A dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system with ejector efficiency enhancement and control method

Abstract

The present invention discloses a dual-temperature condensing air-supplying and heat-increasing heat pump drying system and control method with ejector efficiency enhancement. The system includes a refrigerant circulation circuit and an air circulation circuit. The refrigerant circulation circuit includes: a variable-frequency air-supplying and heat-increasing compressor, a high-temperature condenser, an ejector, a low-temperature condenser, three electronic expansion valves, two flash tanks, an evaporator, and temperature and pressure sensors. In the air circulation circuit, the wet air at the outlet of the drying box is cooled and dehumidified by the evaporator and then passes through the low-temperature and high-temperature condensers in sequence. It is heated to high-temperature dry air and enters the drying box for heat and moisture exchange, thereby drying the material. At the same time, it becomes wet air and circulates again. The present invention utilizes the expansion work recovery effect of the ejector to reduce the dryness of the refrigerant before entering the electronic expansion valve, increase the unit mass cooling capacity of the evaporator, and thus enhance the dehumidification capacity of the evaporator; the dual-temperature condensation reduces the heat transfer temperature difference, improves energy utilization efficiency, and ultimately improves system performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat pumps, and in particular relates to an ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system and a control method for an air source heat pump device. Background Art

[0002] Drying technology is used in industry, agriculture, and everyday life. With economic development, product drying consumes significant amounts of energy, accounting for approximately 12%-15% of total industrial energy consumption. Currently, product drying methods primarily include electric heating, infrared radiation, hot air, and heat pump drying. Compared to traditional drying methods, heat pump drying technology offers significant advantages, including energy savings, a wide range of adjustable temperatures, high drying efficiency, high drying quality, and environmental friendliness. It holds broad application prospects.

[0003] However, the current traditional single-stage compression heat pump drying system can no longer meet the needs of the rapidly growing heat pump drying market. In addition, when in a low-temperature environment, the pressure ratio of the vapor compression heat pump compressor continues to increase, resulting in excessively high exhaust temperatures and the compressor failing to operate normally. At the same time, the compressor suction volume increases at low ambient temperatures, causing the refrigerant circulation flow in the heat pump drying system to decay, resulting in a serious decline in the heating performance of the heat pump drying system. Therefore, the development of a high-efficiency and energy-saving heat pump drying system meets market demand and has great development potential and application value. On the other hand, improving the heat pump cycle configuration, improving the circulating air state, and optimizing system components can all help improve the performance of the heat pump drying system. Among them, variable frequency compressor technology and air injection enthalpy increase technology have received attention and application.

[0004] Air-injection heat pump technology effectively reduces the compressor's exhaust temperature. Furthermore, by replenishing refrigerant through the compressor's air-injection port, it offsets the refrigerant flow rate attenuation caused by low evaporation pressure, increasing the condenser's heating capacity and ultimately increasing the heating capacity per unit volume. However, the expansion device in existing air-injection heat pump systems results in significant expansion work losses. Summary of the Invention

