CN118463562A - Ejector synergistic double-condenser heat pump drying system for material drying and control method - Google Patents
Ejector synergistic double-condenser heat pump drying system for material drying and control method Download PDFInfo
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- CN118463562A CN118463562A CN202410654087.8A CN202410654087A CN118463562A CN 118463562 A CN118463562 A CN 118463562A CN 202410654087 A CN202410654087 A CN 202410654087A CN 118463562 A CN118463562 A CN 118463562A
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- F26B21/50—
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B39/00—Evaporators; Condensers
- F25B39/04—Condensers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/08—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using ejectors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
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Abstract
本发明公开了一种用于物料干燥的喷射器增效双冷凝器热泵干燥系统及控制方法，该系统包括：空气循环回路与制冷剂循环回路；空气循环回路中，干燥箱出口的湿空气经蒸发器降温除湿后依次通过低压、高压冷凝器，被加热为高温干燥空气进入干燥箱进行热湿交换，使物料干燥，同时其变成湿空气再次循环；制冷剂循环回路包括：变频压缩机、高压冷凝器、喷射器、低压冷凝器、两个电子膨胀阀、闪蒸器、过冷器、蒸发器及温度与压力传感器。本发明通过引入喷射器回收膨胀功，降低节流过程的不可逆损失，提升热泵干燥系统效率，闪蒸器和过冷器增大了蒸发器前制冷剂的过冷度，提升了蒸发器的除湿能力，过冷器的回热作用避免了压缩机吸气带液，增强了系统稳定性。
The present invention discloses an ejector-enhanced double-condenser heat pump drying system and control method for material drying, the system comprises: an air circulation loop and a refrigerant circulation loop; in the air circulation loop, the wet air at the outlet of the drying box is cooled and dehumidified by the evaporator and then passes through the low-pressure and high-pressure condensers in sequence, and is heated to high-temperature dry air to enter the drying box for heat and moisture exchange, so that the material is dried, and at the same time, it becomes wet air and circulates again; the refrigerant circulation loop comprises: a variable frequency compressor, a high-pressure condenser, an ejector, a low-pressure condenser, two electronic expansion valves, a flash evaporator, a subcooler, an evaporator and a temperature and pressure sensor. The present invention recovers expansion work by introducing an ejector, reduces the irreversible loss of the throttling process, and improves the efficiency of the heat pump drying system. The flash evaporator and the subcooler increase the subcooling degree of the refrigerant before the evaporator, improve the dehumidification capacity of the evaporator, and the heat recovery effect of the subcooler avoids the compressor from sucking liquid, thereby enhancing the stability of the system.
Description
Technical Field
The invention belongs to the technical field of heat pump drying and dehumidification, and particularly relates to an ejector synergistic double-condenser heat pump drying system for material drying and a control method thereof.
Background
The drying technology relates to various fields of national economy, but is an application technology with high energy consumption, and accounts for about 12% of the total energy consumption of the national economy. Currently, the drying techniques commonly used mainly include hot air drying, microwave drying, infrared drying, vacuum freeze drying and heat pump drying. The heat pump drying technology is used as an important component of the industries of China and agricultural products, and gradually becomes a material drying method which is of great concern due to the characteristics of high efficiency, energy conservation, small pollution, high water extraction rate, low investment cost, high drying quality and the like, and has good development prospect and application value.
In order to optimize the performance of the heat pump drying system in response to the rapid development of the heat pump drying market, improve the energy efficiency of the system and enhance the stability of the system, researchers have made many experiments and improvements in the past decade, wherein the compressor frequency conversion technology has been focused and applied. However, the current heat pump drying technology still faces the limitation of a certain technical level, and the most common heat pump drying system in the current market has the problems of low drying rate, lower drying temperature and the like, and the irreversible loss in the refrigerant circulation process is increased due to the fact that only a throttling expansion mechanism is used for throttling the refrigerant, and the pressure difference before and after throttling is large, so that the system efficiency is low, and particularly when the drying temperature requirement is high, the heat pump drying system efficiency is remarkably reduced; secondly, the air suction pipe of the compressor has the problem of liquid carrying during air suction, and wet compression and liquid impact phenomena are easy to occur, which are unfavorable for the stable operation of the compressor. Therefore, developing an efficient and energy-saving heat pump drying device is an important task in the drying field and is also an important development direction of heat pump drying technology.
