A heat pump clothes dryer based on micro-channel pulsating heat pipe and a control method thereof

Abstract

The present application relates to a kind of heat pump clothes dryer based on microchannel pulsating heat pipe and control method.A kind of heat pump clothes dryer based on microchannel pulsating heat pipe, including fan, drying box, filter, heat pipe assembly, evaporator, compressor, condenser, throttling element, three-way filling valve;Fan drives air first into drying box in drying box clothes, again into filter to remove clothes fiber impurities, again into the evaporator section flat tube of heat pipe assembly precooling, again into evaporator temperature reduction dehumidification, again into the condenser section flat tube of heat pipe assembly preheating, again into condenser reheating, complete cycle.The present application introduces pulsating heat pipe into heat pump clothes dryer, adds precooling and reheating link, and proposes the combination control method of heat pipe and heat pump system, can improve the heat exchange efficiency of evaporator, condenser without additional energy consumption, improve dehumidification effect and reduce energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of dryer technology, and relates to a heat pump dryer based on microchannel pulsating heat pipes and its control method. Background Technology

[0002] Currently, most clothes dryers on the market are electric heating type, using PTC heating elements to raise the air temperature, and then a fan drives the hot air to blow onto the clothes to dry them. Their advantages are simple structure and low price. However, they consume a lot of electricity, and the hot, humid air discharged directly into the room affects the user experience.

[0003] A heat pump dryer is a dryer that uses heat pump technology. It generally consists of a heat pump system, a drying chamber, a circulating air system, and a drainage system. The heat pump system and the circulating air system correspond to the refrigerant flow and air flow, respectively. The heat pump system includes: a compressor, condenser, evaporator, and a throttling device. The circulating air system includes: a fan, air ducts, and an air filter.

[0004] The working process of a heat pump dryer is as follows: The compressor drives the refrigerant to circulate. The refrigerant absorbs heat from the exhaust gas from the drying chamber in the evaporator, and releases this heat in the condenser to heat the air about to enter the drying chamber. Driven by a fan, the high-temperature, high-humidity air exhausted from the drying chamber is cooled and dehumidified in the evaporator to become low-temperature, low-humidity air. This air is then heated again in the condenser to become high-temperature, low-humidity air, continuing to dry clothes inside the drying chamber. It has advantages such as lower energy consumption and minimal impact on indoor air quality.

[0005] However, existing heat pump dryer technology has problems: the air blown out of the drying chamber must first be cooled and dehumidified before being heated. In order to improve the dehumidification effect, the evaporation temperature is relatively low to ensure that it is below the air dew point temperature, and then it is heated by a large temperature rise in the condenser. This consumes a lot of cold source and a lot of heat source, which affects the efficiency of heat exchanger and the energy consumption of equipment.

[0006] To address this issue, auxiliary technologies such as semiconductor refrigeration and heat pipes can improve energy efficiency. For example, patents CN107130415 ("A Heat Pump and Heat Pipe Composite Clothes Dryer") and CN104776739 ("Heat Pipe Heat Exchanger, Evaporator Assembly, and Heat Pump Clothes Dryer") utilize loop heat pipes and capillary heat pipes for pre-cooling and reheating, respectively, reducing energy consumption. However, the combination of heat pipes and heat pump dryers presents the following technical challenges:

[0007] 1. Loop heat pipes require either a refrigerant pump or gravity-assisted drive. Refrigerant pumps require additional pump power and consume energy, resulting in higher manufacturing and operating costs. Gravity-assisted drive requires the condenser section to be higher than the evaporator section, making it more susceptible to installation angle and vibration.

[0008] 2. Capillary heat pipes require a capillary structure inside the evaporator end, such as metal mesh, fiber, or porous ceramics. The structure is complex and prone to clogging.

[0009] 3. Due to the high humidity in the heat pipe's operating environment, the inability to drain condensate in a timely manner will significantly impact heat exchange efficiency. Traditional straight fin structures cannot achieve rapid drainage; if the fin spacing is too close, condensate will adhere to the fins due to surface tension and will be difficult to fall.