[0005] In order to solve the defects and deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a dual-temperature condensing air-supplying enthalpy-increasing heat pump drying system and control method with ejector efficiency enhancement. The ejector is introduced into the drying system, and the ejector is used to realize the recovery of part of the expansion work, thereby reducing the irreversible loss of the throttling process in the throttling expansion mechanism, thereby significantly improving the efficiency of the heat pump drying system. Secondly, through the two condensation processes of high-temperature condensation and low-temperature condensation, the average condensation temperature is reduced, and the energy efficiency of the system is improved. The dry cold air first exchanges heat with the low-temperature condenser, and after being heated and heated once, it enters the high-temperature condenser for secondary heating and heating; the high and low temperature condensers are used to realize step-by-step heating and heating on the air side, which reduces the average heat exchange temperature difference between the air and the refrigerant, thereby reducing the irreversible loss of the condensation heat exchange process and comprehensively improving the system efficiency.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A dual-temperature condensing air-injection heat pump drying system with ejector efficiency enhancement, the system includes a refrigerant circulation circuit and an air circulation circuit, wherein the refrigerant circulation circuit is equipped with a variable frequency air-injection compressor 101, the variable frequency air-injection compressor 101 has a variable speed function, and the speed of the variable frequency air-injection compressor 101 is controlled by adjusting the motor frequency, thereby adjusting the mass flow of the refrigerant in the system; the variable frequency air-injection compressor 101 has an air intake port, an exhaust port and an air intake port; the exhaust port of the variable frequency air-injection compressor 101 is connected to the inlet of the high-temperature condenser 102, and the air is compressed by the variable frequency air-injection compressor 101 at high temperature and high pressure. The refrigerant vapor exchanges heat with the dry air in the high-temperature condenser 102, causing the refrigerant to partially condense; the gas-liquid two-phase refrigerant at the outlet of the high-temperature condenser 102 enters the primary flow inlet of the ejector 103, the outlet of the ejector 103 is connected to the inlet of the low-temperature condenser 104, and the two-phase refrigerant is completely condensed in the low-temperature condenser 104; the saturated liquid phase refrigerant at the outlet of the low-temperature condenser 104 enters the first electronic expansion valve 105 and enters the first flash tank 106 after throttling, and the refrigerant at the saturated gas phase outlet of the first flash tank 106 enters the air supply port of the variable frequency air supply and heat increase compressor 101; the saturated liquid phase outlet of the first flash tank 106 The refrigerant at the outlet enters the second electronic expansion valve 107, and after the isenthalpic throttling process, the two-phase refrigerant enters the second flash tank 108; the saturated gas phase outlet of the second flash tank 108 enters the secondary flow inlet of the ejector 103; the refrigerant at the saturated liquid phase outlet of the second flash tank 108 undergoes isenthalpic throttling in the third electronic expansion valve 109, and the outlet of the third electronic expansion valve 109 is connected to the inlet of the dehumidification evaporator 110. The gas-liquid two-phase refrigerant exchanges heat with the high-humidity air from the drying box in the dehumidification evaporator 110, and the refrigerant completely evaporates after absorbing heat. The saturated gas phase refrigerant at the outlet of the dehumidification evaporator 110 enters the variable frequency air supply and booster. The air intake of the enthalpy compressor 101 completes the refrigerant circulation of the refrigerant circulation loop; for the air circulation loop, the high-humidity humid air passing through the outlet of the drying box 111 first passes through the dehumidification evaporator 110, and the temperature and humidity are reduced to form dry cold air. The dry cold air passes through the low-temperature condenser 104 to exchange heat with the refrigerant for the first time, and then passes through the high-temperature condenser 102 to exchange heat with the refrigerant for the second time, and is heated for the second time to form high-temperature dry air that enters the inlet of the drying box 111, completing the air circulation of the air circulation loop. At the same time, a new air inlet valve 112 and a wet air outlet valve 113 are set in the air circulation loop.

[0008] All the gas-liquid two-phase mixed refrigerant from the outlet of the high-temperature condenser 102 in the ejector 103 serves as the primary fluid, i.e., the working fluid, of the ejector 103, and its pressure is greater than the pressure of the secondary fluid, i.e., the ejected fluid, from the saturated gas phase outlet of the second flash tank 108; and the high-temperature condenser 102 realizes partial condensation of the exhaust gas of the variable frequency air-supply enthalpy-increasing compressor 101, so the refrigerant at the outlet of the high-temperature condenser 102 is a gas-liquid two-phase fluid with a high enthalpy value, which is beneficial to improving the ability of the ejector 103 to recover expansion work; the refrigerant gas at the saturated gas phase outlet of the second flash tank 108 is ejected in the ejector 103 by the gas-liquid two-phase refrigerant from the outlet of the high-temperature condenser 102, and after mixing in the mixing section of the ejector 103, the gas-liquid two-phase refrigerant after being decelerated and pressurized in the diffuser section of the ejector 103 enters the low-temperature condenser 104 for complete condensation.