Disclosure of Invention
In order to solve the problems and the defects in the prior art, the invention provides an ejector synergistic double-condenser heat pump drying system for drying materials and a control method, wherein an ejector is introduced into the system, the recovery of expansion work is realized through the ejector, the irreversible loss in a throttling process in a throttling expansion mechanism is reduced, the efficiency of the heat pump drying system is further remarkably improved, the supercooling degree of refrigerant before a dehumidifying evaporator is increased by a flash evaporator and a supercooler, the cooling and dehumidifying capacity of the evaporator is improved, and meanwhile, the suction liquid of a variable frequency compressor is avoided due to the backheating function of the supercooler, and the system stability is enhanced. And through two condensation processes of high-pressure condensation and low-pressure condensation, the average condensation temperature is reduced, and the energy efficiency of the system is improved. The dry cold air firstly exchanges heat with the low-pressure condenser, after primary temperature rise, the dry cold air enters the high-pressure condenser to carry out secondary temperature rise, the setting of the air side gradient temperature rise through the high-pressure condenser and the low-pressure condenser can reduce the average heat exchange temperature difference between the air and the refrigerant, so that the irreversible loss in the condensation heat exchange process is reduced, and the system efficiency is comprehensively improved. In addition, the flow rate of the refrigerant in the refrigerating system is controlled by detecting the state of the refrigerant at the outlet of the low-pressure condenser and the state of the refrigerant at the air suction port of the variable-frequency compressor.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
An ejector synergistic double-condenser heat pump drying system for material drying comprises an air circulation loop and a refrigerant circulation loop, wherein the refrigerant circulation loop is provided with a variable frequency compressor 101, the variable frequency compressor 101 has a variable speed function, and the rotating speed of the variable frequency compressor 101 is controlled through the frequency change of a motor so as to adjust the mass flow rate of refrigerant in the refrigerant circulation loop; the variable frequency compressor 101 is provided with an air suction port and an air exhaust port, the air exhaust port of the variable frequency compressor 101 is connected with the inlet of the high-pressure condenser 102, the high-temperature refrigerant vapor after temperature rise and pressure rise is compressed by the variable frequency compressor 101, and enters the high-pressure condenser 102, and the refrigerant exchanges heat with dry air to partially condense the refrigerant; the method comprises the steps that a gas-liquid two-phase refrigerant at the outlet of a high-pressure condenser 102 enters a nozzle inlet of an ejector 103 as a primary flow, the outlet of the ejector 103 is connected with the inlet of a low-pressure condenser 104, the two-phase refrigerant is completely condensed in the low-pressure condenser 104, saturated liquid refrigerant at the outlet of the low-pressure condenser 104 enters a first electronic expansion valve 105, after an isenthalpic throttling process, the two-phase refrigerant enters a flash evaporator 106 inlet from the outlet of the first electronic expansion valve 105, wherein the saturated gas-phase refrigerant is used as a secondary fluid and is ejected to the secondary flow inlet of the ejector 103, the saturated liquid-phase refrigerant enters the hot end inlet of a subcooler 107, the cooled refrigerant enters the inlet of a second electronic expansion valve 108, an isenthalpic throttling process is carried out, the outlet of the second electronic expansion valve 108 is connected with the inlet of a dehumidifying evaporator 109, the gas-liquid two-phase refrigerant exchanges heat with high-humidity air from a drying box in the dehumidifying evaporator 109, and is completely evaporated after heat absorption, the saturated gas-phase refrigerant at the outlet of the dehumidifying evaporator 109 enters the inlet of the subcooler 107, and after passing through the saturated gas-phase refrigerant enters the cold end inlet of the frequency conversion compressor 101, and the refrigerant circulation loop is completed; in the air circulation loop, the high-humidity air passing through the drying box firstly passes through the dehumidifying evaporator 109, the temperature and the humidity are reduced, dry cold air is formed, the dry cold air exchanges heat with the refrigerant through the low-pressure condenser 104 to perform primary temperature rise, and then exchanges heat with the refrigerant through the high-pressure condenser 102 to perform secondary temperature rise, so that high-temperature dry air is formed to enter the inlet of the drying box, and the air circulation of the air circulation loop is completed.
In the ejector 103, the partially condensed gas-liquid two-phase mixed refrigerant from the high-pressure condenser 102 is used as the primary fluid of the ejector 103, the pressure of the primary fluid is higher than that of the secondary fluid, namely the ejected fluid, from the gas phase outlet of the flash evaporator 106, and the high-pressure condenser 102 realizes the partial condensation of the exhaust gas of the inverter compressor 101, so that the outlet refrigerant is the gas-liquid two-phase flow, the high-enthalpy value is provided, and the capacity of the ejector 103 for recovering expansion work is improved; the saturated gas phase refrigerant is injected by the gas-liquid two-phase refrigerant at the gas phase outlet in the flash evaporator 106, and enters the mixing section of the ejector 103 together for isobaric mixing, and enters the low-pressure condenser 104 after being subjected to speed reduction and pressure increase through the diffusion section of the ejector 103.
The superheated refrigerant vapor discharged by the variable frequency compressor 101 is condensed in steps in the high-pressure condenser 102 and the low-pressure condenser 104, the refrigerant at the outlet of the high-pressure condenser 102 is in a gas-liquid two-phase state, and the refrigerant at the outlet of the low-pressure condenser 104 is in a saturated liquid phase; the ejector 103 is additionally arranged between the high-pressure condenser and the low-pressure condenser, so that expansion work can be effectively recovered, and the average condensation temperature is reduced and the energy efficiency of the system is improved through two condensation processes of high-pressure condensation and low-pressure condensation; the dry cold air firstly exchanges heat with the low-pressure condenser 104, after primary temperature rise, enters the high-pressure condenser 102 for secondary temperature rise, and the setting of the air side gradient temperature rise through the high-pressure condenser and the low-pressure condenser reduces the average heat exchange temperature difference between the air and the refrigerant, so that the irreversible loss in the condensation heat exchange process is reduced, and the system efficiency is comprehensively improved.
