A closed-loop dehumidification heat pump dryer condensate recovery system and control method thereof

Abstract

The present invention discloses a closed-loop dehumidification heat pump dryer condensate recovery and utilization system and its control method. When the liquid level height H of the insulated water tank is greater than the liquid level threshold h of the level controller, the circulating water pump is started, otherwise the circulating water pump is shut down. When H>h and T0<T3-∆T1, the first two-position three-way valve is connected to the cooler and the precooler, and the condensate enters the subcooler from the precooler for heat exchange. When T2≥T4-∆T2, the second two-position three-way valve channel is connected to the cooler and the drain pipe, and the condensate is discharged to the external environment. The operation is repeated until the liquid level height H of the insulated water tank is less than the liquid level threshold h of the level controller, and the circulating water pump is shut down. The present application can recycle the condensate generated by the evaporator. The condensate recovery system can use the recovered condensate as a cold source to precool the return air entering the heat recovery device and accelerate the supercooling of the refrigerant at the outlet of the condenser of the heat pump system, effectively improving the utilization of the condensate cooling capacity, increasing the cooling capacity of the evaporator, and increasing the dehumidification capacity of the heat pump system, which is beneficial to energy saving and consumption reduction of the heat pump dryer.

Description

Technical Field

[0001] The present invention belongs to the technical field of closed-loop dehumidification heat pump dryers, and in particular relates to a condensed water recovery and utilization system of a closed-loop dehumidification heat pump dryer and a control method thereof. Background Art

[0002] Existing closed-loop dehumidification heat pump dryer systems generally produce a large amount of condensed water. Condensed water contains a large amount of cooling capacity, and direct discharge will cause energy loss. Therefore, it is necessary to design a condensed water recovery system.

[0003] In detail, referring to an energy-saving continuous drying equipment disclosed in Chinese patent 201710760972.4, the drying equipment is provided with a steam condensate recovery mechanism, and the steam condensate recovery mechanism includes a condensate recovery pump, a condensate recovery tank, a condensate heat exchanger and a condensate external circulation pump. The liquid inlet of the condensate recovery pump is connected to the condensate drain outlet of the steam heating mechanism through a pipeline, and the liquid outlet of the condensate recovery pump is connected to the condensate recovery tank through a pipeline. The condensate heat exchanger, the condensate external circulation pump and the condensate recovery tank constitute a condensate circulation loop, and the condensate recovery tank is also connected to the external water use mechanism through the condensate external circulation pump.

[0004] In addition, Chinese patent 201710533184.1 discloses an air source heat pump drying system, including a compressor, a heating condenser, a heat exhaust condenser, a heat absorption evaporator, a dehumidification evaporator, a condensate collection tray and a liquid storage tank; the heating condenser, the compressor, the liquid storage tank, the condensate collection tray and the dehumidification evaporator are arranged in the indoor cavity from bottom to top, and the condensate collection tray is respectively arranged below the heat absorption evaporator and the dehumidification evaporator; a drain outlet is provided at the bottom of the condensate collection tray, and the drain outlet is connected to the outside through a drainage pipe.

[0005] However, the temperature of the condensed water is relatively low, and the condensed water recovered by these drying equipment is mainly used for external water use or direct discharge, and is not recycled and applied to the drying equipment system circulation itself. Therefore, the energy-saving and consumption-reducing performance of the drying equipment needs to be further improved. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention provides a closed-loop dehumidification heat pump dryer condensate water recovery and utilization system.

[0007] In order to achieve the above-mentioned purpose, the invention adopts the following technical measures:

[0008] A closed-loop dehumidification heat pump dryer condensate recovery and utilization system control method is used to control the closed-loop dehumidification heat pump dryer condensate recovery and utilization system, the system includes a heat pump system and a condensate recovery system, the heat pump system includes a condenser, a compressor, an evaporator and a subcooler connected by a refrigerant circulation pipeline, a third temperature sensor is provided on the return air side of the condenser, the condensate recovery system includes an insulated water tank for collecting condensate in the water receiving pan, the insulated water tank is connected to a precooler through an outlet pipeline, a circulating water pump and a first temperature sensor are installed on the outlet pipeline, a water outlet end of the precooler is respectively connected to the subcooler and the water outlet pipeline through a first, two-position, three-way valve, a water outlet end of the subcooler is respectively connected to the insulated water tank and a discharge pipeline through a second, two-position, three-way valve, a second temperature sensor is installed on the water outlet end of the subcooler, and a liquid level controller is provided in the insulated water tank;

[0009] Proceed as follows:

[0010] Step S1: Set the liquid level threshold of the liquid level controller to h. When H>h, start the circulating water pump. When H<h, shut down the circulating water pump. H is the liquid level height of the insulation water tank.

