A jet augmenting high-temperature heat pump system and a capacity configuration method thereof

Abstract

This invention discloses a vapor-jet enthalpy-increasing cascade high-temperature heat pump system and its capacity method. The system uses a low-temperature flash evaporator and a high-temperature flash evaporator to perform gas-liquid separation of the two-stage circulating refrigerant. The gaseous refrigerant separated by the low-temperature flash evaporator enters the compressor's gas supply port in the low-temperature cycle, and the gaseous refrigerant separated by the high-temperature flash evaporator enters the compressor's gas supply port in the high-temperature cycle. The capacity method calculates thermodynamic parameters such as heating capacity, condenser outlet steam temperature, and flow rate using a heat pump cycle simulation model and a heat and mass transfer model. Then, by adjusting the condensing pressure, evaporating pressure, and the pinch point temperatures of the condenser, condenser-evaporator, and evaporator, the desired subcooling, superheating, intermediate temperature, and high / low-temperature flash evaporator outlet temperature are achieved. This invention increases the flow rate of gaseous refrigerant entering the compressor, improves the coefficient of performance of the vapor-jet enthalpy-increasing cascade high-temperature heat pump system under low-temperature conditions, and avoids increasing system complexity.

Description

Technical Field

[0001] This invention relates to the field of vapor-induced enthalpy-enhanced heat pump technology, and in particular to a vapor-induced enthalpy-enhanced cascade high-temperature heat pump system and its capacity configuration method. Background Technology

[0002] High-temperature air source heat pump technology, as a high-energy-consuming technology, is currently widely used in various industries, including food, printing and dyeing, papermaking, chemical, drying, and distillation. As the ambient temperature of the system's low-temperature operating environment further decreases, the compressor's operating pressure ratio increases significantly, and the exhaust temperature rises sharply, resulting in a significant decrease in both compression efficiency and reliability. Furthermore, as the system's high-temperature operating temperature further increases, the compressor's operating pressure differential and load increase substantially, leading to a decline in compressor reliability and performance. This greatly affects the comfort, energy efficiency, and reliability of air source heat pump technology when used in harsher cold / hot regions. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a jet-enthalpy-enhanced cascade high-temperature heat pump system and its capacity configuration method, which can effectively increase the system's heating capacity, reduce the compressor's exhaust temperature, and improve the coefficient of performance of the jet-enthalpy-enhanced cascade high-temperature heat pump system under low-temperature conditions.

[0004] Technical solution: A jet-induced enthalpy-increasing cascade high-temperature heat pump system, comprising an evaporator, a low-temperature compressor, a condenser-evaporator, a first low-temperature expansion valve, a low-temperature flash evaporator, a second low-temperature expansion valve, a high-temperature compressor, a condenser, a first high-temperature expansion valve, a high-temperature flash evaporator, a second high-temperature expansion valve, and a water pump; wherein, the first channel of the low-temperature compressor, the first channel of the condenser-evaporator, the first low-temperature expansion valve, the low-temperature flash evaporator, the second low-temperature expansion valve, and the first channel of the evaporator are sequentially connected through refrigerant piping to form a low-temperature refrigerant circulation loop; the first channel of the high-temperature compressor, the first channel of the condenser, the first high-temperature expansion valve, the high-temperature flash evaporator, the second high-temperature expansion valve, and the second channel of the condenser-evaporator are sequentially connected through refrigerant piping to form a high-temperature refrigerant circulation loop;

[0005] The water pump is connected to the condenser.

[0006] Furthermore, in the cryogenic refrigerant circulation loop, the outlet of the cryogenic compressor is connected to the inlet of the first channel of the condenser-evaporator via a refrigerant line; the outlet of the first channel of the condenser-evaporator is connected to the inlet of the first cryogenic expansion valve via a refrigerant line; the outlet of the first cryogenic expansion valve is connected to the inlet of the cryogenic flash evaporator via a refrigerant line; the gas outlet of the cryogenic flash evaporator is connected to the gas supply inlet of the cryogenic compressor via a refrigerant line; the liquid outlet of the cryogenic flash evaporator is connected to the inlet of the second cryogenic expansion valve via a refrigerant line; the outlet of the second cryogenic expansion valve is connected to the inlet of the first channel of the evaporator via a refrigerant line; and the outlet of the first channel of the evaporator is connected to the inlet of the cryogenic compressor via a refrigerant line.

[0007] In the high-temperature refrigerant circulation loop, the outlet of the high-temperature compressor is connected to the inlet of the first channel of the condenser through a refrigerant line. The outlet of the first channel of the condenser is connected to the inlet of the first high-temperature expansion valve through a refrigerant line. The outlet of the first high-temperature expansion valve is connected to the inlet of the high-temperature flash evaporator through a refrigerant line. The gas outlet of the high-temperature flash evaporator is connected to the gas supply inlet of the high-temperature compressor through a refrigerant line. The liquid outlet of the high-temperature flash evaporator is connected to the inlet of the second high-temperature expansion valve through a refrigerant line. The outlet of the second high-temperature expansion valve is connected to the inlet of the second channel of the condenser-evaporator through a refrigerant line. The outlet of the second channel of the condenser-evaporator is connected to the inlet of the high-temperature compressor through a refrigerant line.

