A high-efficiency dehumidification module and control method of a closed-loop dehumidification heat pump dryer

Abstract

The application provides a closed-loop dehumidification heat pump dryer high-efficiency dehumidification module, which comprises an interlaced heat exchanger composed of multiple cold air channels and hot air channels made of aluminum plates, a dehumidification evaporator and an air duct connected with the interlaced heat exchanger, the hot air channels and the cold air channels of the interlaced heat exchanger are sequentially and interlacedly superposed, multiple side-by-side interlaced top projection structures are arranged in the hot air channels and the cold air channels, the direction of air flow in the cold air channels is from left to right, and the direction of air flow in the hot air channels is perpendicular to that in the cold air channels from front to back. The closed-loop dehumidification heat pump dryer high-efficiency dehumidification module is ingeniously designed, the interlaced top projection structures in the heat exchange air duct can improve the heat exchange coefficient and the heat exchange capacity, reduce the flow resistance of the heat exchange air duct and reduce the volume of the interlaced heat exchanger. The application also provides a control method of the closed-loop dehumidification heat pump dryer, which can accurately control the optimal return air volume entering the dehumidification module, so that the heat pump dryer can dehumidify efficiently and the control accuracy is improved.

Description

Technical Field

[0001] This invention relates to the field of heat exchange equipment technology, specifically to a high-efficiency dehumidification module and control method for a closed-loop dehumidification heat pump dryer. Background Technology

[0002] A closed-loop heat pump dehumidifier is a heat lifting device. The high-temperature heat pump dryer unit uses the reverse Carnot principle to absorb heat from the surrounding environment and transfer it to the object being heated (the object with a higher temperature). It is mainly used in the drying and dehydration process of food, medicine, wood, agricultural and sideline products, industrial products, etc.

[0003] A closed-loop heat pump dehumidification and drying unit mainly consists of six parts: a dehumidifying evaporator (indoor unit), a heat pump evaporator (outdoor unit), a compressor, a condenser, an expansion valve, and a cross-heat exchanger. It transfers heat from the low-temperature external environment to the drying chamber by continuously cycling the refrigerant through evaporation, compression, condensation (releasing heat in the drying chamber), throttling, and re-evaporation. After absorbing heat and humidifying in the drying chamber, some of the hot air is cooled by the cross-heat exchanger according to dehumidification requirements, increasing its relative humidity. It then passes through the dehumidifying evaporator for further cooling and dehumidification. The dehumidified air mixes with the ventilation air near the drying chamber and enters the condenser for heating, further reducing its relative humidity before returning to the drying chamber for heat absorption and humidification. This dehumidification cycle continues. During dehumidification, the air in both the drying chamber and the dehumidification chamber does not exchange heat with the outside. The heat pump dehumidification system within the dehumidification chamber condenses and discharges the moisture in the hot, humid air, thus reducing the humidity inside the drying chamber. The refrigerant undergoes a process of increasing pressure and temperature (up to 100℃) in the compressor. It then enters the condenser, releasing high-temperature heat to heat the air in the drying room. At the same time, the refrigerant is cooled and converted into a liquid state. When it runs to the heat pump evaporator (outdoor unit) or dehumidifier evaporator (indoor unit), the liquid state rapidly absorbs heat and evaporates, converting back into a gaseous state. The refrigerant temperature can drop to -10℃ to 40℃. At this time, the air supplied by the heat pump evaporator or dehumidifier evaporator will continuously transfer heat to the refrigerant.