[0011] Step S2: When H>h and T0<T3-∆T1, the first two-position three-way valve connects the subcooler and precooler, and the condensed water enters the subcooler from the precooler for heat exchange. ∆T1 is the heat transfer temperature difference of the precooler tube wall, T0 is the temperature measured by the first temperature sensor, and T3 is the return air temperature of the condenser.

[0012] Step S3: Under the conditions of S2, when T2 ≥ T4 - ∆T2, the second two-position three-way valve channel connects the subcooler and the drain pipe, and the condensed water is discharged to the outside environment, where T2 is the condensed water temperature at the outlet of the subcooler, ∆T2 is the cooling heat transfer temperature difference of the condenser, and T4 is the condensing temperature set by the heat pump system according to the refrigerant pressure;

[0013] Step S4: Repeat steps S1-S3 until the liquid level H of the insulated water tank is less than the liquid level threshold h of the liquid level controller, and the circulating water pump is turned off.

[0014] Preferably, in step S2, when T0 ≥ T3 - ∆T1, the first two-position three-way valve connects the subcooler and the water outlet pipe, and the condensed water directly enters the subcooler for heat exchange; in step S3, when the condition H>h is satisfied and T2 < T4 - ∆T2, the second two-position three-way valve channel connects the subcooler and the insulated water tank, and the condensed water circulates back to the insulated water tank.

[0015] Preferably, ∆T1 and ∆T2 are preferably 3°C-5°C.

[0016] A closed-loop dehumidification heat pump dryer condensate recovery system includes a heat pump system and a condensate recovery system, the heat pump system includes a condenser, a compressor, an evaporator and a subcooler connected by a refrigerant circulation pipeline, a water receiving pan is provided under the evaporator, the condensate recovery system includes an insulated water tank for collecting condensate in the water receiving pan, the insulated water tank is connected to a precooler through a water outlet pipeline, a circulating water pump and a first temperature sensor are installed on the water outlet pipeline, the water outlet end of the precooler is respectively connected to the subcooler and the water outlet pipeline through a first two-position three-way valve, the water outlet end of the subcooler is respectively connected to the insulated water tank and the discharge pipeline through a second two-position three-way valve, the water outlet end of the subcooler is respectively connected to the insulated water tank and the discharge pipeline through a second two-position three-way valve, the water outlet end of the subcooler is installed with a second temperature sensor, and a liquid level controller is provided in the insulated water tank.

[0017] Preferably, the condenser, compressor, evaporator and subcooler are connected in series through a refrigerant circulation pipeline, a gas-liquid separator is connected between the compressor and the evaporator, and the subcooler, liquid storage tank, dryer and electronic expansion valve are connected to the refrigerant circulation pipeline between the condenser and the evaporator.

[0018] Preferably, a filter is installed on the water outlet pipe between the insulated water tank and the precooler, and a filter is provided at the water inlet of the water outlet pipe.

[0019] Preferably, the condenser includes a first condenser and a second condenser connected in series, the first condenser and the second condenser are arranged in a dehumidification and heating function room on one side of the drying room, a third temperature sensor is arranged on the return air side of the first condenser, and the dehumidification and heating function room is connected to the drying room.

[0020] Preferably, a partition with an inverted Y-shaped cross-section is provided in the dehumidification and heating functional chamber, dividing the dehumidification and heating functional chamber into an air inlet chamber, an air outlet chamber and a heat recovery chamber. The air inlet chamber and the air outlet chamber are connected to the heat recovery chamber through the first condenser and the second condenser respectively.

[0021] Preferably, the air inlet chamber and the air outlet chamber are connected to the heat recovery device through a first one-way valve and a second one-way valve respectively, the evaporator is connected to the heat recovery device, and the air outlet of the evaporator is connected to the heat recovery device channel.

