Energy-saving heat pump drying system for coating production line and control method of energy-saving heat pump drying system

Abstract

The invention discloses an energy-saving heat pump drying system for a coating production line and a control method of the energy-saving heat pump drying system, and relates to the technical field of coating drying equipment, the energy-saving heat pump drying system comprises a high-temperature heat pump unit, a drying room body, a waste gas flow guide module and an intelligent control module, and a low-temperature heat pump unit can be selected to form a cascade structure; the high-temperature heat pump unit comprises a fin type evaporator, a compressor and other components, a drying room is arranged in the fin type condenser to provide a heat source, the evaporator is externally arranged to absorb environment heat, the waste gas flow guide module achieves waste heat recovery of drying waste gas, and the intelligent control module achieves linkage regulation and control of all the components through a PLC. The control method comprises the steps of constant temperature, unit switching, dehumidification linkage control and additional energy efficiency optimization of the cascade system. Compared with a traditional drying mode, the system is outstanding in energy saving performance, safe, environmentally friendly and suitable for various coating drying scenes, the heat exchange efficiency is stable in the low-temperature environment, the coating drying quality can be accurately guaranteed, and meanwhile the operation adaptation flexibility and the operation reliability of equipment are improved.

Description

Technical Field

[0001] This invention relates to the field of coating drying equipment technology, specifically to an energy-saving heat pump drying system and its control method for a coating production line. Background Technology

[0002] The drying process in a coating production line is a crucial step in ensuring the quality of workpiece coating, requiring the maintenance of a stable temperature and humidity environment. Existing coating production line drying equipment mainly uses traditional heating methods such as coal-fired boilers, oil-fired boilers, and pure electric heating, which have many drawbacks: coal-fired and oil-fired boilers generate a large amount of pollutants during combustion, causing serious environmental pollution, and pose safety hazards such as flammability, explosion, and poisoning; pure electric heating consumes a huge amount of electricity, has high operating costs, and low energy utilization.

[0003] Even with conventional heat pump drying equipment used in some production lines, significant shortcomings remain: Firstly, the structural design of conventional heat pump units lacks specificity and is poorly adapted to the drying load and exhaust emission characteristics of the coating production line, making it difficult to achieve flexible configurations for coordinated or independent operation of multiple units. Secondly, the lack of sophisticated intelligent control logic prevents dynamic adjustment of operating parameters based on the temperature and humidity inside the drying chamber and the external ambient temperature, resulting in unstable drying efficiency and limited energy-saving effects. Furthermore, the heat exchange efficiency of conventional heat pumps decreases significantly at low temperatures, making it difficult to guarantee a stable heat source output required for coating drying and limiting their application under various environmental conditions.

[0004] Therefore, developing a heat pump drying system specifically for coating production lines that is highly adaptable, energy-efficient, safe, reliable, and intelligent has become an urgent need to address the pain points of existing technologies. Summary of the Invention

[0005] To solve the above problems, the present invention adopts the following technical solution.

[0006] An energy-saving heat pump drying system for a coating production line includes a high-temperature heat pump unit, a drying chamber body, a waste gas diversion module, and an intelligent control module. The high-temperature heat pump unit includes a finned evaporator, a first gas-liquid separator, a high-temperature compressor, a finned condenser, a first liquid storage tank, and a first electronic expansion valve arranged in series. The finned condenser is located inside the drying chamber body, and the finned evaporator is located outside the drying chamber body. The intelligent control module is electrically connected to a temperature sensor, a humidity sensor, and the high-temperature heat pump unit inside the drying chamber body.

[0007] Preferably, the exhaust gas guiding module includes a heat exchanger, a guiding channel, and an insulation layer. The exhaust port of the drying chamber body is connected to the air inlet of the heat exchanger through the guiding channel. The heat exchange end of the heat exchanger forms a waste heat recovery loop with the finned evaporator of the high-temperature heat pump unit. The insulation layer covers the inner wall of the guiding channel.

[0008] Preferably, it also includes a low-temperature heat pump unit, wherein the high-temperature heat pump unit and the low-temperature heat pump unit form a cascaded variable frequency heat pump unit through a heat exchanger.

