Closed drying heat pump system

Abstract

The closed type drying heat pump system comprises a working medium circulation flow path, a heat preservation box body and a heat carrying system, the working medium circulation flow path comprises a compressor, a condenser, a throttling device and an evaporator which are sequentially connected, and the condenser is located at the air inlet end and the air outlet end of the heat preservation box body; the working medium circulation flow path is of an ultrahigh-temperature type, a high-temperature type and a medium-temperature type, the number of flow paths of the ultrahigh-temperature type, the high-temperature type and the medium-temperature type is larger than or equal to 1, the air inlet end evaporator is sequentially connected into the high-temperature type flow path and the medium-temperature type flow path, and the air outlet end condenser is sequentially connected into the medium-temperature type flow path, the high-temperature type flow path and the ultrahigh-temperature type flow path; a first subcooler, a second subcooler and a third subcooler are arranged among the last stage of the medium-temperature flow path, the last stage of the high-temperature flow path, all stages of the ultra-high-temperature flow path, the condenser and the throttling device; the heat carrying system comprises a plurality of branch pipelines, and the air inlet end of the heat preservation box body, the first subcooler, the second subcooler and the third subcooler are correspondingly provided with the branch pipelines. The heat carrying system is used for discharging redundant heat in the closed heat pump system, the energy utilization efficiency is improved, and the system is more stable and saves more energy.

Description

Technical Field

[0001] The present invention relates to a gas control device for drying, and particularly to a closed - type drying heat pump system. Background Art

[0002] There are mainly two layouts for heat pump drying: open - type and closed - type. In open - type drying, the hot and humid air in the heat - preservation box is directly discharged outside the box through moisture exhaust, and then natural fresh air is supplemented. In closed - type drying, the air in the heat - preservation box does not contact the outside world. The open - type drying system has high energy consumption, while the closed - type drying system has lower energy consumption, but the system temperature is not high enough. Because the air in the closed - type drying heat - preservation box does not contact the outside world, when the outlet air temperature of the closed - type drying is increased, the heat output by the heat pump increases accordingly. However, the heat consumed by the material to be dried and the heat dissipation capacity of the system itself are limited, resulting in an unbalanced system energy and unstable operation.

[0003] For closed - type drying, it is necessary to increase the heat entering the dryer as much as possible to ensure that all the heat produced by the heat pump system is completely transported to the dryer, limit the inlet air temperature from the dryer to the evaporator of the heat pump system, and ensure energy balance. In more application scenarios, it is also necessary to achieve a drying air supply temperature above 140 °C. CN 217275452 U discloses a closed - type drying heat pump system with multi - stage series cooperation, which uses the form of series connection of multi - stage evaporators and multi - stage condensers to improve the drying capacity. A waste - heat condenser and a waste - heat fan adjacent to the waste - heat condenser are arranged between the first - stage condensers to discharge the excess heat into the atmosphere near the unit to ensure stability. In this solution, a part of the heat produced by the heat pump is sacrificed to solve part of the energy balance problem, and not all the heat produced by the heat pump is completely transported to the dryer, so the drying temperature and capacity are limited. CN 112857018 A discloses a multi - heat - exchanger heat pump drying system with temperature / humidity field coordination and its control method. Similar to CN 217275452 U, the solution of CN 112857018 A also sets a method for removing excess heat to maintain energy balance. This solution solves the energy balance problem of the closed - type system, but does not achieve a higher drying air supply temperature. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a closed - type drying heat pump system to solve the problems of heat balance and energy utilization rate, and at the same time have a higher drying air supply temperature.

[0005] Technical Solution: The closed - type drying heat pump system of the present invention includes a working medium circulation flow path, a heat - carrying system, and a heat - preservation box. The working medium circulation flow path includes a compressor, a condenser, a throttling device, and an evaporator connected in sequence. The evaporator and the condenser are respectively located at the inlet air end and the outlet air end of the heat - preservation box.

