Heat pump drying air duct structure and drying control method

Abstract

The invention discloses a heat pump drying air duct structure and a drying control method. The heat pump drying air duct structure comprises a drying chamber, an air duct chamber and a heat pump unit. A return air inlet and an air inlet are formed between the drying chamber and the air duct chamber; the interior of the air duct chamber is divided into a fresh air cavity, an air inlet cavity and an air return cavity through partition plates, the air return cavity and the fresh air cavity form a first channel, the air return cavity and the air inlet cavity form a second channel allowing air to enter the fresh air cavity in a one-way mode, the fresh air cavity and the air inlet cavity form a third channel, and the air return cavity and the air inlet cavity form a fourth channel allowing air to enter in a one-way mode. An open type, semi-open type or closed type circulating flow channel can be selectively formed by adjusting a switch of the blade valve, and the heat pump unit is used for heating air in the air channel chamber. The invention aims to provide a novel heat pump drying air duct structure integrating an open mode, a semi-open mode and a closed mode and a drying control method.

Description

Technical Field

[0001] This invention relates to the field of heat pump drying devices, and in particular to a heat pump drying duct structure and drying control method. Background Technology

[0002] With the popularization of energy conservation and environmental protection concepts and the upgrading of drying needs in various scenarios such as agricultural products, industrial products, and daily necessities, traditional electric heating dryers have been gradually replaced by heat pump dryers due to their high energy consumption and high risk of material thermal damage. Heat pump dryers are based on the reverse Carnot cycle principle. They consist of a compressor, evaporator, condenser, throttling device, and circulating air duct, forming a "cooling and dehumidification-heating cycle" drying process: the evaporator condenses and discharges water vapor from the system to achieve dehumidification; the condenser heats the dehumidified air; and the heated dry air contacts the material to be dried and removes its moisture. Combined with air duct adjustment, three circulation modes can be achieved: full return air, partial return air, and 100% fresh air, forming a continuous and stable drying cycle. Compared to traditional equipment, heat pump dryers can reduce energy consumption by 40%-60%, and the drying temperature can be stably controlled within the 35-60℃ range, effectively avoiding thermal damage to heat-sensitive materials. They are widely applicable to drying clothing, fruits and vegetables, precision parts, agricultural products, and other materials, becoming the mainstream drying equipment in the current market.

[0003] In existing heat pump drying technologies, various devices based on different air duct circulation modes have emerged, but each has significant functional limitations, making it difficult to balance adaptability to multiple scenarios, drying precision, and energy efficiency. For example, patent CN208998443U discloses a top-mounted open-type heat pump dryer, which has a compact structure and is easy to install. It quickly discharges high-humidity air through open circulation, making it suitable for scenarios with low requirements for residual moisture content. However, in applications such as meat and fruit, which have high requirements for drying precision and residual moisture control, it cannot guarantee the stability of drying quality. Patent CN115751928A discloses a closed-type heat pump dryer, which maximizes heat recovery through a fully enclosed circulation, resulting in high energy utilization and low environmental pollution. However, when drying low-value-added materials such as grains, there may be waste due to the mismatch between the material value and the actual product.

[0004] To address the shortcomings of a single circulation mode, some technologies attempt to integrate multiple circulation modes. For example, patent CN111466594A discloses an air source heat pump pepper dryer, which has three hot air circulation modes: open loop, closed loop, and semi-closed loop. However, the semi-closed loop circulation is not fully disclosed, and the system lacks dehumidification and energy recovery components. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems and provide a new heat pump drying duct structure and drying control method that integrates open, semi-open and closed modes.

