CN115183499B - Heat pump type drying system and defrosting method for heat pump type drying system - Google Patents
Heat pump type drying system and defrosting method for heat pump type drying system Download PDFInfo
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- CN115183499B CN115183499B CN202210706306.3A CN202210706306A CN115183499B CN 115183499 B CN115183499 B CN 115183499B CN 202210706306 A CN202210706306 A CN 202210706306A CN 115183499 B CN115183499 B CN 115183499B
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- 238000001035 drying Methods 0.000 title claims abstract description 96
- 238000010257 thawing Methods 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 41
- 238000005057 refrigeration Methods 0.000 claims abstract description 23
- 239000003507 refrigerant Substances 0.000 claims description 72
- 239000007788 liquid Substances 0.000 description 22
- 241000208125 Nicotiana Species 0.000 description 7
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
- F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Drying Of Solid Materials (AREA)
Abstract
The present invention relates to a heat pump type drying system and a defrosting method for the same. The heat pump type drying system comprises: the refrigeration main loop comprises a compressor, a condenser, an expansion device and an evaporator, wherein a bottom coil is arranged at the bottom of the evaporator and is provided with an inlet end connected with the expansion device and an outlet end connected with an air suction port of the compressor, a first electromagnetic valve is arranged between the inlet end and the expansion device, and a second electromagnetic valve is arranged in the bottom coil; a defrosting bypass pipe having a first end connected to the discharge port of the compressor and a second end connected to the inlet end, the defrosting bypass pipe being provided with a third electromagnetic valve; and a capillary line configured to be disposed in the bottom coil in parallel with the second solenoid valve, and when the heat pump type drying system enters the defrost mode, the first solenoid valve and the second solenoid valve are in a closed state, and the third solenoid valve is in an open state. The heat pump type drying system can defrost and prevent the compressor from being frequently started and stopped.
Description
Technical Field
The invention relates to the technical field of refrigeration, in particular to a heat pump type drying system and a defrosting method for the heat pump type drying system.
Background
The drying system is a device combination for drying materials with high water content by utilizing heat energy. According to the different forms of heat energy generation, the drying system can be divided into various types such as an electric heating type, a fuel gas type, a fuel oil type, a fire coal type, a heat pump type and the like. Compared with the traditional fuel type drying system, the heat pump type drying system has the advantages of energy conservation, high efficiency, environmental friendliness, low operation cost and the like, and is widely applied to various fields of tobacco processing, grain storage, metallurgical chemical industry and the like.
In the tobacco processing process, the heat pump type drying system can realize precision adjustment on the temperature and the humidity in the curing barn, so that the tobacco curing efficiency is effectively improved, and the tobacco quality is ensured. Heat pump drying systems of the prior art generally include a compressor, a condenser, an expansion device, and an evaporator, which are connected in sequence by refrigerant lines, to form a refrigeration circuit in which a refrigerant is allowed to flow. Wherein the condenser is typically disposed within the heating chamber adjacent the curing barn for delivering drying air into the curing barn; the evaporator is typically disposed outside the heating chamber so as to exchange heat with the external environment, ensuring the evaporation efficiency of the refrigerant in the evaporator. However, under the low temperature condition, the dry bulb temperature of the external environment is lower, so that the surface of the evaporator (particularly the bottom of the evaporator) is easy to frost.
