Cascade heating self-lifting high-temperature heat pump system and control method

Abstract

A kind of self-recovery cascade heating high-temperature heat pump system and control method, self-recovery cascade heating high-temperature heat pump system includes compressor, condenser, separator, multiple flow heat exchanger, regenerator, evaporator, gas tank, water pump, electronic expansion valve, solenoid valve, valve, control device and temperature sensor, pressure sensor;Control device acquires the signal of compressor outlet pressure sensor and temperature sensor, condenser outlet temperature sensor, evaporator outlet temperature sensor, water side outlet temperature sensor;Through the solenoid valve and electronic expansion valve of control compressor inlet and outlet, adjust the exhaust pressure of compressor to ensure that high-temperature heat pump system is safely started;During the operation of self-recovery cascade high-temperature heat pump system, by adjusting condenser outlet valve and separator liquid phase outlet electronic expansion valve control refrigerant flow and mixed working medium component concentration, during operation by changing refrigerant flow and component concentration and water side flow meet the heating demand of high-temperature heat pump.

Description

Technical Field

[0001] This invention relates to the field of high-temperature heat pump technology, specifically to a cascaded heating self-cascading high-temperature heat pump system and its control method. Background Technology

[0002] Heat pumps are an energy-saving heating technology that can replace electricity, gas, or coal for heating, suitable for residential or industrial applications. The limited heat capacity and large temperature glide of heat sinks such as water or air present new challenges for high-efficiency high-temperature heat pumps. Currently, high-temperature heat pumps mainly employ subcritical vapor compression cycles and transcritical cycles. For traditional subcritical heat pump cycles using a single refrigerant as the working fluid, due to its inherent isothermal phase change property, heat exchange losses are significant for heat sinks with large temperature glide requirements. CO2 transcritical heat pump cycles, due to the large temperature glide in the supercritical region, are advantageous for heating heat sinks. However, the higher exhaust pressure of this heat pump cycle increases the cost of certain components. Therefore, to meet the heating requirements with large temperature glide in subcritical heat pump cycles, the temperature glide characteristics of mixed working fluids are matched to the external heat sink temperature change curve, thereby reducing heat exchange losses and improving system efficiency.

[0003] Cycles employing mixed working fluids include regenerative cycles, self-cascade cycles, and cascade cycles. Compared to regenerative cycles, self-cascade cycles can adjust refrigerant flow and component concentration to adapt to varying operating conditions. Compared to cascade cycles, self-cascade cycles use only a single compressor, saving on system component costs. Therefore, air-source high-temperature heat pump systems using self-cascade cycles offer advantages in flexible control and lower cost. However, when the heating demand needs to be increased from an inlet water temperature of 15–20°C to 70–95°C, the heat exchange temperature difference on the condenser side is large, affecting the condenser's heat exchange... The problem of significant heat pump system performance degradation due to substantial losses persists. Therefore, to meet heating demands with large temperature ranges, the heat exchange process between the water and refrigerant sides needs improvement, including reducing the temperature difference between them and minimizing heat exchange process delays. This reduces losses and improves the performance of high-temperature heat pump systems. Summary of the Invention

[0004] To address the shortcomings and deficiencies of the existing technologies, the present invention aims to propose a cascaded heating self-cascading high-temperature heat pump system and its control method. This self-cascading high-temperature heat pump system utilizes the temperature slip characteristics of the mixed working fluid in the condenser and internal heat exchangers. The water side is first introduced into the internal multi-stream heat exchangers for heat absorption, and then passes through the condenser for further heat absorption. This cascaded heating method reduces irreversible heat exchange losses between the water and refrigerant sides. Simultaneously, leveraging the adjustable refrigerant flow rate and composition of the self-cascading heat pump system, corresponding control methods are set for different heating conditions and different air source temperatures, ensuring the efficient operation of the self-cascading high-temperature heat pump.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0006] A cascaded heating self-reinforcing high-temperature heat pump system includes a compressor 1; the compressor 1 outlet pipe is connected to the refrigerant-side inlet of a condenser 2; a first refrigerant-side outlet pipe of the condenser 2 is connected to the inlet of a first valve 16; the first valve 16 is connected to the hot-side inlet of a multi-stream heat exchanger 4; a second refrigerant-side outlet pipe of the condenser 2 is connected to the inlet of a second valve 17; the second valve 17 is connected to the inlet of a separator 3; the gas phase outlet of the separator 3 and the outlet of the first valve 16 are mixed and connected to the hot-side inlet of the multi-stream heat exchanger 4; the liquid phase outlet of the separator 3 is connected to the inlet of a first electronic expansion valve 8; the hot-side outlet of the multi-stream heat exchanger 4 is connected to the hot-side inlet of a regenerator 5; the regenerator... The hot-side outlet of 5 is connected to the inlet of the second electronic expansion valve 9; the outlet of the second electronic expansion valve 9 is connected to the inlet of the evaporator 6; the outlet of the evaporator 6 is connected to the cold-side inlet of the regenerator 5; the outlet of the first electronic expansion valve 8 is connected to the inlet of the first solenoid valve 18; the outlet of the first solenoid valve 18 and the cold-side outlet of the regenerator 5 are combined and connected to the cold-side inlet of the multi-stream heat exchanger 4; the cold-side outlet of the multi-stream heat exchanger 4 is connected to the inlet of the compressor 1; the outlet of the compressor 1 is also connected to the inlet of the second solenoid valve 13; the outlet of the second solenoid valve 13 is connected to the inlet of the gas storage tank 12; the outlet of the gas storage tank 12 is connected to the inlet of the third electronic expansion valve 14; the outlet of the third electronic expansion valve 14 is connected to the third solenoid valve 15. The inlet is connected to the compressor 1 inlet; the outlet of the third solenoid valve 15 is connected to the compressor 1 inlet; the water inlet pipe is connected to the water pump 11 inlet; the outlet of the water pump 11 is connected to the water-side inlet of the multi-stream heat exchanger 4; the water-side outlet of the multi-stream heat exchanger 4 is connected to the condenser 2 water-side inlet; the condenser 2 water-side outlet is connected to the water supply port; the input terminal of the control device 10 is connected to the first pressure sensor 101 and the first temperature sensor 102 at the compressor 1 outlet; the input terminal of the control device 10 is connected to the second temperature sensor 103 at the evaporator 6 outlet; the input terminal of the control device 10 is connected to the third temperature sensor 104 at the condenser 2 outlet; the input terminal of the control device 10 is connected to the condenser 2 water supply port. The fourth temperature sensor 105 at the side outlet is connected; the output of the control device 10 is connected to the control mechanism of the compressor 1 and the water pump 11; the output of the control device 10 is connected to the regulating mechanism of the first valve 16, the second valve 17, the first electronic expansion valve 8, the second electronic expansion valve 9, the third electronic expansion valve 14, the first solenoid valve 18, the second solenoid valve 13, and the third solenoid valve 15; during operation, the heat pump system regulates the flow rate and refrigerant component concentration in the evaporator 6 by controlling the first valve 16, the second valve 17, the first electronic expansion valve 8, and the second electronic expansion valve 9; and regulates the inlet water flow rate by controlling the speed of the water pump 11 to meet the high-temperature heating demand.