The gas-liquid two-phase refrigerant from the first electronic expansion valve 105 enters the flash evaporator 106, wherein the gas-phase refrigerant provides the secondary fluid of the ejector 103, the liquid-phase refrigerant is supercooled in the supercooler 107, the second electronic expansion valve 108 throttles and then enters the dehumidification evaporator 109, the flash evaporator 106 effectively reduces the temperature of the refrigerant inlet before the second electronic expansion valve 108, the dryness of the refrigerant passing through the second electronic expansion valve 108 is reduced, the unit refrigerating capacity of the refrigerant is increased, the supercooler 107 provides a supercooling effect, the unit refrigerating capacity is further increased, the cooling and dehumidification capacity of the dehumidification evaporator 109 is improved, the system stability is improved due to the supercooling degree, the refrigerant is kept in a stable state before entering the second electronic expansion valve 108, meanwhile, the refrigerant entering the inlet of the inverter compressor 101 obtains the superheat degree after heat exchange, the supercooling compressor 101 is prevented from carrying liquid suction by the supercooling compressor 101, the inverter compressor 101 is protected, and the system stability is further improved.
The working method of the ejector synergistic double-condenser heat pump drying system for material drying comprises the following working processes of a refrigerant circulation loop: the high-temperature high-pressure superheated steam-state refrigerant at the exhaust port of the variable-frequency compressor 101 enters the high-pressure condenser 102 to exchange heat with the preheated drying air, so that the drying and dehumidifying capacities of the high-temperature drying air are obtained; the superheated refrigerant is partially condensed to form a gas-liquid two-phase mixed refrigerant with high enthalpy value after giving off heat, so that the gas-liquid two-phase mixed refrigerant is taken as primary fluid to enter a nozzle inlet of the ejector 103, the gas-liquid two-phase mixed refrigerant is changed into low-pressure high-speed gas-liquid two-phase mixed refrigerant after being expanded in the nozzle, the low-pressure mixed refrigerant and saturated gas-phase refrigerant at a gas phase outlet of the flash evaporator 106 are subjected to isobaric mixing in a mixing section of the ejector 103, the gas-liquid two-phase refrigerant enters a low-pressure condenser 104 after being subjected to deceleration and pressure boosting through a diffusion section of the ejector 103, dry cold air from the dehumidification evaporator 109 is preheated, the refrigerant is completely condensed in the process, the saturated gas-phase refrigerant enters a first electronic expansion valve 105, the saturated gas-phase refrigerant is formed after passing through an isenthalpic throttling process, the gas-liquid two-phase refrigerant is formed into a gas-liquid two-phase refrigerant, the saturated gas-phase refrigerant enters a flash evaporator 107 as secondary fluid to be ejected into the ejector 103, the saturated gas-phase refrigerant enters a hot end inlet of the subcooler 107, the saturated gas-phase refrigerant enters a second electronic expansion valve 108, the saturated gas-phase refrigerant enters a supercooler 107 after passing through the isenthalpic throttling process, the vapor-phase refrigerant enters a vapor-phase evaporator to be subjected to be cooled, the saturated gas-phase refrigerant from the high-phase evaporator to be compressed into a high-temperature air compressor, and the saturated air compressor 101, and the saturated gas-phase refrigerant is returned to the saturated air compressor, and the saturated refrigerant is cooled to the saturated air from the high-phase compressor, the high-phase compressor is compressed air compressor 101, the saturated refrigerant is cooled by the saturated air, the saturated refrigerant has the saturated air, and the saturated refrigerant has the saturated air and the saturated air, and the saturated refrigerant has the high temperature and cooled air; the ejector 103 is introduced to realize the recovery of expansion work, so that irreversible loss in a throttling process in a throttling expansion mechanism is reduced, the efficiency of a heat pump drying system is remarkably improved, the supercooling degree of the refrigerant before the dehumidifying evaporator 109 is increased by the flash evaporator 106 and the supercooler 107, the cooling and dehumidifying capacity of the dehumidifying evaporator 109 is improved, meanwhile, the liquid-carrying during the air suction of the variable frequency compressor 101 is avoided due to the backheating effect of the supercooler 107, and the system stability is enhanced.