[0004] The dehumidification module is a crucial component preceding the dehumidifying evaporator (indoor unit). Its working principle involves cooling the air through heat exchange, causing water vapor in the air to cool or partially condense into condensate. This lowers the return air temperature entering the dehumidifying evaporator, increasing the evaporator's dehumidification capacity and maximizing the reduction of return air moisture content. For example, utility model patent application number 201821220573.5 proposes a heat pump drying device employing high-efficiency dehumidification modules with different area-to-airflow ratios for pre-cooling the inlet air. The device housing contains at least two dehumidification systems. In the early and middle stages of operation of the closed-loop heat pump drying device, a smaller area high-efficiency dehumidification module is used; while in the later stages, a larger area high-efficiency dehumidification module is used. This solves the problems of increased return air temperature, decreased relative humidity, decreased dew point temperature, and failure of the evaporator to condense water in the later stages of drying. However, this heat pump drying device requires at least two dehumidification systems, resulting in higher equipment manufacturing costs.

[0005] A utility model patent with application number 201920970987.8 discloses an air heat exchanger, comprising a frame and several longitudinally stacked polygonal heat exchange fins within the frame. An anti-detachment structure prevents the connecting tongue from disengaging from the slot, thus ensuring a reliable connection between the edge strip and the upper and lower sealing plates. The heat exchange fins are provided with protrusions and grooves, which are staggered in the same row and column, and offset from adjacent rows and columns on the same heat exchange fin. The protrusions and grooves between adjacent heat exchange fins are symmetrically distributed vertically. This air heat exchanger requires no screws or other fasteners, and the installation process is very quick, convenient, and labor-saving, greatly improving installation efficiency. However, after setting the protrusions and grooves, the airflow resistance at the airflow rows and columns of the protrusions and grooves is significantly increased, thus affecting the improvement of heat exchange efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a high-efficiency dehumidification module for a closed-loop dehumidification heat pump dryer. The module features a compact structure and an innovative design with multiple parallel and staggered top protrusions within the heat exchange duct. This design reduces the flow resistance of the air duct, increases the heat transfer coefficient and heat transfer capacity, and reduces the volume of the staggered heat exchanger.

[0007] The present invention also provides a control method for a closed-loop dehumidifying heat pump dryer, which can accurately control the heat pump dryer to perform dehumidification operation based on the temperature, relative humidity, mass flow rate and preset target return air humidity of the drying room, thereby improving the accuracy of control.

[0008] This invention provides a high-efficiency dehumidification module for a closed-loop dehumidification heat pump dryer, comprising: an interleaved heat exchanger consisting of multiple cold air channels and hot air channels formed by aluminum plates, an evaporator, and ventilation ducts connecting the interleaved heat exchanger. The hot air channels and cold air channels of the interleaved heat exchanger are sequentially and interleaved. Multiple parallel and interleaved top protrusions are provided in the hot air channels and cold air channels. The airflow direction in the cold air channel is from left to right, and the airflow direction in the hot air channel is from front to back and perpendicular to the cold air channel.

[0009] In the above technical solution, during actual operation, some of the hot return air in the drying chamber flows through the hot air channel, while the cold air dehumidified by the evaporator flows through the cold air channel. Furthermore, the flow direction of the hot return air in the hot air channel is perpendicular to the flow direction of the cold air dehumidified by the evaporator in the cold air channel. During the actual heat exchange process, both the top and bottom surfaces of the hot return air in the drying chamber can exchange heat with the cold air dehumidified by the evaporator, thereby increasing the heat exchange area and the amount of heat exchanged, and thus significantly improving the heat exchange efficiency. Moreover, because multiple parallel, staggered, opposing protrusions are installed within the air ducts, the turbulence of the airflow can be increased, while simultaneously increasing the overall flow path length of the airflow, thereby improving the heat transfer coefficient and the amount of heat exchanged, and reducing the volume of the staggered heat exchanger.

[0010] Preferably, the top protrusion is composed of an upwardly protruding hemispherical protrusion and a downwardly protruding hemispherical protrusion, with the tips of the upwardly protruding hemispherical protrusion and the tips of the downwardly protruding hemispherical protrusion abutting each other. This structural design can not only improve the turbulence of air flow in the air duct, but also improve the overall strength of the upper and lower sides of the air duct, so that the cold air duct and the hot air duct can resist pressure.