In order to solve the technical problem that an evaporator of a heat pump type drying system is easy to frost under a low-temperature working condition, a technical scheme for defrosting the evaporator by utilizing high-temperature gas of a compressor has been developed in the prior art. For example, chinese patent No. CN215898848U discloses an air source heat pump dryer unit and a tobacco flue-curing house. The air source heat pump dryer unit comprises a compressor, a condenser, a throttling element and a cold evaporator which are sequentially connected through pipelines. And the outlet end of the compressor is connected with a bypass pipeline. The other end of the bypass pipeline is connected into a pipeline between the throttling element and the inlet end of the evaporator. A bypass electromagnetic valve for controlling the on-off of the pipeline is arranged on the bypass pipeline. When the exhaust pressure of the compressor is detected to reach the preset pressure, the bypass solenoid valve is opened, so that part of high-temperature gaseous refrigerant is discharged from the compressor and directly enters the bypass pipeline without passing through the condenser. The part of refrigerant enters the evaporator after passing through the bypass pipeline, so that the high-temperature refrigerant of the compressor is utilized for defrosting the evaporator, and the defrosting without stopping is realized. However, the high-temperature gaseous refrigerant is condensed into a liquid refrigerant after heat exchange in the evaporator and flows into the gas-liquid separator in the refrigeration loop, so that the liquid refrigerant cannot be directly sucked by the compressor in a gaseous form to be compressed again, and the suction pressure of the compressor is excessively low, so that frequent start and stop are caused.
Accordingly, there is a need in the art for a new solution to the above-mentioned problems.
Disclosure of Invention
The invention provides a heat pump type drying system, which aims to solve the technical problem that in the prior art, a compressor is frequently started and stopped due to too small suction pressure when a heat pump type drying system is used for defrosting under a low-temperature working condition. The heat pump type drying system includes: the refrigeration main loop comprises a compressor, a condenser, an expansion device and an evaporator which are sequentially connected through a refrigerant pipeline, wherein a bottom coil is arranged at the bottom of the evaporator, the bottom coil is provided with an inlet end connected with the expansion device and an outlet end connected with an air suction port of the compressor, a first electromagnetic valve capable of being opened and closed is arranged between the inlet end and the expansion device, and a second electromagnetic valve capable of being opened and closed is arranged in the bottom coil; a defrosting bypass pipe, which is provided with a first end connected with the exhaust port of the compressor and a second end connected with the inlet end, and is also provided with a third electromagnetic valve which can be opened and closed; and a capillary line configured to be disposed in the bottom coil in parallel with the second solenoid valve, and when the heat pump type drying system enters a defrost mode, the first solenoid valve and the second solenoid valve are in a closed state, and the third solenoid valve is in an open state.
The heat pump type drying system comprises a refrigeration main circuit, a defrosting bypass pipe and a capillary pipeline. The main refrigerating circuit comprises a compressor, a condenser, an expansion device and an evaporator which are sequentially connected through refrigerant pipelines to form a refrigerant circuit allowing refrigerant to circularly flow in the main refrigerating circuit. A bottom coil is arranged at the bottom of the evaporator, the bottom coil is provided with an inlet end connected with the expansion device and an outlet end connected with the air suction port of the compressor, and a first electromagnetic valve capable of being opened and closed is arranged between the inlet end and the expansion device. A second electromagnetic valve which can be opened and closed is also arranged in the bottom coil pipe. It should be noted that the evaporator is formed by combining a plurality of coils spaced apart from each other, and the bottom coil at the bottom of the evaporator is most prone to frosting due to insufficient air volume supply, too low evaporation temperature, and the like. Therefore, the invention takes the bottom coil pipe as the main object of defrosting of the evaporator, and can remarkably improve the pertinence of defrosting. The first electromagnetic valve and the second electromagnetic valve can conveniently control the on-off of the refrigerant in the bottom coil. The defrosting bypass pipe is provided with a first end connected with the exhaust port of the compressor and a second end connected with the inlet end of the bottom coil pipe, and a third electromagnetic valve capable of being opened and closed is further arranged on the defrosting bypass pipe so as to control the on-off of the refrigerant in the defrosting bypass pipe. The capillary line is configured to be disposed in the bottom coil in parallel with the second solenoid valve. When the heat pump type drying system enters a defrosting mode, the first electromagnetic valve and the second electromagnetic valve are closed, so that the liquid refrigerant subjected to depressurization and expansion by the expansion device cannot enter the bottom coil pipe from the inlet end. At the same time, the third solenoid valve is opened to allow a portion of the high-temperature and high-pressure gaseous refrigerant discharged from the discharge port of the compressor to flow into the bottom coil through the defrost bypass pipe, thereby defrost the bottom coil. In this process, the high-temperature and high-pressure gaseous refrigerant is condensed into a medium-temperature and high-pressure liquid refrigerant. Then, the medium-temperature high-pressure liquid refrigerant flows into the capillary tube, and is depressurized and expanded into a low-temperature low-pressure liquid refrigerant. The low temperature, low pressure liquid refrigerant then continues to flow in the bottom coil between the second solenoid valve and the outlet port, thereby evaporating into a low temperature, low pressure gaseous refrigerant. And finally, the low-temperature low-pressure gaseous refrigerant is re-sucked into the compressor from the air suction port along the refrigerant pipeline, so that the compressor is ensured to have moderate suction pressure, frequent start and stop of the compressor caused by over low suction pressure are prevented, and the service life of the compressor and the running stability of the whole heat pump type drying system are improved.
