Reverse Rankine Cycle Heat Pump System Using Non-Azeotropic Working Fluid and Its Control Method

Abstract

This invention discloses a reverse Rankine cycle heat pump system and its control method using a non-azeotropic working fluid. The system includes an evaporator, a gas-liquid separator, a low-pressure compressor, a high-pressure compressor, an intercooler, a liquid storage tank, a condenser, a throttling valve, a flash tank, a temperature monitor, a concentration monitor, a pressurizing pump, and control components. The evaporated working fluid is separated by the gas-liquid separator into a gaseous mixture rich in low-boiling-point working fluid and a liquid mixture rich in high-boiling-point working fluid. The gaseous working fluid enters a two-stage compression process, while the liquid working fluid is temporarily stored in the liquid storage tank and participates in component adjustment. The throttled working fluid is separated in the flash tank; the gaseous working fluid is used for intermediate gas replenishment and cooling according to concentration requirements, while the liquid working fluid returns to the evaporator. This invention determines the target component concentration based on the condenser's operating temperature and adjusts the valve openings based on concentration deviation and equipment outlet temperature to improve the adaptability of the non-azeotropic working fluid's temperature glide to different operating conditions and enhance the system's operating efficiency and stability.

Description

Technical Field

[0001] This invention relates to the field of heat pump system control technology, specifically to a reverse Rankine cycle heat pump system using a non-azeotropic mixed working fluid and its control method. Background Technology

[0002] Heat pump systems consume a small amount of high-grade energy to raise the temperature of a low-temperature heat source to a higher level, offering advantages such as energy efficiency, high performance, and wide applicability. However, as the operating temperature range and load variation range of heat pumps continue to expand, the limitations of single-component heat exchange temperature matching become increasingly apparent. Non-azeotropic mixtures exhibit temperature glide characteristics during evaporation and condensation, which can improve temperature matching between the heat source and cold source by adjusting the proportions of different components, thereby reducing heat exchange losses and improving system performance. However, the high and low boiling point components in non-azeotropic mixtures undergo varying degrees of compositional changes during evaporation, condensation, and gas-liquid separation. Existing heat pump systems typically employ a fixed charge ratio, primarily adjusting operating conditions through compressors or throttling devices, lacking real-time monitoring and active control of heat pump component concentrations. When ambient temperature, condensing temperature, or heating load changes, the original component proportions may not maintain a suitable temperature glide, thus affecting system operating efficiency and stability. Therefore, a heat pump system and its control method that can dynamically adjust the composition of non-azeotropic mixtures based on operating conditions are currently lacking. Summary of the Invention

[0003] To address the technical problems existing in the current technology, the present invention aims to provide a reverse Rankine cycle heat pump system and its control method using a non-azeotropic working fluid. This system fully utilizes the temperature glide characteristics of the non-azeotropic working fluid to improve the component regulation capability and operational stability of the heat pump system under different operating conditions. It is an effective system and method for enhancing the adaptability of a non-azeotropic working fluid heat pump system to varying operating conditions.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A reverse Rankine cycle heat pump system employing a non-azeotropic working fluid, wherein, The reverse Rankine cycle heat pump system includes an evaporator 101, a gas-liquid separator 102, a gas-liquid separator gas path regulating valve 103, a low-pressure compressor 104, an intercooler 105, a first three-way valve 106, a high-pressure compressor 107, a gas-liquid separator liquid path regulating valve 108, a liquid storage tank 109, an electronic regulating valve 110, a first pressurization pump 111, a second three-way valve 112, a condenser 113, a throttling valve 114, a flash tank 115, and a flash tank gas path regulating valve 116. 6. Flash tank liquid circuit regulating valve 117, second pressurizing pump 118, first temperature monitor 119, concentration monitor 120, and second temperature detector 121; Evaporator 101 outlet is connected to gas-liquid inlet 1021 of gas-liquid separator 102; Gas-side outlet 1022 of gas-liquid separator 102 flows through gas circuit regulating valve 103 of gas-liquid separator and is connected to low-pressure compressor 104; Liquid-side outlet 1023 of gas-liquid separator 102 flows through liquid circuit regulating valve 108 of gas-liquid separator. Connected to the liquid storage tank 109, one end of the electronic regulating valve 110 is connected to the liquid storage tank 109, and the other end is connected to the first pressurizing pump 111. The outlet of the first pressurizing pump 111 is connected to the first inlet of the second three-way valve 112. The outlet of the low-pressure compressor 104 is connected to the inlet of the intercooler 105. The outlet of the intercooler 105 is connected to the first three-way valve 106. The outlet of the first three-way valve 106 is connected to the high-pressure compressor 107. The outlet of the high-pressure compressor 107 is connected to the second three-way valve 112. The connection is as follows: the No. 2 three-way valve 112 and the downstream pipeline are connected to the inlet of the condenser 113; the outlet of the condenser 113 is connected to the throttle valve 114; the inlet 1151 of the flash tank 115 is connected to the throttle valve 114; the gas-side outlet 1152 flows through the flash tank gas path regulating valve 116 and is connected to the No. 1 three-way valve 106; the liquid-side outlet 1153 flows through the flash tank liquid path regulating valve 117 and is connected to the second pressurizing pump 118; the outlet of the second pressurizing pump 118 is connected to the inlet of the evaporator 101. Temperature gauge 119 monitors the working fluid temperature at the outlet of intercooler 105 in real time; concentration gauge 120 monitors the working fluid concentration at the outlet of three-way valve 112 in real time; temperature gauge 121 monitors the working temperature change in condenser 113 in real time.