[0006] The working medium circulation flow path is divided into ultra-high temperature type, high temperature type and medium temperature type flow path, the number of stages of ultra-high temperature type, high temperature type and medium temperature type flow path is ≥1, the evaporator at the air inlet end is connected to the high temperature type and medium temperature type flow path in sequence, and the condenser at the air outlet end is connected to the medium temperature type, high temperature type and ultra-high temperature type flow path in sequence;

[0007] The first, second and third subcoolers are respectively provided between the last stage of the medium-temperature and high-temperature flow paths and the condensers and throttling devices of each stage of the ultra-high-temperature flow path to reduce the temperature of the working fluid entering the throttling device from the condenser. The heat carrier system includes a plurality of branch pipelines, and the first, second and third subcoolers and the air inlet end of the insulation box are correspondingly configured with branch pipelines.

[0008] Preferably, the heat carrier system comprises a heat carrier heat exchange terminal for heat dissipation, and the heat carrier fluid inside the branch pipelines for heat exchange with the first, second and third subcoolers returns to the heat carrier heat exchange terminal for heat dissipation.

[0009] Preferably, a heat carrier heat exchanger is provided at the air inlet end of the thermal insulation box, and a branch pipeline located at the air inlet end of the thermal insulation box is connected to the heat carrier heat exchanger.

[0010] Preferably, the heat transfer system comprises a circulation pump for conveying the heat transfer fluid in the branch pipeline.

[0011] Preferably, the heat transfer fluid of the heat transfer system is a liquid with a freezing point ≤ 0°C.

[0012] Preferably, the evaporator located at the air inlet end of the heat preservation box is connected to the ultra-high temperature type, high temperature type and medium temperature type flow paths in sequence.

[0013] Preferably, the last stage of the medium-temperature working fluid circulation circuit and the first stage of the ultra-high temperature working fluid circulation circuit form a cascade working fluid circulation circuit through a heat exchanger, and the first subcooler is moved to the second last stage of the medium-temperature working fluid circulation circuit.

[0014] Preferably, the number of stages of the medium-temperature flow path is ≥3, the first subcooler and the condenser are connected in parallel, and a flow regulating device is provided at the inlet end of the first subcooler.

[0015] Preferably, the supercooler is arranged outside the thermal insulation box.

[0016] Preferably, the critical temperatures of the working fluids in the ultra-high temperature type, high temperature type and medium temperature type flow paths are respectively above 150°C, 110±10°C and 95±10°C.

[0017] Preferably, the air inlet end and the air outlet end of the heat preservation box and the dryer and the circulating fan are connected in series to form a closed loop.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: 1. The heat produced by the heat pump system is completely delivered to the dryer, improving the energy utilization rate. A heat-carrying heat exchanger is provided at the air inlet end of the heat-insulating box to balance the heat imbalance caused by the temperature rise at the air outlet end of the closed-loop drying heat pump system; 2. Through the subcooler and the heat-carrying system, the refrigerating capacity of each stage of the refrigeration system is increased - that is, the water removal capacity is increased, so that the circulating air of the drying system is completely closed-loop, and zero exhaust gas is emitted during the drying process, and the theoretical energy consumption is reduced by 9%; 3. It can achieve a drying air supply temperature of 140 °C or higher, and can be used for drying cow dung, medicinal materials, chemical materials, sludge, and ore sand; 4. The system can operate stably: compared with the existing closed-loop drying heat pump system, it can operate continuously and stably for 24 hours a day; 5. Improve the drying capacity: the drying capacity is increased by not less than 30%, and the processing capacity is increased by more than 10%; 6. While drying the material, it can also achieve the effect of high-temperature sterilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the closed-loop drying heat pump system according to the first embodiment of the present invention;

[0020] Figure 2 It is a schematic structural diagram of the closed-loop drying heat pump system according to the second embodiment of the present invention;

[0021] Figure 3 It is a schematic structural diagram of the closed-loop drying heat pump system according to the third embodiment of the present invention;

[0022] Figure 4 It is a schematic structural diagram of the closed-loop drying heat pump system according to the fourth embodiment of the present invention;

[0023] Figure 5 It is a schematic structural diagram of the closed-loop drying heat pump system according to the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1 As Figure 1 shown, the closed-loop drying heat pump system of this embodiment mainly consists of a working medium circulation flow path, a heat-carrying system, and a drying room. The drying room includes a heat-insulating box 23, a dryer 22, and a circulation fan 24 connected in series. The heat-insulating box 23 has an air inlet end and an air outlet end. The circulation fan 24 is located at the air outlet end of the heat-insulating box 23 and is connected to the inlet end of the dryer 22. The air in the drying room forms a closed loop.