According to the control method of the ejector synergistic double-condenser heat pump drying system for material drying, a temperature sensor and a pressure sensor are arranged at the outlet of a low-pressure condenser 104, and the temperature T ro1 of refrigerant at the outlet of the low-pressure condenser and the pressure P ro1 of refrigerant at the outlet of the low-pressure condenser are obtained; a temperature sensor and a pressure sensor are arranged at the air suction port of the compressor 101 to obtain the temperature T ric of the refrigerant at the air suction port of the compressor and the pressure P ric of the refrigerant at the air suction port of the compressor; a temperature sensor is arranged at the outlet of the drying box, and the temperature T aod of high-humidity air at the outlet of the drying box is obtained; whether the refrigerant is in a saturated liquid state or not is calculated and judged according to a thermal physical property equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the outlet of the low-pressure condenser 104, so that the opening of the first electronic expansion valve 105 is regulated and controlled; the superheat degree of the refrigerant is calculated and judged according to a thermophysical equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the air suction port of the variable frequency compressor 101, so that the opening degree of the second electronic expansion valve 108 is regulated and controlled; the rotation speed of the variable frequency compressor 101 is controlled by adopting the temperature of high-humidity air from the drying box; the first electronic expansion valve 105 achieves the purpose of controlling the flow rate of the refrigerant by detecting the temperature and pressure parameters of the refrigerant at the outlet of the low-pressure condenser 104, and the second electronic expansion valve 108 achieves the purpose of controlling the flow rate of the refrigerant by detecting the superheat degree of the refrigerant at the suction port of the inverter compressor 101.
The control method of the ejector synergistic double-condenser heat pump drying system for material drying is specifically implemented as follows: when the high humidity air temperature T aod at the outlet of the drying box is detected to be lower than a preset temperature value T aods, controlling the variable frequency compressor 101 to increase the rotating speed; when the high humidity air temperature T aod at the outlet of the drying box is detected to be higher than a preset temperature value T aods, controlling the variable frequency compressor 101 to reduce the rotating speed; When the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be lower than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve 105 is increased; when the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be higher than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve 105 is reduced; When the superheat degree delta T ric of the refrigerant at the suction port of the compressor 101 is higher than the preset superheat degree delta T rics through detection and calculation, increasing the opening degree of the second electronic expansion valve 108; when the degree of superheat Δt ric of the refrigerant at the suction port of the compressor 101 is lower than the preset degree of superheat Δt rics by detecting and calculating, the opening degree of the second electronic expansion valve 108 is reduced.
Compared with the existing single-stage compression heat pump drying system, the invention provides the ejector synergistic double-condenser heat pump drying system for material drying and the control method, wherein the ejector 103 is introduced into the refrigerant circulation loop, the ejector 103 is utilized to realize that the gas-liquid two-phase refrigerant at the outlet of the high-pressure condenser 102 ejects refrigerant vapor from the gas phase outlet of the flash evaporator 106, the acting capacity of the high-pressure refrigerant is converted into ejection and boosting of secondary fluid, the irreversible loss of the system is reduced, and the energy efficiency of the heat pump drying system is effectively improved; the flash evaporator 106 effectively reduces the temperature of the refrigerant inlet before the second electronic expansion valve 108, so that the dryness of the refrigerant passing through the second electronic expansion valve 108 is reduced, the unit refrigerating capacity of the refrigerant is increased, the supercooling effect is provided by the supercooler 107, the unit refrigerating capacity is further increased, the cooling and dehumidifying capacity of the dehumidifying evaporator 109 is improved, the refrigerant keeps a stable state before entering the second electronic expansion valve 108 due to the supercooling degree, the system stability is improved, meanwhile, the refrigerant entering the inlet of the variable frequency compressor 101 after heat exchange is performed at the cold end of the supercooling device 107 obtains the superheat degree, the suction liquid of the variable frequency compressor 101 is avoided by utilizing the backheating effect of the supercooling device 107, and the variable frequency compressor 101 is protected, and the system stability is further improved. The scheme provided by the invention plays a positive role in promoting the overall performance of the heat pump drying system and the energy conservation and emission reduction effects, and can bring better economic benefit and environmental benefit. The invention provides an economic, reliable and efficient innovative scheme, which lays a foundation for wide application of the heat pump drying system in industry and agricultural product processing industry in the future.
Drawings
Fig. 1 is a schematic diagram of a heat pump drying system of the present invention.
Fig. 2 is a cyclic pressure-enthalpy diagram (p-h diagram) of the operation of the heat pump drying system of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and the detailed description.