[0022] Preferably, a first fan and a second fan are respectively provided in the air inlet chamber and the air outlet chamber, and the first fan and the second fan rotate in opposite directions.

[0023] The beneficial effects of the present invention are:

[0024] 1. Compared with the prior art, the present invention discloses a closed-loop dehumidification heat pump dryer condensate recovery and utilization system and its control method. By setting a condensate water insulation water tank to recover the condensate in the water receiving pan, the condensate generated by the evaporator can be recovered and utilized. The condensate recovery system can use the recovered condensate as a cold source to pre-cool the return air entering the heat recovery device and accelerate the supercooling of the refrigerant at the condenser outlet of the heat pump system, effectively improving the utilization of the condensate cooling capacity, increasing the cooling capacity of the evaporator, and increasing the dehumidification capacity of the heat pump system, which is beneficial to energy saving and consumption reduction of the heat pump dryer.

[0025] 2. The present invention discloses a control method for a closed-loop dehumidification heat pump dryer condensate recycling system. The circulating water pump will not be started until the liquid level in the insulated water tank reaches the liquid level threshold set by the liquid level controller, which can prevent the circulating water pump from pumping dry air. The condensed water enters the outlet pipe through the action of the circulating water pump. When the first temperature sensor in the outlet pipe measures that the water temperature of the condensed water is lower than the return air temperature of the condenser minus the heat transfer temperature difference of the precooler pipe wall, that is, the temperature of the condensed water is lower than the refrigerant temperature in the precooler and the subcooler, the first two-position three-way valve is connected to the subcooler and the precooler, and the condensed water is discharged from the outlet pipe. The precooler enters the subcooler for heat exchange, and conversely, the condensed water directly enters the subcooler for heat exchange; when the condensed water temperature at the outlet of the subcooler is lower than the condensing temperature set by the heat pump system according to the refrigerant pressure minus the refrigeration heat transfer temperature difference of the condenser, that is, the condensed water temperature is higher than the refrigerant condensation temperature, the water temperature is too high, and the condensed water needs to be discharged to the external environment; conversely, the condensed water temperature still meets the heat exchange temperature, and the condensed water is circulated back to the insulated water tank. This cyclic operation can make the hot dryer more energy-efficient. Compared with the existing technical system, under the same conditions of use, this application can reduce power consumption by more than 2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a closed-loop dehumidification heat pump dryer condensate recovery and utilization system and its control principle;

[0027] Figure 2 This is a schematic diagram of air flow in a closed-loop dehumidification heat pump dryer condensate water recovery and utilization system of the present invention;

[0028] Figure 3 This is a schematic diagram of the connection between the evaporator and the precooler of a closed-loop dehumidification heat pump dryer condensate water recovery system of the present invention;

[0029] Figure 4 This is a logic principle diagram of a control method for a closed-loop dehumidification heat pump dryer condensate recovery and utilization system of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical connections; direct connections or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0033] refer to Figure 1-Figure 3 A closed-loop dehumidification heat pump dryer condensate recovery system includes a heat pump system and a condensate recovery system. The heat pump system is used to provide heat for the drying chamber 1 of the dryer. It includes a condenser, a compressor 27, an evaporator 9 and a subcooler 16 connected by a refrigerant circulation pipeline. The refrigerant circulation pipeline is filled with refrigerant. The condenser includes a first condenser 6 and a second condenser 7. The first condenser 6 is provided with a third temperature sensor 41 at the circulation return air inlet for measuring the return air temperature. A water receiving tray 18 is provided under the evaporator 9, and the condensed water formed on the tube wall of the evaporator 9 can drip onto the water receiving tray 18.

[0034] In detail, the air inlet end of the compressor 27 is connected to the air outlet end of the gas-liquid separator 28 through a refrigerant circulation pipeline, the air inlet end of the gas-liquid separator 28 is connected to the air outlet end of the evaporator 9, the air outlet end of the compressor 27 is connected to the air inlet end of the condenser, and the air outlet end of the condenser is sequentially connected to the subcooler 16, the liquid storage tank 29, the dryer 30, the electronic expansion valve 31 and the air inlet end of the evaporator 9 through a refrigerant circulation pipeline.