[0011] Preferably, the upward hemispherical protrusion and the downward hemispherical protrusion are the same size to improve the overall strength when the upward and downward hemispherical protrusions abut each other and to improve the uniformity of air flow in the duct.

[0012] Preferably, the top protrusions in the air duct are arranged in groups of three side by side as one top protrusion group, and multiple top protrusion groups are arranged side by side and staggered in the air duct. In actual experiments, it was found that when the top protrusions are arranged in the above-mentioned structure, better airflow turbulence can be obtained, and thus better heat exchange efficiency can be obtained.

[0013] Preferably, both the cold air channel and the hot air channel are made of aluminum plates. The left and right ends of the cold air channel are open, while the front and rear ends are sealed. The front and rear ends of the hot air channel are open, while the left and right ends are sealed. Aluminum plates have high heat exchange efficiency, good strength, and are easy to process.

[0014] Preferably, the upward hemispherical protrusion is located on the bottom surface of the aluminum plate air duct and protrudes upward, while the downward hemispherical protrusion is located on the top surface of the aluminum plate air duct and protrudes downward. The upward and downward hemispherical protrusions in the air duct can be formed by molding.

[0015] This invention also provides a control method for a closed-loop dehumidifying heat pump dryer, including the aforementioned high-efficiency dehumidifying module. The hot return air from the drying chamber flows through a hot air channel, while the cold air dehumidified by the evaporator flows through a cold air channel. The two air streams—the hot return air from the drying chamber and the cold air dehumidified by the evaporator—are completely separated and flow perpendicularly to each other in a cross-flow heat exchanger. They exchange heat through an aluminum plate. After heat exchange, the temperature of the hot return air from the drying chamber decreases, and its relative humidity increases before entering the evaporator for dehumidification. The cold air dehumidified by the evaporator flows through the cold air channel of the cross-flow heat exchanger, exchanges heat with the hot return air in the hot air channel of the cross-flow heat exchanger, and its temperature increases while its relative humidity decreases. It then mixes with the ventilation air passing directly through the second condenser next to the drying chamber and is heated by the first condenser before entering the drying chamber, thus completing the cycle.

[0016] Preferably, the specific steps include:

[0017] S1. Power on, heat pump dryer initialization;

[0018] S2. Setting parameters: Set the drying temperature t0 of the drying chamber, the time controller ΔT, and the relative humidity of the drying chamber.

[0019] S3. Obtain indoor environmental parameters t n , q n And calculate the moisture content d of the humid air in the drying room. n ;

[0020] S4. The sensor at the evaporator outlet measures the relative humidity of the air. and mass flow rate q m The moisture content d is calculated using the parameters above. m And the dehumidification capacity Δm after ΔT cycle;

[0021] S5, based on condition t n The operating conditions of the heat pump evaporator and the dehumidifying evaporator are determined by ≤t0±2℃. If the above conditions are met, the heat pump evaporator will work and the dehumidifying evaporator will not work; otherwise, the heat pump evaporator will not work and the dehumidifying evaporator will work.

[0022] S6. Under the operating conditions of the heat pump evaporator, after a time of ΔT, the environmental parameters are re-acquired to determine the use of condition S5.

[0023] S7. The operation of the heat pump evaporator under condition S6 is changed to the operation of the dehumidifying evaporator. At this time, the following conditions are determined: if the dehumidification amount Δm ≥ a fixed value, the fan frequency is adjusted to the maximum. Under this condition, the dehumidifying evaporator will re-acquire the indoor environmental parameters after working for ΔT time.

[0024] S8. After re-acquiring the indoor environmental parameters under condition S7, if Δm < a constant value, adjust the fan frequency; after ΔT, calculate the optimal flow rate q using the interpolation method. n And provide feedback to adjust the fan frequency;

[0025] S9, when At this time, the system enters standby mode.

[0026] Preferably, in step S3, the control system of the heat pump dryer automatically acquires environmental parameter t at regular intervals during operation. n , q n .

