Solar heat pump coupled with rotary dehumidification system for drying agricultural products

Abstract

The present application relates to the technical field of agricultural product drying processing, in particular to a solar heat pump coupled with a rotary dehumidifier for drying agricultural products, which solves the problems of long drying preheating time and high energy consumption of rotary regeneration operation in the prior art, and comprises a rotary dehumidifier, a heat pump circulation system, a solar water circulation system, a drying air circulation system and a regeneration air system, the solar water circulation system delivers heat to the drying air circulation system and the regeneration air circulation system, in the preheating process, the regeneration air system delivers heat to the heat pump circulation system, and the heat pump circulation system delivers heat to the drying air circulation system through double heat exchangers; in the drying process, the regeneration air system and the heat pump circulation system cooperate to deliver heat to the rotary dehumidifier and the drying air circulation system. The beneficial effect is that the coupling of solar auxiliary heating with heat pump and rotary dehumidification realizes rapid preheating of the drying system, and through switching of the refrigeration loop solenoid valve, the system can flexibly switch between high-temperature drying mode and low-temperature drying mode, and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of agricultural product drying and processing technology, and in particular to a solar heat pump coupled with a rotary dehumidifier agricultural product drying system. Background Technology

[0002] Heat pump drying, as a novel and efficient drying technology suitable for agricultural product processing, possesses core advantages such as high thermal efficiency, superior quality of dried products, significant energy savings, and environmentally friendly zero-pollutant emissions. It has broad application prospects in the fields of post-harvest loss reduction, quality improvement, efficiency enhancement, and industrialized processing of agricultural products. Heat pump drying and rotary dehumidification drying are two widely used high-efficiency technologies. However, traditional single-evaporator heat pump drying systems have significant technical shortcomings. Not only is the drying cycle relatively long, but the overall dehumidification capacity is also limited. In the high-humidity environment of agricultural product drying, it cannot achieve deep air dehumidification, making it difficult to meet the basic process requirements of refined drying. While rotary dehumidification drying features fast drying rates and independent and precise temperature and humidity control, the core characteristics of industrial-grade rotary dehumidification are incompatible with the mild drying requirements of agricultural products. Furthermore, its high-temperature regeneration mode significantly increases energy consumption, making it impossible to balance drying efficiency with low-energy operation requirements, thus limiting the large-scale application of this technology.

[0003] Based on this, the combined heat pump and rotary dehumidification drying technology has emerged, achieving complementary advantages between the two technologies. Simultaneously, by recovering and utilizing waste heat from the heat pump system, overall energy consumption is effectively reduced, better meeting the needs of gentle, low-consumption, and efficient drying processes for agricultural products. In existing technologies, various drying systems coupling heat pumps and rotary dehumidifiers have appeared. For example, patent CN120274505A discloses a heat pump coupled with a low-temperature regeneration rotary dehumidification open / closed integrated drying system. This system cleverly combines parts of open and closed drying systems, fully leveraging the advantages of both. Combined with the characteristics of a low-temperature regeneration rotary dehumidifier, it achieves deep dehumidification and improved drying quality, solving the technical problems of low drying quality or low drying rate in existing drying systems for agricultural products. In the first half of the material drying process, the system uses an evaporator for condensation dehumidification, fully utilizing the latent heat of vaporization released by water vapor condensation; in the second half, a dehumidifying rotary dehumidifier is used for deep dehumidification, increasing the drying rate. Simultaneously, a heat exchanger recovers the waste heat discharged during the rotary dehumidification process, achieving a certain energy-saving effect.

[0004] However, while the aforementioned patents improve system performance through mode switching and partial waste heat recovery, their technical solutions still have room for optimization: First, the system preheating stage relies entirely on the heat pump to absorb external air energy, and the preheating speed may still be limited when the ambient temperature is low, affecting the overall drying efficiency; second, the rotary regeneration air is only heated by the heat pump condenser, resulting in a single heat source, and the heat pump efficiency ratio will decrease significantly when a higher regeneration temperature is required; in addition, most existing heat pump and rotary combined drying systems often have problems such as complex system structure, cumbersome control logic, or insufficient waste heat recovery when switching between open and closed modes. Summary of the Invention

[0005] This invention proposes a solar heat pump coupled with a rotary dehumidifier for agricultural product drying, which solves the problems of long drying preheating time and high energy consumption of rotary regeneration operation in the prior art.