[0008] The capacity configuration method for any of the above-mentioned jet enthalpy-enhanced cascade high-temperature heat pump systems includes the following steps:

[0009] S1. Determine the type of refrigerant for high / low temperature cycles, the boundary and demand conditions of the vapor entering the condenser outlet, the environmental conditions, and determine the geometry of the entire vapor injection enthalpy-increasing cascade high-temperature heat pump system.

[0010] S2, Substitute the set conditions in step S1 into the heat pump cycle simulation model to calculate the refrigerant thermodynamic parameters at the outlet of the compressor, condenser and evaporator of the heat pump system, the condenser heating capacity, the compressor power consumption, the refrigerant circulation flow rate and COP.

[0011] If the system's heating capacity does not meet the feedforward demand, the condenser outlet steam flow rate is adjusted by increasing it by one step from the current value, and the calculation continues.

[0012] If the system's heating capacity meets the feedforward requirement, the COP of the jet enthalpy-increasing cascade high-temperature heat pump system is compared with the preset value A. If the COP is greater than the preset value A, all assumed thermodynamic parameters and thermodynamic calculation results are saved and output as the current optimal values ​​for the current calculation stage. If the COP is less than or equal to the preset value A, the saving step is skipped and the condenser outlet steam temperature is directly checked to see if it meets the requirement. If it does not meet the requirement, the condenser outlet refrigerant temperature is adjusted. If the condenser outlet steam temperature is too high, the condenser outlet refrigerant temperature is lowered; if the condenser outlet steam temperature is too low, the condenser outlet refrigerant temperature is increased. Then, the COP is recalculated according to the design method.

[0013] If the condenser outlet steam temperature has reached its maximum value B, determine if the outlet temperature of the second channel of the condenser-evaporator has reached its maximum value C. If it has not yet reached maximum value C, increase the outlet temperature of the second channel of the condenser-evaporator by one step and continue the calculation. If it has reached maximum value C, determine if the outlet temperature of the low-temperature flash evaporator has reached its maximum value D. If it has not yet reached maximum value D, increase the outlet temperature of the low-temperature flash evaporator by one step and continue the calculation. If it has reached maximum value D, determine if the outlet temperature of the high-temperature flash evaporator has reached its maximum value E. If it has not yet reached maximum value E, increase the outlet temperature of the high-temperature flash evaporator by one step. The temperature is increased by one step, and the calculation continues. If the maximum value E has been reached, it is determined whether the subcooling of the heat pump system has reached the maximum value F. If it has not yet reached the maximum value F, the condensing pressure is increased by one step, and the calculation continues. If the maximum value F has been reached, it is determined whether the superheat of the heat pump system has reached the maximum value G. If it has not yet reached the maximum value G, the evaporating pressure is decreased by one step, and the calculation continues. If the maximum value G has been reached, the entire calculation process ends. The final output is the optimal operating state of the system corresponding to the highest COP in all iterative calculation steps, as well as the capacity of each device.

[0014] Furthermore, after calculating thermodynamic parameters such as heating capacity, condenser outlet steam temperature, and flow rate using a heat pump cycle simulation model and a heat and mass transfer model, the required subcooling, superheating, intermediate temperature, and high / low temperature flash evaporator outlet temperature are achieved by adjusting the condensing pressure, evaporating pressure, and the pinch point temperatures of the condenser, condenser-evaporator, and evaporator. The heat pump cycle simulation model includes a compressor model, a condenser model, an expansion valve model, an evaporator model, and a flash evaporator model. The expressions for each model are as follows:

[0015] The compressor power consumption and actual outlet specific enthalpy are:

[0016]

[0017] In the formula, h″ is the outlet specific enthalpy of the isentropic compression process, kJ / kg; h′ is the intake specific enthalpy, kJ / kg; η s P is the isentropic efficiency of the compressor. c The power consumption of the compressor is measured in kW and m. c The compressor flow rate is expressed in kg / s or h. o ′ ut The actual specific enthalpy at the compressor outlet, kJ / kg;

[0018] In each region of the evaporator and condenser, the heat exchange on the refrigerant side, wall side, and air / water side all satisfy the following equation:

[0019]

[0020] In the formula, Q r For heat exchange with refrigerant, kW; Q w For wall heat exchange, kW; Q a For air heat exchange, kW; q mr q ma These are the mass flow rates of refrigerant and air, respectively, in kg / s; These are the inlet and outlet specific enthalpies of the refrigerant, respectively, in kJ / kg; Specific enthalpy of air inlet and outlet, respectively, kJ / kg; A w For heat exchange area, m 2 ΔT is the heat exchange temperature difference, in °C; H a H r The convective heat transfer coefficients of air and refrigerant, respectively, in kW / (m²). 2 .℃); R is the wall thermal resistance;

[0021] The relationship between the refrigerant enthalpy values ​​on both sides of the expansion valve is as follows:

[0022]

[0023] In the formula, These are the specific enthalpy at the inlet and outlet of the expansion valve, respectively, in kJ / kg;

[0024] The relationship between the vapor phase fraction 'a' of the flash evaporator and the inlet and outlet enthalpies is as follows:

[0025]

[0026] In the formula, and The specific enthalpy (kJ / kg) represents the liquid phase at the inlet and outlet of the flash evaporator, and the vapor phase at the outlet.