[0035] The condensed water recovery system includes an insulated water tank 22 for collecting condensed water in the water receiving pan 18. The bottom of the water receiving pan 18 is connected to the insulated water tank 22 through a water receiving pipe 20. The insulated water tank 22 is connected to the precooler 14 through a water outlet pipe. A circulating water pump 26 and a first temperature sensor 33 are installed on the water outlet pipe. The first temperature sensor 33 is used to detect the temperature of the condensed water output by the insulated water tank 22. The water outlet end of the precooler 14 is respectively connected to the water inlet end and the water outlet pipe of the subcooler 16 through a first two-position three-way valve 32. The water outlet end of the subcooler 16 is respectively connected to the return water end 19 of the insulated water tank 22 and the drain pipe 36 through a second two-position three-way valve 34. The drain pipe 36 is used to supply water to an external water-using mechanism. A second temperature sensor 35 is installed at the water outlet end of the subcooler 16. The second temperature sensor 35 is used to monitor the outlet water temperature of the subcooler 16. A liquid level controller 38 is provided in the insulated water tank 22. The liquid level controller 38 can be a liquid level meter, a liquid level sensor or a liquid level switch, and the liquid level height in the thermal insulation water tank 22 is monitored by the liquid level controller 38 .

[0036] In this embodiment, the first two-position three-way valve 32 and the second two-position three-way valve 34 select two-position three-way solenoid valves, and the condensed water recovery system further includes a PLC controller 37. The PLC controller is connected to the liquid level controller 38, the precooler 14, the circulating water pump 26, the first two-position three-way valve 32, the second two-position three-way valve 34, the first temperature sensor 33, and the second temperature sensor 35 through the wires. The preset height threshold of the liquid level controller 38 can be set by the PLC controller. The liquid level controller 38 selects a liquid level switch. When the liquid level controller 38 detects that the liquid level in the insulated water tank 22 is low, the liquid level controller 38 switches to the liquid level switch. When the liquid level controller 38 reaches the preset height, the PLC controller issues a control instruction to shut down the circulating water pump 26. When the liquid level controller 38 detects that the liquid level in the insulated water tank 22 reaches or exceeds the preset height of the liquid level controller 38, the circulating water pump 26 is started. The first two-position three-way valve 32 and the second two-position three-way valve 34 are preferably solenoid valves. The temperatures of the first temperature sensor 33 and the second temperature sensor 35 are fed back to the PLC controller. The PLC controller issues a control instruction, and the first two-position three-way valve 32 and the second two-position three-way valve 34 are selectively connected in the channels.

[0037] When the condensed water temperature meets the pre-cooling requirement, the first two-position three-way valve 32 connects the precooler 14 and the subcooler 16, the condensed water enters the precooler 14 for heat exchange, and then directly enters the subcooler 16 for heat exchange, and the choice of whether to circulate to the insulated water tank 22 is made according to the condensed water temperature output by the subcooler 16. When the temperature is lower than the set temperature value, the second two-position three-way valve 34 connects the subcooler 16 and the insulated water tank 22, and the condensed water enters the insulated water tank 22. When the temperature is not higher than the set temperature value, the second two-position three-way valve 34 connects the subcooler 16 and the drain pipe 36 to discharge the condensed water to the external environment.

[0038] In other embodiments, the first temperature sensor 33 may also be disposed in the thermal insulation water tank 22 .

[0039] In order to prevent impurities in the coolant from clogging the pipe, a filter 25 is provided on the outlet pipe, and a filter screen 40 is provided at the water inlet of the outlet pipe. In this embodiment, the filter 25 is a Y-type filter.

[0040] An overflow port 21 is provided on the upper side of the insulated water tank 22, and a drainage channel 39 is provided on the lower side of the insulated water tank 22. A ball valve is installed on the drainage channel 39. When the height of the condensate in the insulated water tank 22 is higher than the overflow port 21, the condensate in the insulated water tank 22 can be discharged through the overflow port 21 to prevent the condensate from flowing back to the insulated water tank 22 and to prevent a large amount of condensate from accumulating in the water receiving tray 18. When the insulated water tank 22 needs to be emptied, the ball valve of the drainage channel 39 can be opened, which is conducive to regularly cleaning the condensate in the insulated water tank 22 and ensuring that the condensate circulating in the system remains clean.