[0009] The superheated refrigerant vapor compressed by the variable frequency air injection and reheating compressor 101 is condensed in a stepped manner in the high-temperature condenser 102 and the low-temperature condenser 104. The outlet of the high-temperature condenser 102 is in a gas-liquid two-phase state, while the low-temperature condenser 104 achieves complete condensation. An ejector 103 is installed between the high- and low-temperature condensers to effectively recover the throttling losses generated by the second electronic expansion valve 107. The two condensation processes, high-temperature condensation and low-temperature condensation, reduce the average condensing temperature and improve system energy efficiency. Dry cold air from the dehumidification evaporator 110 first exchanges heat with the low-temperature condenser 104. After a primary heating and temperature increase, it enters the high-temperature condenser 102 for a secondary heating and temperature increase. The high- and low-temperature condensers enable stepped heating and temperature increase on the air side, reducing the average heat exchange temperature difference between the air and the refrigerant, thereby reducing irreversible losses in the condensation heat exchange process and comprehensively improving system efficiency. Furthermore, the triple throttling achieves stepped throttling, reducing the dryness of the refrigerant entering the dehumidification evaporator 110 and increasing the cooling capacity per unit mass.

[0010] The control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system is to set a temperature sensor at the outlet of the low-temperature condenser 104 of the air circulation to obtain the air temperature T at the outlet of the low-temperature condenser. air,1 ; Set a temperature sensor and a pressure sensor at the air inlet of the variable frequency air enthalpy increasing compressor 101 to obtain the refrigerant temperature T at the air inlet of the variable frequency air enthalpy increasing compressor ref,c , refrigerant pressure P at the suction port of the variable frequency air supply and enthalpy increase compressor ref,c ; Set a temperature sensor at the outlet of the drying box 111 to obtain the high humidity air temperature T at the outlet of the drying box air,o; Using the temperature sensor at the outlet of the low-temperature condenser 104 of the air circulation, the control module determines the state of the heated air here according to the preset air temperature, and thereby controls the opening of the new air inlet valve 112 and the humid air outlet valve 113 in a linked manner; using the temperature sensor and pressure sensor at the intake port of the variable frequency air supply and reheating compressor 101, the control module determines the superheat of the refrigerant here according to the thermophysical property equation of the refrigerant, and thereby regulates the opening of the third electronic expansion valve 109; the high humidity and wet air temperature at the outlet of the drying box is fed back to the control module to adjust the speed of the variable frequency air supply and reheating compressor 101; the control module achieves the purpose of controlling the new air flow and humid air flow in the air circulation by detecting the air temperature parameters at the outlet of the low-temperature condenser 104 of the air circulation; the third electronic expansion valve 109 achieves the purpose of controlling the refrigerant flow by detecting the superheat of the refrigerant at the intake port of the variable frequency air supply and reheating compressor 101.

[0011] The control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system is specifically implemented as follows: when the high-humidity air temperature T at the drying box outlet is detected air,o Lower than the preset temperature T air,o,s When the high humidity air temperature T at the drying box outlet is detected, the control module increases the speed by adjusting the variable frequency air supply and enthalpy increasing compressor 101; air,o Higher than the preset temperature T air,o,s When the air temperature T at the outlet of the low-temperature condenser in the air cycle is detected, the control module reduces the speed by adjusting the variable frequency air supply and enthalpy increase compressor 101; air,1 Lower than the preset air temperature value T air,1,s When the control module outputs a signal linkage control to reduce the opening of the fresh air inlet valve 112 and the wet air outlet valve 113; when the air temperature T at the outlet of the low-temperature condenser in the air cycle is detected air,1 Higher than the preset air temperature value T air,1,s When the control module outputs a signal linkage control to increase the opening of the fresh air inlet valve 112 and the wet air outlet valve 113; when the control module detects and calculates the refrigerant superheat ΔT at the suction port of the variable frequency air supply and enthalpy increase compressor 101 ref,c Higher than the preset superheat value ΔT ref,c,s When the control module increases the opening of the third electronic expansion valve 109, the refrigerant superheat ΔT at the suction port of the variable frequency air replenishment and enthalpy increase compressor 101 is detected and calculated. ref,c Lower than the preset superheat value ΔT ref,c,s When , the control module adjusts and reduces the opening of the third electronic expansion valve 109.

