A heat pump drying device with excess heat recovery
By introducing components such as subcoolers, air pre-processors, and air heat exchangers into the heat pump drying system, excess heat is recovered and stored. Combined with the air guide system to adjust the air path, the stability and efficiency issues of the heat pump drying system under different climatic conditions are solved, achieving efficient waste heat utilization and ensuring drying quality.
Patent Information
- Application Number
- CN202522114879.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-09-30
AI Technical Summary
Existing heat pump drying systems suffer from problems such as over-drying in closed systems and the need for defrosting at low temperatures due to weather conditions, making it difficult to operate stably and efficiently under different climatic conditions.
It uses a subcooler, an air pre-processor, and an air heat exchanger to recover refrigerant subcooling heat, fresh air precooling heat, and dehumidification waste heat. Combined with a water pump and control water valve, these are delivered to a water tank for storage. The airflow is adjusted by the air guide system to adapt to different climates, reduce the dehumidification burden, or prevent frost formation. The air pre-processor switches between precooling and preheating modes to adapt to different climatic conditions.
It achieves efficient recovery and storage of multi-source waste heat, adapts to different climatic conditions, avoids excessively low humidity in the later stages of drying, improves energy efficiency, expands the types and regions of applicable materials, and ensures drying quality.
Smart Images
Figure CN224680984U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of waste heat recovery technology, specifically a heat pump drying device for waste heat recovery. Background Technology
[0002] A heat pump drying device is an energy-saving equipment that uses the heat pump cycle principle to dry materials. It transfers heat from the air to the drying chamber through the absorption of heat by refrigerant evaporation and the release of heat by condensation, heating the air to remove moisture from the materials. It is mainly used for dehydration and drying of agricultural products, Chinese medicinal materials, seafood, etc. It has the advantages of controllable temperature and humidity, energy saving and environmental protection, reduced pollution, and preservation of nutrients. It can replace traditional sun-drying and high-energy-consuming drying methods, and improve drying quality and efficiency.
[0003] Existing heat pump drying systems mainly include open-loop and closed-loop heat pump drying systems, which are widely used in the processing industries of rice, fruits and vegetables, medicinal materials and seafood. They have greatly improved the drying effect of traditional sun-drying, effectively reduced the degree of contamination of dried materials by dust and bacteria, reduced the loss of nutrients in materials, and accelerated the drying rate of various materials by adjusting the drying process, thus reducing the damage rate of agricultural and seafood products.
[0004] Existing heat pump drying systems mainly fall into the following categories: First, closed-loop drying systems, which have the advantage of stable production capacity and are not affected by weather, but can only dehumidify, and are prone to low humidity in the later stages of the drying process, limiting the applicable materials; Second, open-loop drying systems, which have the advantage of energy-saving heating, but are affected by weather, with efficiency decreasing rapidly as the temperature drops, and require defrosting when the temperature is below 10°C, making it difficult to guarantee the continuity of drying. Utility Model Content
[0005] The technical problem to be solved by this utility model is to provide a heat pump drying device that can overcome the defects of closed systems being prone to over-drying in the later stage and open systems being greatly affected by weather and requiring defrosting at low temperatures, achieve efficient recovery of multi-source waste heat, adapt to different climatic conditions, prevent frost formation, avoid excessively low humidity in the later stage of drying, improve energy efficiency and ensure drying quality.
[0006] To address the shortcomings of existing technologies, this utility model provides a heat pump drying device with excess heat recovery. It recovers refrigerant subcooling heat, fresh air precooling heat, and dehumidification waste heat through a subcooler, air pre-processor, and air heat exchanger. This heat is then pumped and controlled by a water pump to a water tank for storage and reuse. The air pre-processor can switch between precooling and preheating modes and, in conjunction with the air guide system, adjusts the airflow to adapt to different climates, reducing the dehumidification burden or preventing frost formation, thus avoiding over-drying in the later stages of drying. This solves the problems of existing heat pump drying systems, which are divided into closed and open types, widely used for drying grains, fruits, vegetables, and medicinal herbs. Closed systems are stable but prone to over-drying in the later stages, limiting applicable materials; open systems are energy-efficient but highly susceptible to weather conditions, require defrosting at low temperatures, and have poor sustainability.