[0006] To achieve the above objectives, the technical solutions of the present invention are as follows: A heat pump drying duct structure includes a drying chamber, a duct chamber, and a heat pump unit. The drying chamber has an exhaust vent, and the duct chamber has a fresh air inlet. A return air inlet and an air inlet are located between the drying chamber and the duct chamber. A partition is installed within the duct chamber, dividing its interior into a fresh air chamber, an air inlet chamber, and a return air chamber. The exhaust vent connects to the interior of the drying chamber, the fresh air inlet connects to the fresh air chamber, and the return air inlet and air inlet connect to the return air chamber and the air inlet chamber, respectively. A first channel and a second channel are formed between the return air chamber and the fresh air chamber. The second channel is for unidirectional air intake from the return air chamber to the fresh air chamber. A third channel is formed between the air intake chamber and the fresh air chamber. A fourth channel is formed between the return air chamber and the air intake chamber, allowing air to enter from the return air chamber to the air intake chamber in a unidirectional manner. Gas enters the fresh air chamber through the fresh air inlet. The heat pump unit is used to heat the gas in the duct chamber. The fresh air inlet, exhaust air outlet, and return air outlet are all equipped with adjustable blade valves. By adjusting the opening and closing of the adjustable blade valves, an open circulation channel, a semi-open circulation channel, or a closed circulation channel can be formed in the inner cavity of the drying chamber and the duct chamber.

[0007] The heat pump drying duct structure of this application divides the duct chamber into a fresh air chamber, an inlet air chamber, and a return air chamber through a partition, forming a multi-channel layout. With the adjustable blade valves of the fresh air inlet, exhaust air outlet, and return air outlet, it realizes the integrated switching of three circulation channels: open, semi-open, and closed. There is no need to add an additional independent duct structure, simplifying the overall layout of the equipment and improving space utilization. It truly integrates three channels in one heat pump dryer, which can adapt to the drying needs of different materials, solving the problem of poor adaptability of the traditional single duct mode, and balancing drying efficiency and flexibility.

[0008] Furthermore, the heat pump unit includes a first condenser, a second condenser, a dehumidification and energy recovery component, and an outdoor evaporator. The first and second condensers are installed in the inner cavity of the duct chamber and operate in series to heat the gas in the duct chamber. The dehumidification and energy recovery component is installed in the inner cavity of the duct chamber to dehumidify the gas in the return air chamber and recover heat. The outdoor evaporator is installed on the outside of the drying chamber and the duct chamber to absorb heat from the outside. The first and second condensers are connected in series to improve the uniformity and efficiency of gas heating in the air duct, avoiding local overheating or insufficient heating. In both semi-open and closed circulation channels, the relative humidity of the gas entering the air inlet can be further reduced. The dehumidification and energy recovery components simultaneously achieve gas dehumidification and heat recovery, reducing energy loss, improving energy utilization, and meeting the requirements of energy conservation and environmental protection. At the same time, they realize the integrated functions of heating, dehumidification, and energy recovery, simplifying the system structure. The outdoor evaporator absorbs heat from the external environment, which can quickly raise the temperature to the set temperature when the dryer is turned on in both semi-open and closed circulation channel modes, while ensuring the normal operation of the heat pump drying unit in open mode.

[0009] Furthermore, the first condenser is mounted on the partition to form the first channel, the dehumidification and energy recovery component is mounted on the partition to form the second channel, the second condenser is mounted on the partition to form the third channel, and the partition is also provided with a first one-way vent valve, which forms the fourth channel.

[0010] Furthermore, the dehumidification and energy recovery component includes an indoor evaporator and a cross-flow heat exchanger. The cross-flow heat exchanger includes an in-plate flow and an out-of-plate flow that exchange heat with each other. The upper end of the out-of-plate flow is unidirectionally connected to the return air cavity, and its lower end is connected to the inlet of the indoor evaporator. The outlet of the indoor evaporator is connected to the in-plate flow, and finally connected to the fresh air cavity through the in-plate flow. The bottom of the indoor evaporator is provided with a condensate drain pipe that connects to the outside. By combining an indoor evaporator with a cross-flow heat exchanger, a deep coupling of dehumidification and energy recovery is achieved. The cross-flow heat exchanger utilizes an in-plate and out-of-plate cross heat exchange structure to fully exchange heat between the humid hot air introduced into the return air chamber (out-of-plate process) and the dry air dehumidified by the indoor evaporator (in-plate process), maximizing the recovery of waste heat from the return air, reducing energy loss during the heating process, and significantly improving energy utilization efficiency. The indoor evaporator precisely removes water vapor from the airflow, and, in conjunction with the bottom condensate drain pipe, promptly discharges condensate, avoiding equipment corrosion or material dampness caused by water vapor retention, ensuring drying quality and equipment stability. The path design, with the out-of-plate process connecting the return air chamber in one direction and the in-plate process connecting the indoor evaporator and the fresh air chamber, ensures directional airflow without backflow, and is highly adaptable to the multi-chamber, multi-channel layout of the ductwork, simplifying the integrated structure of dehumidification and energy recovery while improving the smoothness and controllability of airflow circulation.