In the preferred technical scheme of the heat pump type drying system, the bottom coil comprises a first flow path, a second flow path, a third flow path and a fourth flow path which are sequentially connected end to end, the tail ends of the first flow path and the fourth flow path are respectively an inlet end and an outlet end, and the second electromagnetic valve and the capillary pipeline are mutually parallel and arranged between the second flow path and the third flow path. By the arrangement, the bottom coil can have a simple structure. In addition, the second electromagnetic valve and the capillary pipeline are arranged between the second flow path and the third flow path in parallel, so that the liquid refrigerant flowing in from the capillary pipeline can be completely evaporated into the gaseous refrigerant in the fourth flow path, and the compressor is ensured to have moderate suction pressure.
In a preferred technical solution of the heat pump type drying system, the refrigerant pipeline includes an exhaust pipe located between the exhaust port and the condenser, the exhaust pipe has a first inner diameter, and the defrosting bypass pipe has a second inner diameter, wherein the first inner diameter is larger than the second inner diameter. The first inner diameter of the exhaust pipe is set to be larger than the second inner diameter of the defrosting bypass pipe, so that the resistance of the high-temperature and high-pressure gaseous refrigerant discharged from the exhaust port of the compressor when flowing in the exhaust pipe is smaller than the resistance of the high-temperature and high-pressure gaseous refrigerant when flowing in the defrosting bypass pipe, and the distribution proportion of the high-temperature and high-pressure gaseous refrigerant between the exhaust pipe and the defrosting bypass pipe can be conveniently adjusted by adjusting the opening of the expansion device.
In order to solve the technical problem that in the prior art, when the heat pump type drying system is defrosted under the low-temperature working condition, the compressor is frequently started and stopped due to too small suction pressure, the invention also provides a defrosting method for the heat pump type drying system, which is executed in the heat pump type drying system according to any one of the above, and comprises the following steps:
When the condition that the heat pump type drying system enters the defrosting mode is satisfied, the first electromagnetic valve and the second electromagnetic valve of the heat pump type drying system are controlled to be closed, and the third electromagnetic valve is controlled to be opened. When the condition that the heat pump type drying system enters the defrosting mode is satisfied, by controlling the first electromagnetic valve and the second electromagnetic valve to be closed and controlling the third electromagnetic valve to be opened, the high-temperature and high-pressure gaseous refrigerant discharged from the exhaust port of the compressor can flow into the bottom coil through the defrosting bypass pipe so as to defrost the bottom coil. In addition, through the capillary pipeline arranged on the defrosting bypass pipe, partial refrigerant used for defrosting the bottom coil pipe can be converted into low-temperature low-pressure gas refrigerant, so that the compressor is ensured to have moderate suction pressure, and the compressor is prevented from being frequently started and stopped.