[0006] The technical solution of this invention is implemented as follows:

[0007] The solar-powered heat pump coupled rotary dehumidifier agricultural product drying system includes: a rotary dehumidifier, a heat pump circulation system, a solar water circulation system, a drying air circulation system, and a regenerated air system. The solar water circulation system supplies heat to the drying air circulation system and the regenerated air circulation system. During preheating, the regenerated air system transfers heat to the heat pump circulation system, which then transfers heat to the drying air circulation system via dual heat exchangers. During drying, the regenerated air system and the heat pump circulation system work together to supply heat to the rotary dehumidifier and the drying air circulation system. This achieves cascaded utilization of heat and waste heat recovery, reducing the overall energy consumption of the system.

[0008] Furthermore, the heat pump cycle system includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a four-way reversing valve, and a compressor. The compressor's exhaust port and intake port are connected to the first and second ports of the four-way reversing valve, respectively. The third port of the four-way reversing valve is connected sequentially to the first heat exchanger, the first electronic expansion valve, and the second heat exchanger, and then connected to the fourth port of the four-way reversing valve. One end of the third heat exchanger is divided into two paths: one path is connected to the fourth port of the four-way reversing valve via solenoid valve I, and the other path is connected to the third port of the four-way reversing valve via solenoid valve II. The other end of the third heat exchanger is connected to the pipeline between the first heat exchanger and the first electronic expansion valve via solenoid valve IV. The other end of the third heat exchanger is equipped with a second electronic expansion valve arranged in parallel with solenoid valve IV. The two ends of the second electronic expansion valve are equipped with solenoid valve III and solenoid valve V.

[0009] Furthermore, the second and third heat exchangers are thermally coupled to the drying air circulation system, and the first heat exchanger is thermally coupled to the regeneration air system.

[0010] Furthermore, the drying air circulation system includes a drying chamber for containing the materials to be dried, and a drying air duct connected to the return air vent of the drying chamber. The drying air duct passes through the dehumidification zone of a rotary dehumidifier and a second fan. The outlet of the second fan is connected to the inlet of the drying chamber, forming a closed-loop circulation loop for the drying air, ensuring the recycling of the drying air and reducing heat loss. The drying air duct is thermally coupled with a heat pump circulation system, a solar water circulation system, and a regenerated air system. Through the coordinated heating of multiple heat sources, the temperature of the drying air is increased and the humidity is reduced, ensuring the drying effect.

[0011] Furthermore, a third air valve is installed on the drying air duct to control the opening and closing of the return air vent in the drying chamber. This third air valve allows for flexible adjustment of the drying airflow.

[0012] Furthermore, the solar water circulation system includes solar collectors and a water pump. The outlet of the solar collector is divided into two paths: one path flows back to the water pump after passing through air-water heat exchanger I, and the other path flows back to the water pump after passing through air-water heat exchanger II. The water pump is connected to the inlet of the solar collector. The water pump provides power for the solar water heating circulation, ensuring a stable supply of hot water.

[0013] Furthermore, air-water heat exchanger I is thermally coupled to the regeneration air system to heat the fresh air in the regeneration air system, providing a preheating heat source for the regeneration zone of the rotary dehumidifier and reducing the energy consumption of rotary regeneration; air-water heat exchanger II is thermally coupled to the drying air circulation system. It is used to heat the drying air in the drying air circulation system, realizing solar auxiliary heating of the drying air and further improving the energy-saving effect.

[0014] Furthermore, air-to-water heat exchanger I has water flow regulating valve I and water flow regulating valve III at both ends, and air-to-water heat exchanger II has water flow regulating valve II and water flow regulating valve IV at both ends. By adjusting the opening and closing of the four water flow regulating valves, the flow rate of solar water in the two heat exchange pipelines can be controlled, achieving a reasonable distribution of solar heat and adapting to the heat demand under different operating conditions. When weather conditions prevent the use of solar energy, all water flow regulating valves can be closed to stop the operation of the solar water circulation system and avoid ineffective energy consumption.

[0015] Furthermore, the regenerated air system includes a first fan. The fresh air generated by the first fan passes sequentially through an air-to-water heat exchanger I and the first heat exchanger before reaching the regeneration zone of the rotary dehumidifier. The outlet of the regeneration zone of the rotary dehumidifier is divided into two paths: one directly connects to the atmosphere, and the other connects to the atmosphere after passing through an air-to-air heat exchanger. The air-to-air heat exchanger is thermally coupled to the drying air circulation system. This is used to recover the waste heat discharged from the regenerated air, heat the drying air, realize waste heat recovery and utilization, and further reduce system energy consumption.