[0009] The outlet of the high-temperature compressor of the high-temperature heat pump unit is connected to the D end of the first four-way valve. The C end of the first four-way valve is connected to the finned condenser, the first liquid storage tank and the first electronic expansion valve in sequence through the pipeline, and then connected to the first passage of the second heat exchanger, and then connected to the E end of the first four-way valve. The S end of the first four-way valve forms a closed loop with the first gas-liquid separator and the high-temperature compressor through the pipeline.

[0010] The low-temperature heat pump unit includes a low-temperature compressor. The outlet of the low-temperature compressor is connected to the D end of the second four-way valve. The C end of the second four-way valve is connected in sequence through a pipeline to the second passage of the second heat exchanger, the second liquid storage tank, the second electronic expansion valve and the finned evaporator, and then connected to the E end of the second four-way valve. The S end of the second four-way valve forms a closed loop with the second gas-liquid separator and the low-temperature compressor through a pipeline.

[0011] Preferably, the heat exchanger is a plate heat exchanger with a flow regulating valve at its inlet end. The flow regulating valve is electrically connected to the intelligent control module, which adjusts the valve opening according to the temperature sensor signal to control the waste gas flow rate.

[0012] Preferably, the second heat exchanger is a plate heat exchanger. The refrigerant of the high-temperature heat pump unit flows in the first passage of the second heat exchanger, and the refrigerant of the low-temperature heat pump unit flows in the opposite direction in the second passage of the second heat exchanger. The two exchange heat through the wall of the second heat exchanger.

[0013] Preferably, the intelligent control module is a PLC controller, which is electrically connected to the high-temperature compressor, the low-temperature compressor, the first electronic expansion valve, and the second electronic expansion valve, respectively, and is used to adjust the operating frequency of the compressor and the opening degree of the electronic expansion valve.

[0014] Preferably, the air inlet of the drying chamber is equipped with a central pipe, and the air outlets of multiple high-temperature heat pump units are connected to the central pipe through independent branch pipes. Each branch pipe is equipped with an electromagnetic switching valve, and the central pipe is sealed to the air inlet of the drying chamber. By controlling the on / off state of the electromagnetic switching valves on different branch pipes, the connection between multiple high-temperature heat pump units and the drying chamber can be switched, or multiple units can be grouped according to usage requirements and connected to multiple drying chambers through corresponding group central pipes, so as to achieve independent and adaptive operation of the units and the drying chamber.

[0015] A control method for an energy-saving heat pump drying system, characterized by comprising the following steps:

[0016] Step 1, Temperature Control: The PLC controller receives the temperature signal from the temperature sensor inside the drying chamber. When the temperature has not reached the set drying temperature, it controls the high-temperature compressor to start running and releases heat through the finned condenser to heat the air inside the drying chamber until the initial temperature rise is completed. When the temperature reaches the set drying temperature, the PLC controller adjusts the opening of the first electronic expansion valve and the operating frequency of the high-temperature compressor to maintain a stable temperature inside the drying chamber.

[0017] Step 2, Unit Switching Control: The PLC controller controls the on / off of the electromagnetic switching valves on the corresponding branch pipelines according to the real-time drying load of the drying room, so as to realize the alternating switching operation of multiple high-temperature heat pump units and dynamically allocate the number of operating units.

[0018] Step 3, Dehumidification Linkage Control: The PLC controller receives the humidity signal in the drying room collected by the humidity sensor. When the humidity exceeds the set threshold, it synchronously adjusts the refrigerant circulation rate of the high-temperature heat pump unit. The moisture in the air is separated through the condensation process of the refrigerant in the finned condenser, so that drying and dehumidification can be carried out simultaneously.

[0019] A control method for an energy-saving heat pump drying system includes steps one to three, and also includes an energy efficiency optimization control step: the PLC controller collects the ambient temperature signal of the finned evaporator. When the ambient temperature decreases, causing the heat exchange efficiency of the high-temperature heat pump unit to decrease, the cascade heating mode is activated to adjust the operating status of the low-temperature compressor and the refrigerant circulation parameters of the low-temperature heat pump unit, thereby improving the heat exchange effect with the high-temperature heat pump unit and ensuring that the high-temperature heat pump unit outputs hot air stably.