[0005] Furthermore, after the non-azeotropic working fluid flows through the evaporator 101 and absorbs heat through evaporation, it reaches a specific temperature, where the high-boiling-point component and the low-boiling-point component exist simultaneously in the gas and liquid phases. After entering the gas-liquid separator 102, the working fluid is divided into two streams. The gaseous working fluid contains a small amount of high-boiling-point working fluid and a large amount of low-boiling-point working fluid. It enters the low-pressure compressor 104 through the gas-side outlet 1022 of the gas-liquid separator 102, so that the low-pressure compressor 104 only compresses the gaseous working fluid. The liquid working fluid contains a small amount of low-boiling-point working fluid and a large amount of high-boiling-point working fluid. It enters the liquid storage tank 109 through the liquid-side outlet 1023 of the gas-liquid separator 102 for temporary storage.

[0006] Furthermore, the working fluid at the inlet of the flash tank 115 is a two-phase fluid that has undergone a throttling process in the throttling valve 114. After flash evaporation with adjusted pressure, the gaseous working fluid enters the first three-way valve 106 to participate in the intermediate gas replenishment process between the low-pressure compressor 104 and the high-pressure compressor 107. At the same time, it mixes with the gas from the intercooler 105 to cool the working fluid. The liquid working fluid flows through the second pressurizing pump 118 and then enters the evaporator 101 to participate in the evaporation process.

[0007] Furthermore, the non-azeotropic working fluid used in the reverse Rankine cycle heat pump system is R1233zd / R134a, wherein the high-boiling-point working fluid is R1233zd and the low-boiling-point working fluid is R134a.

[0008] Furthermore, the operating temperature range of the evaporator 101 is 289K~338K; the operating temperature range of the condenser 113 is 350K~410K.