[0016] Furthermore, a first air valve is installed on the pipe connecting the regeneration zone of the rotary dehumidifier to the atmosphere, and a second air valve is installed on the pipe connecting the regeneration zone of the rotary dehumidifier to the air-to-air heat exchanger. By switching the opening and closing of the first and second air valves, the exhaust path of the regenerated air can be controlled, and waste heat recovery can be flexibly selected at different stages of drying to adapt to different drying conditions, thereby improving the flexibility and energy efficiency of the system operation.

[0017] The beneficial effects of this invention are: by coupling solar-assisted heating with heat pumps and rotary dehumidification, rapid preheating of the drying system is achieved, and the energy consumption of rotary regeneration is reduced by step-type heating and regeneration air, thereby improving the overall energy efficiency of the system.

[0018] During the preheating stage, the solar water circulation system provides an auxiliary heat source, working in conjunction with the heat pump circulation system and the regenerated air system. By switching the operating conditions through the heat pump four-way reversing valve, the two heat exchangers of the heat pump circulation system and the solar-heated air-water heat exchanger are used to heat the drying air together, thereby overcoming the problem that the preheating speed of the traditional heat pump drying system is limited by the ambient temperature and significantly shortening the drying preparation time.

[0019] During the drying phase, the solar water circulation system directly provides preheating or auxiliary heating for the fresh air and drying air of the regenerated air system, reducing reliance on the heat pump system as a single heat source. Especially during the regeneration process of the rotary dehumidifier, the fresh air is first preheated by the solar air-water heat exchanger I, and then heated by the heat pump's first heat exchanger. This stepped heating method can achieve the required regeneration temperature while reducing the load and exhaust pressure of the heat pump condenser, thereby improving the energy efficiency ratio of the heat pump under higher temperature conditions and solving the problem of high energy consumption in rotary regeneration.

[0020] The waste heat discharged from the regenerated air system can be recovered through an air-to-air heat exchanger to heat the drying air entering the drying chamber, further realizing the cascade utilization of heat and multi-stage waste heat recovery within the system. While ensuring drying rate and quality, the overall energy consumption of the system is significantly reduced.

[0021] By switching the solenoid valves in the refrigeration pipeline, the system can flexibly switch between high-temperature drying and low-temperature drying modes, making it suitable for a wide range of materials and achieving high drying quality. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1This is a schematic diagram of the solar heat pump coupled rotor dehumidification agricultural product drying system of the present invention;

[0024] Figure 2 This is a schematic diagram of a solar water circulation system;

[0025] Figure 3 This is a schematic diagram of a heat pump cycle system;

[0026] Figure 4 It is a dry air circulation system;

[0027] Figure 5 It is a regenerated air system.

[0028] In the diagram: 1. Solar collector, 2. Water pump, 3. Water flow regulating valve I, 4. Water flow regulating valve II, 5. Water flow regulating valve III, 6. Water flow regulating valve IV, 7. Regenerative fan, 8. Air-water heat exchanger I, 9. First heat exchanger, 10. First electronic expansion valve, 11. Second heat exchanger, 12. Rotary dehumidifier, 13. Four-way reversing valve, 14. Compressor, 15. Solenoid valve I, 16. Solenoid valve II, 17. First air valve, 18. Second air valve, 19. Air-to-air heat exchanger, 20. Third heat exchanger, 21. Air-water heat exchanger II, 22. Drying fan, 23. Drying chamber, 24. Solenoid valve III, 25. Second electronic expansion valve, 26. Solenoid valve IV, 27. Solenoid valve V, 28. Third air valve. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1, as Figure 1As shown, an embodiment of the present invention provides a solar-heat pump coupled rotary dehumidifier agricultural product drying system. This system includes a rotary dehumidifier 12, a heat pump circulation system, a solar water circulation system, a drying air circulation system, and a regenerated air system. The solar water circulation system, as an independent clean heat source, supplies heat to the drying air circulation system and the regenerated air system, achieving initial utilization of solar energy. During the preheating process at system startup, the regenerated air system transfers heat from solar energy to the heat pump circulation system. Simultaneously, the heat pump circulation system transfers heat to the drying air circulation system through dual heat exchangers, achieving rapid, multi-stage heating of the air in the drying chamber 23, significantly shortening the preheating time of traditional closed-loop heat pump drying systems. During the actual drying process, the regenerated air system and the heat pump circulation system work together to supply high-temperature regenerated air to the regeneration zone of the rotary dehumidifier 12, desorbing and regenerating the moisture-saturated desiccant material; and providing drying heat to the drying air circulation system. Simultaneously, waste heat from the regeneration exhaust air is recovered through the air-to-air heat exchanger 19, achieving cascaded utilization and maximum recovery of heat, thereby significantly reducing the overall energy consumption of the system.