[0026] The working fluid circulation path is a closed loop formed by sequentially connecting a compressor, a condenser, a throttling device, and an evaporator. Among them, the evaporator and the condenser are respectively located at the air inlet end and the air outlet end of the heat preservation box body 23, so that the temperature and humidity of the circulating air passing through the evaporator gradually decrease, and the outlet air temperature of the circulating air heated by the condenser gradually increases.

[0027] According to the critical temperature of the working fluid, the working fluid circulation path can be divided into three types: ultra-high temperature type, high temperature type, and medium temperature type. The number of stages of each type of flow path ≥ 1. For the last stage of the medium temperature type and high temperature type flow paths, and each stage of the ultra-high temperature type flow path, a subcooler is respectively provided between the condenser and the throttling device; to further lower the temperature of the working fluid entering the throttling device, so as to improve the refrigeration efficiency. For the sake of simplified description, in this embodiment, the number of stages of the medium temperature type is set to 2, and the number of stages of the high temperature type and ultra-high temperature type flow paths is set to 1. Specifically:

[0028] The first stage of the medium temperature type flow path has a first-stage compressor 1, a first-stage condenser 2, a first-stage throttling device 4, and a first-stage evaporator 5, constituting the first medium temperature type single-stage refrigeration cycle; the second stage of the medium temperature type flow path has a second-stage compressor 16, a second-stage throttling device 17, and a second-stage evaporator 18; the first stage of the high temperature type flow path has a first-stage compressor 6, a first-stage condenser 7, a first-stage throttling device 9, and a first-stage evaporator 10, constituting the first high temperature type single-stage refrigeration cycle; the first stage of the ultra-high temperature type flow path has a first-stage compressor 11, a first-stage condenser 12, and a first-stage throttling device 14.

[0029] The number of stages of the high temperature type flow path is 1, and the first stage is the last stage. A subcooler 8 is provided between the corresponding first-stage condenser 7 and the first-stage throttling device 9. The second stage of the medium temperature type flow path close to the high temperature type flow path is the last stage, and the number of stages of the ultra-high temperature type flow path is 1, and the first stage is the first stage. Subcoolers should be respectively provided on these two flow paths. In this embodiment, the subcooler 3 of the second stage of the medium temperature type flow path is transferred to the second-to-last stage (the first stage), and the subcooler 13 of the ultra-high temperature type flow path remains unchanged. Thus, at the air inlet end of the heat preservation box body 23, there are only evaporators connected to the high temperature type and medium temperature type flow paths: the first-stage evaporator 10 (high temperature type), the second-stage evaporator 18 (medium temperature type), and the first-stage evaporator 5 (medium temperature type). At the air outlet end of the heat preservation box body 23, there are condensers connected to the medium temperature type, high temperature type, and ultra-high temperature type flow paths in sequence: the first-stage condenser 2 (medium temperature type), the first-stage condenser 7 (high temperature type), and the first-stage condenser 12 (ultra-high temperature type).

[0030] Regarding the working fluid, for the medium temperature type working fluid, the critical temperature is 95°C ± 10°C; for the high temperature type working fluid, the critical temperature is 110°C ± 10°C; for the ultra-high temperature type working fluid, the critical temperature is above 150°C.