[0027] Furthermore, the initial flow rate step size is set to 5%-10% of the system's rated flow rate, gradually decreasing to 1%-2% with iteration; the initial step size for the condenser, condenser-evaporator, evaporator pinch point temperature, and condenser outlet steam temperature is set to 1-2% of the current temperature, gradually decreasing to 0.5℃ with iteration.

[0028] Compared with the prior art, the significant advantages of this invention are as follows:

[0029] 1. The jet enthalpy-increasing cascade high-temperature heat pump system of the present invention performs gas-liquid separation of the two-stage circulating refrigerant through a low-temperature flash evaporator and a high-temperature flash evaporator respectively. The gaseous refrigerant separated by the low-temperature flash evaporator enters the gas injection port of the compressor in the low-temperature cycle, and the gaseous refrigerant separated by the high-temperature flash evaporator enters the gas injection port of the compressor in the high-temperature cycle. This increases the flow rate of gaseous refrigerant into the compressor, improves the performance coefficient of the jet enthalpy-increasing cascade high-temperature heat pump system under low-temperature conditions, avoids increasing system complexity, enhances low-temperature heating capacity, strengthens system reliability, and achieves significant energy-saving effects.

[0030] 2. The capacity configuration method of this invention mainly calculates thermodynamic parameters such as heating capacity, condenser outlet steam temperature, and flow rate using a heat pump cycle simulation model and a heat and mass transfer model. Then, by adjusting the condensing pressure, evaporating pressure, and the pinch point temperatures of the condenser, condenser-evaporator, and evaporator, the desired subcooling, superheating, intermediate temperature, and high / low temperature flash evaporator outlet temperature are achieved. This significantly improves heating capacity, broadens the system's operating temperature range to adapt to various environments, and enhances system stability. Simultaneously, it optimizes system performance, enabling the system to consume less electrical energy to generate more heat during operation, thus promoting the decarbonization process of the thermal system. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the jet enthalpy-enhancing cascade high-temperature heat pump system of the present invention.

[0032] Figure 2 This is a flowchart of the capacity configuration method for the jet-induced enthalpy-enhanced cascade high-temperature heat pump system of the present invention.

[0033] Figure 3 (a) is a schematic diagram of steam generation in a conventional cascade heat pump system, (b) is a schematic diagram of steam generation in the first jet enthalpy-enhanced cascade heat pump system A, and (c) is a schematic diagram of steam generation in the second jet enthalpy-enhanced cascade heat pump system B.

[0034] Figure 4 This is a schematic diagram showing the comparison of COP results for various cascade heat pump systems under standard operating conditions.

[0035] Figure 5(a) is a schematic diagram comparing the compressor power consumption of each cascade heat pump system under different heat source temperatures;

[0036] Figure 5(b) is a schematic diagram showing the comparison of COP of each cascade heat pump system under different heat source temperatures;

[0037] Figure label:

[0038] 1-Evaporator, 2-Low-temperature compressor, 3-Condenser-evaporator, 4-First low-temperature expansion valve, 5-Low-temperature flash evaporator, 6-Second low-temperature expansion valve, 7-High-temperature compressor, 8-Condenser, 9-First high-temperature expansion valve, 10-High-temperature flash evaporator, 11-Second high-temperature expansion valve, 12-Water pump. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] Enhanced vapor injection (EVI) high-temperature heat pump technology boasts advantages such as high efficiency and energy saving, excellent low-temperature performance, environmental friendliness, and high automation. Common EVI high-temperature heat pump units include a compressor, condenser, evaporator, expansion valve, and flash evaporator. During operation, the refrigerant at the condenser outlet is throttled and enters the flash evaporator in a two-phase gas-liquid state. Due to the reduced velocity, the gas and liquid separate. The gaseous portion mixes with the initially compressed refrigerant gas and undergoes further compression, while the liquid portion, after a second throttling, enters the evaporator for heat exchange. The reduced specific enthalpy at the evaporator inlet effectively improves the evaporator's heat absorption capacity, thereby enhancing the system's heating efficiency.

[0041] like Figure 1 As shown, the vapor-jet enthalpy-increasing cascade high-temperature heat pump system of this invention includes an evaporator 1, a low-temperature compressor 2, a condenser-evaporator 3, a first low-temperature expansion valve 4, a low-temperature flash evaporator 5, a second low-temperature expansion valve 6, a high-temperature compressor 7, a condenser 8, a first high-temperature expansion valve 9, a high-temperature flash evaporator 10, a second high-temperature expansion valve 11, and a water pump 12. The evaporator 1, condenser-evaporator 3, and condenser 8 each contain two channels. The first channel of the low-temperature compressor 2, the first channel of the condenser-evaporator 3, the first low-temperature expansion valve 4, the low-temperature flash evaporator 5, the second low-temperature expansion valve 6, and the first channel of the evaporator 1 are sequentially connected via refrigerant piping to form a low-temperature refrigerant circulation loop. The first channel of the high-temperature compressor 7, the first channel of the condenser 8, the first high-temperature expansion valve 9, the high-temperature flash evaporator 10, the second high-temperature expansion valve 11, and the second channel of the condenser-evaporator 3 are sequentially connected via refrigerant piping to form a high-temperature refrigerant circulation loop. The lines in the figure represent liquid piping and gas piping, respectively.