[0041] In some embodiments, the condenser may be provided with one, two, three, or even more. In this embodiment, the condenser includes a first condenser 6 and a second condenser 7 connected in series. The first condenser 6 and the second condenser 7 are arranged in a dehumidification and heating function chamber 2 on one side of the drying chamber 1, and the dehumidification and heating function chamber 2 is connected to the drying chamber 1.

[0042] A partition is provided in the middle of the drying chamber 1, which divides the drying chamber 1 into a return air chamber and an exhaust chamber. The return air chamber is connected to the exhaust chamber. A partition with an inverted Y-shaped cross-section is provided in the dehumidification and heating function chamber 2, which divides the dehumidification and heating function chamber 2 into an air inlet chamber, an air outlet chamber and a heat recovery chamber. The air inlet chamber and the air outlet chamber are connected to the heat recovery chamber through the first condenser 6 and the second condenser 7 respectively. The air inlet chamber and the air outlet chamber are connected to the return air chamber and the exhaust chamber respectively. The air inlet chamber and the air outlet chamber are connected to the heat recovery device 8 through the first one-way valve 10 and the second one-way valve 11 respectively. The evaporator 9 is closely connected with the heat recovery device 8. The air outlet of the evaporator 9 is connected to the channel of the heat recovery device 8. The first fan 12 and the second fan 13 are respectively provided in the air inlet chamber and the air outlet chamber; the first fan 12 and the second fan 13 rotate in opposite directions, the first fan 12 blows the air in the drying chamber 1 to the dehumidification and heating function chamber 2, and the second fan 13 blows the hot air in the dehumidification and heating function chamber 2 to the drying chamber 1, so as to achieve a drying effect through circulation.

[0043] During heat pump drying, the first fan 12 and the second fan 13 are working, and the air in the drying chamber 1 and the dehumidification and heating function chamber 2 circulates, and the compressor 27 compresses the refrigerant and flows to the first condenser 6 and the second condenser 7. When the refrigerant passes through the first condenser 6 and the second condenser 7, it releases heat and liquefies. The air passing through the first condenser 6 and the second condenser 7 is rapidly heated, and part of the hot air in the drying chamber 1 directly passes through the first one-way valve 10 and the second one-way valve 11 and flows into the heat recovery device 8; the refrigerant after condensation is subcooled. The refrigerant 16 is cooled again and then transferred to the liquid storage tank 29. The refrigerant coming out of the liquid storage tank 29 flows to the evaporator 9 after drying. The refrigerant entering the evaporator 9 quickly absorbs heat and vaporizes, and flows into the gas-liquid separator 28; since the refrigerant absorbs heat in the evaporator 9, the water vapor contained in the air flow directly entering the heat recovery device 8 from the drying chamber 1 can be liquefied when passing through the evaporator 9, thereby achieving the effect of air dehumidification; the condensed liquid liquefied on the surface of the evaporator 9 drops to the water receiving tray 18, and flows from the water receiving tray 18 into the thermal insulation water tank 22.

[0044] refer to Figure 4 Based on this system, this embodiment also provides a closed-loop dehumidification heat pump dryer condensate water recovery system control method, the control method includes the following steps:

[0045] Step S1: Setting the liquid level threshold of the liquid level controller 38 to h, when H>h, starting the circulating water pump 26, and when H<h, shutting down the circulating water pump 26, where H is the liquid level height of the insulation water tank 22;

[0046] Step S2: When H>h and T0<T3-∆T1, the first two-position three-way valve 32 connects the precooler 14 and the subcooler 16, allowing condensed water to flow from the precooler 14 into the subcooler 16 for heat exchange. When T0≥T3-∆T1, the first two-position three-way valve 32 connects the subcooler 16 and the outlet pipe, allowing condensed water to flow directly into the subcooler 16 for heat exchange. ∆T1 is the heat transfer temperature difference across the precooler 14 tube wall, T0 is the temperature measured by the first temperature sensor 33, and T3 is the return air temperature of the condenser measured by the third temperature sensor 41.