[0012] Compared to existing single-stage compression heat pump drying systems, the present invention proposes a dual-temperature condensation, air-supplementation, and heat-increasing heat pump drying system and control method with an ejector. This system incorporates an ejector into the refrigerant circulation loop. This ejector is used to eject refrigerant vapor from the gas-phase outlet of the second flash tank via the two-phase refrigerant at the high-temperature condenser outlet. This converts the work done by the high-pressure refrigerant into ejection and pressure increase of the secondary fluid, minimizing irreversible losses in the system and effectively improving the energy efficiency of the heat pump drying system. Furthermore, the high- and low-temperature condensers enable step-by-step heating and temperature increase on the air side, reducing the average heat exchange temperature difference between the air and refrigerant, thereby reducing irreversible losses in the condensation heat exchange process and further improving system efficiency. Furthermore, step-by-step throttling during the throttling process reduces throttling losses and increases the evaporator's unit cooling capacity. Therefore, the proposed solution significantly improves the overall performance and energy conservation and emission reduction of heat pump drying systems, resulting in improved economic and environmental benefits. This invention provides an economical, reliable, and efficient innovative solution, laying the foundation for the future widespread application of heat pump drying systems in industry and agricultural product processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the heat pump drying system of the present invention.

[0014] Figure 2 It is a cyclic pressure-enthalpy diagram (ph diagram) of the working process of the heat pump drying system of the present invention. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1As shown, the present invention is a dual-temperature condensing air-injection and reheat-increasing heat pump system with ejector efficiency enhancement suitable for heat pump drying, the system includes a refrigerant circulation circuit and an air circulation circuit, wherein the refrigerant circulation circuit is equipped with a variable frequency air-injection and reheat-increasing compressor 101, the variable frequency air-injection and reheat-increasing compressor 101 has a variable speed function, and the speed of the variable frequency air-injection and reheat-increasing compressor 101 can be controlled by adjusting the motor frequency, thereby adjusting the mass flow rate of the refrigerant in the system; the variable frequency air-injection and reheat-increasing compressor 101 has an air intake port, an exhaust port and an air supply port. The exhaust port of the variable frequency air supply and reheat increasing compressor 101 is connected to the inlet of the high temperature condenser 102. After being compressed by the variable frequency air supply and reheat increasing compressor 101, the high temperature and high pressure refrigerant vapor exchanges heat with the dry air in the high temperature condenser 102, so that the refrigerant is partially condensed; the gas-liquid two-phase refrigerant at the outlet of the high temperature condenser 102 enters the primary flow inlet of the ejector 103, and the outlet of the ejector 103 is connected to the inlet of the low temperature condenser 104. The two-phase refrigerant is completely condensed in the low temperature condenser 104; the saturated liquid phase at the outlet of the low temperature condenser 104 The refrigerant enters the first electronic expansion valve 105 and enters the first flash tank 106 after throttling. The refrigerant at the saturated gas phase outlet of the first flash tank 106 enters the gas supply port of the variable frequency air supply and enthalpy increasing compressor 101; the refrigerant at the saturated liquid phase outlet of the first flash tank 106 enters the second electronic expansion valve 107, and after the isenthalpic throttling process, the two-phase refrigerant enters the second flash tank 108; the saturated gas phase outlet of the second flash tank 108 enters the secondary flow inlet of the ejector 103; the refrigerant at the saturated liquid ... The isenthalpic throttling is performed in the sub-expansion valve 109, and the outlet of the third electronic expansion valve 109 is connected to the inlet of the dehumidification evaporator 110. The gas-liquid two-phase refrigerant exchanges heat with the high-humidity air from the drying box in the dehumidification evaporator 110. The refrigerant completely evaporates after absorbing heat, and the saturated gas-phase refrigerant at the outlet of the dehumidification evaporator 110 enters the air intake of the variable frequency air replenishment and enthalpy increase compressor 101, completing the refrigerant cycle of the refrigerant circulation circuit; for the air circulation circuit, the high-humidity air passing through the outlet of the drying box 111 first passes through the dehumidification evaporator 110, and the temperature is The temperature and humidity are reduced to form dry cold air, which passes through the low-temperature condenser 104 to exchange heat with the refrigerant for the first temperature increase, and then passes through the high-temperature condenser 102 to exchange heat with the refrigerant for the second temperature increase to form high-temperature dry air that enters the inlet of the drying box 111, completing the air circulation of the air circulation loop. At the same time, a new air inlet valve 112 is provided at the inlet of the low-temperature condenser 104 and a wet air outlet valve 113 is provided at the outlet of the drying box 111 to adjust the flow rate of the circulating air.