[0042] In one embodiment of the present invention, the high-temperature expansion valve can achieve a throttling function on the one hand, and on the other hand, it can throttle the high-temperature and high-pressure liquid refrigerant into a low-temperature and low-pressure mist-like hydraulic refrigerant, thus creating conditions for gas-liquid separation of the refrigerant.

[0043] The following is combined with Figure 1 The illustrated embodiment demonstrates the working principle of a jet-induced enthalpy-enhanced cascade high-temperature heat pump system.

[0044] like Figure 1 As shown, in the cryogenic refrigerant circulation loop, the outlet of the cryogenic compressor 2 is connected to the inlet of the first channel of the condenser-evaporator 3 via a refrigerant line. The outlet of the first channel of the condenser-evaporator 3 is connected to the inlet of the first cryogenic expansion valve 4 via a refrigerant line. The outlet of the first cryogenic expansion valve 4 is connected to the inlet of the cryogenic flash evaporator 5 via a refrigerant line. The gas outlet of the cryogenic flash evaporator 5 is connected to the gas supply inlet of the cryogenic compressor 2 via a refrigerant line. The liquid outlet of the cryogenic flash evaporator 5 is connected to the inlet of the second cryogenic expansion valve 6 via a refrigerant line. The outlet of the second cryogenic expansion valve 6 is connected to the inlet of the first channel of the evaporator 1 via a refrigerant line. The outlet of the first channel of the evaporator 1 is connected to the inlet of the cryogenic compressor 2 via a refrigerant line.

[0045] In the high-temperature refrigerant circulation loop, the outlet of the high-temperature compressor 7 is connected to the inlet of the first channel of the condenser 8 through a refrigerant line. The outlet of the first channel of the condenser 8 is connected to the inlet of the first high-temperature expansion valve 9 through a refrigerant line. The outlet of the first high-temperature expansion valve 9 is connected to the inlet of the high-temperature flash evaporator 10 through a refrigerant line. The gas outlet of the high-temperature flash evaporator 10 is connected to the gas supply inlet of the high-temperature compressor 7 through a refrigerant line. The liquid outlet of the high-temperature flash evaporator 10 is connected to the inlet of the second high-temperature expansion valve 11 through a refrigerant line. The outlet of the second high-temperature expansion valve 11 is connected to the inlet of the second channel of the condenser-evaporator 3 through a refrigerant line. The outlet of the second channel of the condenser-evaporator 3 is connected to the inlet of the high-temperature compressor 7 through a refrigerant line.

[0046] In a jet-enthalpy-enhanced cascade high-temperature heat pump system, the cryogenic refrigerant flows in a two-stage heat pump loop. For example... Figure 1As shown, the medium-temperature superheated refrigerant vapor compressed in the cryogenic compressor 2 flows out of the compressor outlet and enters the condenser-evaporator 3 through the refrigerant pipeline for condensation and liquefaction. The high-pressure medium-temperature liquid refrigerant output from the condenser-evaporator 3 enters the first cryogenic expansion valve 4 through the refrigerant pipeline for throttling, cooling, and pressure reduction, and then enters the cryogenic flash evaporator 5 through the refrigerant pipeline. In the cryogenic flash evaporator 5, the refrigerant undergoes gas-liquid separation. The gaseous portion mixes with the refrigerant gas that has already undergone quasi-first-stage compression and undergoes quasi-second-stage compression in the cryogenic compressor 2. The liquid portion at the outlet of the cryogenic flash evaporator 5 is further cooled and depressurized through the second cryogenic expansion valve 6 until the refrigerant temperature reaches the required evaporation temperature. Then, it enters the evaporator 1 to absorb heat and become gaseous refrigerant, which is then drawn into the cryogenic compressor 2 for quasi-first-stage compression, thereby realizing the circulation of refrigerant in the cryogenic refrigerant circulation loop.

[0047] In a jet-enthalpy-enhanced cascade high-temperature heat pump system, high-temperature refrigerant flows through a two-stage heat pump loop. For example... Figure 1 As shown, the high-temperature superheated refrigerant vapor compressed in the high-temperature compressor 7 flows out of the compressor outlet and enters the condenser 8 through the refrigerant pipeline for condensation and liquefaction. The high-temperature, high-pressure liquid refrigerant output from the condenser 8 enters the second high-temperature expansion valve 9 through the refrigerant pipeline for throttling, cooling, and pressure reduction, and then enters the high-temperature flash evaporator 10 through the refrigerant pipeline. In the high-temperature flash evaporator 10, the refrigerant undergoes gas-liquid separation. The gaseous portion mixes with the refrigerant gas that has already undergone quasi-first-stage compression and undergoes quasi-second-stage compression in the high-temperature compressor 7. The liquid portion at the outlet of the high-temperature flash evaporator 10 undergoes further cooling and pressure reduction through the second high-temperature expansion valve 11 until the refrigerant temperature reaches the required evaporation temperature. Then, it enters the condenser evaporator 3 to absorb heat and become gaseous refrigerant, which is then drawn into the high-temperature compressor 7 for quasi-first-stage compression, thereby realizing the circulation of refrigerant in the high-temperature refrigerant circulation loop.