The defrosting method for a heat pump type drying system as described above, the defrosting method further comprising:
Detecting the temperature of the external environment;
Comparing the measured temperature of the external environment with a preset temperature;
Detecting a coil temperature of an evaporator of the heat pump type drying system when the temperature of the external environment is less than the preset temperature, and determining a difference value of the temperature of the external environment minus the coil temperature;
Comparing the difference value with a first preset difference value;
And when the difference value is greater than or equal to the first preset difference value, the condition for entering the defrosting mode is satisfied. When the temperature of the external environment is less than the preset temperature, the temperature of the external environment is lower, and the evaporator is at risk of frosting. Accordingly, the coil temperature of the evaporator of the heat pump drying system is detected and a difference of the outside ambient temperature minus the coil temperature is determined. When the difference is greater than or equal to the first preset difference, the condition that the temperature of the coil is lower, the possibility of frosting of the evaporator is higher, and the condition of entering the defrosting mode is satisfied is indicated.
In the defrosting method for a heat pump type drying system, when the first solenoid valve and the second solenoid valve of the heat pump type drying system are controlled to be closed and the third solenoid valve is controlled to be opened, the defrosting method comprises:
Re-detecting the temperature of the external environment and the temperature of the coil after a first preset period of time;
determining a current temperature of the external environment minus the coil temperature;
comparing the current difference value with the first preset difference value and the second preset difference value;
adjusting the opening degree of an expansion device of the heat pump type drying system based on the comparison result,
Wherein the second preset difference is smaller than the first preset difference. Through the arrangement, the distribution proportion of the refrigerant between the refrigeration main loop and the defrosting bypass pipe can be accurately controlled, and the use efficiency of the refrigerant is improved.
In the defrosting method for the heat pump type drying system, when the current difference is greater than the second preset difference and smaller than the first preset difference, the current opening degree of the expansion device is maintained. When the current difference is larger than the second preset difference and smaller than the first preset difference, the temperature of the external environment and the coil temperature of the evaporator have moderate differences, so that the current opening degree of the expansion device is kept.
In the defrosting method for the heat pump type drying system, when the current difference is larger than the second preset difference and smaller than the first preset difference, the expansion device is controlled to reduce the first opening. When the current difference is larger than the second preset difference and smaller than the first preset difference, the temperature of the external environment and the temperature of the coil pipe of the evaporator are moderately different, so that the expansion device can be controlled to properly reduce the first opening degree to ensure the heating efficiency.
In the defrosting method for the heat pump type drying system, when the current difference value is larger than or equal to the first preset difference value, the expansion device is controlled to reduce a second opening, wherein the second opening is larger than the first opening. When the current difference value is greater than or equal to the first preset difference value, the difference value between the temperature of the external environment and the coil temperature of the evaporator is larger, namely the coil temperature of the evaporator is lower, and the evaporator has larger frosting risk, so that the expansion device is controlled to reduce the second opening degree, and more refrigerant flows to the defrosting bypass pipe so as to defrost the evaporator better.
In the defrosting method for the heat pump type drying system, when the current difference value is smaller than or equal to the second preset difference value and is kept for a second preset time period, the current opening of the expansion device is kept, the third electromagnetic valve is controlled to be closed, and the first electromagnetic valve and the second electromagnetic valve are controlled to be opened. When the current difference is smaller than or equal to the second preset difference and is maintained for a second preset period of time, the coil temperature of the evaporator is higher, and the possibility of frosting of the evaporator is smaller. Therefore, the current opening degree of the expansion device is kept, the third electromagnetic valve is controlled to be closed, and the first electromagnetic valve and the second electromagnetic valve are controlled to be opened, so that the liquid refrigerant passing through the expansion device can flow into the bottom coil pipe to participate in the circulation of the refrigeration main loop, and the utilization efficiency of the refrigerant is ensured.