[0031] In this embodiment, the heat pump circulation system includes a first heat exchanger 9, a second heat exchanger 11, a third heat exchanger 20, a four-way reversing valve 13, and a compressor 14. The exhaust port and intake port of the compressor 14 are connected to the first and second ports of the four-way reversing valve 13, respectively. The third port of the four-way reversing valve 13 is connected sequentially to the first heat exchanger 9, the first electronic expansion valve 10, and the second heat exchanger 11, and then to the fourth port of the four-way reversing valve 13, forming the basic circulation loop of the heat pump. The third heat exchanger 20 serves as an auxiliary heat exchanger, with one end divided into two paths: one path connects to the fourth port of the four-way reversing valve 13 via solenoid valve I 15, and the other path connects to the third port of the four-way reversing valve 13 via solenoid valve II 16. The other end of the third heat exchanger 20 is connected to the pipeline between the first heat exchanger 9 and the first electronic expansion valve 10 via solenoid valve IV 26. At the same time, a second electronic expansion valve 25 is provided at this connection point, arranged in parallel with solenoid valve IV 26; solenoid valve III 24 and solenoid valve V 27 are respectively provided at both ends of the second electronic expansion valve 25. This pipeline and valve design allows the first heat exchanger 9, the second heat exchanger 11 and the third heat exchanger 20 to play the role of condenser or evaporator according to the combination of different solenoid valves and the connection direction of the four-way reversing valve 13.

[0032] The second heat exchanger 11 and the third heat exchanger 20 are installed in the piping of the drying air circulation system and are thermally coupled to the system to cool or heat the drying air. The first heat exchanger 9 is installed in the piping of the regeneration air system and is thermally coupled to the system to cool or heat the fresh air, providing the heat required for preheating the drying air or regenerating the turbine. The first electronic expansion valve 10 and the second electronic expansion valve 25 are used for throttling and pressure reduction; the four-way reversing valve 13 and each solenoid valve are electrically controlled components that switch actions according to the instructions of the system controller.

[0033] In this embodiment, the drying air circulation system includes a drying chamber 23 for containing the material to be dried, and a drying air duct connected to the return air inlet of the drying chamber 23. The drying air duct passes sequentially through the dehumidification zone of the rotary dehumidifier 12 and a second fan 22. The outlet of the second fan 22 is connected to the inlet of the drying chamber 23, thus forming a complete closed-loop circulation circuit. The drying air duct is also thermally coupled to the heat pump circulation system, the solar water circulation system, and the regenerated air system through a heat exchanger, allowing the drying air to be heated and processed by multiple heat sources in a coordinated manner, thereby precisely controlling its temperature and humidity. A third air valve 28 is provided on the drying air duct for controlling the opening and closing of the return air inlet of the drying chamber 23. The third air valve 28 can adjust the amount of drying air.

[0034] In this embodiment, the solar water circulation system includes a solar collector 1 and a water pump 2. The outlet of the solar collector 1 is divided into two paths: one path flows back to the water pump 2 after passing through an air-to-water heat exchanger I8, and the other path flows back to the water pump 2 after passing through an air-to-water heat exchanger II21. The outlet of the water pump 2 is connected to the inlet of the solar collector 1, forming a complete solar hot water circulation loop. The water pump 2 provides power for the circulation, ensuring that the hot water heated by the solar collector 1 can be stably delivered to the two heat exchangers. The air-to-water heat exchanger I8 is thermally coupled to the regeneration air system and is mainly used to heat the fresh air in the regeneration air system, reducing the heating load of the subsequent heat pump system. The air-to-water heat exchanger II21 is thermally coupled to the dry air circulation system and is used to heat the dry air, realizing direct auxiliary heating of the dry air by solar energy. To precisely control the distribution of solar heat, air-to-water heat exchanger I8 is equipped with water flow regulating valves I3 and III5 at both ends, and air-to-water heat exchanger II21 is equipped with water flow regulating valves II4 and IV6 at both ends. By adjusting the opening and closing of these four water flow regulating valves, the flow rate of hot water to the two air-to-water heat exchangers can be independently controlled, thereby intelligently distributing heat according to whether the system is currently in preheating, high-temperature drying, or low-temperature drying mode, and changes in solar irradiance intensity. For example, when solar energy is abundant and rapid preheating is required, two valves can be opened simultaneously; at night or in sunny weather, all water flow regulating valves can be closed, completely stopping the solar water circulation system and avoiding pump power loss caused by ineffective circulation.