[0009] The aforementioned control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid. The first step is to measure the actual molar concentration (c) of the high-boiling-point component of the mixed working fluid at the outlet of valve 112 of the No. 2 three-way valve in real time. pv The average operating temperature T1 of condenser 113, the working fluid temperature T2 at the outlet of intercooler 105, and the ambient temperature T amb ; The second step involves obtaining the optimal high-boiling-point component setpoint c under the current operating conditions based on the average operating temperature T1 of the condenser 113 and the pre-calibrated correspondence between the operating temperature of the condenser 113 and the optimal component concentration. sp When T1 is in the low temperature range of 350K~370K, c sp Take c2; when T1 is in the high temperature range of 370K~410K, c sp Take c3; where c2 and c3 are the optimal temperature glide ΔT that produces the best temperature range. opt The content of high-boiling-point components; The third step is to calculate the concentration deviation e of the high-boiling-point component in the non-azeotropic working mixture. c =c sp -c pv ; The fourth step is to adjust the concentration deviation e. c Input the main PID controller to calculate the total component control command U. total ; Fifth step, send the overall component adjustment command U total The basic valve opening command is obtained by allocating the pre-calibrated proportional coefficients k1, k2, and k3 to the three actuators: (i) Basic opening command V103 for gas-liquid separator gas path regulating valve 103 base =V1030+k1×U total ; (ii) Basic opening command V108 for gas-liquid separator liquid circuit regulating valve 108 base =V1080+k2×U total ; (iii) Basic opening command V110 for electronic control valve 110 base =V1100+k3×U total ; Where V1030, V1080, and V1100 are the static opening degrees of each valve under rated operating conditions; k1, k2, and k3 are pre-calibrated proportional coefficients; furthermore, the calibration process for the proportional coefficients is as follows: The overall component control command U is sent... total A step disturbance is applied, and the step responses of the gas path regulating valve, the liquid path regulating valve, and the electronic regulating valve of the gas-liquid separator are tested respectively. The regulating gain of each valve for the high boiling point component concentration is obtained. The weights are assigned according to the regulating gain of each valve. The constraint coefficients satisfy |k1|+|k2|+|k3|=1, and k1 is negative, while k2 and k3 are positive. The component concentration control effect of the system is verified, and the component concentration control overshoot is guaranteed to be no more than 5%. The final proportional coefficients k1, k2, and k3 are obtained. Step 6: Set the ambient temperature T amb Input to a pre-calibrated ambient temperature feedforward function generator f(T) amb The feedforward correction amount U is calculated. ff Furthermore, the ambient temperature feedforward function is predetermined using a steady-state calibration method. The calibration process is as follows: Select multiple typical ambient temperature points, adjust the system to a stable operating state at each temperature point, and record the opening compensation value of each valve relative to the rated operating condition when maintaining the target component concentration; with ambient temperature as the independent variable and the corresponding valve opening compensation value as the dependent variable, obtain the functional relationship between ambient temperature and opening compensation value, i.e., the feedforward correction amount, through linear fitting or piecewise linearization; store this functional relationship in the system controller in the form of formulas, data tables, or characteristic curves; collect the ambient temperature in real time during system operation, and calculate the real-time feedforward correction amount by calling this function. Step 7: Combine the basic opening command of each valve with the feedforward correction amount U. ff By superimposing these values, the final opening command for each valve is obtained: (i) V103=V103 base +U ff ; (ii) V108 = V108 base -U ff ; (iii) V110 = V110 base -U ff ; The eighth step involves adjusting the opening of the gas-liquid separator gas path regulating valve 103, the gas-liquid separator liquid path regulating valve 108, and the electronic regulating valve 110 according to the final opening command. This adjusts the flow rate of the high-boiling-point component working fluid entering the storage tank 109 and the low-boiling-point component working fluid entering the evaporator 101, thereby achieving closed-loop control of the working fluid components within the system.

[0010] The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid includes an independent temperature control step for the intercooler 105. The first step is to set the target temperature T at the outlet of the intercooler 105. 2sp ; The second step is to calculate the temperature deviation e at the outlet of the intercooler 105. T2 =T 2sp -T2; The third step is to measure the temperature deviation e. T2 Input the secondary PID controller to calculate the basic opening V116 of the flash tank gas path regulating valve 116. base .

[0011] The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid includes a flash tank auxiliary component adjustment step: When the concentration deviation e c When the absolute value is greater than the preset threshold ε, the flash tank auxiliary adjustment mode is triggered: When e c >0, then in V116 base Based on this, reduce the opening degree V116 of the flash tank gas path regulating valve 116 and increase the opening degree V117 of the flash tank liquid path regulating valve 117. When e c <0, then in V116 base Based on this, increase the opening degree V116 of the flash tank gas path regulating valve 116 and decrease the opening degree V117 of the flash tank liquid path regulating valve 117.

[0012] Compared with the prior art, the present invention has the following advantages: (1) The present invention separates a gaseous mixture rich in low-boiling-point working fluid and a liquid mixture rich in high-boiling-point working fluid through a gas-liquid separator, so that the compressor mainly compresses the gaseous working fluid, thereby reducing the power consumption of compression and providing conditions for system component adjustment. (2) The present invention determines the optimal component concentration based on the condenser operating temperature, and combines concentration monitoring and valve adjustment to achieve dynamic matching and closed-loop control of non-azeotropic working fluid components, thereby improving the adaptability of the heat pump system to different operating conditions. (3) The present invention utilizes a flash tank for intermediate gas replenishment and auxiliary component adjustment, which can accelerate component deviation correction while reducing the temperature during the compression process, thereby improving the system's operating efficiency and stability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a reverse Rankine cycle heat pump system using a non-azeotropic mixed working fluid according to the present invention.