Drawings
Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:
Fig. 1 is a schematic diagram of a refrigeration circuit embodiment of a heat pump drying system according to the present invention;
Fig. 2 is a schematic structural view of an embodiment of an evaporator of the heat pump type drying system of the present invention;
FIG. 3 is a schematic view of a first refrigerant flow path of an embodiment of a bottom coil of the heat pump drying system of the present invention;
FIG. 4 is a schematic diagram of a second refrigerant flow path of an embodiment of a bottom coil of the heat pump drying system of the present invention;
FIG. 5 is a flow chart of a defrost method for a heat pump drying system according to the present invention;
FIG. 6 is a flow chart of a first embodiment of a defrost method for a heat pump drying system according to the present invention;
Fig. 7 is a flow chart illustrating a defrosting method for a heat pump type drying system according to a second embodiment of the present invention.
List of reference numerals:
1. A heat pump type drying system; 10. a refrigeration main circuit; 11. a compressor; 11a, a first compressor; 11b, a second compressor; 111. an exhaust port; 112. an air suction port; 12. a condenser; 13. an expansion device; 13a, a first expansion device; 13b, a second expansion device; 14. an evaporator; 141. a bottom coil; 1411. an inlet end; 1412. an outlet end; 1413. a first flow path; 1414. a second flow path; 1415. a third flow path; 1416. a fourth flow path; 142. a coiled pipe; 15. a refrigerant pipe; 151. an exhaust pipe; 152. a high-pressure liquid pipe; 153. a low pressure liquid pipe; 154. an air suction pipe; 16. a first electromagnetic valve; 17. a second electromagnetic valve; 20. a defrost bypass line; 21. a first end; 22. a second end; 23. a third electromagnetic valve; 30. a capillary line.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that, in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," "outer," and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Furthermore, it should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected, can be indirectly connected through an intermediate medium, and can also be communicated with the inside of two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
The invention provides a heat pump type drying system 1, which aims to solve the technical problem that in the prior art, a compressor is frequently started and stopped due to too small suction pressure when a heat pump type drying system is defrosted under a low-temperature working condition. The heat pump type drying system 1 includes: a refrigeration main circuit 10, the refrigeration main circuit 10 comprising a compressor 11, a condenser 12, an expansion device 13 and an evaporator 14 which are connected in sequence by a refrigerant pipe 15, a bottom coil 141 being provided at the bottom of the evaporator 14, the bottom coil 141 having an inlet end 1411 connected to the expansion device 13 and an outlet end 1412 connected to the suction port 112 of the compressor 11, and a first electromagnetic valve 16 being provided between the inlet end 1411 and the expansion device 13 to be openable and closable, and a second electromagnetic valve 17 being provided in the bottom coil 141 to be openable and closable; a defrost bypass pipe 20, the defrost bypass pipe 20 having a first end 21 connected to a discharge port 1111 of the compressor 11 and a second end 22 connected to an inlet port 1411, a third solenoid valve 23 being provided on the defrost bypass pipe 20 to be opened and closed; and a capillary line 30, the capillary line 30 being configured to be disposed in the bottom coil 141 in parallel with the second solenoid valve 17, the first solenoid valve 16 and the second solenoid valve 17 being in a closed state and the third solenoid valve 23 being in an open state when the heat pump type drying system 1 enters the defrost mode.
Fig. 1 is a schematic structural view of an embodiment of a refrigeration circuit of a heat pump type drying system of the present invention. As shown in fig. 1, in one or more embodiments, the heat pump type drying system 1 of the present invention includes a refrigeration main circuit 10, a defrost bypass 20, and a capillary line 30, among other components. In one or more embodiments, the heat pump drying system 1 is configured to deliver drying air into a curing barn (not shown) for holding tobacco, thereby adjusting the temperature and humidity in the curing barn for drying the tobacco. Alternatively, the heat pump type drying system 1 may be configured to deliver drying air into other predetermined spaces according to actual needs.