[0011] Furthermore, the conditions for forming the open-loop circulation channel are as follows: the blade valve at the return air inlet is closed, and the blade valves at the fresh air inlet and exhaust air inlet are open, forming two airflow paths. The first airflow path sequentially passes through the fresh air inlet, fresh air chamber, first channel, return air chamber, fourth channel, air inlet chamber, air inlet, and drying chamber. The second airflow path sequentially passes through the fresh air inlet, fresh air chamber, third channel, air inlet chamber, air inlet, and drying chamber, and finally exits outdoors through the exhaust air inlet. By closing the return air inlet and opening the exhaust air inlet, combined with the dual airflow path design, the open-loop circulation channel can quickly introduce outdoor fresh air, which is then doubly heated and sent into the drying chamber, while efficiently exhausting high-humidity air. It is suitable for drying scenarios that require rapid dehumidification and have low requirements for residual moisture. It is also suitable for materials that cannot be dried using return air, especially agricultural products that cannot be dried using return air.

[0012] Furthermore, the semi-open circulating flow channel is formed under the following conditions: the blade valves at the fresh air inlet, return air inlet, and exhaust air outlet are simultaneously opened, forming an exhaust airflow path and a return airflow path. The exhaust airflow path sequentially passes through the fresh air inlet, fresh air chamber, third channel, air inlet chamber, air inlet, and drying chamber. Part of the gas is finally discharged outdoors through the exhaust air outlet, while the other part of the gas flows back to the duct chamber through the return airflow path. The return airflow path sequentially passes through the return air outlet and return air chamber, then passes through the first channel and second channel respectively, and converges in the fresh air chamber, continuing to circulate in the drying chamber and duct chamber. By simultaneously opening the return air inlet and exhaust air outlet, the semi-open circulating flow channel forms a parallel airflow path for exhaust and return air, which can both discharge some high-humidity air and recover some heat from the airflow, balancing energy conservation and humidity control requirements. The return airflow re-enters the fresh air chamber through the first and second channels for reuse, reducing heat energy waste.

[0013] Furthermore, the closed-loop circulation channel is formed under the following conditions: the blade valve at the return air inlet is open, while the blade valves at the fresh air inlet and exhaust air inlet are closed. The airflow path sequentially passes through the fresh air inlet, fresh air chamber, third channel, air inlet chamber, air inlet, drying chamber, return air inlet, and return air chamber, then passes through the first channel and second channel respectively, and converges in the fresh air chamber, completing the closed-loop circulation. By closing the exhaust air inlet and opening the return air inlet, the closed-loop circulation channel achieves a fully enclosed airflow circulation, maximizing the recovery of heat in the airflow and minimizing energy consumption.

[0014] A drying control method using the above-mentioned heat pump drying duct structure includes the following steps: S1: Obtain the precision type of the material to be dried; S2: Collect material moisture content data, and match the corresponding heating temperature, humidity threshold, temperature difference threshold, and baseline drying time according to the material moisture content data and precision type; S3: Select open, semi-open, or closed drying mode according to the precision type of the material, adjust the corresponding blade valve to the open circulation channel, semi-open circulation channel, or closed circulation channel, and start the heat pump unit to heat the gas to the set heating temperature; S4: Real-time detection of humidity, the temperature difference between drying and condenser, and continuous drying time to determine whether the preset shutdown conditions are met; S5: When the preset shutdown conditions are met, stop the machine after running for several minutes.