[0020] Preferably, during the unit switching process in step two, the temperature inside the drying chamber is kept stable to avoid large fluctuations; the operating frequency of the high-temperature compressor and the low-temperature compressor is dynamically adjusted according to the drying requirements, and the opening degree of the first electronic expansion valve and the second electronic expansion valve is precisely adapted according to the refrigerant circulation state to ensure the system's operating efficiency.

[0021] Compared with the prior art, the beneficial effects of this invention are as follows:

[0022] This invention uses a high-temperature heat pump unit to absorb ambient heat and recover waste heat from exhaust gases. The power consumption is only 1 / 3 to 1 / 4 of that of pure electric heating. Compared with coal, oil, and natural gas boilers, it can save about 75% of operating costs. Moreover, there are no combustion products or emissions, which meets environmental protection requirements and achieves energy conservation and emission reduction.

[0023] This invention, through multi-unit configuration and electromagnetic switching valve control, can achieve flexible adaptation of multiple units to one or more drying rooms, meet the drying load requirements of different coating production lines, and has a wide range of applications.

[0024] The system of this invention adopts a semi-closed circulation structure, eliminating the dangers of flammability, explosion, poisoning, and short circuits found in traditional drying equipment. Furthermore, it is based on mature air conditioning technology, resulting in stable processes, long equipment lifespan, and low maintenance costs.

[0025] This invention uses a PLC controller to achieve coordinated control of temperature, humidity, unit operation, and waste heat recovery. It is fully automatic and requires no manual operation, and can operate continuously for 24 hours. The drying temperature and humidity are precisely controlled to ensure the quality of coating drying.

[0026] The design of the cascade variable frequency heat pump unit in this invention enables the system to maintain efficient heat exchange even in low-temperature environments, ensuring stable heat source output and breaking through the application limitations of conventional heat pumps. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structural connection relationship of the high-temperature heat pump unit of the present invention;

[0028] Figure 2 This is a schematic diagram of the connection relationship of the cascade heat pump unit of the present invention.

[0029] In the diagram: 1. Drying chamber body; 2. Finned evaporator; 3. First gas-liquid separator; 4. High-temperature compressor; 5. Finned condenser; 6. First liquid storage tank; 7. First electronic expansion valve; 8. Humidity sensor; 9. Heat exchanger one; 10. Heat exchanger two; 10a. Passage one of heat exchanger two; 10b. Passage two of heat exchanger two; 11. First four-way valve; 11a. D end of the first four-way valve; 11b. C end of the first four-way valve; 11c. E end of the first four-way valve; 11d. S end of the first four-way valve; 12. Second four-way valve; 12a. D end of the second four-way valve; 12b. C end of the second four-way valve; 12c. E end of the second four-way valve; 12d. S end of the second four-way valve; 13. Second gas-liquid separator; 14. Low-temperature compressor; 15. Second liquid storage tank; 16. Second electronic expansion valve. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Example

[0034] like Figure 1-2 As shown, in this embodiment, the system includes a high-temperature heat pump unit, a drying chamber body 1, a waste gas diversion module, an intelligent control module, and an optional low-temperature heat pump unit. The high-temperature heat pump unit is the core heating unit of the system, the drying chamber body 1 provides a closed space for drying the workpiece, the waste gas diversion module realizes waste heat recovery from the drying waste gas, the intelligent control module realizes the linkage control of each unit, and the low-temperature heat pump unit works in conjunction with the high-temperature heat pump unit to form a cascade structure, improving heat exchange efficiency in low-temperature environments.

[0035] In this embodiment, the high-temperature heat pump unit includes a finned evaporator 2, a first gas-liquid separator 3, a high-temperature compressor 4, a finned condenser 5, a first liquid storage tank 6, and a first electronic expansion valve 7, arranged in series. The finned condenser 5 is located inside the drying chamber body 1 and is used to directly release heat into the drying chamber; the finned evaporator 2 is located outside the drying chamber body 1 and is used to absorb heat from the external environment; the first gas-liquid separator 3 is used to separate the liquid components in the refrigerant to prevent liquid refrigerant from entering the high-temperature compressor 4 and causing damage; the first liquid storage tank 6 is used to store the refrigerant and ensure stable refrigerant circulation; and the first electronic expansion valve 7 is used to regulate the refrigerant flow rate to achieve precise control of heat exchange efficiency.