As shown in fig. 1, the refrigeration main circuit 10 includes a compressor 11, a condenser 12, an expansion device 13, and an evaporator 14, which are sequentially connected through a refrigerant line 15 to form a circuit allowing a refrigerant to circulate therein. The refrigerant includes, but is not limited to, R410a, R32a, etc. In one or more embodiments, the compressor 11 includes a first compressor 11a and a second compressor 11b connected in parallel with each other. Each of the first compressor 11a and the second compressor 11b is a fixed-frequency compressor to reduce component costs. The first compressor 11a and the second compressor 11b may be alternately started and stopped. That is, when one of the first compressor 11a and the second compressor 11b is turned on, the other of the first compressor 11a and the second compressor 11b is turned off. Through the arrangement, the frequent start and stop of a single constant-frequency compressor can be effectively avoided, and the service life of the compressor is prolonged. In addition, when the heating demand is large, the first compressor 11a and the second compressor 11b can also be turned on simultaneously to provide a large heating amount in a short time. Alternatively, each of the first compressor 11a and the second compressor 11b may be a variable frequency compressor, or one of the first compressor 11a and the second compressor 11b may be a fixed frequency compressor, and the other may be a variable frequency compressor. The first compressor 11a and the second compressor 11b may be a piston compressor, a screw compressor, a turbo compressor, or the like. Alternatively, the number of compressors 11 may be set to other suitable numbers greater or less than 2, such as 1,3, etc.
With continued reference to fig. 1, the first compressor 11b has a discharge port 111 and a suction port 112. The exhaust port 111 communicates with an inlet end (not shown) of the condenser 12 through an exhaust pipe 151. The exhaust pipe 151 has a first inner diameter. The first inner diameter is 12.7mm. Alternatively, the first inner diameter may be set to other suitable values greater or less than 12.7mm. The condenser 12 includes, but is not limited to, a fin coil heat exchanger and a plate heat exchanger, and is provided with a corresponding fan. The outlet end (not shown) of the condenser 12 communicates with the corresponding expansion device 13 (i.e. the first expansion device 13 a) via a high pressure liquid pipe 152. The first expansion device 13a may be, but is not limited to, an electronic expansion valve, a thermal expansion valve, or the like. The first expansion device 13a communicates with the evaporator 14 through a low pressure liquid pipe 153. The evaporator 14 communicates with the suction port 112 of the first compressor 11a through a suction pipe 154. The first compressor 11a, the condenser 12, the first expansion device 13a and the evaporator 14 together form a refrigeration circuit. In addition, the second compressor 11b, the condenser 12, the second expansion device 13b, and the evaporator 14 together form another refrigeration circuit independent of the above refrigeration circuit.
Fig. 2 is a schematic structural view of an embodiment of an evaporator of the heat pump type drying system of the present invention. In one or more embodiments, as shown in fig. 2, the evaporator 14 is a fin coil heat exchanger. The evaporator 14 has a plurality of coils 142 spaced apart from one another. Each coil 142 has an inlet (not shown) in communication with the first expansion device 13a via a distribution pipe or other distribution device (not shown) and an outlet (not shown) in communication with the suction port 112 of the first compressor 11a via a header (not shown). At the bottom of the evaporator 14 is a bottom coil 141. The bottom coil 141 has opposite inlet and outlet ends 1411, 1412. Wherein the inlet 1411 communicates with the first expansion device 13a and the outlet 1412 communicates with the suction port 112 of the first compressor 11 a. A first solenoid valve 16, which is openable and closable, is also provided between the inlet end 1411 and the first expansion device 13a, and a second solenoid valve 17, which is openable and closable, is also provided in the bottom coil 141. It will be appreciated that when the first solenoid valve 16 and the second solenoid valve 17 are simultaneously opened, the low pressure liquid refrigerant expanded and depressurized by the first expansion device 13a can flow from the inlet port 1411 into the bottom coil 141 and evaporate into a low temperature and low pressure gaseous refrigerant in the bottom coil 141. At this point, the bottom coil 141 functions the same as any of the other coils 142 in the evaporator 14.