[0007] The self-cascade high-temperature heat pump system uses a binary non-azeotropic working fluid. The high-temperature, high-pressure gas, compressed by compressor 1, enters condenser 2, then flows through the first refrigerant-side outlet pipe of condenser 2 and through the first valve 16 into multi-stream heat exchanger 4. After cooling in multi-stream heat exchanger 4, it enters regenerator 5 for further cooling, then passes through the second electronic expansion valve 9 for throttling and pressure reduction before entering evaporator 6 to absorb heat. From the outlet of evaporator 6, it enters regenerator 5 and heats up before entering the cold-side inlet of multi-stream heat exchanger 4. After absorbing heat and heating up in multi-stream heat exchanger 4, it enters compressor 1. The high-temperature, high-pressure gas compressed by compressor 1 then enters condenser 2... The refrigerant enters the separator 3 via the second pipeline and the second valve 17 on the refrigerant side outlet of the condenser 2, where it is separated into a gas phase and a liquid phase. The gas phase is cooled in the multi-stream heat exchanger 4 and then enters the regenerator 5 for further cooling. After being throttled and depressurized by the second electronic expansion valve 9, it enters the evaporator 6 to absorb heat. It then enters the regenerator 5 from the outlet of the evaporator 6 and is heated. The liquid phase is throttled and depressurized by the first electronic expansion valve 8. After mixing with the refrigerant at the outlet of the regenerator 5, it enters the multi-stream heat exchanger 4 to absorb heat and is heated before entering the compressor 1. The water enters the water pump 11 for pressurization and then enters the multi-stream heat exchanger 4 for heating. After that, it passes through the condenser 2 for further heating to meet the heating demand.

[0008] Preferably, the binary non-azeotropic working fluid is composed of 50% R290 and 50% R1233zd(E) to meet the heating requirement of heating the inlet water from 15°C to 95°C.

[0009] During the startup phase of the self-cascading high-temperature heat pump system, the control device 10 receives the signal P1 from the first pressure sensor 101 at the outlet of the compressor 1, and opens the second solenoid valve 13 by controlling the control mechanism of the second solenoid valve 13, storing the refrigerant in the gas storage tank 12 to solve the problem of high startup pressure. During the heating phase of the self-cascading high-temperature heat pump system, the control device 10 opens the third electronic expansion valve 14 and the third solenoid valve 15 by controlling the control mechanism of the third electronic expansion valve 14 and the third solenoid valve 15, transferring the refrigerant in the gas storage tank 12 to the compressor 1 for circulation within the self-cascading high-temperature heat pump system. During the operation phase of the self-cascading high-temperature heat pump system, the control device 10 adjusts the opening of the first valve 16 and the second valve 17 to control the refrigerant composition and concentration at the hot side inlet of the multi-stream heat exchanger 4.

[0010] The evaporator 6 is equipped with a variable frequency fan 7, which can adapt to different working conditions with variable fan speed and save the power consumption of the fan.