[0010] 4. The basic arrangement simply places the two ends of the heat pipe on both sides of the evaporator, but there is no integrated control of the heat pipe and heat pump system in the system. Summary of the Invention

[0011] To address the issue of significant temperature rise affecting heat exchanger efficiency in heat pump dryers, this invention proposes a heat pump dryer based on microchannel pulsating heat pipes. By introducing microchannel pulsating heat pipes into the heat pump dryer system, this invention solves the problems of complex heat pipe structures and drainage difficulties in existing patents, and fills the gap in heat pipe selection and control strategies in heat pump dryer systems.

[0012] The technical solution of this invention to solve the above problems is: a heat pump dryer based on a microchannel pulsating heat pipe, which is special in that:

[0013] Includes fans, drying chambers, filters, heat pipe assemblies, evaporators, compressors, condensers, throttling elements, and three-way charging valves;

[0014] The heat pipe assembly includes: a flat tube, fins, a cover plate, an edge-sealing tube, and a filling tube;

[0015] The flat tube has interconnected microchannels inside, and the ends of the flat tube have holes connecting two microchannels, which are then sealed with a cover plate. The two microchannel holes at the edge are connected by a sealing pipe. The working fluid in the heat pump system enters the flat tube through the filling pipe and the sealing pipe, so that the working fluid forms a closed loop inside the microchannels, thereby improving the heat transfer capacity. The flat tube includes: an evaporation section flat tube, a condensation section flat tube, and an insulation connection section flat tube.

[0016] The three-way charging valve connects the heat pipe assembly and the heat pump system. The three-way charging valve connects the charging pipe at the heat pipe inlet, the outlet of the condenser, and the inlet of the evaporator. A throttling element is installed between the outlet of the condenser and the inlet of the evaporator.

[0017] The fan drives the air to first enter the drying chamber to dry the clothes inside, then enters the filter to remove impurities such as clothing fibers, then enters the evaporation section flat tube of the heat pipe assembly for pre-cooling, then enters the evaporator for cooling and dehumidification, then enters the condensation section flat tube of the heat pipe assembly for preheating, and then enters the condenser for reheating, completing the cycle.

[0018] Furthermore, the aforementioned evaporation section flat tube, insulation connection section flat tube, and condensation section flat tube are connected through their internal microchannels. The evaporation section flat tube and condensation section flat tube are arranged opposite to each other, and the evaporator is arranged between the evaporation section flat tube and the condensation section flat tube.

[0019] Furthermore, the aforementioned fins include evaporation section fins and condensation section fins, with evaporation section flat tubes inserted between the evaporation section fins and condensation section flat tubes inserted between the condensation section fins;

[0020] The evaporator section fins and the condenser section fins have louvered and corrugated sections to enhance heat exchange. There are drainage grooves at the base of the fins to quickly drain the condensate.

[0021] Furthermore, the evaporator also has fins, with louvered and corrugated sections to enhance heat exchange. There are drainage grooves at the base of the fins to quickly drain condensate.

[0022] The fins on the evaporator are connected at both ends to the evaporation section fins and the condensation section fins respectively, forming continuous fins. The corrugations, louvers and drainage grooves on the continuous fins are arranged symmetrically.

[0023] Furthermore, the condenser section flat tube of the aforementioned heat pipe assembly is installed at a higher height than the evaporator section flat tube, which allows for a faster heat pipe start-up response.

[0024] Furthermore, the working fluid of the above-mentioned heat pump system enters the flat tube through the charging pipe. After the initial charging amount m0 ​​is reached, the three-way charging valve connected to the charging pipe is closed. Optionally, the initial charging amount m0 ​​= 30%.

[0025] Furthermore, an air damper is provided after the filter, which divides the air duct into a first air duct and a second air duct. The air damper can control the switching of the air duct. The heat pipe evaporation section flat tube and the evaporator are arranged in the first air duct, and the second air duct is a bypass branch. The first air duct and the second air duct converge in front of the heat pipe condensation section flat tube.

[0026] Furthermore, a temperature sensor is installed inside the condenser, and a humidity sensor is installed inside the drying chamber.