[0017] like Figure 2As shown, it is a pressure-enthalpy diagram (also called ph diagram) of the working process of the dual-temperature condensing air-supplying and reheat-increasing heat pump drying system with ejector enhancement of the present invention. The working process of the refrigerant flow path is that the medium-temperature and medium-pressure superheated gaseous refrigerant (state point 2) at the low-pressure stage outlet of the variable frequency air-supplying and reheat-increasing compressor 101 is mixed with the saturated medium-pressure gaseous refrigerant (state point 8v) at the outlet of the first flash tank 106 and then enters the high-pressure stage inlet (state point 3) of the variable frequency air-supplying and reheat-increasing compressor 101. The high-temperature and high-pressure superheated gaseous refrigerant (state point 4) further compressed by the high-pressure stage of the variable frequency air-supplying and reheat-increasing compressor 101 enters the high-temperature condenser 102; and exchanges heat with the dry air preheated by the low-temperature condenser 104, so that the high-temperature dry air obtains the drying and dehumidifying capacity; the superheated gaseous refrigerant The refrigerant is partially condensed in the high-temperature condenser 102 to become a gas-liquid two-phase refrigerant (state point 5), and enters the nozzle of the ejector 103 as a working fluid, and expands in the nozzle to become a low-pressure, high-speed gas-liquid two-phase mixed refrigerant (state point 5'); the low-pressure, high-speed gas-liquid two-phase mixed refrigerant is mixed with the saturated gaseous refrigerant (state point 9v) coming out of the gas phase outlet of the second flash tank 108 in the mixing section of the ejector 103 (state point 6'), and then decelerated and pressurized in the diffuser section of the ejector 103 to become a gas-liquid two-phase mixed refrigerant (state point 6) and then discharged from the ejector 103; the gas-liquid two-phase mixed refrigerant at the outlet of the ejector 103 enters the low-temperature condenser 104 for complete condensation, and pre-drying the cold air from the dehumidification evaporator 110 Heat; the saturated liquid refrigerant (state point 7) is throttled in the first electronic expansion valve 105, and then the gas-liquid two-phase refrigerant (state point 8) enters the first flash tank 106 for gas-liquid separation, and the saturated gaseous refrigerant (state point 8v) at the gas phase outlet of the first flash tank 106 enters the middle gas supply port of the variable frequency gas supply enthalpy increasing compressor 101; the saturated liquid refrigerant (state point 8l) at the liquid phase outlet of the first flash tank 106 enters the second electronic expansion valve 107, and after the isenthalpic throttling process, forms a gas-liquid two-phase refrigerant (state point 9), and enters the second flash tank 108, wherein the saturated gas-phase refrigerant (state point 9v) is injected into the ejector 103 as a secondary fluid, and the saturated liquid-phase refrigerant (state point 9l) enters the third electronic expansion valve 107. The expansion valve 109 forms a gas-liquid two-phase refrigerant (state point 10) after the isenthalpic throttling process, and enters the dehumidification evaporator 110 to absorb heat to form a saturated gas-phase refrigerant (state point 1), cooling and dehumidifying the high-humidity air from the drying box, completing the circulation of the refrigerant flow path; the air circulation loop is as follows: the high-humidity air passing through the drying box 111 is first cooled and dehumidified by the dehumidification evaporator 110 to form dry cold air, and the dry cold air passes through the low-temperature condenser 104 for preheating heat exchange with the refrigerant, and is heated for the first time, and then passes through the high-temperature condenser 102 for a secondary heat exchange with the refrigerant, and is heated for a secondary time to form high-temperature dry air that enters the inlet of the drying box 111, completing the air circulation of the air circulation loop.The fresh air inlet valve 112 and the moist air outlet valve 113 are used to adjust the flow rate of the circulating air.