[0047] Step S3: Under the conditions of S2, when T2 ≥ T4 - ∆T2, the second two-position three-way valve channel connects the subcooler 16 and the drain pipe 36, and the condensed water is discharged to the outside environment. When T2 < T4 - ∆T2, the second two-position three-way valve channel connects the subcooler 16 and the insulated water tank 22, and the condensed water circulates back to the insulated water tank 22. Wherein, T2 is the condensed water temperature at the outlet of the subcooler 16, ∆T2 is the cooling heat transfer temperature difference of the condenser, and T4 is the condensing temperature set by the heat pump system according to the refrigerant pressure.

[0048] Step S4: Repeat steps S1-S3 until the liquid level H of the thermal insulation water tank 22 is less than the liquid level threshold h of the liquid level controller 38, and the circulating water pump 26 is turned off.

[0049] Furthermore, ∆T1 and ∆T2 are calculated based on the heat transfer temperature difference between the precooler 14 and the subcooler 16 using the logarithmic mean temperature difference method, preferably between 3°C and 5°C. In this embodiment, ∆T1 and ∆T2 are both set to 5°C. ∆T1 and ∆T2 can be adjusted based on the operating requirements of the heat pump condensate recovery system.

[0050] In summary, the present invention discloses a closed-loop dehumidification heat pump dryer condensate recovery and utilization system and a control method thereof, which exchanges heat with the condensate generated during operation and the return air of the drying chamber and the condenser refrigerant, and utilizes the cooling capacity of the condensate to achieve priority utilization of the condensate for the precooler and the subcooler, thereby reducing the return air temperature of the dryer and improving the dehumidification effect and cooling effect of the dryer.

[0051] The above description further details the invention in conjunction with specific preferred embodiments, and the specific implementation of the invention should not be considered to be limited to these descriptions. A person skilled in the art of the invention may make several simple deductions or substitutions without departing from the inventive concept, and all of these should be considered to fall within the scope of protection of the invention.

Claims

1. A closed-loop dehumidification heat pump dryer condensate water recovery and utilization system control method, used to control the closed-loop dehumidification heat pump dryer condensate water recovery and utilization system, characterized in that: The system includes a heat pump system and a condensed water recovery system. The heat pump system includes a condenser, a compressor (27), an evaporator (9) and a subcooler (16) connected through a refrigerant circulation pipeline. A third temperature sensor (41) is provided on the return air side of the condenser. The condensed water recovery system includes an insulated water tank (22) for collecting condensed water in a water receiving tray (18). The insulated water tank (22) is connected to a precooler (14) through a water outlet pipeline. A circulating water pump (26) and a first temperature sensor (33) are installed on the water outlet pipeline. The water outlet end of the precooler (14) is connected to the subcooler (16) and the water outlet pipeline through a first two-position three-way valve (32). The water outlet end of the subcooler (16) is connected to the insulated water tank (22) and the drain pipeline (36) through a second two-position three-way valve (34). A second temperature sensor (35) is installed on the water outlet end of the subcooler (16). A liquid level controller (38) is provided in the insulated water tank (22). Proceed as follows: Step S1: setting the liquid level threshold value of the liquid level controller (38) to h, when H>h, starting the circulating water pump (26), and when H<h, shutting down the circulating water pump (26), where H is the liquid level height of the insulation water tank (22); Step S2: When H>h, T0<T3-∆T1, the first two-position three-way valve (32) is connected to the subcooler (16) and the precooler (14), and the condensed water enters the subcooler (16) from the precooler (14) for heat exchange, wherein ∆T1 is the heat transfer temperature difference of the tube wall of the precooler (14), T0 is the temperature measured by the first temperature sensor (33), and T3 is the return air temperature of the condenser; Step S3: Under the conditions of S2, when T2 ≥ T4 - ∆T2, the second two-position three-way valve channel is connected to the subcooler (16) and the drain pipe (36), and the condensed water is discharged to the external environment, wherein T2 is the condensed water temperature at the outlet of the subcooler (16), ∆T2 is the cooling heat transfer temperature difference of the condenser, and T4 is the condensing temperature set by the heat pump system according to the refrigerant pressure; Step S4: Repeat steps S1-S3 until the liquid level H of the thermal insulation water tank (22) is less than the liquid level threshold h of the liquid level controller (38), and the circulating water pump (26) is turned off.