[0027] In addition, this invention also proposes a control method for a heat pump dryer based on the above-mentioned microchannel pulsating heat pipe, which is characterized by including the following steps:

[0028] S101: After the heat pump dryer starts running, obtain the temperature Tc of the condenser and proceed to step S102;

[0029] S102: Compare the condenser temperature Tc with the set temperature T1. If Tc > T1, proceed to step S103; otherwise, it is still the initial heating stage. Open the second air duct and return to step S101.

[0030] S103: Close the second air duct, i.e. the bypass air duct branch, and enter the stable dehumidification stage.

[0031] When the dryer is first started, the air flowing in driven by the fan is at room temperature, resulting in poor moisture absorption. The efficiency of cooling and then heating up again after passing through the evaporator is very low. At this time, the temperature should be raised quickly to improve the moisture absorption capacity. Therefore, before the temperature drops below a certain set temperature, the evaporator section of the heat pipe and the evaporator are bypassed, allowing air to flow only through the condenser section of the heat pipe and the condenser to absorb heat and raise the temperature.

[0032] S201: After entering the stable dehumidification stage, obtain the condenser temperature Tc and the humidity d in the drying chamber and calculate the humidity change rate Δd, then proceed to S202;

[0033] S202: Compare the condenser temperature Tc with the set temperature Th, and compare the humidity change rate Δd of the drying chamber with the set change rate Δd0; if Tc>Th or Δd<Δd0, proceed to step S203; otherwise, it is still in the stable dehumidification stage and returns to step S201.

[0034] S203: Determine that the dehumidification process has entered the dehumidification phase. To prevent clothes from being burned by excessively high temperatures, open the three-way charging valve to connect the heat pipe charging pipe and the condenser outlet, increase the amount of working fluid charged in the heat pipe, and reduce the compressor frequency and fan speed. Proceed to step S204.

[0035] S204: Compare the humidity d inside the drying chamber with the set value d0. If d > d0, the dehumidification process is still in the rate-reducing stage. Repeat step S204. Otherwise, if the humidity requirement is met, proceed to step S205.

[0036] S205: Switch the three-way charging valve to connect the heat pipe charging pipe and the evaporator inlet, so that the working fluid in the heat pipe flows back to the heat pump system. Then close the three-way charging valve, turn off the compressor and fan, and the heat pipe dryer will stop working.

[0037] After the air has been dehumidified for a period of time, most of the moisture in the clothes has been removed. At this point, the air temperature may be too high, which could damage the fabric. Therefore, a portion of the working fluid in the heat pump system is diverted from the high-pressure condenser side to the heat pipe to protect the clothes and allow the dryer to shut down smoothly. Before shutting down, the low-pressure evaporator side and the heat pipe inlet are connected to allow the working fluid to flow back into the heat pump system, preparing for the next startup.

[0038] Furthermore, the aforementioned set temperature T1 is a critical indicator for judging the initial heating stage and the stable dehumidification stage, and can be optionally set to 50℃; the set temperature Th is one of the critical indicators for judging the stable dehumidification stage and the dehumidification stage, and is used to protect clothes from being burned by high temperature, and can be optionally set to 100℃.

[0039] The humidity change rate Δd0 is set as another critical indicator for judging the steady dehumidification stage and the falling-rate dehumidification stage, and can be optionally set to 10%.

[0040] Set humidity d0 as an indicator to determine if clothes have reached the required dryness level, and control the dryer to stop. Optionally, set it to 50%.

[0041] Advantages of this invention:

[0042] 1. This invention introduces a pulsed heat pipe into a heat pump dryer, adding pre-cooling and reheating stages, which can improve the heat exchange efficiency of the evaporator and condenser without consuming additional energy, thereby improving the dehumidification effect and reducing energy consumption;

[0043] 2. This invention uses microchannel flat tubes to manufacture closed-loop pulsating heat pipes, which are pump-free and capillary-free, solving the problems of complex heat pipe structure and high cost, and improving heat exchange capacity.