[0015] According to the drying control method of this application, the corresponding drying parameters are matched according to the material precision type to realize an intelligent process of "precision adaptation - parameter matching - mode selection", which eliminates the need for manual adjustment and reduces the operation threshold. By real-time detection of key parameters and judgment of shutdown conditions, the drying process is automated, avoiding over-drying or under-drying and improving the consistency of drying quality for different materials. The precise matching of three modes and parameters further optimizes the balance between drying efficiency, energy utilization and drying quality.

[0016] Furthermore, in the open and semi-open modes, the shutdown conditions include: the humidity at the exhaust vent is less than a humidity threshold, and the temperature difference between the exhaust vent and the condenser is less than or equal to a temperature difference threshold. In the closed mode, the shutdown conditions include: the humidity at the return air vent is less than a humidity threshold, and the temperature difference between the drying chamber and the condenser is less than or equal to a temperature difference threshold. Corresponding shutdown judgment parameters are set for the airflow circulation characteristics of the open, semi-open, and closed modes, ensuring that the shutdown conditions are precisely matched to the airflow characteristics of the circulation mode, avoiding deviations in drying effect caused by a uniform judgment standard. By using both humidity and temperature difference thresholds for dual judgment, the accuracy of shutdown judgment is improved, ensuring that the material is dried to the required standard and its quality is stable, reducing the rate of defective products.

[0017] Furthermore, the shutdown conditions also include: the continuous drying time is greater than or equal to the baseline drying time. Based on the temperature, humidity, and temperature difference determinations, the baseline drying time is added as an auxiliary shutdown condition, forming a dual protection mechanism of "parameter threshold + time threshold" to avoid erroneous or premature shutdowns caused by instantaneous sensor fluctuations. The baseline drying time is matched with the material's precision type, further refining the drying process control and ensuring that the material maintains a stable state after reaching the standard, improving the reliability of drying quality, while avoiding unnecessary overtime operation and saving energy. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the open circulation channel of the heat pump drying duct structure of the present invention.

[0019] Figure 2 This is a schematic diagram of the semi-open circulating flow channel of the heat pump drying air duct structure of the present invention.

[0020] Figure 3 This is a schematic diagram of the closed-loop flow channel of the heat pump drying duct structure of the present invention.

[0021] Figure 4 This is a flowchart of the drying control method of the present invention. Detailed Implementation

[0022] The present invention describes a heat pump drying duct structure and a drying control method in conjunction with the accompanying drawings.

[0023] like Figures 1 to 3 The diagram illustrates a heat pump drying duct structure, comprising a drying chamber 2, a duct chamber 1, and a heat pump unit 3. The drying chamber 2 has an exhaust vent 22, and the duct chamber 1 has a fresh air inlet 15. A return air inlet 23 and an air inlet 21 are located between the drying chamber 2 and the duct chamber 1. A storage rack 24 is provided inside the drying chamber 2, on which materials to be dried can be placed. Air guide plates 25 are installed between the storage racks 24 to guide hot air through each rack. A partition 14 is provided inside the duct chamber 1, dividing its interior into a fresh air chamber 11, an air inlet chamber 12, and a return air chamber 13. Figures 1 to 3As shown, the lower half of the inner cavity of the air duct chamber 1 is divided into a fresh air chamber 11 by a partition 14, the left side of the upper half is divided into a return air chamber 13, and the right side is divided into an air inlet chamber 12; the exhaust port 22 connects to the inner cavity of the drying chamber 2, the fresh air inlet 15 connects to the fresh air chamber 11, and the return air inlet 23 and the air inlet 21 connect to the return air chamber 13 and the air inlet chamber 12, respectively; a first channel and a second channel are formed between the return air chamber 13 and the fresh air chamber 11, the second channel is for unidirectional air intake from the return air chamber 13 to the fresh air chamber 11, a third channel is formed between the air inlet chamber 12 and the fresh air chamber 11, and a fourth channel is formed between the return air chamber 13 and the air inlet chamber 12, for unidirectional air intake from the return air chamber 13 to the air inlet chamber 12; the gas flows from the fresh air chamber 13 to the air inlet chamber 12. Air vent 15 enters the fresh air chamber 11. The heat pump unit 3 is used to heat the gas in the air duct chamber 1. The exhaust vent 22 and return vent 23 are both equipped with adjustable blade valves 4. By adjusting the opening and closing of the adjustable blade valves 4, an open circulation channel, a semi-open circulation channel, or a closed circulation channel can be formed in the inner cavity of the drying chamber 2 and the air duct chamber 1. Preferably, a blower is set at the fresh air vent 15 to guide outside air into the fresh air chamber 11. A circulating fan 5 is set at the air inlet 21, the return vent 23, and the fourth channel. The circulating fan 5 guides the air in the air inlet 21, the return vent 23, and the fourth channel to complete various circulation channels. The circulating fan 5 is preferably an axial flow fan.