[0007] To achieve the above objectives, this utility model provides the following technical solution: a heat pump drying device for waste heat recovery, comprising a heat pump system, a waste heat recovery system, and a heat storage system; the heat pump system includes a compressor, an indoor condenser, a subcooler, an expansion valve, and a dehumidifying evaporator, wherein the subcooler is located after the indoor condenser and before the expansion valve; the waste heat recovery system includes the aforementioned subcooler, an air pre-processor, an exhaust fan, and an air heat exchanger; when the outdoor fresh air temperature is high, the air guiding system guides the fresh air to pass through the air pre-processor for pre-cooling; when the outdoor fresh air temperature is low, the air guiding system guides the fresh air to pass through the air pre-processor for pre-cooling. After dehumidification by the dehumidifying evaporator, the air enters the air preheater for preheating. The exhaust fan is located at the air outlet of the drying chamber, and the air heat exchanger is located after the exhaust fan. It is used to exchange heat with the circulating water before the exhaust high-temperature and high-humidity air is discharged into the environment. The heat storage system includes a water tank, a water pump, and a control water valve. The water tank is connected to the subcooler, the air preheater, and the air heat exchanger through pipes. Each connecting pipe is equipped with a water pump and a control water valve. The water flows through the heat exchanger to recover the waste heat of the refrigerant subcooling, the waste heat of the air to be dehumidified, and the waste heat of the exhaust air, and stores the heat in the water tank.
[0008] Furthermore, the air pre-processor is a heat exchange device that exchanges heat with air using a liquid heat transfer medium, and its water side is connected to the circulating water circuit of the heat storage system; when high-temperature fresh air flows through the air pre-processor, the circulating water absorbs heat from the air and is heated; when low-temperature fresh air flows through the air pre-processor, the circulating water releases heat to the air and is cooled.
[0009] Furthermore, the air guiding system includes an electric air valve. The opening and closing status of the electric air valve is controlled by the output signal of the outdoor temperature sensor. When the electric air valve is activated, the fresh air first enters the air pre-processor and then the dehumidifying evaporator under high temperature conditions. When the electric air valve is closed, the fresh air first enters the dehumidifying evaporator and then the air pre-processor under low temperature conditions.
[0010] Furthermore, the dehumidification fan is a variable frequency fan, which is connected to a frequency converter. The frequency converter receives real-time signals from the humidity sensor in the drying room and adjusts the speed of the dehumidification fan according to the humidity sensor signal.
[0011] Furthermore, the subcooler is a plate-fin heat exchanger. When the liquid refrigerant flows out from the indoor condenser, it enters the subcooler. The liquid refrigerant exchanges heat with the circulating water in the subcooler, causing the refrigerant temperature to decrease and the circulating water temperature to increase.
[0012] Furthermore, the water tank is equipped with a temperature detector and an electric heater. The temperature detector continuously monitors the temperature of the water in the tank and outputs the detection value to the control system. When the detection value is lower than the set lower limit, the control system starts the electric heater to heat the water.
[0013] Furthermore, the heat pump system also includes a pressure relay, a liquid receiver, and a gas-liquid separator. The pressure sensing end of the pressure relay is connected to the high-pressure exhaust pipe of the compressor, and the control output end of the pressure relay is connected to the power supply circuit of the compressor. When the pressure detected by the pressure sensing end exceeds the set threshold, the pressure relay disconnects the power supply circuit of the compressor.
[0014] Compared with the prior art, the technical solution of this application has the following beneficial effects:
[0015] 1. The air pre-processor has a dual function of pre-cooling and pre-heating: it pre-cools the fresh air in high-temperature and high-humidity environments to reduce the load on the dehumidifier evaporator; in low-temperature environments, it uses stored hot water to preheat the dehumidified air, preventing evaporator frosting or insufficient drying temperature. Combined with the path switching function of the air guiding system, it can reduce the impact of local climate and weather, making it suitable for different regions and all seasons across the country, expanding its application range, avoiding the phenomenon of low humidity that is difficult to correct in the later stages of the drying process, ensuring the quality of dried materials, and expanding the types of materials that can be dried.