[0027] The beneficial effects of the high-efficiency dehumidification module for a closed-loop dehumidification heat pump dryer provided by this invention are as follows:

[0028] (1) The high-efficiency dehumidification module of this closed-loop dehumidification heat pump dryer has a simple structure and ingenious design. Through the innovative design of multiple parallel and staggered top protrusions in the heat exchange duct, the manufacturing cost is low and the operating cost is low. Furthermore, by making the air flow direction in the hot air duct perpendicular to the air flow direction in the cold air duct, in actual operation, part of the hot return air in the drying chamber flows through the hot air duct, and the cold air dehumidified by the evaporator flows through the cold air duct. Moreover, the direction of the hot return air in the drying chamber in the hot air duct is perpendicular to the direction of the cold air dehumidified by the evaporator in the cold air duct. In the actual heat exchange process, the top and bottom surfaces of the hot return air in the drying chamber can exchange heat with the cold air dehumidified by the evaporator, thereby increasing the heat exchange area and heat exchange capacity, and thus significantly improving the heat exchange efficiency. In addition, since multiple parallel and staggered top protrusions are set in the duct, the turbulence of the airflow can be increased, and the overall flow length of the airflow can be increased, thereby increasing the heat exchange coefficient and heat exchange capacity, and reducing the volume of the staggered heat exchanger.

[0029] (2) The closed-loop dehumidification heat pump dryer control method provided by the present invention completely separates the flow of the hot return air in the drying room and the cold air dehumidified by the evaporator, which can improve the heat exchange efficiency. Furthermore, the heat pump dryer can be accurately controlled to perform dehumidification operation by means of the relative humidity of the air at the evaporator outlet, the mass flow rate, and the preset relative humidity of the drying room, thereby improving the accuracy of control. Attached Figure Description

[0030] Figure 1 This is a front view of the structure of the staggered heat exchanger section in this invention.

[0031] Figure 2 This is a left view of the structure of the staggered heat exchanger section in this invention.

[0032] Figure 3 This is a three-dimensional perspective view of the staggered heat exchanger section of the present invention. Figure I .

[0033] Figure 4 This is a three-dimensional perspective view of the staggered heat exchanger section of the present invention. Figure II .

[0034] Figure 5 This is a perspective view of the three-dimensional structure of the staggered heat exchanger in this invention.

[0035] Figure 6 This is a schematic diagram of the high-efficiency dehumidification module system of the closed-loop dehumidification heat pump dryer of the present invention.

[0036] Figure 7 This is a flowchart of the control method of the present invention.

[0037] In the diagram: 1. Hot air duct bottom plate; 2. Cold air duct; 21. Plate body; 3. Hot air duct top plate; 4. First layer hot air duct; 5. Second layer hot air duct; 6. Top protrusion; 7. First layer cold air duct; 8. Hot air duct bottom plate; 9. Cold air duct top plate; 10. Cold air duct bottom plate; 11. Drying room; 12. First fan; 13. First condenser; 14. Interleaved heat exchanger; 15. Dehumidifying evaporator; 16. Dehumidifying functional chamber; 17. Second condenser; 18. Second fan. Detailed Implementation

[0038] 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. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] Example 1: A high-efficiency dehumidification module for a closed-loop dehumidification heat pump dryer.

[0040] Reference Figures 1 to 6As shown, a high-efficiency dehumidification module for a closed-loop dehumidification heat pump dryer includes: an interleaved heat exchanger 14 with multiple cold and hot air channels formed by aluminum plates, a dehumidifying evaporator 15, and ventilation ducts connecting the interleaved heat exchanger. The hot air channels and cold air channels of the interleaved heat exchanger 14 are stacked alternately. The hot air channels are fitted onto the cold air channels, and the top plate 9 of the cold air channels is fitted onto the bottom plate 8 of the hot air channels. The interleaved distribution and top protrusion design of the cold and hot air channels in the heat exchange duct facilitates direct heat exchange between the top plate 9 of the cold air channels and the bottom plate 8 of the hot air channels, thereby improving heat exchange efficiency. The plate 21 is a multi-layer aluminum plate. Hot air channels and cold air channels with perpendicular air ducts are stacked between the layers of the plate 21. The left and right ends of the cold air channel 2 are open, while the front and rear ends are sealed. The front and rear ends of the hot air channels 4 and 5 are open, while the left and right ends are sealed. This structure is easy to process, and the aluminum plate has high heat exchange efficiency, good strength, and is easy to process.