As shown in fig. 1, the invention is an ejector-enhanced dual-condenser heat pump drying system for drying materials, which comprises an air circulation loop and a refrigerant circulation loop, wherein the refrigerant circulation loop is provided with a variable frequency compressor 101, the variable frequency compressor 101 has a variable speed function, and the rotating speed of the variable frequency compressor 101 can be controlled through the change of the frequency of a motor, so that the mass flow rate of refrigerant in a refrigerating system is regulated. The inverter compressor 101 has an air inlet and an air outlet, the air outlet of the inverter compressor 101 is connected with the inlet of the high-pressure condenser 102, the high-temperature refrigerant vapor after temperature and pressure rise is compressed by the inverter compressor 101 and enters the high-pressure condenser 102, and the refrigerant exchanges heat with dry air to partially condense the refrigerant. The method comprises the steps that a gas-liquid two-phase refrigerant at the outlet of a high-pressure condenser 102 enters a nozzle inlet of an ejector 103 as a primary flow, the outlet of the ejector 103 is connected with the inlet of a low-pressure condenser 104, the two-phase refrigerant is completely condensed in the low-pressure condenser 104, saturated liquid refrigerant at the outlet of the low-pressure condenser 104 enters a first electronic expansion valve 105, after an isenthalpic throttling process, the two-phase refrigerant enters a flash evaporator 106 inlet from the outlet of the first electronic expansion valve 105, wherein the saturated gas-phase refrigerant is used as a secondary fluid and is ejected to the secondary flow inlet of the ejector 103, the saturated liquid-phase refrigerant enters the hot end inlet of a subcooler 107, the cooled refrigerant enters the inlet of a second electronic expansion valve 108, an isenthalpic throttling process is carried out, the outlet of the second electronic expansion valve 108 is connected with the inlet of a dehumidifying evaporator 109, the gas-liquid two-phase refrigerant exchanges heat with high-humidity air from a drying box in the dehumidifying evaporator 109, and is completely evaporated after heat absorption, the saturated gas-phase refrigerant at the outlet of the dehumidifying evaporator 109 enters the inlet of the subcooler 107, and after passing through the saturated gas-phase refrigerant enters the cold end inlet of the frequency conversion compressor 101, and the refrigerant circulation loop is completed; in the air circulation loop, the high-humidity air passing through the drying box firstly passes through the dehumidifying evaporator 109, the temperature and the humidity are reduced, dry cold air is formed, the dry cold air exchanges heat with the refrigerant through the low-pressure condenser 104 to perform primary temperature rise, and then exchanges heat with the refrigerant through the high-pressure condenser 102 to perform secondary temperature rise, so that high-temperature dry air is formed to enter the inlet of the drying box, and the air circulation of the air circulation loop is completed.
As shown in fig. 2, the pressure-enthalpy diagram (i.e. p-h diagram) of the working process of the ejector-enhanced double-condenser heat pump drying system for drying materials of the invention is shown, and the working process of the heat pump system is as follows: the refrigerant cycle operates as follows. The high-temperature high-pressure superheated vapor state refrigerant (state point 2) at the exhaust port of the variable frequency compressor 101 enters the high-pressure condenser 102 to exchange heat with the preheated drying air, so that the drying and dehumidifying capacity of the high-temperature drying air is achieved. The superheated refrigerant forms a gas-liquid two-phase mixed refrigerant (state point 3) after partial condensation of the released heat, and has a relatively high enthalpy value, so that the superheated refrigerant is taken as a primary fluid to enter a nozzle inlet of the ejector 103, is expanded in the nozzle to become a low-pressure high-speed gas-liquid two-phase mixed refrigerant, is subjected to isobaric mixing with the saturated gas-phase refrigerant from a gas phase outlet of the flash evaporator 106 in a mixing section of the ejector 103, is subjected to deceleration and pressure boosting through a diffusion section of the ejector 103, enters the low-pressure condenser 104 as a gas-liquid two-phase refrigerant (state point 4), preheats dry cold air from the dehumidification evaporator 109, completely condenses the refrigerant in the process, and forms the gas-liquid two-phase refrigerant (state point 6) after the isenthalpic throttling process, enters a flash evaporator 106, wherein saturated gas-phase refrigerant (state point 6 v) is injected into the injector 103 as secondary fluid, saturated liquid-phase refrigerant (state point 6 l) enters a hot end inlet of a subcooler 107, and is regenerated with saturated gas-phase refrigerant (state point 9) at an outlet of a dehumidifying evaporator 109, the refrigerant obtains supercooling degree (state point 7) in the subcooler 107, enters a second electronic expansion valve 108, forms gas-liquid two-phase refrigerant (state point 8) after undergoing an isenthalpic throttling process, enters the dehumidifying evaporator 109 to absorb heat to form saturated gas-phase refrigerant (state point 9), cools and dehumidifies high-humidity wet air from a drying box, then enters a cold end inlet of the subcooler 107 to provide supercooling degree for the saturated liquid-phase refrigerant from the flash evaporator 106, the refrigerant returns to the suction port (state point 1) of the inverter compressor 101 after acquiring the degree of superheat. According to the invention, the recovery of expansion work is realized by introducing the ejector 103, the irreversible loss in the throttling process in the throttling expansion mechanism is reduced, the efficiency of a heat pump drying system is remarkably improved, the supercooling degree of the refrigerant before the dehumidifying evaporator 109 is increased by the flash evaporator 106 and the supercooler 107, the cooling and dehumidifying capacity of the dehumidifying evaporator 109 is improved, meanwhile, the liquid-carrying during the air suction of the variable frequency compressor 101 is avoided by the backheating action of the supercooler 107, and the system stability is enhanced.