[0016] 2. By setting up a multi-source waste heat recovery system consisting of a subcooler, an air pre-processor, and an air heat exchanger, and combining it with a heat storage system consisting of a water tank, a water pump, and a control water valve, the system can simultaneously recover the waste heat from refrigerant subcooling, the waste heat from precooling the air to be dehumidified, and the sensible and latent heat in the exhaust air. These three streams of low-grade heat that would otherwise be released into the environment are collected and stored in the water tank, achieving cascaded utilization of energy, significantly improving the overall energy efficiency ratio of the device, effectively enhancing the waste heat utilization of the heat pump drying system, and reducing the energy consumption of the device. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of this utility model;
[0018] Figure 2 This is a three-dimensional structural diagram of the location of the compressor in this utility model;
[0019] Figure 3 This is a three-dimensional structural diagram of the location of the water tank in this utility model;
[0020] Figure 4 This is a three-dimensional structural diagram of the location of the air heat exchanger of this utility model;
[0021] Figure 5 This is a three-dimensional structural diagram of the location of the dehumidifying evaporator of this utility model.
[0022] In the diagram: 1. Pressure relay; 2. Compressor; 3. Indoor condenser; 4. Air heat exchanger; 5. Dehumidifier fan; 6. Water tank; 7. Water pump; 8. Control water valve; 9. Subcooler; 10. Liquid receiver; 11. Expansion valve; 12. Air pre-processor; 13. Dehumidifier evaporator; 14. Gas-liquid separator. Detailed Implementation
[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0024] It should be noted that the accompanying drawings are only schematic representations of this utility model, and the structures shown in each drawing are only partial displays and do not fully reflect the three-dimensional form of all components. The actual structure is subject to the textual description in the instruction manual.
[0025] The term "excess heat" as used in this article refers to the low-grade heat that can be recovered but is usually discharged during the operation of a heat pump, such as refrigerant subcooling, dehumidification of air, and fresh air treatment. "Liquid heat transfer medium" refers to a medium that is liquid at room temperature and pressure and is used to transfer heat, preferably water.
[0026] Please see Figure 1 The heat pump drying device for waste heat recovery in this embodiment includes a heat pump system, a waste heat recovery system and a heat storage system; the heat pump system includes a compressor 2, an indoor condenser 3, a subcooler 9, an expansion valve 11 and a dehumidifying evaporator 13, wherein the subcooler 9 is located after the indoor condenser 3 and before the expansion valve 11.
[0027] In this embodiment, a multi-source waste heat recovery system is constructed by setting up a subcooler 9, an air pre-processor 12, and an air heat exchanger 4. Combined with a heat storage system consisting of a water tank 6, a water pump 7, and a control water valve 8, the system recovers and stores the refrigerant subcooling heat, fresh air precooling heat, and dehumidification waste heat for use. At the same time, the air pre-processor 12 has dual functions of precooling and preheating. It works with the air guide system to switch air paths, reducing the dehumidification load or preventing frost formation under different climatic conditions, avoiding excessive drying in the later stage, improving energy efficiency while ensuring the quality of material drying, and expanding the applicable regions and types of materials.
[0028] The above-mentioned technical effects are achieved by the following technical features: the air pre-processor 12 and the air guide system work together to switch the fresh air path, solving the problems of easy frosting at low temperatures and high load at high temperatures; the connection between the subcooler 9, the air heat exchanger 4 and the water tank 6 realizes multi-source waste heat recovery and storage, improving energy utilization efficiency; the linkage between the variable frequency fan and the humidity sensor realizes precise humidity control, avoiding excessive dryness in the later stage.
[0029] Please see Figure 1 , Figure 3 , Figure 4 and Figure 5 In this embodiment, to enable the air pre-processor 12 to both pre-cool and pre-heat, it cools the fresh air at high temperatures and heats the air with hot water at low temperatures. The airflow system automatically switches ducts to adapt to different weather conditions and prevent excessive dryness in the later stages of drying. The waste heat recovery system in this embodiment includes the aforementioned subcooler 9, air pre-processor 12, dehumidifying fan 5, and air heat exchanger 4. When the outdoor fresh air temperature is high, the airflow system guides the fresh air to pass through the air pre-processor 12 for pre-cooling. When the outdoor fresh air temperature is low, the airflow system guides the fresh air to pass through the dehumidifying evaporator 13 for dehumidification before entering the air conditioner. The air preheater 12 preheats the air; the dehumidifying fan 5 is located at the air outlet of the drying chamber, and the air heat exchanger 4 is located after the dehumidifying fan 5. It is used to exchange heat with the circulating water before the exhaust high-temperature and high-humidity air is discharged into the environment. The heat storage system includes a water tank 6, a water pump 7, and a control water valve 8. The water tank 6 is connected to the subcooler 9, the air preheater 12, and the air heat exchanger 4 through pipes. Each connecting pipe is equipped with a water pump 7 and a control water valve 8. Water flows through the heat exchangers to recover the waste heat of the refrigerant subcooling, the waste heat of the air to be dehumidified, and the waste heat of the exhaust air, and stores the heat in the water tank 6.