[0014] Figure 2 This is a schematic diagram of the control logic of a reverse Rankine cycle heat pump system using a non-azeotropic mixed working fluid according to the present invention, where f(x) is the ambient temperature feedforward function and g(x) is the pre-calibrated function relating the condenser operating temperature to the optimal component concentration. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the preferred embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0016] like Figure 1 As shown, this invention provides a reverse Rankine cycle heat pump system using a non-azeotropic working fluid and its control method, wherein... The reverse Rankine cycle heat pump system includes an evaporator 101, a gas-liquid separator 102, a gas-liquid separator gas path regulating valve 103, a low-pressure compressor 104, an intercooler 105, a first three-way valve 106, a high-pressure compressor 107, a gas-liquid separator liquid path regulating valve 108, a liquid storage tank 109, an electronic regulating valve 110, a first pressurization pump 111, a second three-way valve 112, a condenser 113, a throttling valve 114, a flash tank 115, and a flash tank gas path regulating valve 116. 6. Flash tank liquid circuit regulating valve 117, second pressurizing pump 118, first temperature monitor 119, concentration monitor 120, and second temperature detector 121; Evaporator 101 outlet is connected to gas-liquid inlet 1021 of gas-liquid separator 102; Gas-side outlet 1022 of gas-liquid separator 102 flows through gas circuit regulating valve 103 of gas-liquid separator and is connected to low-pressure compressor 104; Liquid-side outlet 1023 of gas-liquid separator 102 flows through liquid circuit regulating valve 108 of gas-liquid separator. Connected to the liquid storage tank 109, one end of the electronic regulating valve 110 is connected to the liquid storage tank 109, and the other end is connected to the first pressurizing pump 111. The outlet of the first pressurizing pump 111 is connected to the first inlet of the second three-way valve 112. The outlet of the low-pressure compressor 104 is connected to the inlet of the intercooler 105. The outlet of the intercooler 105 is connected to the first three-way valve 106. The outlet of the first three-way valve 106 is connected to the high-pressure compressor 107. The outlet of the high-pressure compressor 107 is connected to the second three-way valve 112. The connection is as follows: the No. 2 three-way valve 112 and the downstream pipeline are connected to the inlet of the condenser 113; the outlet of the condenser 113 is connected to the throttle valve 114; the inlet 1151 of the flash tank 115 is connected to the throttle valve 114; the gas-side outlet 1152 flows through the flash tank gas path regulating valve 116 and is connected to the No. 1 three-way valve 106; the liquid-side outlet 1153 flows through the flash tank liquid path regulating valve 117 and is connected to the second pressurizing pump 118; the outlet of the second pressurizing pump 118 is connected to the inlet of the evaporator 101. Temperature gauge 119 monitors the working fluid temperature at the outlet of intercooler 105 in real time and reports the temperature monitoring results to flash tank 115; concentration gauge 120 monitors the working fluid concentration at the outlet of three-way valve 112 in real time and reports the concentration monitoring results to gas-liquid separator 102 and electronic regulating valve 110; temperature gauge 121 monitors the working temperature change in condenser 113 in real time.

[0017] Furthermore, after the non-azeotropic working fluid flows through the evaporator 101 and absorbs heat through evaporation, it reaches a specific temperature, where the high-boiling-point component and the low-boiling-point component exist simultaneously in the gas and liquid phases. After entering the gas-liquid separator 102, the working fluid is divided into two streams. The gaseous working fluid contains a small amount of high-boiling-point working fluid and a large amount of low-boiling-point working fluid. It enters the low-pressure compressor 104 through the gas-side outlet 1022 of the gas-liquid separator 102, so that the low-pressure compressor 104 only compresses the gaseous working fluid, reducing the power consumption of compression. The liquid working fluid contains a small amount of low-boiling-point working fluid and a large amount of high-boiling-point working fluid. It enters the storage tank 109 through the liquid-side outlet 1023 of the gas-liquid separator 102 for temporary storage, waiting for control commands to participate in the component regulation process.