[0044] 3. This invention uses composite fins, which solves the problems of high air humidity, excessive condensate, and difficult drainage in heat pump dryers;

[0045] 4. The system control strategy of coupling heat pipe and heat pump system proposed in this invention improves the energy efficiency of the entire system. Attached Figure Description

[0046] Figure 1 This is a flowchart of a heat pump dryer system based on microchannel pulsating heat pipes provided by the present invention;

[0047] Figure 2 This is a structural diagram of a heat pipe assembly;

[0048] Figure 3 This is a structural diagram of the fins;

[0049] Figure 4 This is a structural diagram of continuous fins;

[0050] Figure 5 This is a flowchart of the first part of the control method for a heat pump dryer based on a microchannel pulsating heat pipe provided by the present invention.

[0051] Figure 6 This is the second part of the flowchart of the control method for a heat pump dryer based on a microchannel pulsating heat pipe provided by the present invention.

[0052] The components include: 1. Fan, 2. Drying chamber, 3. Filter, 4. Heat pipe assembly, 5. Evaporator, 6. Compressor, 7. Condenser, 8. Throttling element, and 9. Three-way charging valve.

[0053] 41. Flat tube, 42. Fin, 43. Cover plate, 44. Edge sealing tube, 45. Filling tube, 411. Evaporation section flat tube, 412. Condensation section flat tube, 413. Insulation connection section flat tube, 421. Louver section, 422. Corrugated section, 423. Drainage groove. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 a part of the embodiments of the present invention, not all of them. 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. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0055] See Figures 1-4 A heat pump dryer based on microchannel pulsating heat pipes includes a fan 1, a drying chamber 2, a filter 3, a heat pipe assembly 4, an evaporator 5, a compressor 6, a condenser 7, a throttling element 8, and a three-way charging valve 9.

[0056] The heat pipe assembly 4 includes: a flat tube 41, fins 42, a cover plate 43, an edge sealing tube 44, and a filling tube 45.

[0057] The flat tube 41 contains interconnected microchannels. Each end of the flat tube 41 has holes connecting two microchannels, and a cover plate 43 is applied. The two microchannel holes at the edge are connected by a sealing pipe 44. The working fluid in the heat pump system enters the flat tube 41 through the filling pipe 45 and the sealing pipe 44, forming a closed loop within the microchannels and improving heat transfer capacity. The flat tube 41 includes an evaporation section flat tube 411, a condensation section flat tube 412, and an insulating connection section flat tube 413. After the working fluid evaporates in the evaporation section flat tube 411, it forms bubbles and releases heat to condense in the condensation section flat tube 412. Due to the microchannel size effect, surface tension forms a gas-liquid spacer, which oscillates and transfers heat under pressure. Under a certain heat flux density, if a closed loop is formed inside the heat pipe, unidirectional circulation can be achieved, greatly improving heat transfer capacity. In this invention, the structure of the sealing pipe 44 and the cover plate 43 realizes an interconnected microchannel pulsating heat pipe, which can achieve better start-up and heat transfer characteristics. The three-way charging valve 9 connects the heat pipe assembly and the heat pump system. The three-way charging valve 9 connects the charging pipe 45 at the heat pipe inlet, the outlet of the condenser 7, and the inlet of the evaporator 5. The throttling element 8 is located between the outlet of the condenser 7 and the inlet of the evaporator 5.

[0058] The fan 1 drives the air to first enter the drying chamber 2 to dry the clothes inside, then enters the filter 3 to remove impurities such as clothing fibers, then enters the evaporation section flat tube 411 of the heat pipe assembly 4 for pre-cooling, then enters the evaporator 5 for cooling and dehumidification, then enters the condensation section flat tube 412 of the heat pipe assembly 4 for preheating, and then enters the condenser 7 for reheating, completing the cycle.

[0059] In a preferred embodiment of the present invention, the evaporation section flat tube 411, the thermal insulation connection section flat tube 413, and the condensation section flat tube 412 are connected by microchannels inside them. The evaporation section flat tube 411 and the condensation section flat tube 412 are arranged opposite to each other, and the evaporator 5 is arranged between the evaporation section flat tube 411 and the condensation section flat tube 412.