[0030] The embodiments described in this utility model are merely preferred embodiments and are not intended to limit the scope of this utility model. For example, the subcooler 9 can be replaced with a plate or shell-and-tube heat exchanger, the air pre-processor 12 can adopt other forms of water-air heat exchange structures, and the air guiding system can also adopt a manual switching or three-way valve structure, all of which are within the protection scope of this utility model.
[0031] In this embodiment, the air pre-processor 12 is used to pre-cool or preheat the fresh air to adapt to different ambient temperatures. The air guiding system automatically switches the air path according to the outdoor temperature, so that the fresh air is pre-cooled or dehumidified first. The dehumidification fan 5 discharges the moisture in the box to maintain a stable dry environment. The air heat exchanger 4 recovers the heat in the dehumidified air and transfers it to the circulating water. The subcooler 9 further cools the refrigerant and heats the circulating water at the same time. The water tank 6 stores the recovered heat for subsequent use. The water pump 7 drives the circulating water to flow between the heat exchangers. The water valve 8 controls the water flow direction and on / off to realize the recovery and release of heat. The whole system improves energy efficiency and reduces energy consumption through waste heat recovery and heat reuse, ensures that the temperature and humidity are controllable during the drying process, prevents over-drying in the later stage, and ensures the quality of materials.
[0032] It should be noted that the air guiding system includes an electric damper. The opening and closing status of the electric damper is controlled by the output signal of the outdoor temperature sensor. When the electric damper is activated, fresh air first enters the air pre-processor 12 and then the dehumidifier evaporator 13 under high-temperature conditions. When the electric damper is closed, fresh air first enters the dehumidifier evaporator 13 and then the air pre-processor 12 under low-temperature conditions. The exhaust fan 5 is a variable frequency fan, which is connected to a frequency converter. The frequency converter receives real-time signals from the humidity sensor in the drying room and adjusts the speed of the exhaust fan 5 according to the humidity sensor signal. The electric damper is used to switch the fresh air flow path and select the air pre-processor 12 to enter according to the operating conditions. The sequence of processor 12 or dehumidifying evaporator 13 is as follows: outdoor temperature sensor is used to detect the outside air temperature and output a signal to control the opening and closing state of electric air valve; air pre-processor 12 is used to pre-cool fresh air at high temperature and preheat dehumidified air at low temperature; dehumidifying evaporator 13 is used to cool and remove moisture from the air to achieve air dehumidification; exhaust fan 5 is used to exhaust humid air from the drying chamber to maintain internal humidity balance; frequency converter is used to receive humidity signal and adjust the operating speed of exhaust fan 5; and indoor humidity sensor is used to monitor the humidity change inside the chamber in real time and provide feedback signal to frequency converter.
[0033] Please see Figure 1 , Figure 3 , Figure 4 and Figure 5In this embodiment, to recover the heat that would otherwise be wasted using the subcooler 9, air pre-processor 12, and air heat exchanger 4, the heat is stored in the water tank 6 for reuse through water circulation, which is both energy-saving and efficient, greatly reducing energy consumption. In this embodiment, the air pre-processor 12 is a heat exchange device that exchanges heat with the air using a liquid heat transfer medium, and its water side is connected to the circulating water circuit of the heat storage system. When high-temperature fresh air flows through the air pre-processor 12, the circulating water absorbs the heat of the air and is heated; when low-temperature fresh air flows through the air pre-processor 12, the circulating water releases heat to the air and is cooled. The subcooler 9 is a plate-fin heat exchanger. When the liquid refrigerant flows out from the indoor condenser 3, the liquid refrigerant enters the subcooler 9. The liquid refrigerant exchanges heat with the circulating water in the subcooler 9, the refrigerant temperature decreases, and the circulating water temperature increases.