[0018] Furthermore, the working fluid at the outlet of condenser 113 undergoes a throttling process in throttling valve 114, becoming a two-phase fluid with a reduced temperature, predominantly liquid phase, and carrying a small amount of flash vapor, before entering flash tank 115. A certain intermediate pressure is maintained within flash tank 115. By adjusting this pressure, some of the liquid working fluid undergoes adiabatic flash evaporation within the tank, achieving efficient separation of the gas and liquid phases. The gaseous working fluid, according to the flash tank control method, enters the first three-way valve 106 to participate in the intermediate gas supply process between low-pressure compressor 104 and high-pressure compressor 107. Simultaneously, it mixes with gas from intercooler 105 to cool the working fluid, effectively suppressing the high-pressure stage exhaust temperature, reducing the high-pressure stage compression work, and improving system energy efficiency and operational reliability. The liquid working fluid flows through the second pressurization pump 118 and enters evaporator 101 to participate in the evaporation process, ensuring the continuity of the working fluid circulation on the evaporation side and the stability of the hydraulic pressure supply.

[0019] Furthermore, the system uses a mixed working fluid of R1233zd / R134a, wherein the high-boiling-point working fluid is R1233zd with a boiling point of approximately 291.45K, and the low-boiling-point working fluid is R134a with a boiling point of approximately 247.05K. R1233zd has both extremely low global warming potential and non-flammability, making it environmentally friendly and safe, while R134a has moderate volumetric refrigeration capacity and good chemical stability. The mixture of the two can meet both environmental requirements and system volumetric energy efficiency.

[0020] Furthermore, the evaporator 101 operates in a temperature range of 289K~338K, and the condenser 113 operates in a temperature range of 350K~410K. These temperature ranges meet the evaporation and condensation requirements of the mixed working fluid under different component ratios, while avoiding the critical temperatures of each component working fluid, thus ensuring the safety and reliability of the system operation.

[0021] like Figure 2 As shown, the present invention discloses a control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid. The first step is to measure the actual molar concentration (c) of the high-boiling-point component of the mixed working fluid at the outlet of valve 112 of the No. 2 three-way valve in real time. pv The average operating temperature T1 of condenser 113, the working fluid temperature T2 at the outlet of intercooler 105, and the ambient temperature T amb ; The second step is to consult the pre-calibrated optimal concentration mapping table based on the average operating temperature T1 of condenser 113 to obtain the optimal high-boiling-point component setpoint c under the current operating conditions. sp When T1 is in the low temperature range, c sp Take c2; when T1 is in the high temperature range, c sp Take c3; where c2 and c3 are the optimal temperature glide ΔT that produces the best temperature range. opt The content of high-boiling-point components; The third step is to calculate the concentration deviation e of the high-boiling-point component in the non-azeotropic working mixture. c =c sp -c pv ; The fourth step is to adjust the concentration deviation e. c Input the main PID controller to calculate the total component control command U. total ; Fifth step, send the overall component adjustment command U total The basic valve opening command is obtained by allocating the pre-calibrated proportional coefficients k1, k2, and k3 to the three actuators: (i) Basic opening command V103 for gas-liquid separator gas path regulating valve 103 base =V1030+k1×U total ; (ii) Basic opening command V108 for gas-liquid separator liquid circuit regulating valve 108 base =V1080+k2×U total ; (iii) Basic opening command V110 for electronic control valve 110 base =V1100+k3×U total ; Where V1030, V1080, and V1100 are the static opening degrees of each valve under rated operating conditions; k1, k2, and k3 are pre-calibrated proportional coefficients; furthermore, the calibration process for the proportional coefficients is as follows: The overall component control command U is sent... totalA step disturbance is applied, and the step responses of the gas path regulating valve, the liquid path regulating valve, and the electronic regulating valve of the gas-liquid separator are tested respectively. The regulating gain of each valve for the high boiling point component concentration is obtained. The weights are assigned according to the regulating gain of each valve. The constraint coefficients satisfy |k1|+|k2|+|k3|=1, and k1 is negative, while k2 and k3 are positive. The component concentration control effect of the system is verified, and the component concentration control overshoot is guaranteed to be no more than 5%. The final proportional coefficients k1, k2, and k3 are obtained. Step 6: Set the ambient temperature T amb Input to a pre-calibrated ambient temperature feedforward function generator f(T) amb The feedforward correction amount U is calculated. ff Furthermore, the ambient temperature feedforward function is predetermined using a steady-state calibration method. The calibration process is as follows: Select multiple typical ambient temperature points, adjust the system to a stable operating state at each temperature point, and record the opening compensation value of each valve relative to the rated operating condition when maintaining the target component concentration; with ambient temperature as the independent variable and the corresponding valve opening compensation value as the dependent variable, obtain the functional relationship between ambient temperature and opening compensation value, i.e., the feedforward correction amount, through linear fitting or piecewise linearization; store this functional relationship in the system controller in the form of formulas, data tables, or characteristic curves; collect the ambient temperature in real time during system operation, and calculate the real-time feedforward correction amount by calling this function. Step 7: Combine the basic opening command with the feedforward correction amount U ff By superimposing these values, the final opening command for each valve is obtained: (i) V103=V103 base +U ff ; (ii) V108 = V108 base -U ff ; (iii) V110 = V110 base -U ff ; The eighth step involves adjusting the opening of the gas-liquid separator gas path regulating valve 103, the gas-liquid separator liquid path regulating valve 108, and the electronic regulating valve 110 according to the final opening command. This adjusts the flow rate of the high-boiling-point component working fluid entering the storage tank 109 and the low-boiling-point component working fluid entering the evaporator 101, thereby achieving closed-loop control of the working fluid components within the system.