[0031] The heat-carrying system includes a circulation pump 20 and several branch pipelines. Each subcooler 3, 8, 13 is correspondingly equipped with a branch pipeline, so that the heat-carrying fluid in the branch pipeline exchanges heat with the subcooler, further reducing the temperature of the working medium passing through the subcooler. The air inlet end of the heat preservation box body 23 is also equipped with a branch pipeline to pre-cool the temperature of the air flow entering the heat preservation box body 23. The circulation pump 20 is located on the main trunk of the branch pipeline and is used to pump the heat-carrying fluid to the subcooler. Specifically:

[0032] The heat-carrying system has four branch pipelines. The first branch pipeline is sent to the air inlet end of the heat preservation box body 23 and enters the heat-carrying heat exchanger 19 located at the air inlet end of the heat preservation box body 23 to pre-cool the circulating air entering the heat preservation box body 23. The remaining three branch pipelines are respectively connected to the subcooler 3, the subcooler 8, and the subcooler 13 to cool and exchange heat with the working medium liquid therein. The heat-carrying system also has a heat-carrying heat exchange end 21. After the heat-carrying fluid in the branch pipeline exchanges heat with the circulating air and the subcooler, it returns to the heat-carrying heat exchange end 21 for heat dissipation. The heat-carrying fluid is a liquid with a freezing point ≤ 0°C, which can be water, alcohol solvents such as ethylene glycol, or a mixed solvent.

[0033] The working medium circulation route of this embodiment is as follows: In the first stage of the medium-temperature flow path, the working medium enters the first-stage compressor 1 in the form of low-pressure gas and is compressed into high-temperature gas. The high-temperature gas enters the first-stage condenser 2 to heat the circulating air at the air outlet end of the heat preservation box body 23 and then condenses into liquid. The liquid passes through the subcooler 3 and exchanges heat with the heat-carrying fluid to be cooled and subcooled. After the subcooled liquid passes through the first-stage throttling device 4, it is throttled and depressurized and then evaporates in the first-stage evaporator 5 to cool the circulating air entering the air inlet end of the heat preservation box body 23.

[0034] In the first stage of the high-temperature flow path, the working medium enters the first-stage compressor 6 in the form of low-pressure gas and is compressed into high-temperature gas. The high-temperature gas enters the first-stage condenser 7 to heat the circulating air at the air outlet and then condenses into high-temperature liquid. The liquid passes through the subcooler 8 and exchanges heat with the heat-carrying fluid branch to be cooled and subcooled. After the subcooled liquid passes through the first-stage throttling device 9, it is throttled and depressurized and then enters the first-stage evaporator 10 to evaporate, cooling the circulating air entering the air inlet end of the heat preservation box body 23.

[0035] In the ultra-high temperature flow path, the working medium enters the first-stage compressor 11 in the form of low-pressure gas and is compressed into ultra-high temperature gas. The ultra-high temperature gas enters the first-stage condenser 12 to heat the circulating air at the air outlet end of the heat preservation box body 23 and then condenses into ultra-high temperature liquid. The ultra-high temperature liquid passes through the subcooler 13 and exchanges heat with the heat-carrying fluid to be cooled and subcooled. After the subcooled ultra-high temperature type working medium liquid passes through the first-stage throttling device 14, it is throttled and depressurized and then enters the heat exchanger 15 to evaporate and cool the medium-temperature type working medium gas discharged from the second-stage compressor 16 of the cascade system. After the gas discharged from the second-stage compressor 16 is cooled, it passes through the second-stage throttling device 17 to be throttled and depressurized and then evaporates in the second-stage evaporator 18 to cool the circulating air entering the air inlet end.

[0036] The air circulation route of the closed - type drying heat pump system is as follows: The circulating air comes out of the dryer 22 and enters the heat - preservation box 23 in a medium - temperature and high - humidity state. It undergoes the first - stage cooling and condensation for water removal through the heat - carrying heat exchanger 19, the second - stage cooling and condensation for water removal through the primary evaporator 10 of the high - temperature flow path, the third - stage cooling and condensation for water removal through the secondary evaporator 18 of the medium - temperature flow path, and finally, it undergoes the fourth - stage condensation for water removal through the primary evaporator 5 of the medium - temperature flow path. After the water removal, the low - temperature and low - humidity circulating air enters the primary condenser 2 of the medium - temperature flow path for the first - stage heating and temperature rise, then enters the primary condenser 7 of the high - temperature flow path for the second - stage heating and temperature rise, and then undergoes the third - stage heating and temperature rise through the primary condenser 12 of the ultra - high - temperature flow path to form high - temperature and low - humidity (dry) air and exit the heat - preservation box 23. After being pressurized by the circulating fan 24, it enters the dryer 22 to dehydrate and dry the wet material. The circulating air that absorbs the moisture from the wet material in the dryer 22 becomes high - temperature and high - humidity and then returns to the heat - preservation box 23 for circulation.