[0011] The control method of a cascading heating self - cascading high - temperature heat pump system. The control device 10 collects the signals of the pressure sensors and temperature sensors in the self - cascading high - temperature heat pump system and the time signal of the system operation. The control device 10 controls the opening and closing of the first solenoid valve 18, the second solenoid valve 13, and the third solenoid valve 15, controls the opening degrees of the first electronic expansion valve 8, the second electronic expansion valve 9, the third electronic expansion valve 14, the first valve 16, and the second valve 17, and controls the start and stop of the compressor 1 to ensure the stable operation of the self - cascading high - temperature heat pump system. The safety pressure at the outlet of the compressor is P10, and the deviation value is Δ10; the safety temperature at the outlet of the compressor is T10, and the deviation value is Δ11; the set temperature of the hot water outlet is T40, and the deviation value is Δ40; the start - up time is t0. The specific control method is as follows:

[0012] 1) The control device 10 collects the operation time t of the self - cascading high - temperature heat pump system. When t < t0, the self - cascading high - temperature heat pump system is in the start - up stage. The control device 10 receives the pressure signal P1 from the first pressure sensor 101 at the outlet of the compressor 1. When P1 > P10 - Δ10, the control device 10 controls the control mechanism of the second solenoid valve 13 to open the second solenoid valve 13 and store the refrigerant in the gas storage tank 12. When P1 < P10 - Δ10, the second solenoid valve 13 is closed. The control device 10 controls the control mechanisms of the first valve 16 and the second valve 17 to close the first valve 16 and open the second valve 17. The control device 10 adjusts the opening degrees of the first electronic expansion valve 8 and the second electronic expansion valve 9 through the adjustment mechanisms to make P1 < P10 - Δ10;

[0013] 2) The control device 10 collects the operation time t of the self - cascading high - temperature heat pump system, the pressure signal P1 from the first pressure sensor 101 at the outlet of the compressor 1, the temperature signal T1 from the first temperature sensor 102, and the temperature signal T4 from the fourth temperature sensor 105 at the outlet of the hot water pipeline. When t ≥ t0 and T4 < T40 + Δ40, the self - cascading high - temperature heat pump system is in the heating - up stage. The control device 10 controls the on - off of the third solenoid valve 15 and the opening degree of the third electronic expansion valve 14 to release the refrigerant in the gas storage tank 12 into the compressor 1 for circulation in the self - cascading high - temperature heat pump system. The control device 10 increases the opening degree of the first valve 16, reduces the opening degree of the second valve 17, increases the refrigerant flow rate of the self - cascading high - temperature heat pump system, and increases the concentration of the high - boiling - point components of the refrigerant in the self - cascading high - temperature heat pump system. When T1 > T10 - Δ11, the control device 10 reduces the opening degree of the first valve 16, increases the opening degree of the second valve 17, reduces the refrigerant flow rate of the self - cascading high - temperature heat pump system, and increases the concentration of the low - boiling - point components of the refrigerant in the self - cascading high - temperature heat pump system. Ensure T4 > T40 - Δ40, T1 < T10 - Δ11, and P1 < P10 - Δ10;

[0014] 3) The control device 10 collects the temperature signal T4 of the fourth temperature sensor 105 at the outlet of the hot water pipeline, and the control device 10 collects the temperature signal T2 of the second temperature sensor 103 at the outlet of the evaporator 6; when T40 - Δ40 ≤ T4 ≤ T40 + Δ40, the auto-cascade high-temperature heat pump system is in a stable operation stage, and the compressor 1 stops operating; when the set temperature T40 increases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8, increases the opening degrees of the first valve 16 and the first electronic expansion valve 8, reduces the opening degree of the second valve 17, increases the concentration of the high-boiling component in the evaporator 6, raises the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating; when the set temperature T40 decreases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8, reduces the opening degrees of the first valve 16 and the first electronic expansion valve 8, increases the opening degree of the second valve 17, increases the concentration of the low-boiling component in the evaporator 6, reduces the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating; when the temperature signal T2 of the second temperature sensor 103 at the outlet of the evaporator 6 increases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, the first electronic expansion valve 8, and the second electronic expansion valve 9, increases the opening degrees of the first valve 16, the first electronic expansion valve 8, and the second electronic expansion valve 9, reduces the opening degree of the second valve 17, increases the concentration of the high-boiling component in the evaporator 6, raises the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating; when the temperature signal T2 of the second temperature sensor 103 at the outlet of the evaporator 6 decreases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8, reduces the opening degrees of the first valve 16, the first electronic expansion valve 8, and the second electronic expansion valve 9, increases the opening degree of the second valve 17, increases the concentration of the low-boiling component in the evaporator 6, reduces the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating; when T4 < T40 - Δ40 during the adjustment process, the control device 10 controls the regulating mechanism of the water pump 11, reduces the rotational speed of the water pump 11, and reduces the water supply side flow rate, so that the temperature signal T4 of the fourth temperature sensor 105 reaches the target temperature T40.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. Considering the significant heat exchange caused by the direct heat exchange between the water side of the heat pump system and the refrigerant inside the condenser. To address the heat loss issue, the significant temperature glide of both the condenser and internal heat exchanger in the self-cascade system is utilized. The water is first introduced into a multi-stream heat exchanger to exchange heat with the refrigerant at the separator outlet before entering the condenser for further refrigerant exchange. This improves the heat exchange between the water and the refrigerant. Losses, thereby improving system performance;

[0017] 2. Utilizing the adjustable refrigerant flow rate and component concentration within the self-cascade system, the refrigerant flow rate and the concentration of high / low boiling point circulating components within the system can be altered by regulating valves at different heating temperatures and air temperatures, thereby achieving efficient operation of the high-temperature heat pump system under various scenarios. Attached Figure Description

[0018] Figure 1 This is a flowchart of a cascaded heating self-cascading high-temperature heat pump system according to the present invention.

[0019] Figure 2 This is a temperature distribution diagram of the refrigerant side and the water side using cascade heating and direct heating methods.