[0036] The drying chamber body 1 is a closed cavity structure, equipped with temperature and humidity sensors 8 for real-time collection of temperature and humidity data within the drying chamber. The air inlet of the drying chamber body 1 is connected to a collection pipe to receive hot air output from the high-temperature heat pump unit. The exhaust port is connected to a waste gas guiding module for waste gas discharge. The waste gas guiding module includes a heat exchanger 9, a guiding channel, and an insulation layer. The exhaust port of the drying chamber body 1 is connected to the air inlet of the heat exchanger 9 via the guiding channel. The heat exchange end of the heat exchanger 9 forms a waste heat recovery loop with the finned evaporator 2 of the high-temperature heat pump unit. The heat carried by the drying waste gas is transferred to the finned evaporator 2 through the heat exchanger 9, achieving heat recovery and reuse. The cross-sectional area of ​​the guiding channel is adapted to the waste gas exhaust volume of the drying chamber body 1 to ensure smooth waste gas discharge. The insulation layer covers the inner wall of the guiding channel to reduce heat loss.

[0037] The intelligent control module uses a PLC controller, which is electrically connected to the high-temperature compressor 4 of the high-temperature heat pump unit, the first electronic expansion valve 7, the temperature sensor and humidity sensor 8 in the drying chamber body 1, the flow regulating valve of the exhaust gas diversion module, and related components of the low-temperature heat pump unit, to realize real-time monitoring and parameter adjustment of the operating status of each component.

[0038] When a low-temperature heat pump unit is configured, the high-temperature heat pump unit and the low-temperature heat pump unit form a cascaded variable frequency heat pump unit through heat exchanger 2 10. Specifically, the outlet of the high-temperature compressor 4 of the high-temperature heat pump unit is connected to terminal D 11a of the first four-way valve 11. Terminal C 11b of the first four-way valve 11 is connected sequentially to the finned condenser 5, the first liquid storage tank 6, and the first electronic expansion valve 7 via pipelines, then connected to passage 10a of heat exchanger 2 10, and then to terminal E 11c of the first four-way valve 11. Terminal S 11d of the first four-way valve 11 connects the first gas-liquid separator 3 and the high-temperature compressor 4 to form a closed loop via pipelines. The low-temperature heat pump unit includes a low-temperature compressor 14 and a second gas-liquid separator... The system includes a second gas-liquid separator 13, a second liquid storage tank 15, a second electronic expansion valve 16, and a second four-way valve 12. The outlet of the cryogenic compressor 14 is connected to the D end 12a of the second four-way valve 12. The C end 12b of the second four-way valve 12 is connected sequentially through a pipeline to the second passage 10b of the second heat exchanger 10, the second liquid storage tank 15, the second electronic expansion valve 16, and the finned evaporator 2, and then connected to the E end 12c of the second four-way valve 12. The S end 12d of the second four-way valve 12 connects the second gas-liquid separator 13 and the cryogenic compressor 14 to form a closed loop through a pipeline. The second heat exchanger 10 is a plate heat exchanger. The refrigerant of the high-temperature heat pump unit flows in the first passage 10a of the second heat exchanger 10, while the refrigerant of the low-temperature heat pump unit flows in the opposite direction in the second passage 10b of the second heat exchanger 10, achieving efficient heat exchange through the wall. The air inlet of the drying chamber 1 is connected to the air outlet of multiple high-temperature heat pump units via a central conduit. Each high-temperature heat pump unit has an independent branch conduit at its air outlet, and each branch conduit is equipped with an electromagnetic switching valve. By controlling the on / off state of the electromagnetic switching valve through an intelligent control module, the connection between multiple high-temperature heat pump units and the drying chamber 1 can be switched. Alternatively, multiple units can be grouped according to usage requirements, and connected to multiple drying chambers 1 separately through corresponding group conduits, thus meeting the unit adaptation requirements for different drying scenarios.