[0048] Under the boundary and demand conditions, environmental conditions, and system geometry characteristics of the high / low temperature refrigerant and the vapor at the input condenser outlet, the flowchart of the capacity configuration method for each device in a jet enthalpy-increasing cascade high-temperature heat pump system based on COP target optimization is as follows: Figure 2 As shown, it includes the following steps:

[0049] Step one: Determine the type of high / low temperature cycle refrigerant and input the boundary and demand conditions of the condenser outlet vapor, as well as the environmental conditions (air temperature, air flow rate, etc.); secondly, determine the geometry of the entire jet enthalpy-enhancing cascade high-temperature heat pump system (flash evaporator placement and structural form, etc.), and then begin the design work.

[0050] First, assume the condenser outlet steam flow rate (including lower and upper flow limits and adjustment step size). Then, assume the condenser, condenser-evaporator, and evaporator pinch point temperatures (including lower and upper temperature limits and adjustment step size). Next, assume the condenser outlet steam temperature. Then, assume the condenser-evaporator second channel outlet temperature. Next, assume the low-temperature flash evaporator outlet temperature (including lower and upper temperature limits and adjustment step size). Next, assume the high-temperature flash evaporator outlet temperature (including lower and upper temperature limits and adjustment step size). Next, assume the heat pump system subcooling (including lower and upper subcooling limits and adjustment step size). Next, assume the heat pump system superheat (including lower and upper superheat limits and adjustment step size). Finally, assume the compressor isentropic efficiency and mechanical efficiency. Since flow rate directly affects system performance, the initial step size is set to 5%-10% of the system's rated flow rate, gradually decreasing to 1%-2% with iterations. Since the condenser, condenser-evaporator, evaporator pinch point temperatures, and condenser outlet steam temperature significantly affect the system COP, the initial step size is set to 1-2°C of the current temperature. Since the effects of subcooling and superheating are relatively small, the initial step size for evaporator superheating and condenser subcooling is set to 2-5℃, which can be appropriately reduced with iteration.

[0051] Step two: Based on all the assumptions made in step one, the heat pump cycle simulation model can be used to calculate parameters such as the refrigerant thermodynamic parameters at the compressor, condenser, and evaporator outlets of the heat pump system, the condenser heating capacity, compressor power consumption, refrigerant circulation flow rate, and COP (Coefficient of Performance).

[0052] Determine if the system's heating capacity meets the feedforward requirements:

[0053] If the system's heating capacity does not meet the feedforward demand, the condenser outlet steam flow rate is adjusted by increasing it by one step from the current value, and the calculation continues.

[0054] If the system's heating capacity meets the feedforward requirement, the COP of the vapor jet enthalpy-enhanced cascade high-temperature heat pump system is compared with the preset value A. If the COP is greater than the preset value A, all assumed thermodynamic parameters and thermodynamic calculation results are saved and output as the current optimal values ​​for the current calculation stage. If the COP is less than or equal to the preset value A, the saving step is skipped and the condenser outlet steam temperature is directly checked to see if it meets the requirement. If it does not meet the requirement, the condenser outlet refrigerant temperature is adjusted. If the condenser outlet steam temperature is too high, the condenser outlet refrigerant temperature is lowered; if the condenser outlet steam temperature is too low, the condenser outlet refrigerant temperature is increased. Then, the COP is recalculated according to the design method.

[0055] If the condenser outlet steam temperature has reached its maximum value B, determine if the outlet temperature of the second channel of the condenser-evaporator has reached its maximum value C. If it has not yet reached maximum value C, increase the outlet temperature of the second channel of the condenser-evaporator by one step and continue the calculation. If it has reached maximum value C, determine if the outlet temperature of the low-temperature flash evaporator has reached its maximum value D. If it has not yet reached maximum value D, increase the outlet temperature of the low-temperature flash evaporator by one step and continue the calculation. If it has reached maximum value D, determine if the outlet temperature of the high-temperature flash evaporator has reached its maximum value E. If it has not yet reached maximum value E, increase the outlet temperature of the high-temperature flash evaporator by one step. The temperature is increased by one step, and the calculation continues. If the maximum value E has been reached, it is determined whether the subcooling of the heat pump system has reached the maximum value F. If it has not yet reached the maximum value F, the condensing pressure is increased by one step, and the calculation continues. If the maximum value F has been reached, it is determined whether the superheat of the heat pump system has reached the maximum value G. If it has not yet reached the maximum value G, the evaporating pressure is decreased by one step, and the calculation continues. If the maximum value G has been reached, the entire calculation process ends. The final output is the optimal operating state of the system corresponding to the highest COP in all iterative calculation steps, as well as the capacity of each device.