[0041] Reference Figure 5 As shown, air ducts penetrating the plate are provided between each layer of the plate 21 (refer to...). Figure 1 and Figure 2 As shown, hot air channels and cold air channels are respectively provided. The hot air inlet is the duct inlet for part of the hot return air in the drying room, where the hot air flows from front to back. The cold air inlet is the duct inlet for the cold air dehumidified by the evaporator, where the cold air flows from left to right. Since the direction of the hot return air in the drying room in the hot air channel is perpendicular to the direction of the cold air dehumidified by the evaporator in the cold air channel, in the actual heat exchange process, the top and bottom surfaces of the cold air dehumidified by the evaporator can exchange heat with the hot return air in the drying room, thereby increasing the heat exchange area and the amount of heat exchanged, and thus greatly improving the heat exchange efficiency.

[0042] Reference Figures 1 to 5 As shown, the hot air channel and cold air channel are equipped with multiple parallel, staggered, opposing protrusions 6. Each opposing protrusion 6 consists of an upwardly convex hemispherical protrusion and a downwardly convex hemispherical protrusion. The tips of the upwardly convex and downwardly convex hemispherical protrusions abut against each other. This structural design not only improves the turbulence of airflow within the duct but also enhances the overall strength of the upper and lower sides of the channel between the plates, making the plate 21 more resistant to pressure. The upwardly and downwardly convex hemispherical protrusions are the same size to improve the overall strength when they abut against each other and to enhance the uniformity of airflow within the duct.

[0043] Reference Figures 4 to 5As shown, the top protrusions 6 set in the hot air channel and the cold air channel are arranged in groups of three top protrusions arranged side by side. Multiple top protrusion groups are arranged side by side and staggered in the air duct. In actual experiments, it was found that when the top protrusions are arranged in the above-mentioned structure, good airflow turbulence can be obtained, and thus good heat exchange efficiency can be obtained.

[0044] Because multiple parallel and staggered top protrusions 6 are provided in the air duct, the turbulence of the airflow can be increased, and the overall flow length of the airflow can be increased, thereby improving the heat transfer coefficient and heat transfer capacity, and reducing the volume of the staggered heat exchanger 14.

[0045] This closed-loop dehumidifying heat pump dryer features a simple and ingeniously designed high-efficiency dehumidification module. Its innovative sandwich structure reduces manufacturing and operating costs. By aligning the direction of the cold air dehumidified by the evaporator in the cold air duct with the direction of the hot air return flow in the hot air duct, during operation, some of the hot return air from the drying chamber flows through the hot air duct, while the cold air dehumidified by the evaporator flows through the cold air duct. Furthermore, the direction of the hot return air flow in the hot air duct is perpendicular to the direction of the cold air flow in the cold air duct. This ensures that both the top and bottom surfaces of the dehumidified cold air from the evaporator can exchange heat with the hot return air from the drying chamber during heat exchange, thereby increasing the heat exchange area and heat transfer capacity, and significantly improving heat exchange efficiency. Additionally, the presence of multiple staggered, parallel-mounted protrusions 6 in both the hot and cold air ducts enhances airflow turbulence and increases the overall flow path length, further improving the heat transfer coefficient and heat transfer capacity while reducing the volume of the staggered heat exchanger.

[0046] Example 2: A control method for a closed-loop dehumidification heat pump dryer.