[0037] The circulation route of the heat - carrying fluid in the heat - carrying system is as follows: The heat - carrying fluid comes out of the circulation pump 20 and branches into four paths: The first path enters the heat - carrying heat exchanger 19, and after absorbing heat, the heat - carrying fluid enters the heat - carrying heat - exchange end 21 to release heat; the second path passes through the sub - cooler 8 to cool and exchange heat for the working fluid liquid in it, and after absorbing heat, the high - temperature heat - carrying fluid enters the heat - carrying heat - exchange end 21 to release heat; the third path passes through the sub - cooler 3 to cool and exchange heat for the working fluid liquid in it, and after absorbing heat, the high - temperature heat - carrying fluid enters the heat - carrying heat - exchange end 21 to release heat; the fourth path passes through the sub - cooler 13 to cool and exchange heat for the working fluid liquid in it, and after absorbing heat, the high - temperature heat - carrying fluid enters the heat - carrying heat - exchange end 21 to release heat. The heat - carrying fluid that has completed heat release from the heat - carrying heat - exchange end 21 then returns to the circulation pump 20 for circulation. Each branch pipeline of the heat - carrying system can be in series or in parallel.

[0038] In this embodiment, by setting a circulation system with three working - fluid temperatures, the critical - temperature limitations of various working fluids are overcome, and a drying temperature above 140 °C can be achieved, greatly expanding the application scenarios of the heat - pump drying system. The heat - carrying system is also used to discharge the excess heat in the closed - type heat - pump system, ensure energy balance, increase the refrigeration capacity of the refrigeration system, improve the water - removal capacity, ensure the effective utilization of energy, and enhance the drying efficiency. Compared with the current heat - pump drying system, the three - stage heat - pump system in this embodiment is more stable, more environmentally friendly, and more energy - efficient. The sub - coolers 3, 8, and 13 are configured outside the heat - preservation box to improve the sub - cooling efficiency and reduce the volume of the heat - preservation box at the same time.

[0039] Example 2 is as Figure 2 shown. On the basis of Example 1, there are the following variations in this embodiment: The number of stages of the medium - temperature flow path is set to 3.

[0040] The second stage of the medium-temperature flow path has a two-stage compressor 16, a two-stage condenser 2-1, a two-stage throttling device 17, and a two-stage evaporator 18, constituting a second medium-temperature single-stage refrigeration cycle; the original third stage (the last stage) of the medium-temperature flow path has a three-stage compressor 1-1, a three-stage throttling device 4-1, and a three-stage evaporator 5-1; the third stage of the medium-temperature flow path and the first stage of the ultra-high-temperature flow path form a cascade refrigerant cycle flow path through a heat exchanger 15, and the subcooler 3 of the third stage of the medium-temperature flow path is transferred to the penultimate stage (the second stage), and the subcooler 13 of the ultra-high-temperature flow path remains unchanged.

[0041] Example 3 is as Figure 3 shown. Based on Example 2, there are the following modifications in this example: the number of stages of the medium-temperature flow path is increased to 4, the number of stages of the high-temperature flow path is set to 1, and the number of stages of the ultra-high-temperature flow path is set to 1.

[0042] The third stage of the medium-temperature flow path has a three-stage compressor 1-1, a three-stage condenser 2-2, a three-stage throttling device 4-1, and a three-stage evaporator 5-1, constituting a third medium-temperature single-stage refrigeration cycle; the fourth stage (the last stage) of the medium-temperature flow path has a four-stage compressor 1-2, a four-stage throttling device 4-2, and a four-stage evaporator 5-2, and forms a cascade refrigerant cycle flow path with the first stage (the first stage) of the ultra-high-temperature flow path through a heat exchanger 15. The third stage of the medium-temperature flow path is the penultimate stage, and the subcooler 3 is arranged in the third stage (at this time, the subcooler 3 is used as a condenser).