[0020] Figure 3 A comparison chart of the energy efficiency of high-temperature heat pump systems at different heating temperatures for cascade heating and direct heating methods.

[0021] 1. Compressor; 2. Condenser; 3. Separator; 4. Multi-stream heat exchanger; 5. Regenerator; 6. Evaporator; 7. Variable frequency fan; 8. First electronic expansion valve; 9. Second electronic expansion valve; 10. Control device; 11. Water pump; 12. Gas receiver; 13. Second solenoid valve; 14. Third electronic expansion valve; 15. Third solenoid valve; 16. First valve; 17. Second valve; 18. First solenoid valve; 101. First pressure sensor; 102. First temperature sensor; 103. Second temperature sensor; 104. Third temperature sensor; 105. Fourth temperature sensor Detailed Implementation

[0022] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and an embodiment. It should be understood that the embodiment described herein is only for explaining the invention and is not intended to limit the invention.

[0024] Implementation Cases

[0025] like Figure 1 As shown, a cascaded heating self-reinforcing high-temperature heat pump system includes a compressor 1. The outlet pipe of the compressor 1 is connected to the refrigerant-side inlet of the condenser 2. The first refrigerant-side outlet pipe of the condenser 2 is connected to the inlet of the first valve 16. The first valve 16 is connected to the hot-side inlet of the multi-stream heat exchanger 4. The second refrigerant-side outlet pipe of the condenser 2 is connected to the inlet of the second valve 17. The second valve 17 is connected to the inlet of the separator 3. The gas phase outlet of the separator 3 and the outlet of the first valve 16 are mixed and connected to the hot-side inlet of the multi-stream heat exchanger 4. The liquid phase outlet of the separator 3 is connected to the inlet of the first electronic expansion valve 8. The hot-side outlet of the multi-stream heat exchanger 4 is connected to the hot-side inlet of the regenerator 5. The hot-side outlet of 5 is connected to the inlet of the second electronic expansion valve 9; the outlet of the second electronic expansion valve 9 is connected to the inlet of the evaporator 6; a variable frequency fan 7 is installed outside the evaporator; the outlet of the evaporator 6 is connected to the cold-side inlet of the regenerator 5; the outlet of the first electronic expansion valve 8 is connected to the inlet of the first solenoid valve 18; the outlet of the first solenoid valve 18 and the cold-side outlet of the regenerator 5 are mixed and connected to the cold-side inlet of the multi-stream heat exchanger 4; the cold-side outlet of the multi-stream heat exchanger 4 is connected to the inlet of the compressor 1; the outlet of the compressor 1 is also connected to the inlet of the second solenoid valve 13; the outlet of the second solenoid valve 13 is connected to the inlet of the gas storage tank 12; the outlet of the gas storage tank 12 is connected to the inlet of the third electronic expansion valve 14. The outlet is connected to the inlet of the third solenoid valve 15; the outlet of the third solenoid valve 15 is connected to the inlet of the compressor 1; the water inlet pipe is connected to the inlet of the water pump 11; the outlet of the water pump 11 is connected to the water-side inlet of the multi-stream heat exchanger 4; the water-side outlet of the multi-stream heat exchanger 4 is connected to the water-side inlet of the condenser 2; the water-side outlet of the condenser 2 is connected to the water supply port; the input terminal of the control device 10 is connected to the first pressure sensor 101 and the first temperature sensor 102 at the outlet of the compressor 1; the input terminal of the control device 10 is connected to the second temperature sensor 103 at the outlet of the evaporator 6; the input terminal of the control device 10 is connected to the third temperature sensor 104 at the outlet of the condenser 2; the input terminal of the control device 10... The output of the control device 10 is connected to the fourth temperature sensor 105 at the water outlet of the condenser 2; the output of the control device 10 is connected to the control mechanism of the compressor 1; the output of the control device 10 is connected to the regulating mechanism of the first valve 16, the second valve 17, the first electronic expansion valve 8, the second electronic expansion valve 9, the third electronic expansion valve 14, the first solenoid valve 18, the second solenoid valve 13, and the third solenoid valve 15; during operation, the heat pump system controls the flow rate and refrigerant component concentration in the evaporator 6 through the first valve 16, the second valve 17, the first electronic expansion valve 8, and the second electronic expansion valve 9; and adjusts the inlet water flow rate by controlling the speed of the water pump 11 to meet the high-temperature heating demand.