[0060] In a preferred embodiment of the present invention, the fins 42 include evaporation section fins and condensation section fins. Evaporation section flat tubes 411 are inserted between the evaporation section fins, and condensation section flat tubes 412 are inserted between the condensation section fins. The evaporation section fins and condensation section fins have louvered portions 421 and corrugated portions 422 to enhance heat exchange. A drainage groove 423 is located at the root of the fins to quickly drain condensate. The drainage groove 423 is formed by bending the thin sheet at the root of the fins.

[0061] In a preferred embodiment of the present invention, the evaporator 5 is also provided with fins 42, and the fins have louvered portions 421 and corrugated portions 422 to enhance heat exchange. The fin roots have drainage grooves 423 to quickly drain condensate.

[0062] The fins on the evaporator 5 are connected at both ends to the evaporation section fins and the condensation section fins respectively to form continuous fins. The corrugations, louvers and drainage grooves on the continuous fins are arranged symmetrically.

[0063] In a preferred embodiment of the present invention, the condenser section flat tube 412 of the heat pipe assembly is installed at a higher height than the evaporator section flat tube 411, which can achieve a faster heat pipe start-up response.

[0064] In a preferred embodiment of the present invention, the working fluid of the heat pump system enters the flat tube 41 through the charging pipe 45, and after the initial charging amount m0 ​​is reached, the three-way charging valve 9 connected to the charging pipe 45 is closed. Optionally, the initial charging amount m0 ​​= 30%.

[0065] In a preferred embodiment of the present invention, a damper is provided after the filter 3, which divides the air duct into a first air duct and a second air duct. The damper can control the switching of the air duct. The heat pipe evaporation section flat tube 411 and the evaporator 5 are arranged in the first air duct, and the second air duct is a bypass branch. The first air duct and the second air duct converge in front of the heat pipe condensation section flat tube 412.

[0066] In a preferred embodiment of the present invention, a temperature sensor is installed in the condenser 7 and a humidity sensor is installed in the drying chamber 2.

[0067] In addition, this invention also proposes a control method for a heat pump dryer based on the above-mentioned microchannel pulsating heat pipe, see [link to relevant documentation]. Figure 5 and Figure 6 This includes the following steps:

[0068] S101: After the heat pump dryer starts running, obtain the temperature Tc of the condenser 7 and proceed to step S102;

[0069] S102: Compare the temperature Tc of condenser 7 with the set temperature T1. If Tc > T1, proceed to step S103; otherwise, it is still the initial heating stage. Open the second air duct and return to step S101.

[0070] S103: Close the second air duct, i.e. the bypass air duct branch, and enter the stable dehumidification stage.

[0071] When the dryer is first started, the air flowing in driven by the fan is at room temperature, resulting in poor moisture absorption. The efficiency of cooling and then heating up again after passing through the evaporator is very low. Therefore, the temperature should be raised quickly to improve the moisture absorption capacity. Thus, before the temperature drops below a certain set temperature, the heat pipe evaporator section flat tube 411 and evaporator 5 are bypassed, allowing only the air to flow through the heat pipe condenser section flat tube 412 and condenser 7 to absorb heat and raise the temperature.

[0072] S201: After entering the stable dehumidification stage, obtain the temperature Tc of condenser 7 and the humidity d in drying box 2 and calculate the humidity change rate Δd, then proceed to S202;

[0073] S202: Compare the condenser 7 temperature Tc with the set temperature Th, and compare the humidity change rate Δd of the drying chamber 2 with the set change rate Δd0; if Tc>Th or Δd<Δd0, proceed to step S203; otherwise, it is still in the stable dehumidification stage and returns to step S201.

[0074] S203: Determine that the dehumidification process has entered the dehumidification stage. To avoid overheating and damaging clothes, open the three-way charging valve 9 to connect the heat pipe charging pipe 45 and the condenser outlet 7, increase the amount of working fluid charged in the heat pipe, and reduce the compressor frequency and fan speed. Proceed to step S204.

[0075] S204: Obtain the humidity d inside the drying chamber 2 and the set value d0. If d > d0, it is still in the dehumidification stage and step S204 is repeated. Otherwise, the humidity requirement has been met and the process proceeds to step S205.