[0022] The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid includes an independent temperature control step for the intercooler 105. The first step is to set the target temperature T at the outlet of the intercooler 105. 2sp ; The second step is to calculate the temperature deviation e at the outlet of the intercooler 105. T2 =T 2sp -T2; The third step is to measure the temperature deviation e. T2 Input the secondary PID controller to calculate the basic opening V116 of the flash tank gas path regulating valve 116. base .

[0023] The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid includes a flash tank auxiliary component adjustment step: When the concentration deviation e c When the absolute value is greater than the preset threshold ε, the flash tank auxiliary adjustment mode is triggered: When e c >0, then in V116 base Based on this, reduce the opening degree V116 of the flash tank gas path regulating valve 116 and increase the opening degree V117 of the flash tank liquid path regulating valve 117. When e c <0, then in V116 base Based on this, increase the opening degree V116 of the flash tank gas path regulating valve 116 and decrease the opening degree V117 of the flash tank liquid path regulating valve 117.

[0024] The system and control method of this invention employ a gas-liquid separator 102 to separate the vaporized non-azeotropic working fluid, allowing the gas phase working fluid rich in low-boiling-point components to enter the compressor for compression, while the liquid phase working fluid rich in high-boiling-point components is temporarily stored in the storage tank 109. This reduces the risk of liquid phase compression and the power consumption of the compressor, while providing conditions for subsequent adjustment of the working fluid components. A two-stage compression process is adopted, and the temperature of the working fluid after the first stage compression is reduced by an intercooler 105, reducing compressor power consumption and improving the stability of the compression process. A flash evaporator 115 is used to flash separate the throttled working fluid, allowing the gas phase working fluid to enter the two-stage compression process for intermediate gas replenishment, while the liquid phase working fluid returns to the evaporator 101 to continue participating in the circulation, thereby improving the system's circulation performance. A concentration monitor 120 is used to detect the concentration of the mixed working fluid components in real time, and combined with the operating temperature of the condenser 113, the ambient temperature, and the opening degree of the electronic regulating valve, to achieve dynamic control and variable operating condition matching of the non-azeotropic working fluid components. The system of this invention can make full use of the temperature glide characteristics of non-azeotropic working fluids, improve the component regulation capability and operational stability of heat pump systems under different operating conditions, and is an effective method to enhance the adaptability of non-azeotropic working fluid heat pump systems to varying operating conditions.