[0024] The heat pump unit 3 includes a first condenser 31, a second condenser 32, a dehumidification and energy recovery component 33, and an outdoor evaporator 34. The first condenser 31 and the second condenser 32 are arranged in series in the inner cavity of the air duct chamber 1 to heat the gas in the air duct chamber 1. The dehumidification and energy recovery component 33 is arranged in the inner cavity of the air duct chamber 1 to dehumidify the gas in the air duct chamber 1 and recover heat. The outdoor evaporator 34 is arranged outside the drying chamber 2 and the air duct chamber 1 to absorb heat from the outside. The compressor, throttle valve, and the connection of the pipes of each component of the heat pump unit 3 are common technical solutions in the art and will not be described in detail here.

[0025] The first condenser 31 is mounted on the partition 14 to form the first channel, the dehumidification and energy recovery component 33 is mounted on the partition 14 to form the second channel, the second condenser 32 is mounted on the partition 14 to form the third channel, and the partition 14 is also provided with a first one-way vent valve 141, which forms the fourth channel.

[0026] The dehumidification and energy recovery assembly 33 includes an indoor evaporator 331, a cross-flow heat exchanger 332, and a second one-way vent valve. The cross-flow heat exchanger 332 includes an in-plate flow and an out-of-plate flow that exchange heat with each other. The upper end of the out-of-plate flow is connected to the return air chamber 13 through the second one-way vent valve, and its lower end is connected to the inlet of the indoor evaporator 331. The outlet of the indoor evaporator 331 is connected to the in-plate flow and finally connected to the fresh air chamber 11 through the in-plate flow. The indoor evaporator 331 is provided with a condensate drain pipe 333 connecting to the outside. A mounting cavity for installing the dehumidification and energy recovery assembly 33 is formed on the partition 14. The second one-way vent valve is installed at the front of the mounting cavity, and the indoor evaporator 331 is installed at the rear of the mounting cavity. The cross-flow heat exchanger 332 is installed between the second one-way vent valve and the indoor evaporator 331. During this process, when the hot and humid gas from the dried material enters the return air chamber 13 through the return air inlet 23, some of the hot and humid gas will flow into the indoor evaporator 331 through the second one-way vent valve and the external flow of the cross-flow heat exchanger 332. In the heat pump system, the evaporator is used for heat exchange and dehumidification. The water vapor in the hot and humid gas condenses on the heat exchange tubes of the indoor evaporator 331. After collecting the condensate, the indoor evaporator 331 discharges it through the condensate drain pipe 333. The dry air after being dehumidified by the indoor evaporator flows into the internal flow of the cross-flow heat exchanger 332, where it undergoes full heat exchange, maximizing the recovery of waste heat from the return air, reducing energy loss during the heating process, significantly improving energy utilization efficiency, and reducing the heat load of the condenser. Finally, the reheated dry air flows into the fresh air chamber to continue circulating, achieving the functions of dehumidification and energy recovery.

[0027] like Figure 1 As shown, the conditions for forming the open circulation channel are as follows: the blade valve 4 at the return air inlet 23 is closed, and the blade valve 4 at the exhaust air inlet 22 is open, forming two airflow paths. The first airflow path passes through the fresh air inlet 15, the fresh air chamber 11, the first channel, the return air chamber 13, the fourth channel, the air inlet chamber 12, the air inlet 21, and the drying chamber 2 in sequence. The second airflow path passes through the fresh air inlet 15, the fresh air chamber 11, the third channel, the air inlet chamber 12, the air inlet 21, and the drying chamber 2 in sequence, and is finally discharged to the outside at the exhaust air inlet 22. After the fresh air enters the fresh air chamber 11, part of it is heated by the first condenser 31 and flows into the return air chamber 13, and then flows into the air inlet chamber 12 through the first one-way ventilation valve 141. Part of it is heated by the second condenser 32 and flows into the air inlet chamber 12. The two parts of heated air finally converge in the air inlet chamber 12 and enter the drying chamber 2 through the air inlet 21 to dry the materials in the drying chamber 2.

