, pentane, isopentane, ethylene, and propylene.

[0024] Further, the hydrofluorocarbon includes at least one of refrigerant R23, refrigerant R32, refrigerant R41, refrigerant R125, refrigerant R134a, refrigerant R143a, refrigerant R152a, refrigerant R161, refrigerant R227ea, and refrigerant R365mfc.

[0025] Furthermore, the hydrofluoroolefin includes refrigerant R1234yf and / or refrigerant R1234ze(E).

[0026] Furthermore, this invention also proposes a device for predicting the group contribution of a CO2 binary mixed working fluid in gas-liquid phase equilibrium, the device comprising:

[0027] The acquisition module is used to acquire the CO2 binary working fluid;

[0028] The traversal calculation module is used to traverse each temperature value within a given temperature range and a liquid phase molar composition range of CO2, while keeping the currently traversed temperature value unchanged. Based on the cubic equation of state and the group contribution prediction model, it calculates the pressure of the mixed working fluid and the gas phase molar composition of CO2 under each liquid phase molar composition within the liquid phase molar composition range of CO2.

[0029] The prediction system determination module is used to obtain the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value within the temperature range after all temperature values ​​within the temperature range have been traversed.

[0030] Furthermore, this invention also proposes a CO2 binary mixed working fluid gas-liquid phase equilibrium prediction device, the device including a memory and a processor; wherein, the processor reads executable program code stored in the memory to run a program corresponding to the executable program code, so as to implement the group contribution prediction method for CO2 binary mixed working fluid gas-liquid phase equilibrium as described above.

[0031] Furthermore, the present invention also proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the group contribution prediction method for the gas-liquid phase equilibrium of a CO2 binary working fluid as described above.

[0032] The advantages of this invention are:

[0033] (1) The present invention adopts the group contribution prediction method. Through the interaction between groups, it overcomes the defect that the correlation model needs to rely on a large amount of experimental data, simplifies the experimental workload, and improves the prediction accuracy. Under a certain temperature and any liquid phase molar fraction, the corresponding pressure and gas phase molar composition can be calculated, thereby realizing the prediction of gas-liquid phase equilibrium. The prediction results can be widely used for the analysis and calculation of the saturated liquid pressure of CO2 mixed working fluid in thermodynamic cycle.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating a method for predicting the group contribution of a CO2 binary mixed working fluid in gas-liquid phase equilibrium, as proposed in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of a group contribution prediction device for the gas-liquid phase equilibrium of a CO2 binary mixed working fluid proposed in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] First, it should be noted that the purity of the test materials used in this invention is not particularly limited. This invention preferably uses analytical grade or conventional purity in the field of refrigerant preparation.

[0039] All materials of this invention are conventional in the field, and each designation and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the designation, abbreviation, and corresponding application.

[0040] All processes in this invention are referred to by abbreviations that are common abbreviations in the field. Each abbreviation is clear and specific in its relevant application area, and those skilled in the art can understand its conventional process steps based on the abbreviation.

[0041] like Figure 1 As shown, the first embodiment of the present invention proposes a method for predicting the group contribution of a CO2 binary mixed working fluid in gas-liquid phase equilibrium. The method includes the following steps:

[0042] S10, Obtain a binary mixed working fluid of CO2;

[0043] S20. For a given temperature range and a liquid phase molar composition range of CO2, traverse each temperature value within the temperature range and keep the currently traversed temperature value unchanged. Based on the cubic equation of state and the group contribution prediction model, calculate the pressure of the mixed working fluid and the gas phase molar composition of CO2 under each liquid phase molar composition within the liquid phase molar composition range of CO2.

[0044] S30. When all temperature values ​​within the temperature range have been traversed, the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value within the temperature range are obtained.

[0045] The embodiments of this invention employ a group contribution prediction method, which overcomes the shortcomings of correlation models that rely on a large amount of experimental data through the interaction between groups, simplifies the experimental workload, and improves prediction accuracy. Under certain temperatures and any liquid phase molar fraction, the corresponding pressure and gas phase molar composition can be calculated, thereby realizing the prediction of gas-liquid phase equilibrium. Moreover, the prediction results can be widely used for the analysis and calculation of saturated liquid pressure of CO2 mixed working fluid in thermodynamic cycles.