[0026] The cascaded high-temperature heat pump system of this invention employs a binary non-azeotropic working fluid. The high-temperature, high-pressure gas, compressed by compressor 1, enters condenser 2, and then flows through first valve 16 into multi-stream heat exchanger 4. After cooling in multi-stream heat exchanger 4, it enters regenerator 5 for further cooling, and then, after being throttled and depressurized by second electronic expansion valve 9, enters evaporator 6 to absorb heat. From the outlet of evaporator 6, it enters regenerator 5 for heating and then enters the cold-side inlet of multi-stream heat exchanger 4. After absorbing heat and heating in multi-stream heat exchanger 4, it enters compressor 1. The high-temperature, high-pressure gas compressed by compressor 1 enters condenser 2 and then, via the second pipe and second valve 17 at the refrigerant side outlet of condenser 2, enters separator 3, where it is separated into gas and liquid phases. The gas phase is rich in low-boiling-point components, and the liquid phase is rich in high-boiling-point components. The gas phase, after cooling in multi-stream heat exchanger 4, enters regenerator 5 for further cooling. Heater 5 continues to cool down, then enters evaporator 6 to absorb heat after being throttled and depressurized by the second electronic expansion valve 9; it then enters regenerator 5 from the outlet of evaporator 6 to be heated; the liquid phase is throttled and depressurized by the first electronic expansion valve 8; then it mixes with the refrigerant at the outlet of regenerator 5 and enters multi-stream heat exchanger 4 to absorb heat and be heated before entering compressor 1; at the same time, the outlet of condenser 2 can mix with the gas phase separated after entering the separator via the second valve 17 after passing through the first valve 16 and enters multi-stream heat exchanger 4. Since the refrigerant composition at the outlet of condenser and the gas phase refrigerant composition separated by the separator are different, the component concentration and refrigerant flow rate entering the multi-stream heat exchanger, regenerator and evaporator can be adjusted by mixing the two flow rates; water enters water pump 11 to be pressurized and then enters multi-stream heat exchanger 4 for heating, and then passes through condenser 2 for further heating to meet the heating demand.

[0027] The present invention discloses a control method for a cascaded high-temperature heat pump system. The control device 10 collects signals from pressure and temperature sensors within the system, along with system operation time signals. The control device 10 controls the opening and closing of the first solenoid valve 18, the second solenoid valve 13, and the third solenoid valve 15. It also controls the opening degrees of the first electronic expansion valve 8, the second electronic expansion valve 9, the third electronic expansion valve 14, the first valve 16, and the second valve 17. Finally, the control device 10 controls the start and stop of the compressor 1, ensuring stable operation of the cascaded high-temperature heat pump system. The compressor outlet safety pressure P10 is 2.5 MPa, with a deviation of Δ10 of 0.02 MPa. The compressor outlet safety temperature T10 is 125°C, with a deviation of Δ11 of 2°C. The hot water outlet temperature setting range T40 is 70–95°C, with a deviation of Δ40 of 2°C. The start-up time t0 is 20 minutes. The specific control method is as follows:

[0028] 1) The control device 10 collects the operating time t of the cascade high-temperature heat pump system. When t < 20 min, the cascade high-temperature heat pump system is in the startup phase, and the control device 10 receives the pressure signal P1 from the first pressure sensor 101 at the outlet of the compressor 1. When P1 > 2.48 MPa, the control device 10 controls the control mechanism of the second solenoid valve 13 to open the second solenoid valve 13 and store the refrigerant in the gas storage tank 12. When P1 < 2.48 MPa, the second solenoid valve 13 is closed. The control device 10 controls the control mechanisms of the first valve 16 and the second valve 17 to close the first valve 16 and open the second valve 17. The control device 10 adjusts the opening degrees of the first electronic expansion valve 8 and the second electronic expansion valve 9 through their regulating mechanisms to make P1 < 2.48 MPa.

[0029] 2) The control device 10 collects the operating time t of the cascade high-temperature heat pump system, the pressure signal P1 from the first pressure sensor 101 at the outlet of the compressor 1, the temperature signal T1 from the first temperature sensor 102, and the temperature signal T4 from the fourth temperature sensor 105 at the outlet of the hot water pipeline. When t ≥ t0 and T4 < T40 + Δ40, where the range of T40 + Δ40 is 72 - 97 °C, the cascade high-temperature heat pump system is in the heating-up phase. The control device 10 controls the opening of the third solenoid valve 15 and the opening degree of the third electronic expansion valve 14 to release the refrigerant in the gas storage tank 12 into the compressor 1 for circulation in the cascade high-temperature heat pump system. The control device 10 increases the opening degree of the first valve (16) and decreases the opening degree of the second valve 17 with an opening degree adjustment step of 5% to increase the refrigerant flow rate of the cascade high-temperature heat pump system and increase the concentration of the high-boiling-point component of the refrigerant in the cascade high-temperature heat pump system. When T1 > 123 °C, the control device 10 decreases the opening degree of the first valve 16 and increases the opening degree of the second valve 17 with an opening degree adjustment step of 5% to decrease the refrigerant flow rate of the cascade high-temperature heat pump system and increase the concentration of the low-boiling-point component of the refrigerant in the cascade high-temperature heat pump system. Ensure that T4 > T40 - Δ40, T1 < 123 °C, and P1 < 2.48 MPa, where the range of T40 - Δ40 is 68 - 93 °C.