[0034] In this embodiment, the air pre-processor 12 is used to realize heat exchange between fresh air and circulating water. It absorbs heat from the air under high temperature conditions and releases heat to the air under low temperature conditions. The liquid heat transfer medium carries heat in the air pre-processor 12 for recovery or release. The circulating water transfers heat through flow and is heated or cooled under different conditions to achieve energy storage and utilization. The subcooler 9 is used to further reduce the temperature of the liquid refrigerant and improve the cooling efficiency. The plate-fin heat exchanger structure enhances the heat exchange effect and improves the heat transfer efficiency between the refrigerant and the circulating water. The liquid refrigerant releases heat during the subcooling process and transfers the heat to the circulating water. The high-temperature liquid refrigerant discharged from the indoor condenser 3 enters the subcooler 9 to continue releasing heat.
[0035] It should be added that the hot water stored in the heat storage system can be used to regulate the temperature and humidity of the air supply in the later stage of drying, to prevent the material from cracking, discoloring or losing nutrients due to over-drying. At the same time, the exhaust fan 5 adopts frequency conversion control and dynamically adjusts the exhaust volume according to the real-time humidity in the drying room to achieve humidity control and ensure a stable and controllable drying curve. It is especially suitable for processing materials with high quality requirements such as Chinese medicinal materials, fruits and vegetables, and seafood.
[0036] The airflow system automatically controls the opening and closing of electric air valves based on outdoor temperature sensor signals, enabling automatic switching between "pre-cooling before dehumidification" and "dehumidification before preheating" modes. The variable frequency fan automatically adjusts its speed based on humidity feedback. The water tank's temperature detector is linked to the electric heater, activating auxiliary heating when residual heat is insufficient. The entire system can complete operating condition identification and parameter adjustment without manual intervention, improving the equipment's intelligence and ease of operation.
[0037] Please see Figure 1 , Figure 2 , Figure 3 and Figure 5It should be noted that the water tank 6 is equipped with a temperature detector and an electric heater. The temperature detector continuously detects the temperature of the water in the water tank 6 and outputs the detection value to the control system. When the detection value is lower than the set lower limit, the control system starts the electric heater to heat the water. The heat pump system also includes a pressure relay 1, a liquid receiver 10 and a gas-liquid separator 14. The pressure sensing end of the pressure relay 1 is connected to the high-pressure exhaust pipe of the compressor 2, and the control output end of the pressure relay 1 is connected to the power supply circuit of the compressor 2. When the pressure detected by the pressure sensing end exceeds the set threshold, the pressure relay 1 disconnects the power supply circuit of the compressor 2.
[0038] The working principle of the above embodiments is as follows:
[0039] During operation, outdoor fresh air enters the device. At high temperatures, the air guiding system guides the fresh air through the air pre-processor 12, where circulating water absorbs heat from the fresh air to cool it down. At low temperatures, the fresh air first passes through the dehumidifying evaporator 13 for dehumidification before entering the air pre-processor 12, where circulating water releases heat to heat the air. The treated air then enters the indoor condenser 3 and is heated to a high-temperature, low-humidity state. This air is then sent into the drying chamber to remove moisture from the materials, becoming a high-temperature, high-humidity air. After being discharged from the drying chamber, it is accelerated by the exhaust fan 5 and enters the air heat exchanger 4, where it transfers heat to the circulating water. After cooling down, it is discharged. The circulating water flows through the air heat exchanger 4 under the drive of the water pump 7. Air pre-processor 12 and subcooler 9 absorb waste heat from dehumidification, pre-cooling, and refrigerant subcooling. After the temperature rises, the refrigerant enters water tank 6 for storage. A temperature detector in water tank 6 monitors the water temperature. If the temperature is too low, an electric heater is activated for auxiliary heating. The liquid refrigerant from indoor condenser 3 in subcooler 9 is further cooled, releasing heat to the circulating water. The cooled refrigerant is throttled by expansion valve 11 and enters dehumidifying evaporator 13 to absorb heat and evaporate, completing the refrigeration cycle. Pressure relay 1 monitors the discharge pressure of compressor 2. If the pressure exceeds the limit, the power is cut off to protect the equipment. The frequency converter adjusts the speed of dehumidification fan 5 according to the humidity of the drying room to achieve energy-saving and stable operation.