2. A closed-loop dehumidification heat pump dryer condensate recovery system control method according to claim 1, characterized in that: In step S2, when T0 ≥ T3 - ∆T1, the first two-position three-way valve (32) connects the subcooler (16) and the water outlet pipe, and the condensed water directly enters the subcooler (16) for heat exchange; in step S3, when the condition H>h is satisfied and T2 < T4 - ∆T2, the second two-position three-way valve channel connects the subcooler (16) and the insulated water tank (22), and the condensed water circulates back to the insulated water tank (22).

3. A closed-loop dehumidification heat pump dryer condensate recovery and utilization system control method according to claim 1 or 2, characterized in that: ∆T1 and ∆T2 are 3℃-5℃.

4. A closed-loop dehumidification heat pump dryer condensate recovery system, comprising a heat pump system and a condensate recovery system, wherein the heat pump system comprises a condenser, a compressor (27), an evaporator (9), and a subcooler (16) connected by a refrigerant circulation pipeline, a water receiving pan (18) is provided below the evaporator (9), and is characterized in that: The condensed water recovery system includes an insulated water tank (22) for collecting condensed water in the water receiving pan (18), the insulated water tank (22) is connected to the precooler (14) through a water outlet pipeline, a circulating water pump (26) and a first temperature sensor (33) are installed on the water outlet pipeline, the water outlet end of the precooler (14) is respectively connected to the subcooler (16) and the water outlet pipeline through a first two-position three-way valve (32), the water outlet end of the subcooler (16) is respectively connected to the insulated water tank (22) and the drain pipeline (36) through a second two-position three-way valve (34), the water outlet end of the subcooler (16) is installed with a second temperature sensor (35), and a liquid level controller (38) is provided in the insulated water tank (22).

5. A closed-loop dehumidification heat pump dryer condensate recovery and utilization system according to claim 4, characterized in that: The condenser, the compressor (27), the evaporator (9) and the subcooler (16) are connected in series via a refrigerant circulation pipeline; a gas-liquid separator (28) is connected between the compressor (27) and the evaporator (9); and the subcooler (16), the liquid storage tank (29), the dryer (30) and the electronic expansion valve (31) are connected to the refrigerant circulation pipeline between the condenser and the evaporator (9).

6. The closed-loop dehumidification heat pump dryer condensate water recovery and utilization system according to claim 4, characterized in that: A filter (25) is installed on the water outlet pipe between the thermal insulation water tank (22) and the precooler (14), and a filter screen (40) is provided at the water inlet of the water outlet pipe.

7. The closed-loop dehumidification heat pump dryer condensate water recovery and utilization system according to claim 4, characterized in that: The condenser comprises a first condenser (6) and a second condenser (7) connected in series. The first condenser (6) and the second condenser (7) are arranged in a dehumidification and heating function chamber (2) on one side of the drying chamber (1). A third temperature sensor (41) is arranged on the return air side of the first condenser (6). The dehumidification and heating function chamber (2) is communicated with the drying chamber (1).

8. The closed-loop dehumidification heat pump dryer condensate water recovery and utilization system according to claim 7, characterized in that: A partition with an inverted Y-shaped cross section is provided in the dehumidification and heating functional chamber (2), dividing the dehumidification and heating functional chamber (2) into an air inlet chamber, an air outlet chamber, and a heat recovery chamber. The air inlet chamber and the air outlet chamber are connected to the heat recovery chamber through a first condenser (6) and a second condenser (7), respectively.

9. The closed-loop dehumidification heat pump dryer condensate water recovery and utilization system according to claim 8, characterized in that: The air inlet chamber and the air outlet chamber are connected to the heat recovery device (8) via a first one-way valve (10) and a second one-way valve (11), respectively. The evaporator (9) is connected to the heat recovery device (8), and the air outlet of the evaporator (9) is connected to the channel of the heat recovery device (8).

10. The closed-loop dehumidification heat pump dryer condensate water recovery and utilization system according to claim 9, characterized in that: A first fan (12) and a second fan (13) are respectively provided in the air inlet cavity and the air outlet cavity, and the first fan (12) and the second fan (13) rotate in opposite directions.

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