[0030] 3) Control device 10 collects the temperature signal T4 from the fourth temperature sensor 105 at the outlet of the hot water pipe and the temperature signal T2 from the second temperature sensor 103 at the outlet of the evaporator 6. When T40-Δ40≤T4≤T40+Δ40, the range of T40-Δ40 is 68~93℃, and the range of T40+Δ40 is 72~97℃. The self-cascade high-temperature heat pump system is in a stable operating phase, and compressor 1 is shut down. When the set temperature T40 increases, control device 10 controls the adjustment mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8 to increase the opening of the first valve 16 and the first electronic expansion valve 8, and decrease the opening of the second valve 17. The adjustment step of the first valve 16 and the second valve 17 is 5%, and the adjustment step of the first electronic expansion valve 8 is 10%, which increases the concentration of high-boiling-point components in the evaporator 6 and increases the exhaust gas of compressor 1. The temperature is set to meet the current heating demand, ensuring that the temperature signal T1 from the first temperature sensor 102 at the compressor 1 outlet is <123℃, and that T40-Δ40≤T4≤T40+Δ40. After this, the compressor 1 stops operating. When the set temperature T40 decreases, the control device 10 controls the adjustment mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8, reducing the opening of the first valve 16 and the first electronic expansion valve 8, and increasing the opening of the second valve 17. The adjustment step of the first valve 16 and the second valve 17 is 5%, and the adjustment step of the first electronic expansion valve 8 is 10%. This increases the concentration of low-boiling-point components in the evaporator 6, reduces the discharge temperature of the compressor 1, meets the current heating demand, ensures that the temperature signal T1 from the first temperature sensor 102 at the compressor 1 outlet is <123℃, and that T40-Δ40≤T4≤T40+Δ40. After this, the compressor 1 stops operating.When the temperature signal T2 of the second temperature sensor 103 at the outlet of the evaporator 6 increases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, the first electronic expansion valve 8, and the second electronic expansion valve 9, increases the opening degrees of the first valve 16, the first electronic expansion valve 8, and the second electronic expansion valve 9, decreases the opening degree of the second valve 17, increases the concentration of the high-boiling component in the evaporator 6, raises the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 + Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating; when the temperature signal T2 of the second temperature sensor 103 at the outlet of the evaporator 6 decreases, the control device 10 controls the regulating mechanisms of the first valve 16, the second valve 17, and the first electronic expansion valve 8, decreases the opening degrees of the first valve 16, the first electronic expansion valve 8, and the second electronic expansion valve 9, increases the opening degree of the second valve 17, increases the concentration of the low-boiling component in the evaporator 6, reduces the exhaust temperature of the compressor 1, meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor 102 at the outlet of the compressor 1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor 1 stops operating. When T4 < T40 - Δ40 during the adjustment process, the control device controls the regulating mechanism of the water pump, reduces the rotational speed of the water pump 11, and reduces the water supply side flow rate, so that the temperature signal T4 of the fourth temperature sensor 105 reaches the target temperature T40.

[0031] As Figure 2 shown, a cascaded heating self - cascading high - temperature heat pump system uses a binary azeotropic mixture of R290 and R1233zd(E) each accounting for 50% to meet the heating demand of heating the inlet water temperature from 15°C to 95°C. When direct heating is adopted, that is, the water side is directly heated in the condenser, the heat transfer temperature difference between the refrigerant side and the water side is relatively large. When cascaded heating is adopted, the water side first passes through a multi - stream heat exchanger and then through the condenser. After passing through the multi - stream heat exchanger, the intermediate stage temperature is heated to 55°C, and the heat transfer temperature difference between the refrigerant side and the water side is reduced, Figure 2 and the area A in it is reduced, that is, the heat transfer loss is reduced.

[0032] As Figure 3 shown, for the energy efficiency comparison of a cascaded heating self - cascading high - temperature heat pump system in different heating temperatures in the cascaded heating and direct heating forms, the direct heating form is that the water side (inlet water temperature 15°C) is directly heated to the heating temperature through the condenser, and the cascaded heating form is that the water side (inlet water temperature 15°C) first passes through a multi - stream heat exchanger to be heated to the intermediate stage temperature (55°C) and then through the condenser heater to the heating temperature. It can be seen from the figure that when the cascaded heating form is adopted, the coefficient of performance COP of the high - temperature heat pump system hCompared to direct heating, the refrigerant flow rate increased by 43.2% to 53.5%, while the refrigerant flow rate required for the cascade heating method was reduced by 55.98% to 68.72% compared to direct heating under the same heat supply conditions. Therefore, it can be demonstrated that the energy efficiency of the self-cascade high-temperature heat pump system with cascade heating described in this invention is significantly improved, and the refrigerant flow rate is significantly reduced.