[0043] Furthermore, the subcooler 3 and the three-stage condenser 2-2 are in parallel. Specifically: the pipeline at the outlet of the three-stage compressor 1-1 is divided into two branches. The first branch is directly connected to the three-stage condenser 2-2, and the second branch is connected to the subcooler 3 through a front throttling device 4-0 (at this time, the front throttling device 4-0 is used as a flow regulating device). The first branch and the second branch merge after passing through the three-stage condenser 2-2 and the subcooler 3 respectively, and are connected to the three-stage evaporator 5-1 through the three-stage throttling device 4-1, and finally return to the three-stage compressor 1-1 through the three-stage evaporator 5-1.

[0044] In this example, the number of stages of the heat pump system with the medium-temperature refrigerant increases. The three-stage condenser 2-2, as the condenser closest to the first-stage condenser 7 with the high-temperature refrigerant, has a working medium close to the critical temperature and has a risk of overpressure. By paralleling the subcooler 3, a part of the heat exchange capacity of the original three-stage condenser 2-2 is separated to avoid the condensation pressure exceeding the critical pressure and ensure the stable operation of the system.

[0045] Similarly, in this embodiment, the air inlet end of the heat preservation box body 23 only has the evaporators connected to the high-temperature type and medium-temperature type flow paths: the first-stage evaporator 10 (high temperature), the fourth-stage evaporator 5-2 (medium temperature), the third-stage evaporator 5-1 (medium temperature), the second-stage evaporator 18 (medium temperature), and the first-stage evaporator 5 (medium temperature); the air outlet end of the heat preservation box body 23 has condensers connected to the medium-temperature type, high-temperature type, and ultra-high-temperature type flow paths in sequence: the first-stage condenser 2 (medium temperature), the second-stage condenser 2-1 (medium temperature), the third-stage condenser 2-2 (medium temperature), the first-stage condenser 7 (high temperature), and the first-stage condenser 12 (ultra-high temperature).

[0046] Embodiment 4 is as Figure 4 shown. On the basis of Embodiment 3, there are the following deformations in this embodiment: the number of stages of the medium-temperature type flow path is 3, the number of stages of the high-temperature type flow path is set to 1, and the number of stages of the ultra-high-temperature type flow path is set to 1.

[0047] The third stage of the medium-temperature type flow path has a three-stage compressor 1-1, a three-stage condenser 2-2, a three-stage throttling device 4-1, and a three-stage evaporator 5-1, constituting the third medium-temperature type single-stage refrigeration cycle.

[0048] The first stage of the ultra-high-temperature type flow path has a first-stage compressor 11, a first-stage condenser 12, a first-stage throttling device 14, and a first-stage evaporator 15-1, constituting the first ultra-high-temperature type single-stage refrigeration cycle.

[0049] The medium-temperature type flow path and the ultra-high-temperature type flow path are independent of each other and do not form a cascade refrigerant cycle flow path. The third stage of the medium-temperature type flow path is the last stage, and the subcooler 3 is directly arranged in the third stage. The subcooler 3 is in parallel with the three-stage condenser 2-2. The ultra-high-temperature type flow path has only one stage and is provided with a subcooler 13.

[0050] The air inlet end of the heat preservation box body 23 has evaporators connected to the ultra-high-temperature type, high-temperature type, and medium-temperature type flow paths: the first-stage evaporator 15-1 (ultra-high temperature), the first-stage evaporator 10 (high temperature), the third-stage evaporator 5-1 (medium temperature), the second-stage evaporator 18 (medium temperature), and the first-stage evaporator 5 (medium temperature); the air outlet end of the heat preservation box body 23 has condensers connected to the medium-temperature type, high-temperature type, and ultra-high-temperature type flow paths in sequence: the first-stage condenser 2 (medium temperature), the second-stage condenser 2-1 (medium temperature), the third-stage condenser 2-2 (medium temperature), the first-stage condenser 7 (high temperature), and the first-stage condenser 12 (ultra-high temperature).