[0056] In this embodiment of the invention, thermodynamic parameters such as heating capacity, condenser outlet steam temperature, and flow rate are calculated primarily using a heat pump cycle simulation model and a heat and mass transfer model. The desired subcooling, superheating, intermediate temperature, and high / low temperature flash evaporator outlet temperature are then achieved by adjusting the condensing pressure, evaporating pressure, and the pinch point temperatures of the condenser, condenser-evaporator, and evaporator. The heat pump cycle simulation model includes a compressor model, a condenser model, an expansion valve model, an evaporator model, and a flash evaporator model.

[0057] The compressor power consumption and actual outlet specific enthalpy are:

[0058]

[0059] In the formula, h″ is the outlet specific enthalpy of the isentropic compression process, kJ / kg; h′ is the intake specific enthalpy, kJ / kg; η s P is the isentropic efficiency of the compressor. c The power consumption of the compressor is measured in kW and m. c The compressor flow rate is expressed in kg / s or h. o ′ ut The output specific enthalpy of the compressor is kJ / kg.

[0060] In each region of the evaporator (or condenser), the heat exchange on the refrigerant side, wall side, and air (water) side all satisfy equation (2).

[0061]

[0062] In the formula, Q r For heat exchange of refrigerant, kW; Q w For wall heat exchange, kW; Q a For air heat exchange, kW; q mr and q ma The mass flow rates of refrigerant and air are kg / s. and Enthalpy of the refrigerant at the inlet and outlet, kJ / kg; and Specific enthalpy of air inlet and outlet, kJ / kg; A w For heat exchange area, m 2 ΔT is the heat exchange temperature difference, in °C; H a and H r The convective heat transfer coefficient between air and refrigerant, kW / (m²). 2 .℃); R is the wall thermal resistance.

[0063] The relationship between the refrigerant enthalpy values ​​on both sides of the expansion valve is as follows:

[0064]

[0065] In the formula, and These are the specific enthalpy at the inlet and outlet of the expansion valve, respectively, in kJ / kg.

[0066] The relationship between the vapor phase fraction 'a' of the flash evaporator and the inlet and outlet enthalpy is as follows:

[0067]

[0068] In the formula, and The specific enthalpy (kJ / kg) represents the liquid phase at the inlet and outlet of the flash evaporator, and the gas phase at the outlet.

[0069] like Figure 3 As shown, the purpose of setting up a low-temperature flash evaporator 5 and a high-temperature flash evaporator 10 in the high and low temperature cycles is that, considering that the application of ordinary multi-stage compression technology is more complex than that of refrigerant injection technology and is difficult to adapt to low-temperature environments, setting up low-temperature flash evaporators 5 and high-temperature flash evaporators 10 can increase subcooling and circulation flow, thereby improving the heating capacity of the system and widening the operating temperature range for heating in low ambient temperatures. Furthermore, the vapor injection enthalpy enhancement technology can effectively reduce the compressor exhaust temperature, greatly improving the energy efficiency of the entire vapor injection enthalpy enhancement cascade high-temperature heat pump system.

[0070] With ambient temperature and condenser outlet steam temperature of 25℃ and 110℃ respectively, this invention provides a calculation example. The high-temperature circulating refrigerant is R1233zd(E), the low-temperature circulating refrigerant is R1234yf, the second outlet temperature of condenser-evaporator 3 is 62℃, the outlet temperature of low-temperature flash evaporator 5 is 39.9℃, the outlet temperature of high-temperature flash evaporator 10 is 81.7℃, the superheat is 5℃, and the subcooling is 3℃. The calculations are performed using the following methods: Figure 3 Images (a), (b), and (c) show steam generation in a conventional cascade heat pump system, a low-temperature jet enthalpy-increasing cascade heat pump system, and a high-temperature jet enthalpy-increasing cascade heat pump system, respectively. The conventional cascade heat pump system does not employ the second high-temperature expansion valve 11, the high-temperature flash evaporator 10, the second low-temperature expansion valve 6, and the low-temperature flash evaporator 5. The low-temperature jet enthalpy-increasing cascade heat pump system does not employ the second high-temperature expansion valve 11 and the high-temperature flash evaporator 10. The high-temperature jet enthalpy-increasing cascade heat pump system does not employ the second low-temperature expansion valve 6 and the low-temperature flash evaporator 5. Calculations yield the following results: Figure 4 The comparison results of COP for various cascade heat pump systems are shown. (See also...) Figure 4 It can be observed that, compared with conventional cascade heat pump systems, low-temperature stage vapor injection enthalpy-increasing cascade heat pump systems, and high-temperature stage vapor injection enthalpy-increasing cascade heat pump systems, the compressor power consumption of the vapor injection enthalpy-increasing cascade heat pump system of the present invention is reduced by 1.90kW, 1.27kW, and 1.51kW, respectively, with reductions of 6.94%, 4.75%, and 5.60%; the COP is increased by 0.16, 0.11, and 0.13, respectively, with increases of 7.46%, 4.99%, and 5.93%.