[0028] like Figure 2As shown, the conditions for forming the semi-open circulating flow channel are as follows: the blade valves 4 at the return air inlet 23 and the exhaust air inlet 22 are opened simultaneously, forming an exhaust airflow path and a return airflow path. The exhaust airflow path passes sequentially through the fresh air inlet 15, the fresh air chamber 11, the third channel, the air inlet chamber 12, the air inlet 21, and the drying chamber 2. Part of the gas is finally discharged outdoors at the exhaust air inlet 22, and the other part of the gas flows back to the duct chamber 1 through the return airflow path. The return airflow path passes sequentially through the return air inlet 23 and the return air chamber 13, and then passes through the first channel and the second channel respectively, and gathers in the fresh air chamber 11, continuing to circulate in the drying chamber 2 and the duct chamber 1. Fresh air enters the fresh air chamber 11. After being heated by the second condenser 32, the gas flows into the air inlet chamber 12, where the material is dried to form a high-temperature and high-humidity gas. The high-temperature and high-humidity gas is discharged outdoors through the exhaust port 22, while another part of the high-temperature and high-humidity gas flows back through the return air port 23. The returned high-temperature and high-humidity gas is divided into two parts again. One part of the high-temperature and high-humidity gas is reheated by the first condenser 31 and flows into the fresh air chamber 11. The other part of the high-temperature and high-humidity gas is dehumidified and energy recovered by the dehumidification and energy recovery component 33 and then flows into the fresh air chamber 11, where it recirculates with the fresh air. The semi-open circulation channel takes advantage of the dehumidification and energy recovery component 33 to increase the dehumidification capacity while recovering some of the heat in the gas.

[0029] like Figure 3 As shown, the conditions for forming the closed-loop circulation channel are as follows: the blade valve 4 at the return air inlet 23 is open, the blade valve 4 at the exhaust air outlet 22 is closed, and the airflow path sequentially passes through the fresh air inlet 15, the fresh air chamber 11, the third channel, the air inlet chamber 12, the air inlet 21, the drying chamber 2, the return air inlet 23, and the return air chamber 13, and then passes through the first channel and the second channel respectively, and converges in the fresh air chamber 11 to complete the closed loop. No fresh air enters the closed-loop circulation channel, and the drying relies on the original gas in the drying chamber 2 and the air duct chamber 1. In the closed loop, part of the gas participates in the circulation through the first channel and the third channel. This part of the gas will be heated by the condenser twice. Another part of the gas participates in the circulation through the second channel and the third channel. Under the closed loop, this part of the gas will recover heat to the maximum extent and reduce the relative humidity of the airflow entering the drying chamber 2 to the maximum extent.

[0030] The one-way vent valve described in this application is an electrically controlled valve. It opens and closes in a timely manner through electric control, thereby achieving the effect of one-way synchronization. That is, the one-way vent valve can be an electrically controlled valve such as a vane valve to achieve the effect of one-way venting. For example, in an open circulation channel, the first one-way vent valve 141 is opened accordingly, and in a closed circulation and a semi-open circulation, the first one-way vent valve 141 is closed accordingly. The control of vane valves is a common solution in the art, and will not be described in detail here.

[0031] like Figure 4As shown, a drying control method using the above-described heat pump drying duct structure includes the following steps: S1: Obtain the precision type of the material to be dried, wherein the precision type includes low precision material, medium precision material and high precision material, low precision material such as grain material, medium precision material such as dried fruit material, and high precision material such as meat or fruit material. S2: Collect material moisture content data, and match the corresponding heating temperature, humidity threshold, temperature difference threshold and baseline drying time according to the material moisture content data and accuracy type; Each precision type has a preset data table of heating temperature, humidity threshold, temperature difference threshold and reference drying time corresponding to the material moisture content data. For example, when it is a low precision material, the corresponding heating temperature, humidity threshold, temperature difference threshold and reference drying time can be found in the data table by using the material moisture content data.