[0018] like Figure 1 As shown, the control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system of the present invention is as follows: a temperature sensor is set at the outlet of the low-temperature condenser 104 of the air circulation to obtain the air temperature T at the outlet of the low-temperature condenser air,1 ; Set a temperature sensor and a pressure sensor at the air inlet of the variable frequency air enthalpy increasing compressor 101 to obtain the refrigerant temperature T at the air inlet of the variable frequency air enthalpy increasing compressor ref,c , refrigerant pressure P at the suction port of the variable frequency air supply and enthalpy increase compressor ref,c ; Set a temperature sensor at the outlet of the drying box 111 to obtain the high humidity air temperature T at the outlet of the drying box air,o ; Using the temperature sensor at the outlet of the low-temperature condenser 104 of the air circulation, the control module determines the state of the heated air here according to the preset air temperature, and thereby controls the opening of the new air inlet valve 112 and the humid air outlet valve 113 in a linked manner; using the temperature sensor and pressure sensor at the intake port of the variable frequency air supply and reheating compressor 101, the control module determines the superheat of the refrigerant here according to the thermophysical property equation of the refrigerant, and thereby regulates the opening of the third electronic expansion valve 109; the high humidity and wet air temperature at the outlet of the drying box is fed back to the control module to adjust the speed of the variable frequency air supply and reheating compressor 101; the control module achieves the purpose of controlling the new air flow and humid air flow in the air circulation by detecting the air temperature parameters at the outlet of the low-temperature condenser 104 of the air circulation; the third electronic expansion valve 109 achieves the purpose of controlling the refrigerant flow by detecting the superheat of the refrigerant at the intake port of the variable frequency air supply and reheating compressor 101.

[0019] The control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system is specifically implemented as follows: when the high-humidity air temperature T at the drying box outlet is detected air,o Lower than the preset temperature T air,o,s When the high humidity air temperature T at the drying box outlet is detected, the control module increases the speed by adjusting the variable frequency air supply and enthalpy increasing compressor 101; air,o Higher than the preset temperature T air,o,s When the air temperature T at the outlet of the low-temperature condenser in the air cycle is detected, the control module reduces the speed by adjusting the variable frequency air supply and enthalpy increase compressor 101; air,1 Lower than the preset air temperature value T air,1,s When the control module outputs a signal linkage control to reduce the opening of the fresh air inlet valve 112 and the wet air outlet valve 113; when the air temperature T at the outlet of the low-temperature condenser in the air cycle is detected air,1 Higher than the preset air temperature value Tair,1,s When the control module outputs a signal linkage control to increase the opening of the fresh air inlet valve 112 and the wet air outlet valve 113; when the control module detects and calculates the refrigerant superheat ΔT at the suction port of the variable frequency air supply and enthalpy increase compressor 101 ref,c Higher than the preset superheat value ΔT ref,c,s When the control module increases the opening of the third electronic expansion valve 109, the refrigerant superheat ΔT at the suction port of the variable frequency air replenishment and enthalpy increase compressor 101 is detected and calculated. ref,c Lower than the preset superheat value ΔT ref,c,s When , the control module adjusts and reduces the opening of the third electronic expansion valve 109.

[0020] Compared with conventional single-stage compression heat pump drying systems, the novel heat pump drying system of the present invention introduces an ejector into the refrigerant circulation loop. The ejector is used to realize the ejection of the gas-liquid two-phase refrigerant at the outlet of the high-temperature condenser into the refrigerant vapor from the gas phase outlet of the second flash tank, converting the work capacity of the high-pressure refrigerant into the ejection and pressure increase of the secondary fluid, reducing the irreversible loss of the system and effectively improving the energy efficiency of the heat pump drying system. Secondly, the high and low temperature condensers are used to achieve step-by-step heating and temperature increase on the air side, reducing the average heat exchange temperature difference between the air and the refrigerant, thereby reducing the irreversible loss of the condensation heat exchange process and further improving the system efficiency. Secondly, the throttling process realizes step-by-step throttling to reduce throttling losses and improve the unit mass cooling capacity of the evaporator.