[0051] Embodiment 5 is as Figure 5 shown. On the basis of Embodiment 3, there are the following deformations in this embodiment: the number of stages of the medium-temperature type flow path is increased to 4, the number of stages of the high-temperature type flow path is set to 1, and the number of stages of the ultra-high-temperature type flow path is set to 2.

[0052] The second stage of the ultra-high temperature type flow path is provided with a two-stage compressor 11-1, a two-stage condenser 12-1, a two-stage throttling device 13-1, and a two-stage evaporator 15-2. Sub-coolers 13 and 13-1 are respectively arranged in the first stage and the second stage of the ultra-high temperature type flow path. The heat-carrying system has five branch pipelines, and the sub-cooler 13-1 is configured with branch pipelines. The air inlet end and the air outlet end of the heat preservation box body 23 are respectively connected to the evaporators and condensers of the ultra-high temperature type, high temperature type, and medium temperature type flow paths.

Claims

1. A closed drying heat pump system, characterized in that, It includes a working medium circulation flow path, a heat preservation box and a heat carrier system, wherein the working medium circulation flow path includes a compressor, a condenser, a throttling device and an evaporator connected in sequence, and the evaporator and the condenser are respectively located at the air inlet end and the air outlet end of the heat preservation box; the working medium circulation flow path is divided into ultra-high temperature type, high temperature type and medium temperature type flow paths, and the number of stages of the ultra-high temperature type, high temperature type and medium temperature type flow paths is ≥1, the evaporator located at the air inlet end is sequentially connected to the high temperature type and medium temperature type flow paths, and the condenser located at the air outlet end is sequentially connected to the medium temperature type, high temperature type and ultra-high temperature type flow paths; The first, second and third subcoolers are respectively provided between the last stage of the medium-temperature and high-temperature flow paths, and the condensers and throttling devices of each stage of the ultra-high-temperature flow path; the heat carrier system includes a plurality of branch pipelines, and the first, second and third subcoolers are correspondingly configured with branch pipelines at the air inlet end of the insulation box.

2. The closed drying heat pump system according to claim 1, characterized in that, The evaporator located at the air inlet end is connected to the ultra-high temperature type, high temperature type and medium temperature type flow paths in sequence.

3. The closed-loop drying heat pump system according to claim 1, wherein The last stage of the medium temperature working medium circulation flow path and the first stage of the ultra-high temperature working medium circulation flow path form a cascade working medium circulation flow path through a heat exchanger, and the first subcooler is moved to the second last stage of the medium temperature flow path.

4. The closed-loop drying heat pump system according to any one of claims 1 to 3, characterized in that, The number of stages of the medium-temperature flow path is ≥3, the first subcooler and the condenser are connected in parallel, and a flow regulating device is provided at the inlet end of the first subcooler.

5. The closed drying heat pump system according to claim 4, wherein, The first, second and third subcoolers are located outside the insulation box.

6. The closed-loop drying heat pump system according to claim 1, wherein The critical temperatures of the working fluids in the ultra-high temperature type, high temperature type and medium temperature type flow paths are respectively above 150°C, 110±10°C and 95±10°C.

7. The closed-loop drying heat pump system according to claim 1, wherein The heat transfer system comprises a heat transfer heat exchange terminal for heat dissipation, and the heat transfer fluid inside the branch pipelines for heat exchange with the first, second and third subcoolers returns to the heat transfer heat exchange terminal for heat dissipation.

8. The closed drying heat pump system according to claim 7, wherein The heat transfer system further comprises a circulation pump for conveying the heat transfer fluid in the branch pipeline, and the heat transfer fluid is a liquid with a freezing point of ≤0°C.

9. The closed drying heat pump system according to claim 8, wherein The air inlet end of the thermal insulation box is provided with a heat carrier heat exchanger, and the branch pipeline located at the air inlet end of the thermal insulation box is connected to the heat carrier heat exchanger.

10. The closed-loop drying heat pump system according to claim 1, characterized in that, The air inlet end, the air outlet end of the heat preservation box, the dryer and the circulating fan are connected in series to form a closed loop.

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