Claims

1. A reverse Rankine cycle heat pump system employing a non-azeotropic working fluid, characterized in that, The reverse Rankine cycle heat pump system uses a non-azeotropic working fluid. The reverse Rankine cycle heat pump system includes an evaporator (101). The outlet of the evaporator (101) is connected to the gas-liquid inlet (1021) of the gas-liquid separator (102). The gas-side outlet (1022) of the gas-liquid separator (102) flows through the gas-liquid separator gas path regulating valve (103) and is connected to the low-pressure compressor (104). The liquid-side outlet (1023) of the gas-liquid separator (102) flows through the gas-liquid separator liquid path regulating valve (108) and is connected to the liquid storage tank (109). One end of the electronic regulating valve (110) is connected to the liquid storage tank (109), and the other end is connected to the inlet of the first pressurizing pump (111). The outlet of the first pressurizing pump (111) is connected to the first inlet of the second three-way valve (112). The outlet of the low-pressure compressor (104) is connected to the intercooler (105). The inlet of the intercooler (105) is connected to the outlet of the first three-way valve (106), the outlet of the first three-way valve (106) is connected to the high-pressure compressor (107), the outlet of the high-pressure compressor (107) is connected to the second inlet of the second three-way valve (112), the second three-way valve (112) and the downstream pipe are connected to the inlet of the condenser (113), the outlet of the condenser (113) is connected to the throttle valve (114), the inlet (1151) of the flash tank (115) is connected to the throttle valve (114), the gas side outlet (1152) flows through the flash tank gas circuit regulating valve (116) and is connected to the first three-way valve (106), the liquid side outlet (1153) flows through the flash tank liquid circuit regulating valve (117) and is connected to the second pressurizing pump (118), and the outlet of the second pressurizing pump (118) is connected to the inlet of the evaporator (101). Temperature gauge 1 (119) monitors the working fluid temperature at the outlet of the intercooler (105) in real time; concentration gauge (120) monitors the working fluid concentration at the outlet of the three-way valve 2 (112) in real time; temperature detector 2 (121) monitors the working temperature change in the condenser (113) in real time.

2. The reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 1, characterized in that, The reverse Rankine cycle heat pump system includes a gas-liquid separator (102). The non-azeotropic mixed working fluid that flows through the evaporator (101) after evaporation and heat absorption has a temperature higher than the saturation temperature of the high-boiling-point working fluid at the evaporator outlet working pressure. The high-boiling-point component and the low-boiling-point component exist simultaneously in the gas phase and the liquid phase. After the mixed working fluid enters the gas-liquid separator (102), it is divided into two working fluids. The gaseous working fluid contains a small amount of high-boiling-point working fluid and a large amount of low-boiling-point working fluid. It enters the low-pressure compressor (104) through the gas side outlet (1022) of the gas-liquid separator (102), so that the low-pressure compressor (104) only compresses the gas phase working fluid. The liquid working fluid contains a small amount of low-boiling-point working fluid and a large amount of high-boiling-point working fluid. It enters the liquid storage tank (109) through the liquid side outlet (1023) of the gas-liquid separator (102) for temporary storage.

3. The reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 1, characterized in that, The reverse Rankine cycle heat pump system includes a flash tank (115), whose inlet working fluid is a two-phase fluid after passing through the throttling process in the throttling valve (114). After flash evaporation by adjusting the pressure, the gaseous working fluid enters the first three-way valve (106) to participate in the intermediate gas replenishment process between the low-pressure compressor (104) and the high-pressure compressor (107), and at the same time mixes with the gas from the intercooler (105) to cool the working fluid; the liquid working fluid flows through the second pressurizing pump (118) and enters the evaporator (101) to participate in the evaporation process.

4. The reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 1, characterized in that, The reverse Rankine cycle heat pump system uses a non-azeotropic mixture of R1233zd and R134a, with R1233zd being the high-boiling-point medium and R134a being the low-boiling-point medium.

5. The reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 1, characterized in that, The evaporator (101) of the reverse Rankine cycle heat pump system operates in a temperature range of 289K~338K; the condenser (113) operates in a temperature range of 350K~410K.