[0032] S3: Select the open, semi-open, or closed drying mode according to the precision type of the material. Low-precision materials correspond to the open drying mode, medium-precision materials to the semi-open drying mode, and high-precision materials to the closed drying mode. Adjust the corresponding blade valve to the open, semi-open, or closed circulation channel. Start the heat pump unit to heat the gas to the set heating temperature. In the open drying mode, the outdoor evaporator of the heat pump unit works, while the indoor evaporator does not work. The outdoor evaporator quickly absorbs heat from the outside, and then releases heat through the first and second condensers to quickly heat to the set heating temperature. In the semi-open and closed drying modes, the outdoor evaporator of the heat pump unit first works to quickly heat the gas in the air duct chamber to the set heating temperature. Then, the indoor evaporator works to recover heat and dehumidify the high-temperature and high-humidity gas after drying. When the gas temperature is lower than the set heating temperature, the outdoor evaporator works again to reheat the gas to the set heating temperature. S4: Real-time detection of humidity, drying temperature and condenser temperature difference, and continuous drying time to determine whether the preset shutdown conditions are met; In the open and semi-open modes, the shutdown conditions include: the humidity at the exhaust vent is less than the humidity threshold and the temperature difference between the exhaust vent and the condenser is less than or equal to the temperature difference threshold; in the closed mode, the shutdown conditions include: the humidity at the return air vent is less than the humidity threshold and the temperature difference between the drying chamber and the condenser is less than or equal to the temperature difference threshold.

[0033] Only after the above conditions are met can it be determined that the continuous drying time is greater than or equal to the benchmark drying time.

[0034] S5: When the preset shutdown conditions are met, the machine will continue to run for a certain number of minutes before shutting down. The preferred continuous running time is 3-5 minutes.

[0035] Humidity, temperature, and operating time detection are common technical solutions in this field, and will not be elaborated here.

[0036] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A heat pump drying air duct structure, characterized in that, The system includes a drying chamber, an air duct chamber, and a heat pump unit. The drying chamber is equipped with an exhaust vent, and the air duct chamber is equipped with a fresh air inlet. A return air inlet and an air inlet are provided between the drying chamber and the air duct chamber. The air duct chamber is equipped with a partition that divides the inner cavity of the air duct chamber into a fresh air chamber, an air inlet chamber, and a return air chamber. The exhaust vent connects to the inner cavity of the drying chamber, the fresh air inlet connects to the fresh air chamber, and the return air inlet and air inlet connect to the return air chamber and the air inlet chamber, respectively. A first channel and a second channel are formed between the return air chamber and the fresh air chamber. The second channel allows air to enter the fresh air chamber in one direction from the return air chamber. A third channel is formed between the inlet air chamber and the fresh air chamber. A fourth channel is formed between the return air chamber and the inlet air chamber, allowing air to enter the inlet air chamber in one direction from the return air chamber. Gas enters the fresh air chamber through the fresh air inlet. The heat pump unit is used to heat the gas in the duct chamber. The fresh air inlet, exhaust air outlet, and return air outlet are all equipped with adjustable blade valves. By adjusting the opening and closing of the adjustable blade valves, an open circulation channel, a semi-open circulation channel, or a closed circulation channel can be formed in the inner cavity of the drying chamber and the duct chamber.

2. The heat pump drying duct structure according to claim 1, characterized in that, The heat pump unit includes a first condenser, a second condenser, a dehumidification and energy recovery component, and an outdoor evaporator. The first and second condensers are installed in the inner cavity of the duct chamber and operate in series to heat the gas in the duct chamber. The dehumidification and energy recovery component is installed in the inner cavity of the duct chamber to dehumidify the gas in the return air chamber and recover heat. The outdoor evaporator is installed on the outside of the drying chamber and the duct chamber to absorb heat from the outside.