[0039] Based on the above-mentioned energy-saving heat pump drying system, the present invention also provides a corresponding control method, including a basic control method and a cascaded optimization control method, as detailed below:

[0040] The basic control method is applicable to systems without low-temperature heat pump units. This method includes step one: constant temperature control; step two: unit switching control; and step three: dehumidification linkage control. The specific process is as follows:

[0041] Step 1: During constant temperature control, the PLC controller receives the temperature signal from the temperature sensor inside the drying chamber. When the temperature has not reached the set drying temperature, it controls the high-temperature compressor 4 to start running. After the refrigerant is pressurized and heated in the high-temperature compressor 4, it enters the finned condenser 5 to release heat and heat the air inside the drying chamber until the initial temperature rise is completed. When the temperature reaches the set drying temperature, the PLC controller maintains the temperature inside the drying chamber stable and avoids temperature fluctuations by adjusting the opening of the first electronic expansion valve 7 and the operating frequency of the high-temperature compressor 4.

[0042] Step 2: In the unit switching control, the PLC controller controls the on / off of the electromagnetic switching valve on the corresponding branch pipeline based on the real-time drying load of the drying room (combined with the data collected by the temperature sensor, humidity sensor 8 and the workpiece drying progress). This enables the alternating operation of multiple high-temperature heat pump units, dynamically allocates the number of operating units, and ensures drying efficiency while avoiding energy waste.

[0043] Step 3: In the dehumidification linkage control, the PLC controller receives the humidity signal in the drying room collected by the humidity sensor 8. When the humidity exceeds the set threshold, the refrigerant circulation rate of the high-temperature heat pump unit is adjusted synchronously. The moisture in the air is separated through the condensation process of the refrigerant in the finned condenser 5, realizing simultaneous drying and dehumidification without the need for additional dehumidification equipment. The cascade optimization control method is suitable for systems equipped with low-temperature heat pump units. Based on steps one to three of the basic control method, this method adds an energy efficiency optimization control step: The PLC controller collects the external ambient temperature signal of the finned evaporator 2. When the ambient temperature decreases, causing the heat exchange efficiency of the high-temperature heat pump unit to decrease, the cascade heating mode is activated. The operating status of the low-temperature compressor 14 and the refrigerant circulation parameters of the low-temperature heat pump unit, including the refrigerant circulation rate and the opening of the second electronic expansion valve 16, are adjusted to improve the heat exchange effect between the low-temperature heat pump unit and the high-temperature heat pump unit through the second heat exchanger 10, ensuring that the high-temperature heat pump unit outputs hot air stably to meet the temperature requirements of coating drying.

[0044] In one specific application embodiment, the energy-saving heat pump drying system includes four high-temperature heat pump units, two drying chamber bodies 1, two sets of exhaust gas diversion modules, one intelligent control module, and two low-temperature heat pump units. The high-temperature compressor 4 of the high-temperature heat pump units is a variable frequency compressor, heat exchanger 9 and heat exchanger 10 are both plate heat exchangers, the intelligent control module uses a Siemens S7-200 series PLC controller, and the temperature sensor and humidity sensor 8 are respectively a PT100 platinum resistance sensor and a capacitive humidity sensor.