[0076] S205: Switch the three-way charging valve 9 to connect the heat pipe charging pipe 45 and the evaporator 5 inlet, so that the working fluid in the heat pipe flows back to the heat pump system. Then close the three-way charging valve 9, shut down the compressor 6 and the fan 1, and the heat pipe dryer stops working.

[0077] After the air has been dehumidified for a period of time, most of the moisture in the clothes has been removed. At this point, the air temperature may be too high, which could damage the fabric. Therefore, a portion of the working fluid in the heat pump system is diverted from the high-pressure condenser side to the heat pipe to protect the clothes and allow the dryer to shut down smoothly. Before shutting down, the low-pressure evaporator side and the heat pipe inlet are connected to allow the working fluid to flow back into the heat pump system, preparing for the next startup.

[0078] Furthermore, the aforementioned set temperature T1 is a critical indicator for judging the initial heating stage and the stable dehumidification stage, and can be optionally set to 50℃; the set temperature Th is one of the critical indicators for judging the stable dehumidification stage and the dehumidification stage, used to protect clothes from being scalded by high temperatures, and can be optionally set to 100℃; the set humidity change rate △d0 is another critical indicator for judging the stable dehumidification stage and the dehumidification stage, and can be optionally set to 10%; the set humidity d0 is an indicator for judging whether the clothes have reached the drying requirements, controlling the shutdown of the dryer, and can be optionally set to 50%.

[0079] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. A heat pump dryer based on a microchannel pulsating heat pipe, characterized in that: Includes a fan (1), a drying box (2), a filter (3), a heat pipe assembly (4), an evaporator (5), a compressor (6), a condenser (7), a throttling element (8), and a three-way charging valve (9); The heat pipe assembly (4) includes: a flat tube (41), fins (42), a cover plate (43), an edge sealing tube (44), and a filling tube (45). The flat tube (41) is a microchannel pulsating heat pipe with interconnected microchannels inside. The ends of the flat tube (41) are respectively provided with holes connecting two microchannels and are sealed with a cover plate (43). The two microchannel holes at the edge are connected through a sealing pipe (44). The working fluid in the heat pump system enters the flat tube (41) through the filling pipe (45) and the sealing pipe (44), so that the working fluid forms a closed loop without external driving force inside the microchannel. The heat pipe assembly (4) has no capillary wick structure. The flat tube (41) includes an evaporation section flat tube (411), a condensation section flat tube (412), and an insulation connection section flat tube (413). The three-way charging valve (9) connects the heat pipe assembly and the heat pump system. The three-way charging valve (9) connects the charging pipe (45) at the heat pipe inlet, the outlet of the condenser (7), and the inlet of the evaporator (5). The throttling element (8) is set between the outlet of the condenser (7) and the inlet of the evaporator (5). The fan (1) drives the air to first enter the drying box (2) to dry the clothes in the box, then enters the filter (3) to remove impurities, then enters the evaporation section flat tube (411) of the heat pipe assembly (4) for pre-cooling, then enters the evaporator (5) for cooling and dehumidification, then enters the condensation section flat tube (412) of the heat pipe assembly (4) for preheating, then enters the condenser (7) for reheating, and completes the cycle; The fins include evaporation section fins and condensation section fins, with evaporation section flat tubes (411) inserted between the evaporation section fins and condensation section flat tubes (412) inserted between the condensation section fins. The evaporator section fins and the condenser section fins have louvered sections (421) and corrugated sections (422) to enhance heat exchange. The fin roots have drainage grooves (423) to quickly drain the condensate. The filter (3) is provided with a damper, which divides the air duct into a first air duct and a second air duct. The damper can control the switching of the air duct. The heat pipe evaporation section flat tube (411) and the evaporator (5) are set in the first air duct. The second air duct is a bypass branch. The first air duct and the second air duct converge in front of the heat pipe condensation section flat tube (412).

2. A heat pump dryer based on a microchannel pulsating heat pipe according to claim 1, characterized in that: The evaporation section flat tube (411), the heat insulation connection section flat tube (413), and the condensation section flat tube (412) are connected through their internal microchannels. The evaporation section flat tube (411) and the condensation section flat tube (412) are arranged opposite to each other, and the evaporator (5) is arranged between the evaporation section flat tube (411) and the condensation section flat tube (412).