Claims

1. A dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system with ejector efficiency enhancement, characterized by: The system comprises a refrigerant circulation circuit and an air circulation circuit, wherein the refrigerant circulation circuit is equipped with a variable frequency air-injection and reheat-increasing compressor (101), the variable frequency air-injection and reheat-increasing compressor (101) having a variable speed function, and the speed of the variable frequency air-injection and reheat-increasing compressor (101) is controlled by adjusting the motor frequency, thereby adjusting the mass flow of the refrigerant in the system; the variable frequency air-injection and reheat-increasing compressor (101) has an air intake port, an air discharge port and an air intake port; The exhaust port of the variable frequency air supply and reheat increasing compressor (101) is connected to the inlet of the high temperature condenser (102); the high temperature and high pressure refrigerant vapor compressed by the variable frequency air supply and reheat increasing compressor (101) is heat exchanged with dry air in the high temperature condenser (102), so that the refrigerant is partially condensed; the gas-liquid two-phase refrigerant at the outlet of the high temperature condenser (102) enters the primary flow inlet of the ejector (103); the outlet of the ejector (103) is connected to the inlet of the low temperature condenser (104); the two-phase refrigerant is completely condensed in the low temperature condenser (104); the low temperature condenser The saturated liquid phase refrigerant at the outlet of the refrigerant (104) enters the first electronic expansion valve (105) and enters the first flash tank (106) after throttling. The refrigerant at the saturated gas phase outlet of the first flash tank (106) enters the gas supply port of the variable frequency gas supply and enthalpy increasing compressor (101); the refrigerant at the saturated liquid phase outlet of the first flash tank (106) enters the second electronic expansion valve (107), and after the isenthalpic throttling process, the two-phase refrigerant enters the second flash tank (108); the saturated gas phase outlet of the second flash tank (108) enters the secondary flow inlet of the ejector (103) The refrigerant at the saturated liquid phase outlet of the second flash tank (108) is subjected to isenthalpic throttling in the third electronic expansion valve (109). The outlet of the third electronic expansion valve (109) is connected to the inlet of the dehumidification evaporator (110). The gas-liquid two-phase refrigerant exchanges heat with the high-humidity air from the drying box in the dehumidification evaporator (110). The refrigerant completely evaporates after absorbing heat. The saturated gas phase refrigerant at the outlet of the dehumidification evaporator (110) enters the air intake of the variable frequency air replenishment and enthalpy increase compressor (101), completing the refrigerant cycle of the refrigerant circulation circuit. For the air circulation circuit, The high-humidity air passing through the outlet of the drying box (111) first passes through the dehumidification evaporator (110), and the temperature and humidity are reduced to form dry cold air. The dry cold air passes through the low-temperature condenser (104) to exchange heat with the refrigerant for the first time and then passes through the high-temperature condenser (102) to exchange heat with the refrigerant for the second time and then is heated to form high-temperature dry air that enters the inlet of the drying box (111), completing the air circulation of the air circulation loop. At the same time, a new air inlet valve (112) and a wet air outlet valve (113) are set in the air circulation loop.

2. The dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system with ejector efficiency enhancement according to claim 1 is characterized in that: The entire gas-liquid two-phase mixed refrigerant from the outlet of the high-temperature condenser (102) in the ejector (103) serves as the primary fluid, i.e., the working fluid, of the ejector (103), and its pressure is greater than the pressure of the secondary fluid, i.e., the ejected fluid, from the saturated gas phase outlet of the second flash tank (108); and the high-temperature condenser (102) realizes partial condensation of the exhaust gas of the variable frequency air supply and enthalpy increasing compressor (101), so that the refrigerant at the outlet of the high-temperature condenser (102) is a gas-liquid two-phase fluid with a high enthalpy value, which is beneficial to improving the ability of the ejector (103) to recover expansion work; the refrigerant gas at the saturated gas phase outlet of the second flash tank (108) is ejected in the ejector (103) by the gas-liquid two-phase refrigerant from the outlet of the high-temperature condenser (102), and after mixing in the mixing section of the ejector (103), the gas-liquid two-phase refrigerant, which is decelerated and pressurized in the expansion section of the ejector (103), enters the low-temperature condenser (104) for complete condensation.