[0045] The operation process is as follows: In the initial stage, the workpiece to be dried is placed in the drying chamber body 1, the doors and windows of the drying chamber are closed, and the drying temperature and humidity thresholds are set through the intelligent control module. In the constant temperature heating stage, the PLC controller receives the temperature sensor signal. If the temperature in the drying chamber does not reach the set value, it controls the high-temperature compressor 4 to start. The refrigerant absorbs heat from the external environment through the finned evaporator 2 and then enters the first gas-liquid separator 3 to separate the liquid components. Subsequently, it is pressurized and heated in the high-temperature compressor 4 and then flows into the finned condenser 5 to release heat and heat the air in the drying chamber. When the temperature reaches the set value, the PLC controller adjusts the opening of the first electronic expansion valve 7 and the frequency of the high-temperature compressor 4 to maintain a stable temperature. During the waste heat recovery process, the waste gas generated during the drying process enters the heat exchanger 9 through the guide channel. The heat carried by the waste gas is transferred to the finned evaporator 2 of the high-temperature heat pump unit to achieve heat recovery. The insulation layer effectively reduces heat loss in the guide channel. The flow regulating valve adjusts the waste gas flow rate according to the instructions of the intelligent control module to ensure heat exchange efficiency. During unit switching operation, when the drying load increases, the PLC controller controls the corresponding branch's electromagnetic switching valve to open, starting an additional high-temperature heat pump unit; when the drying load decreases, some units are shut down, achieving dynamic adaptation. Temperature fluctuations during switching are minimal, ensuring no impact on drying quality. During dehumidification linkage operation, when humidity sensor 8 detects excessive humidity in the drying chamber, the PLC controller increases the refrigerant circulation rate of the high-temperature heat pump unit. The refrigerant rapidly condenses in the finned condenser 5, separating moisture from the air and achieving simultaneous dehumidification. In the low-temperature environment adaptation phase, when the external ambient temperature decreases and the PLC controller detects a decline in the heat exchange efficiency of the high-temperature heat pump unit, the low-temperature heat pump unit is started, entering cascade heating mode. The refrigerant in the low-temperature heat pump unit cools and absorbs heat on the finned evaporator 2 side. After being pressurized by the low-temperature compressor 14, the heat is transferred to the refrigerant in the high-temperature heat pump unit through heat exchanger 10, improving the heat source output stability of the high-temperature heat pump unit and ensuring continuous and efficient drying.

[0046] The following is a comparison table of energy consumption compared to other methods:

[0047]

[0048] The above are merely preferred embodiments of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. An energy-saving heat pump drying system for a coating production line, characterized in that, The system includes a high-temperature heat pump unit, a drying chamber body (1), a waste gas diversion module, and an intelligent control module. The high-temperature heat pump unit includes a finned evaporator (2), a first gas-liquid separator (3), a high-temperature compressor (4), a finned condenser (5), a first liquid storage tank (6), and a first electronic expansion valve (7) arranged in series. The finned condenser (5) is located inside the drying chamber body (1), and the finned evaporator (2) is located outside the drying chamber body (1). The intelligent control module is electrically connected to the temperature sensor, humidity sensor (8), and high-temperature heat pump unit inside the drying chamber body (1).

2. The energy-saving heat pump drying system according to claim 1, characterized in that, The exhaust gas guiding module includes a heat exchanger (9), a guiding channel and an insulation layer. The exhaust port of the drying chamber body (1) is connected to the air inlet of the heat exchanger (9) through the guiding channel. The heat exchange end of the heat exchanger (9) forms a waste heat recovery loop with the finned evaporator (2) of the high-temperature heat pump unit. The cross-sectional area of ​​the guiding channel is adapted to the exhaust gas volume of the drying chamber body (1). The insulation layer covers the inner wall of the guiding channel.

3. The energy-saving heat pump drying system according to claim 1, characterized in that, It also includes a low-temperature heat pump unit, wherein the high-temperature heat pump unit and the low-temperature heat pump unit form a cascaded variable frequency heat pump unit through heat exchanger two (10); the outlet of the high-temperature compressor (4) of the high-temperature heat pump unit is connected to the D end (11a) of the first four-way valve (11), the C end (11b) of the first four-way valve (11) is connected in sequence to the finned condenser (5), the first liquid storage tank (6) and the first electronic expansion valve (7) through pipelines, and then connected to the first passage (10a) of heat exchanger two (10), and then connected to the E end (11c) of the first four-way valve (11), and the S end (11d) of the first four-way valve (11) is connected to the first gas-liquid separator (3) through pipelines. The low-temperature heat pump unit includes a low-temperature compressor (14), the outlet of which is connected to the D end (12a) of the second four-way valve (12), the C end (12b) of the second four-way valve (12) is connected to the second passage (10b) of the heat exchanger (10), the second liquid storage tank (15), the second electronic expansion valve (16) and the finned evaporator (2) in sequence through the pipeline, and then connected to the E end (12c) of the second four-way valve (12), and the S end (12d) of the second four-way valve (12) connects the second gas-liquid separator (13) and the low-temperature compressor (14) to form a closed loop through the pipeline.