[0035] In this embodiment, the regeneration air system includes a first fan 7. The fresh air generated by the first fan 7 passes sequentially through an air-to-water heat exchanger Ⅰ8 and a first heat exchanger 9 before reaching the regeneration zone of the rotary dehumidifier 12, where it desorbs and regenerates the moisture-saturated dehumidifying rotor. The fresh air is air drawn in from the external environment. The outlet of the regeneration zone of the rotary dehumidifier 12 is divided into two paths: one path directly connects to the atmosphere through a first air valve 17; the other path connects to the atmosphere through an air-to-air heat exchanger 19 after passing through a second air valve 18. The air-to-air heat exchanger 19 is also thermally coupled to the dry air circulation system, allowing the high-temperature, high-humidity regeneration exhaust air to cross-exchange heat with the low-temperature dry air, thereby recovering the sensible heat in the regeneration exhaust air for preheating the dry air and achieving waste heat recovery. By controlling the opening and closing of the first air valve 17 and the second air valve 18, the exhaust path of the regeneration air can be flexibly selected. When it is necessary to quickly remove high humidity exhaust gas or when the system is running simply, the first air valve 17 can be opened and the second air valve 18 can be closed to allow the regenerated air to be directly discharged. When pursuing maximum energy saving, the first air valve 17 can be closed and the second air valve 18 can be opened to allow the regenerated air to flow through the air-to-air heat exchanger 19 to recover waste heat before being discharged.

[0036] The system operates primarily in three modes: preheating, high-temperature drying, and low-temperature drying. These modes are achieved through the coordinated operation of the four-way directional valve 13, various solenoid valves, air valves, and water flow regulating valves. The detailed operating processes of these three modes are described below.

[0037] 1. Preheating stage

[0038] When the system is initially started or the drying batch is changed, the drying chamber 23 and the air inside it need to be heated from the ambient temperature to the set drying start temperature.

[0039] The control logic is as follows: Four-way reversing valve 13 is energized and reverses direction; solenoid valves II 16 and IV 26 are closed, while solenoid valves I 15, III 24, and V 27 are opened. First air valve 17 is opened, and second air valve 18 is closed. Third air valve 28 is opened. Water flow regulating valves I 3, II 4, III 5, and IV 6 are opened when solar energy is available and closed when it is not. Second heat exchanger 11 switches to condenser mode, first heat exchanger 9 switches to evaporator mode, and third heat exchanger 20 switches to condenser mode.

[0040] In this state, the refrigerant flow in the heat pump cycle system is as follows: Low-temperature, low-pressure refrigerant gas flows into compressor 14 through four-way reversing valve 13, is compressed into high-temperature, high-pressure refrigerant vapor, and then splits into two paths after passing through four-way reversing valve 13. The first path enters the third heat exchanger 20 via solenoid valve I 15, releasing heat to heat the flowing dry air and condensing into a high-pressure liquid. This liquid is then throttled and depressurized by solenoid valve III 24 and the second electronic expansion valve 25, becoming a low-temperature, low-pressure gas-liquid mixture, and then flows through solenoid valve V 27. The second path enters the second heat exchanger 11, which is now in condenser mode, heating the dry air and condensing into a high-pressure liquid. This liquid is then throttled and depressurized by the first electronic expansion valve 10. The refrigerant from the two throttled paths merges and enters the first heat exchanger 9, which is now in evaporator mode, absorbing heat from the flowing fresh air and evaporating into low-temperature, low-pressure vapor. Finally, it returns to compressor 14 via four-way reversing valve 13, completing the cycle.

[0041] The hot water flow direction in the solar water circulation system is:

[0042] The airflow process is as follows: Driven by the second fan 22, the dry air flows out from the return air vent of the drying chamber 23, sequentially passing through the second heat exchanger 11 (which acts as a condenser), the dehumidification zone of the rotary dehumidifier 12 (the rotor may not operate or operate at low speed during this stage, serving only as a passageway), the air-to-air heat exchanger 19 (no heat exchange occurs at this stage), the third heat exchanger 20 (which acts as a condenser), and the air-to-water heat exchanger II 21, finally returning to the drying chamber 23, forming a closed-loop rapid preheating cycle. Simultaneously, driven by the first fan 7, the fresh air flows sequentially through the air-to-water heat exchanger I 8, the first heat exchanger 9 (which acts as an evaporator), then enters the regeneration zone of the rotary dehumidifier 12, and finally is directly discharged into the atmosphere through the first air valve 17.