[0046] In one embodiment, the formula for the group contribution prediction model is expressed as:

[0047]

[0048]

[0049] In the formula: a m b m These are the gravitational term and co-volume term of the mixed working fluid, respectively; a i b i These are the gravitational term and co-volume term of the working fluid, respectively; a ij C represents the interaction term between component i and component j of the mixed working fluid; HV C WS G represents the parameters of the cubic equation of state. E R is the excess Helmholtz free energy under infinite pressure; T is the universal gas constant; k is the temperature. ij x represents the interaction parameters of the mixed working fluid; i x is the molar composition of component i; j Let J be the molar composition of component j; C be the parameters related to the equation of state, for the PR equation C = -0.62323.

[0050] It should be noted that for cubic state equations, i.e., Peng and Robinson state equations, C HV CWS The values ​​are all -0.62323; R is the universal gas constant, taken as 8.314 J / (mol·K); T is temperature, in K; p is pressure, in MPa.

[0051] In one embodiment, the formula for the interaction parameters of the mixed working fluid is expressed as:

[0052]

[0053] In the formula: x, y are fitting parameters; M is the refrigerant mixed with CO2; This is the critical pressure of CO2; The eccentricity factor for CO2; This represents the number of fluorine atoms in the refrigerant. ω is the critical pressure of the refrigerant; M The eccentricity factor of the refrigerant; T is the critical temperature of CO2. c,M This is the critical temperature of the refrigerant.

[0054] Where Tc is the critical temperature and pc is the critical pressure.

[0055] This embodiment can quickly calculate the binary mutual parameter k. ij The interaction parameters of the groups can be used to quickly and accurately predict the gas-liquid equilibrium properties of CO2 and mixtures of hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins refrigerants without the need for a large amount of experimental data.

[0056] In one embodiment, the refrigerant mixed with CO2 in the CO2 binary working fluid includes hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins.

[0057] It should be noted that this group contribution model can predict the gas-liquid phase equilibrium of CO2 and HC (hydrocarbons), HFC (hydrofluorocarbons), and HFO (hydrofluoroolefins) working fluids.

[0058] In one embodiment, the hydrocarbon includes at least one selected from ethane, propane, butane, isobutane, pentane, isopentane, ethylene, and propylene.

[0059] More preferably, the hydrocarbon is ethane, propane, butane, isobutane, pentane, isopentane, ethylene, or propylene.

[0060] In one embodiment, the hydrofluorocarbon includes at least one of refrigerant R23, refrigerant R32, refrigerant R41, refrigerant R125, refrigerant R134a, refrigerant R143a, refrigerant R152a, refrigerant R161, refrigerant R227ea, and refrigerant R365mfc.

[0061] More preferably, the hydrofluorocarbon is refrigerant R23, refrigerant R32, refrigerant R41, refrigerant R125, refrigerant R134a, refrigerant R143a, refrigerant R152a, refrigerant R161, refrigerant R227ea, or refrigerant R365mfc.

[0062] In one embodiment, the hydrofluoroolefin includes refrigerant R1234yf and / or refrigerant R1234ze(E).

[0063] More preferably, the hydrofluoroolefin is refrigerant R1234yf or refrigerant R1234ze(E).

[0064] It should be noted that in this embodiment, the calculated pressure of the mixing system in each temperature range is compared with the actual measured pressure of the mixing system to calculate the relative deviation of the average pressure; and the calculated gaseous molar composition of CO2 in the mixing system in each temperature range is compared with the actual measured gaseous molar composition of CO2 in the mixing system to calculate the absolute deviation of the average gaseous molar composition.

[0065] Taking CO2 / propane binary working fluid as an example, see Table 1 for the deviation between the predicted values ​​and experimental measurements of this prediction method.

[0066] Table 1. Deviation between predicted and experimental values ​​of CO2 / propane binary working fluid

[0067] <![CDATA[CO2 / Propane]]> Average pressure relative deviation Absolute deviation of average gas phase molar composition 273K 1.51％ 0.0017 283K 1.98％ 0.0047 293K 0.69％ 0.0072 303K 0.72％ 0.0068 313K 0.78％ 0.0062 323K 0.85％ 0.0050

[0068] As can be seen from the comparison of the prediction results in the embodiments of the present invention, the prediction model provided by the present invention calculates the relative deviation of the average pressure within 1.98% and the absolute deviation of the average gas phase molar composition within 0.0072, which shows that the prediction accuracy is very high.