Claims

1. A cascaded heating self-cascading high-temperature heat pump system, characterized in that, The system includes a compressor (1), whose outlet pipe is connected to the refrigerant side inlet of the condenser (2); the first outlet pipe of the refrigerant side of the condenser (2) is connected to the inlet of the first valve (16); the first valve (16) is connected to the hot side inlet of the multi-stream heat exchanger (4); the second outlet pipe of the refrigerant side of the condenser (2) is connected to the inlet of the second valve (17); the second valve (17) is connected to the inlet of the separator (3); the gas phase outlet of the separator (3) and the outlet of the first valve (16) are mixed and connected to the hot side inlet of the multi-stream heat exchanger (4); the liquid phase outlet of the separator (3) is connected to the inlet of the first electronic expansion valve (8); the hot side outlet of the multi-stream heat exchanger (4) is connected to the hot side inlet of the regenerator (5); and the hot side outlet of the regenerator (5) is connected to the first... The inlet of the second electronic expansion valve (9) is connected; the outlet of the second electronic expansion valve (9) is connected to the inlet of the evaporator (6); the outlet of the evaporator (6) is connected to the cold-side inlet of the regenerator (5); the outlet of the first electronic expansion valve (8) is connected to the inlet of the first solenoid valve (18); the outlet of the first solenoid valve (18) and the cold-side outlet of the regenerator (5) are mixed and connected to the cold-side inlet of the multi-stream heat exchanger (4); the cold-side outlet of the multi-stream heat exchanger (4) is connected to the inlet of the compressor (1); the outlet of the compressor (1) is also connected to the inlet of the second solenoid valve (13); the outlet of the second solenoid valve (13) is connected to the inlet of the gas storage tank (12); the outlet of the gas storage tank (12) is connected to the inlet of the third electronic expansion valve (14); the outlet of the third electronic expansion valve (14) is connected to the third solenoid valve (13). The valve (15) inlet is connected; the outlet of the third solenoid valve (15) is connected to the compressor (1) inlet; the water inlet pipe is connected to the water pump (11) inlet; the water pump (11) outlet is connected to the water-side inlet of the multi-stream heat exchanger (4); the water-side outlet of the multi-stream heat exchanger (4) is connected to the water-side inlet of the condenser (2); the water-side outlet of the condenser (2) is connected to the water supply port; the input end of the control device (10) is connected to the first pressure sensor (101) and the first temperature sensor (102) at the compressor (1) outlet; the input end of the control device (10) is connected to the second temperature sensor (103) at the evaporator (6) outlet; the input end of the control device (10) is connected to the third temperature sensor (104) at the condenser (2) outlet; the control device... The input end of the device (10) is connected to the fourth temperature sensor (105) at the water side outlet of the condenser (2); the output end of the control device (10) is connected to the control mechanism of the compressor (1) and the water pump (11); the output end of the control device (10) is connected to the regulating mechanism of the first valve (16), the second valve (17), the first electronic expansion valve (8), the second electronic expansion valve (9), the third electronic expansion valve (14), the first solenoid valve (18), the second solenoid valve (13), and the third solenoid valve (15); during operation, the heat pump system regulates the flow rate and refrigerant component concentration in the evaporator (6) by controlling the first valve (16), the second valve (17), the first electronic expansion valve (8), and the second electronic expansion valve (9);The inlet water flow rate is adjusted by controlling the speed of the water pump (11) to meet the high-temperature heating demand; During the startup phase of the self-cascading high-temperature heat pump system, the control device (10) receives the signal P1 from the first pressure sensor (101) at the outlet of the compressor (1), and opens the second solenoid valve (13) by controlling the control mechanism of the second solenoid valve (13) to store the refrigerant in the gas storage tank (12) to solve the problem of high startup pressure. During the heating phase of the self-cascading high-temperature heat pump system, the control device (10) opens the third electronic expansion valve (14) and the third solenoid valve (15) by controlling the control mechanism of the third electronic expansion valve (14) and the third solenoid valve (15) to transfer the refrigerant in the gas storage tank (12) to the compressor (1) for circulation within the self-cascading high-temperature heat pump system. During the operation phase of the self-cascading high-temperature heat pump system, the control device (10) adjusts the opening of the first valve (16) and the second valve (17) to control the refrigerant composition and concentration at the hot side inlet of the multi-stream heat exchanger (4).

2. The cascaded heating self-cascading high-temperature heat pump system according to claim 1, characterized in that, The self-cascade high-temperature heat pump system uses a binary non-azeotropic mixture as the working fluid. The high-temperature and high-pressure gas, after being compressed by the compressor (1), enters the condenser (2), and then enters the multi-stream heat exchanger (4) through the first pipe of the refrigerant side outlet of the condenser (2) and through the first valve (16). After being cooled in the multi-stream heat exchanger (4), it enters the regenerator (5) for further cooling, and then enters the evaporator (6) for heat absorption after being throttled and depressurized by the second electronic expansion valve (9). After being heated from the outlet of the evaporator (6) into the regenerator (5), it enters the cold side inlet of the multi-stream heat exchanger (4). After being heated in the multi-stream heat exchanger (4), it enters the compressor (1). The high-temperature and high-pressure gas, after being compressed by the compressor (1), enters the condenser (2) and then... The refrigerant enters the separator (3) through the second pipeline and the second valve (17) on the refrigerant side outlet of the condenser (2) and is separated into gas phase and liquid phase. The gas phase is cooled in the multi-stream heat exchanger (4) and then enters the regenerator (5) for further cooling. After being throttled and depressurized by the second electronic expansion valve (9), it enters the evaporator (6) to absorb heat. It enters the regenerator (5) from the outlet of the evaporator (6) and is heated. The liquid phase is throttled and depressurized by the first electronic expansion valve (8). After being mixed with the refrigerant at the outlet of the regenerator (5), it enters the multi-stream heat exchanger (4) to absorb heat and be heated before entering the compressor (1). The water enters the water pump (11) for pressurization and then enters the multi-stream heat exchanger (4) for heating. After being heated again by the condenser (2), it meets the heating demand.

3. The cascaded heating self-cascading high-temperature heat pump system according to claim 2, characterized in that, The binary non-azeotropic working fluid uses 50% R290 and 50% R1233zd(E) to meet the heating requirement of heating the inlet water from 15℃ to 95℃.

4. The cascaded heating self-cascading high-temperature heat pump system according to claim 1, characterized in that, The evaporator (6) is equipped with a variable frequency fan (7).