[0043] The preheating mode employs a solar-assisted heating scheme combined with heating from the second heat exchanger 11 and the third heat exchanger 20. Solar energy directly provides some heat; the heat pump system uses a four-way reversing valve to temporarily convert the second heat exchanger 11, originally used for dehumidification, into a heater, and activates the third heat exchanger 20 as another heater. Simultaneously, it absorbs ambient heat from the regenerated fresh air side through the first heat exchanger 9. This effectively mobilizes almost all of the system's heat source and heat exchange capacity to heat the dry air during the preheating stage, resulting in an order-of-magnitude increase in preheating speed and less susceptibility to ambient temperature, effectively solving the problem of long preheating times.

[0044] 2. High-temperature drying mode

[0045] When the temperature of the drying chamber 23 reaches the set value, and the material to be dried is suitable or needs accelerated dehydration in the later stage of drying, the high-temperature drying mode can be switched. The feature of this mode is that the heat pump circulation system heats the regeneration air through the first heat exchanger 9, heats the drying air through the third heat exchanger 20, and uses a rotary dehumidifier 12 for deep dehumidification.

[0046] The control logic is as follows: Four-way reversing valve 13 is reset. Solenoid valves I 15, III 24, and V 27 are closed; solenoid valves II 16 and IV 26 are opened. The second heat exchanger 11 switches to evaporator mode, the first heat exchanger 9 switches to condenser mode, and the third heat exchanger 20 switches to condenser mode. The second air valve 18 is opened, and the first air valve 17 is closed. The third air valve 28 is opened. Valve control for the solar water circulation system is the same as in the preheating stage.

[0047] In this state, the refrigerant flow in the heat pump cycle system is as follows: the high-temperature, high-pressure refrigerant vapor discharged from the compressor 14 is divided into two paths after passing through the four-way reversing valve 13. The first path enters the first heat exchanger 9, heating the flowing regenerated fresh air and condensing itself. The second path enters the third heat exchanger 20 through the solenoid valve II 16, heating the flowing dry air and condensing itself. The two condensed high-pressure refrigerant liquids merge through pipelines, one flowing out from the first heat exchanger 9 and the other from the third heat exchanger 20 through the solenoid valve IV 26. After being throttled and depressurized by the first electronic expansion valve 10, they enter the second heat exchanger 11, absorbing heat from the dry air to cool and dehumidify it. After absorbing heat and evaporating, the refrigerant returns to the compressor 14 through the four-way reversing valve 13.

[0048] The airflow process is as follows: Dry air flows out of the drying chamber 23, first passing through the second heat exchanger 11, which acts as an evaporator, where it is cooled and some moisture is removed. Then, it enters the dehumidification zone of the rotary dehumidifier 12, where it exchanges heat and mass with the dehumidifying material to achieve dehumidification and temperature increase. The heated dry air then enters the air-to-air heat exchanger 19 to exchange heat with the high-temperature regeneration exhaust air. It then enters the third heat exchanger 20, which acts as a condenser, where it is heated by the heat pump refrigerant. Afterward, it flows through the air-to-water heat exchanger II 21, where it is heated by solar energy. Finally, it is sent back to the drying chamber 23 by the second fan 22 for high-temperature drying.

[0049] The regenerated fresh air enters from the first fan 7 and is heated in two stages—by the air-to-water heat exchanger I8 and the first heat exchanger 9 (which acts as a condenser)—to become high-temperature regenerated air. This high-temperature, high-humidity regenerated air is then sent to the regeneration zone of the rotary dehumidifier 12 to desorb the desiccant. The desorbed high-temperature, high-humidity regenerated air is then introduced into the air-to-air heat exchanger 19 through the second air valve 18. After exchanging heat with the dry air to cool down and recover waste heat, it is then discharged into the atmosphere.