[0069] In addition, such as Figure 2 As shown, the second embodiment of the present invention also proposes a device for predicting the group contribution of a CO2 binary mixed working fluid in gas-liquid phase equilibrium, the device comprising:

[0070] Module 10 is used to acquire a binary working fluid of CO2;

[0071] The traversal calculation module 20 is used to traverse each temperature value within a given temperature range and a liquid phase molar composition range of CO2, while keeping the currently traversed temperature value unchanged. Based on the cubic equation of state and the group contribution prediction model, it calculates the pressure of the mixed working fluid and the gas phase molar composition of CO2 under each liquid phase molar composition within the liquid phase molar composition range of CO2.

[0072] The prediction system determination module 30 is used to obtain the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value in the temperature range after all temperature values ​​in the temperature range have been traversed.

[0073] The embodiments of this invention employ a group contribution prediction method, which overcomes the shortcomings of correlation models that rely on a large amount of experimental data through the interaction between groups, simplifies the experimental workload, and improves prediction accuracy. Under certain temperatures and any liquid phase molar fraction, the corresponding pressure and gas phase molar composition can be calculated, thereby realizing the prediction of gas-liquid phase equilibrium. Moreover, the prediction results can be widely used for the analysis and calculation of saturated liquid pressure of CO2 mixed working fluid in thermodynamic cycles.

[0074] In one embodiment, the formula for the group contribution prediction model is expressed as:

[0075]

[0076]

[0077] In the formula: a m b m These are the gravitational term and co-volume term of the mixed working fluid, respectively; a i b i These are the gravitational term and co-volume term of the working fluid, respectively; a ij C represents the interaction term between component i and component j of the mixed working fluid; HV C WS G represents the parameters of the cubic equation of state. E R is the excess Helmholtz free energy under infinite pressure; T is the universal gas constant; k is the temperature. ij x represents the interaction parameters of the mixed working fluid; i x is the molar composition of component i; j Let J be the molar composition of component j; C be the parameters related to the equation of state, for the PR equation C = -0.62323.

[0078] In one embodiment, the formula for the interaction parameters of the mixed working fluid is expressed as:

[0079]

[0080] In the formula: x, y are fitting parameters; M is the refrigerant mixed with CO2; This is the critical pressure of CO2; The eccentricity factor for CO2; This represents the number of fluorine atoms in the refrigerant. ω is the critical pressure of the refrigerant; M The eccentricity factor of the refrigerant; T is the critical temperature of CO2. c,M This is the critical temperature of the refrigerant.

[0081] In one embodiment, the refrigerant mixed with CO2 in the CO2 binary working fluid includes hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins.

[0082] In one embodiment, the hydrocarbon includes at least one selected from ethane, propane, butane, isobutane, pentane, isopentane, ethylene, and propylene.

[0083] In one embodiment, the hydrofluorocarbon includes at least one of refrigerant R23, refrigerant R32, refrigerant R41, refrigerant R125, refrigerant R134a, refrigerant R143a, refrigerant R152a, refrigerant R161, refrigerant R227ea, and refrigerant R365mfc.

[0084] In one embodiment, the hydrofluoroolefin includes refrigerant R1234yf and / or refrigerant R1234ze(E).

[0085] It should be noted that other embodiments or implementation methods of the CO2 binary mixed working fluid gas-liquid phase equilibrium prediction device of the present invention can refer to the above-described method embodiments, and will not be repeated here.

[0086] Furthermore, the third embodiment of the present invention also proposes a CO2 binary mixed working fluid gas-liquid phase equilibrium prediction device, the device including a memory and a processor; wherein, the processor reads the executable program code stored in the memory to run a program corresponding to the executable program code, so as to implement the method described in the first embodiment above.

[0087] Furthermore, the fourth embodiment of the present invention also proposes a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the method described in the first embodiment above.