6. The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The first step is to measure the actual molar concentration c of the high-boiling-point component of the mixed working fluid at the outlet of the No. 2 three-way valve (112) in real time. pv The average operating temperature T1 of the condenser (113), the working fluid temperature T2 at the outlet of the intercooler (105), and the ambient temperature T amb ; The second step involves obtaining the optimal high-boiling-point component setpoint c under the current operating conditions based on the average operating temperature T1 of the condenser (113) and the pre-calibrated correspondence between the operating temperature of the condenser (113) and the optimal component concentration. sp When T1 is in the low temperature range of 350K~370K, c sp Take c2; when T1 is in the high temperature range of 370K~410K, c sp Take c3; where c2 and c3 are the optimal temperature glide ΔT that produces the best temperature range. opt The content of high-boiling-point components; The third step is to calculate the concentration deviation e of the high-boiling-point component in the non-azeotropic working mixture. c =c sp -c pv ; The fourth step is to adjust the concentration deviation e. c Input the main PID controller to calculate the total component control command U. total ; Fifth step, send the overall component adjustment command U total The basic valve opening command is obtained by allocating the pre-calibrated proportional coefficients k1, k2, and k3 to the three actuators: (i) Basic opening command V103 of the gas-liquid separator gas path regulating valve (103) base =V1030+k1×U total ; (ii) Basic opening command V108 for the liquid circuit regulating valve (108) of the gas-liquid separator base =V1080+k2×U total ; (iii) Basic opening command V110 of electronic control valve (110) base =V1100+k3×U total ; Where V1030, V1080, and V1100 are the static opening degrees of each valve under rated operating conditions; k1, k2, and k3 are pre-calibrated proportional coefficients that satisfy |k1|+|k2|+|k3|=1, with k1 being a negative value and k2 and k3 being positive values; Step 6: Set the ambient temperature T amb Input to a pre-calibrated ambient temperature feedforward function generator f(T) amb The feedforward correction amount U is calculated. ff ; Step 7: Combine the basic opening command of each valve with the feedforward correction amount U. ff By superimposing these values, the final opening command for each valve is obtained: (i)V103=V103 base +U ff ; (ii) V108 = V108 base -U ff ; (iii) V110=V110 base -U ff ; The eighth step involves adjusting the opening of the gas-liquid separator gas path regulating valve (103), the gas-liquid separator liquid path regulating valve (108), and the electronic regulating valve (110) according to the final opening command, thereby regulating the flow rate of the high-boiling-point component working fluid entering the storage tank (109) and the low-boiling-point component working fluid entering the evaporator (101) to achieve closed-loop control of the working fluid components in the system.

7. The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 6, characterized in that, It also includes an independent temperature control step for the intercooler (105): The first step is to set the target temperature T at the outlet of the intercooler (105). 2sp ; The second step is to calculate the temperature deviation e at the outlet of the intercooler (105). T2 =T 2sp -T2; The third step is to measure the temperature deviation e. T2 Input the secondary PID controller to calculate the basic opening V116 of the flash tank gas path regulating valve (116). base .

8. The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 7, characterized in that, It also includes the auxiliary component adjustment step of the flash evaporator (115): when the concentration deviation e c When the absolute value is greater than the preset threshold ε, the flash tank auxiliary adjustment mode is triggered: When e c >0, then in V116 base Based on this, reduce the opening degree V116 of the flash tank gas path regulating valve (116) and increase the opening degree V117 of the flash tank liquid path regulating valve (117); When e c <0, then in V116 base Based on this, increase the opening degree V116 of the flash tank gas path regulating valve (116) and decrease the opening degree V117 of the flash tank liquid path regulating valve (117).

9. The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 6, characterized in that, The process of pre-calibrating the proportionality coefficients k1, k2, and k3 through experiments is as follows: Adjust the total command U to the components. total A step disturbance is applied, and the step responses of the gas path regulating valve, the liquid path regulating valve, and the electronic regulating valve of the gas-liquid separator are tested respectively. The regulating gain of each valve for the high-boiling-point component concentration is obtained. The weights are assigned according to the regulating gain of each valve, and the constraint coefficients satisfy |k1|+|k2|+|k3|=1, where k1 is negative and k2 and k3 are positive. The component concentration control effect of the system is verified, and the component concentration control overshoot is guaranteed to be no more than 5%. The final proportional coefficients k1, k2, and k3 are obtained.

10. The control method for a reverse Rankine cycle heat pump system using a non-azeotropic working fluid according to claim 6, characterized in that, ambient temperature T amb Input to a pre-calibrated ambient temperature feedforward function generator f(T) amb The feedforward correction amount U is calculated. ff The process is as follows: The ambient temperature feedforward function is predetermined using a steady-state calibration method. The calibration process is as follows: Select multiple typical ambient temperature points, adjust the system to a stable operating state at each temperature point, and record the opening compensation value of each valve relative to the rated operating condition when maintaining the target component concentration; with ambient temperature as the independent variable and the corresponding valve opening compensation value as the dependent variable, obtain the functional relationship between ambient temperature and opening compensation value, i.e., the feedforward correction amount, through linear fitting or piecewise linearization; store this functional relationship in the system controller in the form of formulas, data tables, or characteristic curves; collect the ambient temperature in real time during system operation, and calculate the real-time feedforward correction amount by calling this function.

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