[0040] It should be noted that the control method of this utility model is controlled by a controller. The control circuit of the controller can be implemented by those skilled in the art through simple programming. The power supply is also common knowledge in the field. Furthermore, this utility model is mainly used to protect mechanical devices, so the control method and circuit connection will not be explained in detail here.
[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0042] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A heat pump drying device for recovering excess heat, comprising a heat pump system, characterized in that: It also includes a waste heat recovery system and a heat storage system; the heat pump system includes a compressor (2), an indoor condenser (3), a subcooler (9), an expansion valve (11) and a dehumidifying evaporator (13), wherein the subcooler (9) is located after the indoor condenser (3) and before the expansion valve (11); The waste heat recovery system includes the aforementioned subcooler (9), air pre-processor (12), dehumidifying fan (5), and air heat exchanger (4). When the outdoor fresh air temperature is high, the air guiding system guides the fresh air to pass through the air pre-processor (12) for pre-cooling. When the outdoor fresh air temperature is low, the air guiding system guides the fresh air to pass through the dehumidifying evaporator (13) for dehumidification before entering the air pre-processor (12) for preheating. The dehumidifying fan (5) is located at the air outlet of the drying box, and the air heat exchanger (4) is located after the dehumidifying fan (5) to allow the high-temperature and high-humidity air discharged to exchange heat with the circulating water before being discharged into the environment. The heat storage system includes a water tank (6), a water pump (7), and a control water valve (8). The water tank (6) is connected to a subcooler (9), an air pre-processor (12), and an air heat exchanger (4) through pipes. Each connecting pipe is equipped with a water pump (7) and a control water valve (8). Water flows through the heat exchangers to recover the waste heat from the refrigerant subcooling, the waste heat from the pre-cooling of the air to be dehumidified, and the waste heat from the exhaust air, and stores the heat in the water tank (6).
2. The heat pump drying device for waste heat recovery according to claim 1, characterized in that: The air pre-processor (12) is a heat exchange device that exchanges heat with air using a liquid heat transfer medium. Its water side is connected to the circulating water circuit of the heat storage system. When high-temperature fresh air flows through the air pre-processor (12), the circulating water absorbs the heat of the air and is heated. When low-temperature fresh air flows through the air pre-processor (12), the circulating water releases heat to the air and is cooled.
3. The heat pump drying device for excess heat recovery according to claim 1, characterized in that: The air guiding system includes an electric air valve. The opening and closing status of the electric air valve is controlled by the output signal of the outdoor temperature sensor. When the electric air valve is activated, the fresh air first enters the air pre-processor (12) and then enters the dehumidifying evaporator (13) under high temperature conditions. When the electric air valve is closed, the fresh air first enters the dehumidifying evaporator (13) and then enters the air pre-processor (12) under low temperature conditions.
4. The heat pump drying device for waste heat recovery according to claim 1, characterized in that: The dehumidification fan (5) is a variable frequency fan. The variable frequency fan is connected to a frequency converter. The frequency converter receives the real-time signal from the humidity sensor in the drying room and adjusts the speed of the dehumidification fan (5) according to the humidity sensor signal.
5. A heat pump drying device for excess heat recovery according to claim 1, characterized in that: The subcooler (9) is a plate-fin heat exchanger. When the liquid refrigerant flows out from the indoor condenser (3), the liquid refrigerant will enter the subcooler (9). The liquid refrigerant exchanges heat with the circulating water in the subcooler (9), the refrigerant temperature decreases and the circulating water temperature increases.
6. The heat pump drying device for waste heat recovery according to claim 1, characterized in that: The water tank (6) is equipped with a temperature detector and an electric heater. The temperature detector continuously detects the temperature of the water in the water tank (6) and outputs the detection value to the control system. When the detection value is lower than the set lower limit, the control system starts the electric heater to heat the water.
7. A heat pump drying device for waste heat recovery according to claim 1, characterized in that: The heat pump system also includes a pressure relay (1), a liquid receiver (10) and a gas-liquid separator (14). The pressure sensing end of the pressure relay (1) is connected to the high-pressure exhaust pipe of the compressor (2), and the control output end of the pressure relay (1) is connected to the power supply circuit of the compressor (2). When the pressure detected by the pressure sensing end exceeds the set threshold, the pressure relay (1) disconnects the power supply circuit of the compressor (2).