[0088] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0089] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0090] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0091] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0092] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for predicting the functional group contribution in the gas-liquid phase equilibrium of a CO2 binary mixed working fluid, characterized in that, The method includes the following steps: Obtain a binary working fluid containing CO2; For a given temperature range and a liquid phase molar composition range of CO2, traversing each temperature value within the range while keeping the currently traversed temperature value constant, the pressure of the mixed working fluid and the gas phase molar composition of CO2 are calculated based on the cubic equation of state and the group contribution prediction model at each liquid phase molar composition range of CO2. The formula for the group contribution prediction model is expressed as follows: In the formula: a m b m These are the gravitational term and the co-volume term of the mixed working fluid, respectively; a i b i These are the gravitational term and co-volume term of the pure working fluid, respectively; C HV , C WS The parameters of the cubic equation of state; G E R is the excess Helmholtz free energy under infinite pressure; T is the universal gas constant; and T is the temperature. These are the interaction parameters of the mixed working fluid; for i Molar composition of the component; for j Molar composition of the component; The parameters related to the state equations are C = -0.62323 for the PR equations; When all temperature values ​​within the temperature range have been traversed, the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value within the temperature range are obtained.

2. The method for predicting group contributions in the gas-liquid phase equilibrium of a CO2 binary working fluid as described in claim 1, characterized in that, The formula for the interaction parameters of the mixed working fluid is expressed as follows: In the formula: x , y These are the fitting parameters; M A refrigerant mixed with CO2; This is the critical pressure of CO2; The eccentricity factor for CO2; This represents the number of fluorine atoms in the refrigerant. This is the critical pressure of the refrigerant; The eccentricity factor of the refrigerant; This is the critical temperature of CO2; This is the critical temperature of the refrigerant.

3. The method for predicting the functional group contribution of CO2 binary mixed working fluid gas-liquid phase equilibrium as described in claim 1 or 2, characterized in that, In the CO2 binary working fluid, the refrigerant mixed with CO2 includes hydrocarbons, hydrofluorocarbons, and hydrofluoroolefins.

4. The method for predicting the functional group contribution of CO2 binary mixed working fluid gas-liquid phase equilibrium as described in claim 3, characterized in that, The hydrocarbons include at least one of ethane, propane, butane, isobutane, pentane, isopentane, ethylene, and propylene.

5. The method for predicting the group contribution of CO2 binary mixed working fluid gas-liquid phase equilibrium as described in claim 3, characterized in that, The hydrofluorocarbons include at least one of refrigerant R23, refrigerant R32, refrigerant R41, refrigerant R125, refrigerant R134a, refrigerant R143a, refrigerant R152a, refrigerant R161, refrigerant R227ea, and refrigerant R365mfc.

6. The method for predicting group contributions in the gas-liquid phase equilibrium of a binary CO2 working fluid as described in claim 3, characterized in that, The hydrofluoroolefins include refrigerant R1234yf and / or refrigerant R1234ze(E).

7. A device for predicting the functional group contribution in the gas-liquid phase equilibrium of a CO2 binary mixed working fluid, characterized in that, The device includes: The acquisition module is used to acquire CO2 binary working fluid; The traversal calculation module is used to traverse each temperature value within a given temperature range and a liquid phase molar composition range of CO2, keeping the currently traversed temperature value unchanged. Based on the cubic equation of state and the group contribution prediction model, it calculates the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each liquid phase molar composition within the liquid phase molar composition range of CO2. The formula for the group contribution prediction model is expressed as follows: In the formula: a m b m These are the gravitational term and the co-volume term of the mixed working fluid, respectively; a i b i These are the gravitational term and co-volume term of the pure working fluid, respectively; C HV , C WS The parameters of the cubic equation of state; G E R is the excess Helmholtz free energy under infinite pressure; T is the universal gas constant; and T is the temperature. These are the interaction parameters of the mixed working fluid; for i Molar composition of the component; for j Molar composition of the component; The parameters related to the state equations are C = -0.62323 for the PR equations; The prediction system determination module is used to obtain the pressure of the mixed working fluid and the gas phase molar composition of CO2 at each temperature value within the temperature range after all temperature values ​​within the temperature range have been traversed.

8. A device for predicting the gas-liquid phase equilibrium of a CO2 binary mixed working fluid, characterized in that, The device includes a memory and a processor; wherein the processor runs a program corresponding to the executable program code by reading executable program code stored in the memory, so as to implement the method as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-6.

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