3. The dual-temperature condensing, air-supplementing, enthalpy-increasing heat pump drying system with ejector efficiency enhancement according to claim 1 is characterized in that: The superheated refrigerant vapor compressed by the variable frequency air supply and enthalpy increase compressor (101) is condensed in a high-temperature condenser (102) and a low-temperature condenser (104) in a stepwise manner. The outlet of the high-temperature condenser (102) is in a gas-liquid two-phase state, while the low-temperature condenser (104) achieves complete condensation. An ejector (103) is provided between the high and low temperature condensers to effectively recover the throttling loss generated by the second electronic expansion valve (107). Furthermore, the average condensation temperature is reduced through the two condensation processes of high-temperature condensation and low-temperature condensation, thereby improving the energy efficiency of the system. The dry cold air from the dehumidification evaporator (110) first exchanges heat with the low-temperature condenser (104), and after the first heating and temperature increase, enters the high-temperature condenser (102) for the second heating and temperature increase; the high and low temperature condensers are used to achieve step-by-step heating and temperature increase on the air side, thereby reducing the average heat exchange temperature difference between the air and the refrigerant, thereby reducing the irreversible loss in the condensation heat exchange process and comprehensively improving the system efficiency; in addition, the three-stage throttling realizes step-by-step throttling, reducing the dryness of the refrigerant that finally enters the dehumidification evaporator (110), and improving the unit mass cooling capacity.

4. The control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system according to any one of claims 1 to 3, characterized in that: A temperature sensor is set at the outlet of the low-temperature condenser (104) of the air circulation to obtain the air temperature T at the outlet of the low-temperature condenser air,1 A temperature sensor and a pressure sensor are set at the air inlet of the variable frequency air supply and enthalpy increasing compressor (101) to obtain the refrigerant temperature T at the air inlet of the variable frequency air supply and enthalpy increasing compressor ref,c , refrigerant pressure P at the suction port of the variable frequency air supply and enthalpy increase compressor ref,c ; Set a temperature sensor at the outlet of the drying box (111) to obtain the high humidity air temperature T at the outlet of the drying box air,o The invention relates to a method for controlling the opening of a new air inlet valve (112) and a humid air outlet valve (113) by using a temperature sensor at the outlet of a low-temperature condenser (104) of the air circulation system and judging the state of the heated air therein according to a preset air temperature in a control module. The method further comprises the following steps: using a temperature sensor and a pressure sensor at the air inlet of a variable-frequency air-supply and enthalpy-increasing compressor (101) and judging the superheat of the refrigerant therein according to a thermophysical property equation of the refrigerant in a control module. The method further comprises the following steps: feeding back the high-humidity air temperature at the outlet of the drying box to the control module and adjusting the rotation speed of the variable-frequency air-supply and enthalpy-increasing compressor (101). The control module controls the fresh air flow rate and the humid air flow rate in the air circulation system by detecting the air temperature parameter at the outlet of the low-temperature condenser (104). The third electronic expansion valve (109) controls the refrigerant flow rate by detecting the superheat of the refrigerant at the air inlet of the variable-frequency air-supply and enthalpy-increasing compressor (101).

5. The control method of the ejector-enhanced dual-temperature condensing air-supplementing enthalpy-increasing heat pump drying system according to claim 4 is specifically implemented as follows: when the high-humidity air temperature T at the outlet of the drying box is detected air,o Lower than the preset temperature T air,o,s When the high humidity air temperature T at the drying box outlet is detected, the control module increases the speed by adjusting the variable frequency air supply and enthalpy increasing compressor (101); air,o Higher than the preset temperature T air,o,s When the air temperature T at the outlet of the low-temperature condenser in the air circulation is detected, the control module reduces the speed by adjusting the variable frequency air supply and enthalpy increasing compressor (101); air,1 Lower than the preset air temperature value T air,1,s When the control module outputs a signal linkage control to reduce the opening of the fresh air inlet valve (112) and the wet air outlet valve (113); when the air temperature T at the outlet of the low-temperature condenser in the air circulation is detected air,1 Higher than the preset air temperature value T air,1,s When the control module outputs a signal to control the increase of the opening of the new air inlet valve (112) and the wet air outlet valve (113); when the control module detects and calculates the refrigerant superheat ΔT at the suction port of the variable frequency air supply and enthalpy increase compressor (101), ref,c Higher than the preset superheat value ΔT ref,c,s When the control module increases the opening of the third electronic expansion valve (109), the refrigerant superheat ΔT at the air inlet of the variable frequency air supply and enthalpy increase compressor (101) is detected and calculated. ref,c Lower than the preset superheat value ΔT ref,c,s When the control module adjusts and reduces the opening of the third electronic expansion valve (109).

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