4. The energy-saving heat pump drying system according to claim 2, characterized in that, The heat exchanger (9) is a plate heat exchanger with a flow regulating valve at its inlet end. The flow regulating valve is electrically connected to the intelligent control module. The intelligent control module adjusts the valve opening according to the temperature sensor signal to control the waste gas flow rate.

5. The energy-saving heat pump drying system according to claim 3, characterized in that, The second heat exchanger (10) is a plate heat exchanger. The refrigerant of the high-temperature heat pump unit flows in the first passage (10a) of the second heat exchanger (10), and the refrigerant of the low-temperature heat pump unit flows in the second passage (10b) of the second heat exchanger (10). The two exchange heat through the wall of the second heat exchanger (10). The refrigerant of the high-temperature heat pump unit is pressurized and heated in the high-temperature compressor (4), and the refrigerant of the low-temperature heat pump unit is cooled on the side of the finned evaporator (2).

6. The energy-saving heat pump drying system according to claim 1 or 3, characterized in that, The intelligent control module is a PLC controller, which is electrically connected to the high-temperature compressor (4), the low-temperature compressor (14), the first electronic expansion valve (7), and the second electronic expansion valve (16) to adjust the operating frequency of the compressor and the opening degree of the electronic expansion valve.

7. The energy-saving heat pump drying system according to claim 1, characterized in that, The air inlet of the drying chamber body (1) is provided with a central pipe. The air outlets of multiple high-temperature heat pump units are connected to the central pipe through independent branch pipes. Each branch pipe is equipped with an electromagnetic switching valve. The central pipe is sealed and connected to the air inlet of the drying chamber body (1). By controlling the opening and closing of the electromagnetic switching valves on different branch pipes, multiple high-temperature heat pump units can be switched and connected to the drying chamber body (1). Alternatively, multiple units can be grouped according to usage requirements and connected to multiple drying chamber bodies (1) through corresponding group central pipes to achieve independent adaptation and operation of the units and the drying chamber.

8. A control method for the energy-saving heat pump drying system of claim 1, characterized in that, Includes the following steps: Step 1, Temperature Control: The PLC controller receives the temperature signal in the drying room collected by the temperature sensor. When the temperature has not reached the set drying temperature, it controls the high-temperature compressor (4) to start running and release heat through the finned condenser (5) to heat the air in the drying room until the initial temperature rise is completed. When the temperature reaches the set drying temperature, the PLC controller adjusts the opening of the first electronic expansion valve (7) and the operating frequency of the high-temperature compressor (4) to maintain the temperature in the drying room. Step 2, Unit Switching Control: The PLC controller controls the on / off of the electromagnetic switching valves on the corresponding branch pipelines according to the real-time drying load of the drying room, so as to realize the alternating switching operation of multiple high-temperature heat pump units and dynamically allocate the number of operating units. Step 3, Dehumidification linkage control: The PLC controller receives the humidity signal in the drying room collected by the humidity sensor (8). When the humidity exceeds the set threshold, the refrigerant circulation rate of the high-temperature heat pump unit is adjusted synchronously. The moisture in the air is separated by the condensation process of the refrigerant in the finned condenser (5), so that drying and dehumidification are carried out simultaneously.

9. A control method for the energy-saving heat pump drying system of claim 3, characterized in that, Including steps one to three as described in claim 8, it also includes an energy efficiency optimization control step: the PLC controller collects the ambient temperature signal of the finned evaporator (2), and when the ambient temperature decreases, causing the heat exchange efficiency of the high-temperature heat pump unit to decrease, it starts the cascade heating mode, adjusts the operating status of the low-temperature compressor (14) and the refrigerant circulation parameters of the low-temperature heat pump unit, improves the heat exchange effect with the high-temperature heat pump unit, and ensures that the high-temperature heat pump unit outputs hot air stably.

10. The control method according to claim 8 or 9, characterized in that, In step two, the temperature inside the drying room is kept stable during the unit switching process to avoid large fluctuations. The operating frequency of the high-temperature compressor (4) and the low-temperature compressor (14) is dynamically adjusted according to the drying requirements. The opening degree of the first electronic expansion valve (7) and the second electronic expansion valve (16) is precisely adapted according to the refrigerant circulation state to ensure the system's operating efficiency.

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