5. A control method for a cascaded heating self-cascading high-temperature heat pump system according to any one of claims 1 to 4, characterized in that, The control device (10) collects signals from the pressure sensors and temperature sensors in the cascade high-temperature heat pump system and the time signal of the system operation. The control device (10) controls the on / off of the first solenoid valve (18), the second solenoid valve (13), and the third solenoid valve (15). The control device (10) controls the opening degrees of the first electronic expansion valve (8), the second electronic expansion valve (9), the third electronic expansion valve (14), the first valve (16), and the second valve (17). The control device (10) controls the start / stop of the compressor (1) to ensure the stable operation of the cascade high-temperature heat pump system; the safety pressure at the outlet of the compressor is P10, and the deviation value is Δ10; The safety temperature at the outlet of the compressor is T10, and the deviation value is Δ11; the set temperature of the hot water outlet is T40, and the deviation value is Δ40; the start time is t0; the specific control method is as follows: 1) The control device (10) collects the operation time t of the cascade high-temperature heat pump system. When t < t0, the cascade high-temperature heat pump system is in the startup stage. The control device (10) receives the pressure signal P1 from the first pressure sensor (101) at the outlet of the compressor (1). When P1 > P10 - Δ10, the control device (10) controls the control mechanism of the second solenoid valve (13) to open the second solenoid valve (13) and store the refrigerant in the gas storage tank (12). When P1 < P10 - Δ10, the second solenoid valve (13) is closed; the control device (10) controls the control mechanisms of the first valve (16) and the second valve (17) to close the first valve (16) and open the second valve (17); the control device (10) adjusts the opening degrees of the first electronic expansion valve (8) and the second electronic expansion valve (9) by controlling the adjustment mechanisms of the first electronic expansion valve (8) and the second electronic expansion valve (9) so that P1 < P10 - Δ10; 2) The control device (10) collects the operating time t of the cascade high-temperature heat pump system, the pressure signal P1 of the first pressure sensor (101) at the outlet of the compressor (1), the temperature signal T1 of the first temperature sensor (102), and the temperature signal T4 of the fourth temperature sensor (105) at the outlet of the hot water pipeline; when t≥t0 and T4<T40+Δ40, the cascade high-temperature heat pump system is in the heating stage, and the control device (10) controls the on / off of the third solenoid valve (15) and the opening degree of the third electronic expansion valve (14), releases the refrigerant in the gas storage tank (12) into the compressor (1) to circulate in the cascade high-temperature heat pump system, the control device (10) increases the opening degree of the first valve (16), decreases the opening degree of the second valve (17), increases the refrigerant flow rate of the cascade high-temperature heat pump system, and increases the concentration of the high-boiling-point component of the refrigerant in the cascade high-temperature heat pump system; when T1>T10-Δ11, the control device (10) decreases the opening degree of the first valve (16), increases the opening degree of the second valve (17), decreases the refrigerant flow rate of the cascade high-temperature heat pump system, and increases the concentration of the low-boiling-point component of the refrigerant in the cascade high-temperature heat pump system; ensure that T4>T40-Δ40, T1<T10-Δ11, and P1<P10-Δ10; 3) The control device (10) collects the temperature signal T4 of the fourth temperature sensor (105) at the outlet of the hot water pipeline, and the control device (10) collects the temperature signal T2 of the second temperature sensor (103) at the outlet of the evaporator (6); when T40 - Δ40 ≤ T4 ≤ T40 + Δ40, the auto-cascade high-temperature heat pump system is in a stable operation stage, and the compressor (1) stops operating; when the set temperature T40 increases, the control device (10) controls the regulating mechanisms of the first valve (16), the second valve (17), and the first electronic expansion valve (8), increases the opening degrees of the first valve (16) and the first electronic expansion valve (8), reduces the opening degree of the second valve (17), increases the concentration of the high-boiling-point component in the evaporator (6), raises the exhaust temperature of the compressor (1), meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor (102) at the outlet of the compressor (1) < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor (1) stops operating; when the set temperature T40 decreases, the control device (10) controls the regulating mechanisms of the first valve (16), the second valve (17), and the first electronic expansion valve (8), reduces the opening degrees of the first valve (16) and the first electronic expansion valve (8), increases the opening degree of the second valve (17), increases the concentration of the low-boiling-point component in the evaporator (6), reduces the exhaust temperature of the compressor (1), meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor (102) at the outlet of the compressor (1) < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor (1) stops operating; when the temperature signal T2 of the second temperature sensor (103) at the outlet of the evaporator (6) increases, the control device (10) controls the regulating mechanisms of the first valve (16), the second valve (17), the first electronic expansion valve (8), and the second electronic expansion valve (9), increases the opening degrees of the first valve (16), the first electronic expansion valve (8), and the second electronic expansion valve (9), reduces the opening degree of the second valve (17), increases the concentration of the high-boiling-point component in the evaporator (6), raises the exhaust temperature of the compressor (1), meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor (102) at the outlet of the compressor (1) < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor (1) stops operating;When the temperature signal T2 of the second temperature sensor (103) at the outlet of the evaporator (6) decreases, the control device (10) controls the regulating mechanisms of the first valve (16), the second valve (17), and the first electronic expansion valve (8), reduces the opening degrees of the first valve (16), the first electronic expansion valve (8), and the second electronic expansion valve (9), increases the opening degree of the second valve (17), increases the concentration of the low-boiling component in the evaporator (6), reduces the exhaust temperature of the compressor (1), meets the heating demand at this time, ensures that the temperature signal T1 of the first temperature sensor (102) at the outlet of the compressor (1) is T1 < T10 - Δ11, ensures that T40 - Δ40 ≤ T4 ≤ T40 + Δ40, and then the compressor (1) stops operating; when T4 < T40 - Δ40 during the adjustment process, the control device (10) controls the regulating mechanism of the water pump (11), reduces the rotational speed of the water pump (11), reduces the water supply side flow rate, and makes the temperature signal T4 of the fourth temperature sensor (105) reach the target temperature T40.;

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