[0071] The thermodynamic performance of a heat pump system is largely determined by its different structures. To investigate the operating characteristics of vapor injection enthalpy enhancement technology and its impact on the performance of cascade heat pump systems, a comparative analysis was conducted on three cascade heat pumps enhanced with vapor injection enthalpy technology. The low-temperature stage vapor injection enthalpy cascade heat pump system incorporates vapor injection enthalpy technology only in the low-temperature cycle; the high-temperature stage vapor injection enthalpy cascade heat pump system incorporates vapor injection enthalpy technology only in the high-temperature cycle; and the novel vapor injection enthalpy cascade heat pump system of this invention incorporates vapor injection enthalpy technology in both the high-temperature and low-temperature cycles. In addition, a group of conventional cascade heat pump systems without vapor injection enthalpy technology in either the high-temperature or low-temperature cycles was used as a reference group. By comparing the simulation results, the heating operation characteristics of the three vapor injection enthalpy cascade heat pump systems and the ordinary cascade heat pump system at different evaporation temperatures were analyzed. The comparison results are as follows: Figure 4 As shown.

[0072] As shown in Figure 5(a), the compressor power consumption of all three vapor injection enthalpy-enhanced cascade heat pump systems is lower than that of the conventional cascade heat pump system; Figure 5(b) shows that the COP of all three systems is higher than that of the conventional cascade heat pump system. The effect of vapor injection enthalpy enhancement on the characteristics of the cascade heat pump system differs between high-temperature and low-temperature cycles. Because vapor injection enthalpy enhancement effectively increases the heat absorption of the refrigerant in the evaporator and the refrigerant flow rate in the condenser evaporator in the low-temperature cycle, its effect on the system is more significant than in the high-temperature cycle. Furthermore, among the three different vapor injection enthalpy-enhanced cascade heat pump systems, the novel vapor injection enthalpy-enhanced cascade heat pump system of this invention has the highest COP. This is because the novel vapor injection enthalpy-enhanced cascade heat pump system of this invention adds an auxiliary loop in both high-temperature and low-temperature cycles, which can enhance the overall circulation flow rate of the refrigerant in the system at various evaporation temperatures and effectively reduce the exhaust vapor temperature.

[0073] The vapor jet enthalpy-enhancing cascade high-temperature heat pump system of the present invention achieves gradient recovery of air heat, adaptive subcooling and superheating, and steam production by constructing a high-temperature refrigerant circulation loop and a low-temperature refrigerant circulation loop. By setting up a low-temperature flash evaporator 5 and a high-temperature flash evaporator 10 for two-stage throttling and intermediate gas injection, the enthalpy of the refrigerant at the inlet of the evaporator 1 is reduced, and the heat absorption of the refrigerant in the evaporator 1 is increased. At the same time, an additional gas injection branch is added to increase the refrigerant flow rate in the condenser 8, achieving adaptive subcooling and superheating, thereby improving the energy efficiency and service life of the vapor jet enthalpy-enhancing cascade high-temperature heat pump system.

[0074] Under the defined boundary and demand conditions, environmental conditions, and structural characteristics of high / low temperature refrigerants and target products, this invention provides a design method for the capacity configuration of each device in a jet-induced enthalpy-increasing cascade high-temperature heat pump system based on COP target optimization. This method enables the establishment of an effective thermodynamic model of the jet-induced enthalpy-increasing cascade high-temperature heat pump system, given the operating conditions, external requirements, and structural dimensions. Through several iterative calculations within the thermodynamic model, the optimal operating state corresponding to the highest COP of the entire jet-induced enthalpy-increasing cascade high-temperature heat pump system can be quickly found, and all thermodynamic parameters and the capacity of each device under the optimal state are output. This method enables the matching and optimization of structural and thermodynamic parameters of the heat pump system under the special requirements of steam production, and significantly reduces the operating energy consumption of the jet-induced enthalpy-increasing cascade high-temperature heat pump system, making a significant contribution to energy conservation and emission reduction in the steam production field.