3. The heat pump drying duct structure according to claim 2, characterized in that, The first condenser is mounted on the partition to form the first channel, the dehumidification and energy recovery component is mounted on the partition to form the second channel, the second condenser is mounted on the partition to form the third channel, and the partition is also provided with a first one-way vent valve, which forms the fourth channel.

4. The heat pump drying duct structure according to claim 3, characterized in that, The dehumidification and energy recovery assembly includes an indoor evaporator and a cross-flow heat exchanger. The cross-flow heat exchanger includes an in-plate flow and an out-of-plate flow that exchange heat with each other. The upper end of the out-of-plate flow is unidirectionally connected to the return air cavity, and its lower end is connected to the inlet of the indoor evaporator. The outlet of the indoor evaporator is connected to the in-plate flow and finally connected to the fresh air cavity through the in-plate flow. The bottom of the indoor evaporator is provided with a condensate drain pipe that connects to the outside.

5. The heat pump drying duct structure according to any one of claims 1 to 4, characterized in that, The conditions for forming the open circulation channel are as follows: the blade valve at the return air inlet is closed, and the blade valves at the fresh air inlet and the exhaust air inlet are open, forming two airflow paths. The first airflow path passes through the fresh air inlet, fresh air cavity, first channel, return air cavity, fourth channel, air inlet cavity, air inlet, and drying chamber in sequence. The second airflow path passes through the fresh air inlet, fresh air cavity, third channel, air inlet cavity, air inlet, and drying chamber in sequence, and finally exits outdoors through the exhaust air inlet.

6. The heat pump drying duct structure according to any one of claims 1 to 4, characterized in that, The semi-open circulating flow channel is formed under the following conditions: the blade valves at the fresh air inlet, return air inlet, and exhaust air outlet are opened simultaneously to form an exhaust airflow path and a return airflow path. The exhaust airflow path passes through the fresh air inlet, fresh air chamber, third channel, air inlet chamber, air inlet, and drying chamber in sequence. Part of the gas is finally discharged outdoors through the exhaust air outlet, and another part of the gas flows back to the air duct chamber through the return airflow path. The return airflow path passes through the return air inlet and return air chamber in sequence, and then passes through the first channel and the second channel respectively, and converges in the fresh air chamber, continuing to circulate in the drying chamber and air duct chamber.

7. The heat pump drying duct structure according to any one of claims 1 to 4, characterized in that, The conditions for forming the closed-loop flow channel are as follows: the blade valve at the return air inlet is open, the blade valves at the fresh air inlet and the exhaust air inlet are closed, and the airflow path passes through the fresh air inlet, fresh air cavity, third channel, air inlet cavity, air inlet, drying chamber, return air inlet, and return air cavity in sequence, and then passes through the first channel and the second channel respectively, and converges in the fresh air cavity to complete the closed-loop circulation.

8. A drying control method using the heat pump drying duct structure according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Obtain the precision type of the material to be dried; S2: Collect the material moisture content data, and match the corresponding heating temperature, humidity threshold, temperature difference threshold and baseline drying time according to the material moisture content data and precision type; S3: Select the open, semi-open or closed drying mode according to the material precision type, adjust the corresponding blade valve to the open circulation channel, semi-open circulation channel or closed circulation channel, and start the heat pump unit to heat the gas to the set heating temperature; S4: Real-time detection of humidity, drying temperature and condenser temperature difference, and continuous drying time to determine whether the preset shutdown conditions are met; S5: When the preset shutdown conditions are met, the machine will continue to run for several minutes before shutting down.

9. The drying control method according to claim 8, characterized in that, In the open and semi-open modes, the shutdown conditions include: the humidity at the exhaust vent is less than the humidity threshold and the temperature difference between the exhaust vent and the condenser is less than or equal to the temperature difference threshold; in the closed mode, the shutdown conditions include: the humidity at the return air vent is less than the humidity threshold and the temperature difference between the drying chamber and the condenser is less than or equal to the temperature difference threshold.

10. The drying control method according to claim 8, characterized in that, The shutdown conditions also include: the continuous drying time is greater than or equal to the baseline drying time.

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