As shown in fig. 1, the control method of the ejector synergistic dual-condenser heat pump drying system for material drying of the invention comprises the steps of arranging a temperature sensor and a pressure sensor at the outlet of a low-pressure condenser 104, and obtaining the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser and the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser; a temperature sensor and a pressure sensor are arranged at the air suction port of the compressor 101 to obtain the temperature T ric of the refrigerant at the air suction port of the compressor and the pressure P ric of the refrigerant at the air suction port of the compressor; a temperature sensor is arranged at the outlet of the drying box, and the temperature T aod of high-humidity air at the outlet of the drying box is obtained; whether the refrigerant is in a saturated liquid state or not is calculated and judged according to a thermal physical property equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the outlet of the low-pressure condenser 104, so that the opening of the first electronic expansion valve 105 is regulated and controlled; the superheat degree of the refrigerant is calculated and judged according to a thermal physical property equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the air suction port of the compressor 101, so that the opening degree of the second electronic expansion valve 108 is regulated and controlled; the rotation speed of the variable frequency compressor 101 is controlled by adopting the temperature of high-humidity air from the drying box; the first electronic expansion valve 105 achieves the purpose of controlling the flow rate of the refrigerant by detecting the temperature and pressure parameters of the refrigerant at the outlet of the low-pressure condenser 104, and the second electronic expansion valve 108 achieves the purpose of controlling the flow rate of the refrigerant by detecting the superheat degree of the refrigerant at the suction port of the inverter compressor 101.
The control method of the ejector synergy double-condenser heat pump drying system for drying materials is specifically implemented as follows: when the high humidity air temperature T aod at the outlet of the drying box is detected to be lower than a preset temperature value T aods, controlling the variable frequency compressor 101 to increase the rotating speed; when the high humidity air temperature T aod at the outlet of the drying box is detected to be higher than a preset temperature value T aods, controlling the variable frequency compressor 101 to reduce the rotating speed; When the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be lower than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve 105 is increased; when the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be higher than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve 105 is reduced; When the superheat degree delta T ric of the refrigerant at the suction port of the compressor 101 is higher than the preset superheat degree delta T rics through detection and calculation, increasing the opening degree of the second electronic expansion valve 108; when the degree of superheat Δt ric of the refrigerant at the suction port of the compressor 101 is lower than the preset degree of superheat Δt rics by detecting and calculating, the opening degree of the second electronic expansion valve 108 is reduced.
Compared with a conventional single-stage compression heat pump drying system, the novel heat pump drying system realizes the recovery of expansion work of a traditional throttling mechanism by introducing the ejector 103, reduces irreversible loss in a throttling process in the throttling type expansion mechanism, further remarkably improves the efficiency of the heat pump drying system, increases the supercooling degree of the refrigerant before the dehumidifying evaporator 109 by the flash evaporator 106 and the supercooler 107, improves the unit mass refrigerating capacity of the refrigerant, improves the cooling and dehumidifying capacity of the dehumidifying evaporator 109, and meanwhile, the heat regeneration effect of the supercooler 107 avoids the suction of the compressor 101 and enhances the system stability. Superheated refrigerant vapor discharged from the compressor 101 is subjected to step condensation in the high-pressure condenser 102 and the low-pressure condenser 104, and the average condensation temperature is reduced through high-pressure condensation and low-pressure condensation, so that irreversible loss in the condensation heat exchange process is reduced, and the system efficiency is comprehensively improved. The rotation speed of the variable frequency compressor 101 is controlled by adopting the high humidity air temperature at the outlet of the drying box; the temperature and the pressure of the refrigerant at the outlet of the low-pressure condenser 104 are adopted, and whether the refrigerant is in a saturated liquid state or not is calculated and judged according to a thermal physical property equation of the refrigerant, so that the opening degree of the first electronic expansion valve 105 is regulated and controlled; the superheat degree of the refrigerant is calculated and judged according to a thermophysical equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the air suction port of the variable frequency compressor 101, so that the opening degree of the second electronic expansion valve 108 is regulated and controlled; the first electronic expansion valve 105 achieves the purpose of controlling the flow rate of the refrigerant by detecting the temperature and pressure parameters of the refrigerant at the outlet of the low-pressure condenser 104, and the second electronic expansion valve 108 achieves the purpose of controlling the flow rate of the refrigerant by detecting the superheat degree of the refrigerant at the suction port of the inverter compressor 101.