[0075] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0076] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0077] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0078] Although embodiments of the present invention have been shown and described above, it is worth noting that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for configuring the capacity of a jet-induced enthalpy-enhanced cascade high-temperature heat pump system, wherein, The system includes an evaporator (1), a low-temperature compressor (2), a condenser-evaporator (3), a first low-temperature expansion valve (4), a low-temperature flash evaporator (5), a second low-temperature expansion valve (6), a high-temperature compressor (7), a condenser (8), a first high-temperature expansion valve (9), a high-temperature flash evaporator (10), a second high-temperature expansion valve (11), and a water pump (12); wherein, the first channel of the low-temperature compressor (2), the first low-temperature expansion valve (4), the low-temperature flash evaporator (5), the second low-temperature expansion valve (6), and the first channel of the evaporator (1) are sequentially connected through refrigerant pipelines to form a low-temperature refrigerant circulation loop; the first channel of the high-temperature compressor (7), the first high-temperature expansion valve (9), the high-temperature flash evaporator (10), the second high-temperature expansion valve (11), and the second channel of the condenser-evaporator (3) are sequentially connected through refrigerant pipelines to form a high-temperature refrigerant circulation loop; the water pump (12) is connected to the condenser (8); Its features include the following steps: S1. Determine the type of refrigerant for high / low temperature cycles, the boundary and demand conditions of the vapor entering the condenser outlet, the environmental conditions, and determine the geometry of the entire vapor injection enthalpy-increasing cascade high-temperature heat pump system. S2, Substitute the set conditions in step S1 into the heat pump cycle simulation model to calculate the refrigerant thermodynamic parameters at the outlet of the compressor, condenser and evaporator of the heat pump system, the condenser heating capacity, the compressor power consumption, the refrigerant circulation flow rate and COP. If the system's heating capacity does not meet the feedforward demand, the condenser outlet steam flow rate is adjusted by increasing it by one step from the current value, and the calculation continues. If the system's heating capacity meets the feedforward requirement, the COP of the jet enthalpy-increasing cascade high-temperature heat pump system is compared with the preset value A. If the COP is greater than the preset value A, all assumed thermodynamic parameters and thermodynamic calculation results are saved and output as the current optimal values ​​for the current calculation stage. If the COP is less than or equal to the preset value A, the saving step is skipped and the condenser outlet steam temperature is directly checked to see if it meets the requirement. If it does not meet the requirement, the condenser outlet refrigerant temperature is adjusted. If the condenser outlet steam temperature is too high, the condenser outlet refrigerant temperature is lowered; if the condenser outlet steam temperature is too low, the condenser outlet refrigerant temperature is increased. Then, the COP is recalculated according to the design method. If the condenser outlet steam temperature has reached its maximum value B, determine if the outlet temperature of the second channel of the condenser-evaporator has reached its maximum value C. If it has not yet reached maximum value C, increase the outlet temperature of the second channel of the condenser-evaporator by one step and continue the calculation. If it has reached maximum value C, determine if the outlet temperature of the low-temperature flash evaporator has reached its maximum value D. If it has not yet reached maximum value D, increase the outlet temperature of the low-temperature flash evaporator by one step and continue the calculation. If it has reached maximum value D, determine if the outlet temperature of the high-temperature flash evaporator has reached its maximum value E. If it has not yet reached maximum value E, increase the outlet temperature of the high-temperature flash evaporator by one step. The temperature is increased by one step, and the calculation continues. If the maximum value E has been reached, it is determined whether the subcooling of the heat pump system has reached the maximum value F. If it has not yet reached the maximum value F, the condensing pressure is increased by one step, and the calculation continues. If the maximum value F has been reached, it is determined whether the superheat of the heat pump system has reached the maximum value G. If it has not yet reached the maximum value G, the evaporating pressure is decreased by one step, and the calculation continues. If the maximum value G has been reached, the entire calculation process ends. The final output is the optimal operating state of the system corresponding to the highest COP in all iterative calculation steps, as well as the capacity of each device.

2. The capacity configuration method of the jet-enthalpy-enhanced cascade high-temperature heat pump system according to claim 1, characterized in that, After calculating thermodynamic parameters such as heating capacity, condenser outlet steam temperature, and flow rate using a heat pump cycle simulation model and a heat and mass transfer model, the desired subcooling, superheating, intermediate temperature, and high / low temperature flash evaporator outlet temperature are achieved by adjusting the condensing pressure, evaporating pressure, and the pinch point temperatures of the condenser, condenser-evaporator, and evaporator. The heat pump cycle simulation model includes a compressor model, a condenser model, an expansion valve model, an evaporator model, and a flash evaporator model. The expressions for each model are as follows: The compressor power consumption and actual outlet specific enthalpy are: ， In the formula, The specific enthalpy at the outlet of the isentropic compression process is kJ / kg; The specific enthalpy is the inhalation enthalpy, in kJ / kg; The isentropic efficiency of the compressor. The power consumption of the compressor is measured in kW. The compressor flow rate is expressed in kg / s. The actual specific enthalpy at the compressor outlet, kJ / kg; In each region of the evaporator and condenser, the heat exchange on the refrigerant side, wall side, and air / water side all satisfy the following equation: ， In the formula, Heat exchange for refrigerant, kW; For wall heat exchange, kW; For air heat exchange, kW; , These are the mass flow rates of refrigerant and air, respectively, in kg / s; , These are the inlet and outlet specific enthalpies of the refrigerant, respectively, in kJ / kg; , Specific enthalpy of air inlet and outlet, respectively, in kJ / kg; For heat exchange area, m 2 ; The temperature difference during heat exchange is expressed in °C. , The convective heat transfer coefficients of air and refrigerant, respectively, in kW / (m²). 2 .℃); For wall thermal resistance; The relationship between the refrigerant enthalpy values ​​on both sides of the expansion valve is as follows: ， In the formula, , These are the specific enthalpy at the inlet and outlet of the expansion valve, respectively, in kJ / kg; Vapor phase fraction of flash evaporator The relationship between enthalpy and import / export is as follows: ， In the formula, , and The specific enthalpy (kJ / kg) represents the liquid phase at the inlet and outlet of the flash evaporator, and the vapor phase at the outlet.

3. The capacity configuration method of the jet-enthalpy-enhanced cascade high-temperature heat pump system according to claim 1, characterized in that, The initial flow rate step size is set to 5%-10% of the system rated flow rate, and gradually reduced to 1%-2% with iteration; the initial step size of the condenser, condenser-evaporator, evaporator pinch point temperature and condenser outlet steam temperature is set to 1-2% of the current temperature, and gradually reduced to 0.5℃ with iteration.

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