[0047] Reference Figures 1 to 7 As shown, a control method for a closed-loop dehumidifying heat pump dryer includes the high-efficiency dehumidification module described in Example 1. In this method, the hot return air from the drying chamber flows through a hot air channel, while the cold air dehumidified by the evaporator flows through a cold air channel. The two streams of air—the hot return air from the drying chamber and the cold air dehumidified by the evaporator—are completely separated and flow perpendicularly to each other in a cross-flow heat exchanger. They exchange heat through an aluminum plate. After heat exchange, the temperature of the hot return air from the drying chamber decreases, and its relative humidity increases before entering the evaporator for dehumidification. The cold air dehumidified by the evaporator flows through the cold air channel of the cross-flow heat exchanger, exchanges heat with the hot return air in the hot air channel of the cross-flow heat exchanger, and its temperature increases while its relative humidity decreases. It then mixes with the ventilation air passing directly through the second condenser next to the drying chamber and is heated by the first condenser before entering the drying chamber, thus completing the cycle.

[0048] Reference Figure 7 As shown, this method specifically includes the following steps:

[0049] S1. Power on, heat pump dryer initialization;

[0050] S2. Setting parameters: Set the drying temperature t0 of the drying chamber, the time controller ΔT, and the relative humidity of the drying chamber.

[0051] S3. Obtain indoor environmental parameters t n , q n And calculate the moisture content d of the humid air in the drying room. n ;

[0052] S4. The sensor at the evaporator outlet measures the relative humidity of the air. and mass flow rate q m The moisture content d is calculated using the parameters above. m And the dehumidification capacity Δm after ΔT cycle;

[0053] S5, based on condition t n The operating conditions of the heat pump evaporator and the dehumidifying evaporator are determined by ≤t0±2℃. If the above conditions are met, the heat pump evaporator will work and the dehumidifying evaporator will not work; otherwise, the heat pump evaporator will not work and the dehumidifying evaporator will work.

[0054] S6. Under the operating conditions of the heat pump evaporator, after a time of ΔT, the environmental parameters are re-acquired to determine the use of condition S5.

[0055] S7. The operation of the heat pump evaporator under condition S6 is changed to the operation of the dehumidifying evaporator. At this time, the following conditions are determined: if the dehumidification amount Δm ≥ a fixed value, the fan frequency is adjusted to the maximum. Under this condition, the dehumidifying evaporator will re-acquire the indoor environmental parameters after working for ΔT time.

[0056] S8. After re-acquiring the indoor environmental parameters under condition S7, if Δm < a constant value, adjust the fan frequency; after ΔT, calculate the optimal flow rate q using the interpolation method. n And provide feedback to adjust the fan frequency;

[0057] S9, when At this time, the system enters standby mode.

[0058] The closed-loop dehumidification heat pump dryer control method provided by this invention completely separates the flow of the hot return air from the drying chamber and the cold air from the evaporator for dehumidification, which can improve the heat exchange efficiency. It can also accurately control the return air volume of the heat pump dryer by using the relative humidity of the air at the evaporator outlet, the mass flow rate, and the preset relative humidity of the drying chamber, thereby precisely executing the dehumidification operation and improving the accuracy of control.