Claims (7)
1. An ejector synergistic double condenser heat pump drying system for material drying, characterized in that: the system comprises an air circulation loop and a refrigerant circulation loop, wherein the refrigerant circulation loop is provided with a variable frequency compressor (101), the variable frequency compressor (101) has a variable speed function, and the rotating speed of the variable frequency compressor (101) is controlled through the change of the frequency of a motor so as to adjust the mass flow rate of the refrigerant in the refrigerant circulation loop; the variable frequency compressor (101) is provided with an air suction port and an air exhaust port, the air exhaust port of the variable frequency compressor (101) is connected with the inlet of the high-pressure condenser (102), the high-temperature refrigerant vapor after temperature rise and pressure rise is compressed by the variable frequency compressor (101) and enters the high-pressure condenser (102), and the refrigerant exchanges heat with dry air to partially condense the refrigerant; the method comprises the steps that a gas-liquid two-phase refrigerant at the outlet of a high-pressure condenser (102) enters a nozzle inlet of an ejector (103) as a primary flow, the outlet of the ejector (103) is connected with the inlet of a low-pressure condenser (104), the two-phase refrigerant is completely condensed in the low-pressure condenser (104), saturated liquid refrigerant at the outlet of the low-pressure condenser (104) enters a first electronic expansion valve (105), after an isenthalpic throttling process, the two-phase refrigerant enters a flash evaporator (106) inlet from the outlet of the first electronic expansion valve (105), wherein saturated gas-phase refrigerant is injected to a secondary flow inlet of the ejector (103), saturated liquid-phase refrigerant enters a hot end inlet of a supercooler (107), the supercooled refrigerant enters an inlet of a second electronic expansion valve (108) for isenthalpic throttling process, the outlet of the second electronic expansion valve (108) is connected with an inlet of a dehumidifying evaporator (109), the gas-liquid two-phase refrigerant exchanges heat with high-humidity air from a drying box in the dehumidifying evaporator (109), and then is completely evaporated, the saturated gas-phase refrigerant enters a cold-phase refrigerant enters a heat-exchange air compressor (101) through a cold-phase refrigerant circulation loop of the supercooled evaporator (109), and then enters a cold-phase refrigerant circulation loop (101) through a cold-phase refrigerant inlet of the heat exchanger; in the air circulation loop, the high-humidity air passing through the drying box firstly passes through the dehumidifying evaporator (109), the temperature and the humidity are reduced, dry cold air is formed, the dry cold air exchanges heat with the refrigerant through the low-pressure condenser (104), the temperature is increased for the first time, and then exchanges heat with the refrigerant through the high-pressure condenser (102), the temperature is increased for the second time, so that high-temperature dry air is formed to enter the inlet of the drying box, and the air circulation of the air circulation loop is completed.
2. The ejector synergistic dual condenser heat pump drying system for material drying of claim 1, wherein: in the ejector (103), the partially condensed gas-liquid two-phase mixed refrigerant from the high-pressure condenser (102) is used as primary fluid of the ejector (103), the pressure of the primary fluid is higher than that of secondary fluid, namely ejected fluid, from a gas phase outlet of the flash evaporator (106), and the high-pressure condenser (102) realizes the partial condensation of the exhaust gas of the variable-frequency compressor (101), so that the outlet refrigerant is a gas-liquid two-phase flow, has a higher enthalpy value, and the capacity of the ejector (103) for recovering expansion work is improved; the saturated gas-phase refrigerant is injected by the gas-liquid two-phase refrigerant at the gas-phase outlet in the flash evaporator (106), and enters the mixing section of the ejector (103) together for isobaric mixing, and enters the low-pressure condenser (104) after being subjected to speed reduction and pressure increase through the diffusion section of the ejector (103).
3. The ejector synergistic dual condenser heat pump drying system for material drying of claim 1, wherein: the superheated refrigerant vapor discharged by the variable frequency compressor (101) is condensed in steps of a high-pressure condenser (102) and a low-pressure condenser (104), the refrigerant at the outlet of the high-pressure condenser (102) is in a gas-liquid two-phase state, and the refrigerant at the outlet of the low-pressure condenser (104) is in a saturated liquid phase; an ejector (103) is additionally arranged between the high-pressure condenser and the low-pressure condenser, so that expansion work can be effectively recovered, and the average condensation temperature is reduced and the energy efficiency of the system is improved through two condensation processes of high-pressure condensation and low-pressure condensation; the dry cold air firstly exchanges heat with the low-pressure condenser (104), after primary temperature rise, enters the high-pressure condenser (102) to carry out secondary temperature rise, and the setting of the air side gradient temperature rise reduces the average heat exchange temperature difference between the air and the refrigerant through the high-pressure condenser and the low-pressure condenser, so that the irreversible loss in the condensation heat exchange process is reduced, and the system efficiency is comprehensively improved.
4. The ejector synergistic dual condenser heat pump drying system for material drying of claim 1, wherein: the gas-liquid two-phase refrigerant from the first electronic expansion valve (105) enters the flash evaporator (106), wherein the gas-phase refrigerant provides secondary fluid of the ejector (103), the liquid-phase refrigerant is supercooled in the supercooler (107), the second electronic expansion valve (108) throttles and then enters the dehumidifying evaporator (109), the flash evaporator (106) effectively reduces the temperature of the refrigerant inlet before the second electronic expansion valve (108), the dryness of the refrigerant passing through the second electronic expansion valve (108) is reduced, the unit refrigerating capacity of the refrigerant is increased, the supercooler (107) provides a supercooling effect, the unit refrigerating capacity is further increased, the cooling and dehumidifying capacity of the dehumidifying evaporator (109) is improved, the system stability is enhanced due to the supercooling degree, the refrigerant entering the inlet of the variable frequency compressor (101) after heat exchange is carried out at the cold end of the supercooler (107), the variable frequency compressor (101) is prevented from being overheated, the variable frequency compressor (101) is prevented from being sucked by the aid of the supercooler (107), and the variable frequency compressor (101) is further protected, and the system stability is further improved.