3. A heat pump dryer based on a microchannel pulsating heat pipe according to claim 2, characterized in that: The evaporator (5) is also provided with fins, and the fins have louvered parts (421) and corrugated parts (422) to enhance heat exchange. There are drainage grooves (423) at the root of the fins to quickly drain the condensate. The fins on the evaporator (5) are connected at both ends to the evaporation section fins and the condensation section fins respectively to form continuous fins. The corrugations, louvers and drainage grooves on the continuous fins are arranged symmetrically.

4. A heat pump dryer based on a microchannel pulsating heat pipe according to claim 3, characterized in that: The condensing section flat tube (412) of the heat pipe assembly is installed at a higher height than the evaporating section flat tube (411), which can achieve a faster heat pipe start-up response. In the closed loop formed by the evaporating section flat tube (411) and the condensing section flat tube (412), the working fluid relies on the surface tension effect in the microchannel and the pressure difference generated by evaporation / condensation to oscillate and flow autonomously for heat transfer.

5. A heat pump dryer based on a microchannel pulsating heat pipe according to claim 4, characterized in that: The working fluid of the heat pump system enters the flat tube (41) through the charging pipe (45). After the initial charging amount m0 ​​is reached, the three-way charging valve (9) connected to the charging pipe (45) is closed. The initial charging amount m0 ​​= 30%.

6. A heat pump dryer based on a microchannel pulsating heat pipe according to claim 5, characterized in that: A temperature sensor is installed inside the condenser (7), and a humidity sensor is installed inside the drying oven (2).

7. A control method for a heat pump dryer based on a microchannel pulsating heat pipe as described in any one of claims 1-6, characterized in that, Includes the following steps: S101: After the heat pump dryer starts running, obtain the temperature Tc of the condenser (7) and proceed to step S102; S102: Compare the temperature Tc of the condenser (7) with the set temperature T1. If Tc > T1, proceed to step S103; otherwise, it is still the initial heating stage. Open the second air duct and return to step S101. S103: Close the second air duct, i.e. the bypass air duct branch, and enter the stable dehumidification stage S201; S201: After entering the stable dehumidification stage, obtain the temperature Tc of the condenser (7) and the humidity d inside the drying box (2) and calculate the humidity change rate Δd, then enter S202; S202: Compare the condenser (7) temperature Tc with the set temperature Th, and compare the humidity change rate Δd of the drying box (2) with the set change rate Δd0; if Tc>Th or Δd<Δd0, proceed to step S203; otherwise, it is still in the stable dehumidification stage and returns to step S201. S203: Determine that the dehumidification process has entered the dehumidification stage. To avoid the clothes being burned by excessively high temperature, open the three-way charging valve (9) to connect the heat pipe charging pipe (45) and the condenser (7) outlet, increase the amount of working fluid charged in the heat pipe, and reduce the compressor frequency and fan speed. Proceed to step S204. S204: Obtain the relative humidity d inside the drying chamber (2) and the set value d0. If d > d0, it is still in the dehumidification stage and step S204 is repeated. Otherwise, the humidity requirement has been met and step S205 is entered. S205: Switch the three-way charging valve (9) to connect the heat pipe charging pipe (45) and the evaporator (5) inlet, so that the working fluid in the heat pipe flows back to the heat pump system, then close the three-way charging valve (9), shut down the compressor (6) and the fan (1), and the heat pipe dryer stops working.

8. The control method for a heat pump dryer based on a microchannel pulsating heat pipe according to claim 7, characterized in that: The set temperature T1 is the critical index for judging the initial heating stage and the stable dehumidification stage, and is set to 50℃; The temperature Th is set as one of the critical indicators for judging the steady dehumidification stage and the falling-rate dehumidification stage, and is set to 100℃. The humidity change rate Δd0 is set as another critical indicator for judging the steady dehumidification stage and the falling-rate dehumidification stage, and is set to 10%. Set humidity d0 as the indicator to determine if clothes have reached the required dryness level, and control the dryer to stop; set it to 50%.

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