[0059] The above description is only a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in the embodiments and drawings. Therefore, any equivalent or modified embodiments made without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A control method for a closed-loop dehumidifying heat pump dryer, characterized in that... include: The high-efficiency dehumidification module consists of an aluminum plate forming a staggered heat exchanger with multiple cold and hot air channels, a dehumidifying evaporator, and air ducts connecting the staggered heat exchanger. The hot and cold air channels of the staggered heat exchanger are stacked alternately. Multiple parallel staggered top protrusions are provided in the hot and cold air channels. The airflow direction in the cold air channel is from left to right, and the airflow direction in the hot air channel is from front to back and perpendicular to the cold air channel. The control method of the closed-loop dehumidification heat pump dryer includes: after the hot return air from the drying room enters the dehumidification chamber through the second fan, according to the dehumidification requirements, part of the hot return air flows through the hot air channel of the cross heat exchanger, and the cold air dehumidified by the evaporator flows through the cold air channel. The hot return air and the cold air dehumidified by the evaporator are completely separated and flow perpendicular to each other. They exchange heat through the aluminum plate. After the heat exchange, the temperature of the hot return air from the drying room decreases and the relative humidity increases before entering the evaporator for dehumidification. After the cold air dehumidified by the evaporator exchanges heat with the hot return air from the drying room in the hot air channel, the temperature increases and the relative humidity decreases. After mixing with the hot air bypassing the drying room that does not pass through the cross heat exchanger, it is then heated by the first condenser and enters the drying room. The control method for the closed-loop dehumidification heat pump dryer further includes the following steps: S1. Power on, heat pump dryer initialization; S2. Setting parameters: Set the drying temperature t0 of the drying room, the time controller ΔT, and the relative humidity of the drying room φ0; S3. Obtain indoor environmental parameters t n φ n q n And calculate the moisture content d of the humid air in the drying room. n , where t n φ represents the indoor ambient temperature. n q represents the relative humidity of indoor air. n Indoor air mass flow rate; S4. The relative humidity φ of the air is measured by the sensor at the outlet of the dehumidifier evaporator. m and mass flow rate q m The moisture content d is calculated using the parameters above. m And the dehumidification amount Δm after ΔT cycle; S5, based on condition t n The operating conditions of the heat pump evaporator and the dehumidifying evaporator are determined by ≤t0±2℃. If the above conditions are met, the heat pump evaporator will work and the dehumidifying evaporator will not work; otherwise, the heat pump evaporator will not work and the dehumidifying evaporator will work. S6. Under the operating conditions of the heat pump evaporator, after a time of ΔT, the environmental parameters are re-acquired to determine the use of condition S5. S7. The operation of the heat pump evaporator under condition S6 is changed to the operation of the dehumidifying evaporator. At this time, the following conditions are determined: if the dehumidification amount Δm ≥ a fixed value, the fan frequency is adjusted to the maximum. Under this condition, the dehumidifying evaporator will re-acquire the indoor environmental parameters after working for ΔT time. S8. After re-acquiring the indoor environmental parameters under condition S7, if Δm < a constant value, adjust the fan frequency; after ΔT, calculate the optimal mass flow rate q using the interpolation method. n And provide feedback to adjust the fan frequency; S9, when φ n When ≤φ0, the system enters standby mode.

2. The control method for the closed-loop dehumidification heat pump dryer as described in claim 1, characterized in that: The opposing protrusion is composed of an upwardly convex hemispherical protrusion and a downwardly convex hemispherical protrusion, with the tips of the upwardly convex hemispherical protrusion and the tips of the downwardly convex hemispherical protrusion abutting each other.

3. The control method for the closed-loop dehumidification heat pump dryer as described in claim 2, characterized in that: The upward-convex hemispherical protrusion and the downward-convex hemispherical protrusion are the same size.

4. The control method for the closed-loop dehumidification heat pump dryer as described in claim 1, characterized in that: The top protrusions installed in the air duct are arranged in groups of three top protrusions arranged side by side, and multiple top protrusion groups are distributed side by side and staggered in the air duct.

5. The control method for the closed-loop dehumidification heat pump dryer as described in claim 2, characterized in that: The left and right ends of the cold air duct are both open, while the front and rear ends are sealed; the front and rear ends of the hot air duct are both open, while the left and right ends are sealed.

6. The control method for a closed-loop dehumidification heat pump dryer as described in claim 5, characterized in that: An upward-convex hemispherical protrusion is located on the bottom surface of the aluminum plate air duct and protrudes upwards, while a downward-convex hemispherical protrusion is located on the top surface of the aluminum plate air duct and protrudes downwards.

7. The control method for the closed-loop dehumidification heat pump dryer as described in claim 1, characterized in that: In step S3, the control system of the heat pump dryer automatically acquires environmental parameter t at regular intervals during operation. n φ n q n .

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