5. A method of operating an ejector synergistic dual condenser heat pump drying system for material drying as claimed in any one of claims 1 to 4, wherein: the refrigerant cycle works as follows: the high-temperature high-pressure superheated steam-state refrigerant at the exhaust port of the variable-frequency compressor (101) enters the high-pressure condenser (102) to exchange heat with the preheated drying air, so that the drying and dehumidifying capacity of the high-temperature drying air is achieved; the superheated refrigerant forms a gas-liquid two-phase mixed refrigerant with high enthalpy after partial condensation of the released heat, so the gas-liquid two-phase mixed refrigerant is taken as a primary fluid to enter a nozzle inlet of an ejector (103), is changed into a low-pressure high-speed gas-liquid two-phase mixed refrigerant after expansion in the nozzle, is isobarically mixed with the saturated gas-phase refrigerant from a gas phase outlet of a flash evaporator (106) in a mixing section of the ejector (103), enters a low-pressure condenser (104) through a gas-liquid two-phase refrigerant after being subjected to speed reduction and pressure increase by a diffusion section of the ejector (103), preheats dry cold air from a dehumidifying evaporator (109), completely condenses the refrigerant in the process, and forms the gas-liquid two-phase refrigerant after the isenthalpic throttling process, the saturated gas-phase refrigerant is injected into the ejector (103) as a secondary fluid, the saturated liquid-phase refrigerant enters the hot end inlet of the subcooler (107) and is regenerated with the saturated gas-phase refrigerant at the outlet of the dehumidifying evaporator (109), the refrigerant obtains supercooling degree in the subcooler (107), enters the second electronic expansion valve (108), forms gas-liquid two-phase refrigerant after isenthalpic throttling process, enters the dehumidifying evaporator (109) to absorb heat to form saturated gas-phase refrigerant, cools and dehumidifies high-humidity wet air from the drying box, then enters the cold end inlet of the subcooler (107) to provide supercooling degree for the saturated liquid-phase refrigerant from the flash evaporator (106), the superheat degree is obtained and then returned to the air suction port of the variable frequency compressor (101); the recovery of expansion work is realized by introducing the ejector (103), the irreversible loss of a throttling process in a throttling expansion mechanism is reduced, the efficiency of a heat pump drying system is remarkably improved, the supercooling degree of the refrigerant before the dehumidifying evaporator (109) is increased by the flash evaporator (106) and the supercooling device (107), the cooling and dehumidifying capacity of the dehumidifying evaporator (109) is improved, meanwhile, the liquid-carrying during the air suction of the variable frequency compressor (101) is avoided by the regenerative action of the supercooling device (107), and the system stability is enhanced.
6. A method of controlling an ejector-enhanced dual condenser heat pump drying system for material drying as recited in any one of claims 1 to 4, wherein: a temperature sensor and a pressure sensor are arranged at the outlet of the low-pressure condenser (104), and the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser and the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser are obtained; a temperature sensor and a pressure sensor are arranged at an air suction port of a compressor (101) to obtain the temperature T ric of the refrigerant at the air suction port of the compressor and the pressure P ric of the refrigerant at the air suction port of the compressor; a temperature sensor is arranged at the outlet of the drying box, and the temperature T aod of high-humidity air at the outlet of the drying box is obtained; calculating and judging whether the refrigerant is in a saturated liquid state according to a thermal physical property equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the outlet of the low-pressure condenser (104), so as to regulate and control the opening of the first electronic expansion valve (105); the superheat degree of the refrigerant is calculated and judged according to a thermal physical property equation of the refrigerant by utilizing the temperature and the pressure of the refrigerant at the air suction port of the variable frequency compressor (101), so that the opening degree of the second electronic expansion valve (108) is regulated and controlled; the rotating speed of the variable frequency compressor (101) is controlled by adopting the temperature of high-humidity air from the drying box; the first electronic expansion valve (105) achieves the purpose of controlling the flow of the refrigerant by detecting the temperature and pressure parameters of the refrigerant at the outlet of the low-pressure condenser (104), and the second electronic expansion valve (108) achieves the purpose of controlling the flow of the refrigerant by detecting the superheat degree of the refrigerant at the air suction port of the variable-frequency compressor (101).
7. The method for controlling an ejector synergistic dual condenser heat pump drying system for material drying of claim 6, wherein: the specific implementation is as follows: when the high humidity air temperature T aod at the outlet of the drying box is detected to be lower than a preset temperature value T aods, controlling the variable frequency compressor (101) to increase the rotating speed; when the high humidity air temperature T aod at the outlet of the drying box is detected to be higher than a preset temperature value T aods, controlling the variable frequency compressor (101) to reduce the rotating speed; When the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be lower than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve (105) is increased; When the temperature T ro1 of the refrigerant at the outlet of the low-pressure condenser is detected to be higher than the calculated saturated liquid-phase refrigerant temperature which is the same as the pressure P ro1 of the refrigerant at the outlet of the low-pressure condenser, namely a preset temperature value T ro1s, the opening degree of the first electronic expansion valve (105) is reduced; When the superheat delta T ric of the refrigerant at the air suction port of the compressor (101) is higher than a preset superheat delta T rics through detection and calculation, increasing the opening of the second electronic expansion valve (108); when the degree of superheat DeltaT ric of the refrigerant at the suction port of the compressor (101) is lower than a preset degree of superheat DeltaT rics by detection and calculation, the opening degree of the second electronic expansion valve (108) is reduced.
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