[0050] In high-temperature drying mode, the rotary dehumidifier 12 undertakes the task of deep dehumidification, overcoming the shortcomings of a single heat pump in terms of reduced dehumidification capacity under low-humidity conditions in the later stages of material drying. The regenerated air employs a tiered heating method combining solar preheating and heat pump condensation heating, significantly reducing the temperature rise load of the first heat exchanger 9 of the heat pump, allowing it to operate in a more efficient range and solving the problem of high energy consumption in rotary regeneration. Simultaneously, waste heat from the regeneration exhaust air is recovered through the air-to-air heat exchanger 19, further improving system energy efficiency. The drying air undergoes multi-stage treatment—heat pump evaporative dehumidification, rotary deep dehumidification, waste heat recovery, heat pump condensation heating, and solar heating—ensuring precise and independent temperature and humidity control, achieving both rapid drying and guaranteed drying quality.

[0051] 3. Low-temperature drying mode

[0052] The control logic is as follows: Four-way reversing valve 13 remains in the reset state, the same as in the high-temperature drying mode. Solenoid valves II 16 and IV 26 are closed; solenoid valves I 15, III 24, and V 27 are open. The second heat exchanger 11 switches to evaporator mode, the first heat exchanger 9 switches to condenser mode, and the third heat exchanger 20 switches to evaporator mode. The first air valve 17 is open, and the second air valve 18 is closed. The third air valve 28 is open. In the solar water circulation system, water flow regulating valves I 3 and III 5 are open, and water flow regulating valves II 4 and IV 6 are closed. This means that solar heat is only used to heat the regenerated fresh air, not to heat the drying air, in order to maintain the low temperature of the drying air.

[0053] In this state, the refrigerant flow in the heat pump cycle system is as follows: the high-temperature, high-pressure refrigerant vapor discharged from the compressor 14 enters the first heat exchanger 9 through the four-way reversing valve 13. After heating and regenerating the fresh air, it condenses into a high-pressure liquid and splits into two paths. The first path is throttled by the first electronic expansion valve 10 and enters the second heat exchanger 11. The second path is throttled by the solenoid valve V 27 and the second electronic expansion valve 25, and then enters the third heat exchanger 20 through the solenoid valve III 24. The two refrigerant streams evaporate in the second heat exchanger 11 and the third heat exchanger 20 respectively, absorbing heat from the dry air, significantly reducing their temperature and moisture content. The two low-pressure refrigerant vapors after evaporation merge, one flowing out from the second heat exchanger 11 and the other flowing out from the third heat exchanger 20 through the solenoid valve I 15, and both returning to the compressor 14 through the four-way reversing valve 13.

[0054] The airflow process is as follows: Dry air flows out of the drying chamber 23, sequentially passing through the second heat exchanger 11 (which acts as an evaporator), the dehumidification zone of the rotary dehumidifier 12, the air-to-air heat exchanger 19, and the third heat exchanger 20 (which also acts as an evaporator). Then it flows through the air-to-water heat exchanger II 21 and is finally returned to the drying chamber 23 by the second fan 22. In this mode, the air-to-air heat exchanger 19 does not have high-temperature regeneration air passing through it; it only serves as a passageway. The air-to-water heat exchanger II 21 does not have hot water passing through it; it only serves as a passageway. The temperature of the dry air after passing through the dehumidification zone of the rotary dehumidifier 12 increases, requiring evaporative cooling through the third heat exchanger 20 for temperature regulation to achieve a suitable temperature for low-temperature drying.

[0055] The regenerated fresh air is heated by the air-water heat exchanger I8 and the first heat exchanger 9 in two stages, and then desorbed and regenerated on the rotor before being directly discharged through the first air valve 17.

[0056] The low-temperature drying mode significantly enhances the system's dehumidification and cooling capabilities by switching the third heat exchanger 20 to an evaporator, forming a dual-evaporator system in parallel with the second heat exchanger 11. This is particularly suitable for operating conditions requiring the maintenance of low drying temperatures (e.g., 30-45℃). Turning off the solar heating of the drying air avoids unnecessary temperature rise. Although the regeneration side still consumes energy, solar preheating reduces the condensation load on the heat pump.

[0057] In summary, the system of this invention integrates solar thermal collection, a heat pump, and rotary dehumidification, and incorporates a sophisticated valve control system to achieve flexible switching between three modes: preheating, high-temperature drying, and low-temperature drying. The preheating mode addresses the issue of slow start-up; the high-temperature drying mode achieves deep dehumidification and rapid drying while significantly reducing regeneration energy consumption through solar cascade heating and waste heat recovery; and the low-temperature drying mode provides a reliable technical path for high-quality drying. These three modes can be intelligently selected or switched according to material characteristics and drying stage, achieving a balance between system efficiency, energy saving, and drying quality.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solar-powered heat pump coupled with a rotary dehumidifier for drying agricultural products, characterized in that: include: Rotary dehumidifier (12), heat pump circulation system, solar water circulation system, dry air circulation system and regenerated air system. The solar water circulation system delivers heat to the dry air circulation system and the regenerated air circulation system. During the preheating process, the regenerated air system delivers heat to the heat pump circulation system. The heat pump circulation system delivers heat to the dry air circulation system through a double heat exchanger. During the drying process, the regenerated air system and the heat pump circulation system work together to deliver heat to the rotary dehumidifier (12) and the dry air circulation system.

2. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 1, characterized in that, The heat pump cycle system includes a first heat exchanger (9), a second heat exchanger (11), a third heat exchanger (20), a four-way reversing valve (13), and a compressor (14). The exhaust port and intake port of the compressor (14) are connected to the first and second ports of the four-way reversing valve (13), respectively. The third port of the four-way reversing valve (13) is connected to the first heat exchanger (9), the first electronic expansion valve (10), and the second heat exchanger (11) in sequence, and then connected to the fourth port of the four-way reversing valve (13). One end of the third heat exchanger (20) is divided into two paths, one of which passes through... Solenoid valve I (15) is connected to the fourth port of the four-way reversing valve (13), and another path is connected to the third port of the four-way reversing valve (13) through solenoid valve II (16). The other end of the third heat exchanger (20) is connected to the pipeline between the first heat exchanger (9) and the first electronic expansion valve (10) through solenoid valve IV (26). The other end of the third heat exchanger (20) is provided with a second electronic expansion valve (25) arranged in parallel with solenoid valve IV (26). Solenoid valve III (24) and solenoid valve V (27) are provided at both ends of the second electronic expansion valve (25).

3. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 2, characterized in that, The second heat exchanger (11) and the third heat exchanger (20) are thermally coupled to the drying air circulation system, and the first heat exchanger (9) is thermally coupled to the regeneration air system.

4. The solar heat pump coupled rotary dehumidification agricultural product drying system according to any one of claims 1 to 3, characterized in that, The drying air circulation system includes a drying chamber (23) for containing the material to be dried, and a drying air duct connected to the return air inlet of the drying chamber (23). The drying air duct passes through the dehumidification zone of the rotary dehumidifier (12) and the second fan (22). The outlet of the second fan (22) is connected to the inlet of the drying chamber (23). The drying air duct is thermally coupled to the heat pump circulation system, the solar water circulation system and the regenerated air system.

5. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 4, characterized in that, A third air valve (28) is provided on the drying air duct to control the opening and closing of the return air inlet of the drying chamber (23).

6. The solar-powered heat pump coupled rotary dehumidification agricultural product drying system according to any one of claims 1 to 3 and 5, characterized in that, The solar water circulation system includes a solar collector (1) and a water pump (2). The outlet of the solar collector (1) is divided into two paths. One path flows back to the water pump (2) after passing through the air-water heat exchanger I (8), and the other path flows back to the water pump (2) after passing through the air-water heat exchanger II (21). The water pump (2) is connected to the inlet of the solar collector (1).

7. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 6, characterized in that, Air-water heat exchanger I (8) is thermally coupled to the regenerated air system, and air-water heat exchanger II (21) is thermally coupled to the dry air circulation system.

8. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 7, characterized in that, The air-water heat exchanger I (8) has a water flow regulating valve I (3) and a water flow regulating valve III (5) at both ends, and the air-water heat exchanger II (21) has a water flow regulating valve II (4) and a water flow regulating valve IV (6) at both ends.

9. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 1 or 8, characterized in that, The regeneration air system includes a first fan (7). The fresh air generated by the first fan (7) passes through the air-water heat exchanger I (8) and the first heat exchanger (9) in sequence before reaching the regeneration zone of the rotary dehumidifier (12). The outlet of the regeneration zone of the rotary dehumidifier (12) is divided into two paths: one path is directly connected to the atmosphere, and the other path is connected to the atmosphere after passing through the air-air heat exchanger (19). The air-air heat exchanger (19) is thermally coupled to the dry air circulation system.

10. The solar heat pump coupled rotor dehumidification agricultural product drying system according to claim 9, characterized in that, A first air valve (17) is provided on the pipeline connecting the regeneration zone of the rotary dehumidifier (12) to the atmosphere, and a second air valve (18) is provided on the pipeline connecting the regeneration zone of the rotary dehumidifier (12) to the air-to-air heat exchanger (19).

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