In one or more embodiments, as shown in FIG. 1, the defrost bypass 20 has opposite first and second ends 21, 22. Wherein the first end 21 communicates with the discharge port 111 of the first compressor 11 a. In one or more embodiments, the first end 21 is positioned on the discharge line 151 between the first compressor 11a and the condenser 12. The second end 22 communicates with the inlet end 1411 of the bottom coil 141 of the evaporator 14. The defrost bypass pipe 20 is further provided with a third solenoid valve 23 which can be opened and closed. That is, the third solenoid valve 23 is located between the first end 21 and the second end 22. It will be appreciated that when the third solenoid valve 23 is opened, a portion of the high temperature, high pressure gaseous refrigerant discharged from the discharge port 111 of the first compressor 11a may flow from the first end 21 into the defrost bypass tube 20 and into the bottom coil 141 to defrost it. The defrost bypass duct 20 has a second inner diameter, and the second inner diameter is smaller than the first inner diameter of the discharge duct 151. The second inner diameter includes, but is not limited to, 9.52mm, 7mm, etc. With the above arrangement, when the third solenoid valve 23 is opened, the distribution ratio of the refrigerant between the refrigeration main circuit 10 and the defrost bypass pipe 20 can be conveniently controlled by adjusting the opening degree of the first solenoid valve 13 a.
As shown in fig. 1, the capillary line 30 is disposed in the bottom coil 141 and is connected in parallel with the second solenoid valve 17. FIG. 3 is a schematic view of a first refrigerant flow path of an embodiment of a bottom coil of the heat pump drying system of the present invention; fig. 4 is a schematic diagram of a second refrigerant flow path of an embodiment of a bottom coil of the heat pump drying system of the present invention. As shown in fig. 3 and 4, in one or more embodiments, the bottom coil 141 has a first flow path 1413, a second flow path 1414, a third flow path 1415, and a fourth flow path 1416 that are connected end to end in order to form a serpentine coil. The end of the first flow path 1413 is the inlet end 1411 of the bottom coil 141 and the end of the fourth flow path 1416 is the outlet end 1412 of the bottom coil 141. The capillary line 30 and the second electromagnetic valve 17 are arranged in parallel with each other between the second flow path 1414 and the third flow path 1415. It should be noted that when the heat pump type drying system 1 of the present invention does not require defrosting, the first solenoid valve 16 and the second solenoid valve 17 are opened, and the third solenoid valve 23 is closed, and the refrigerant flows in the direction indicated by the arrow in fig. 3. As described above, the bottom coil 141 evaporates the liquid refrigerant sent from the first expansion device 13a into a low-temperature low-pressure gas refrigerant together with the other coils 142 in the evaporator 14. When the heat pump type drying system 1 of the present invention needs to defrost, the first and second solenoid valves 16 and 17 are closed, and the third solenoid valve 23 is opened, and the refrigerant flows in the direction indicated by the arrow in fig. 1 and 4. Since the first solenoid valve 16 is closed, the liquid refrigerant expanded and depressurized by the first expansion device 13a cannot enter the bottom coil 141. Accordingly, since the third solenoid valve 23 is opened, a portion of the high-temperature and high-pressure gas refrigerant discharged from the discharge port 111 of the first compressor 11a can enter the bottom coil 141 along the defrost bypass pipe 20. Then, the high-temperature and high-pressure gaseous refrigerant flows through the first flow path 1413 and the second flow path 1414 in this order, thereby heating and defrosting the bottom coil 141. In this process, the high temperature and high pressure gaseous refrigerant condenses into a low temperature and high pressure liquid refrigerant. Then, the portion of the low-temperature high-pressure liquid refrigerant flows to the capillary tube 30 due to the blocking by the second electromagnetic valve 17, and expands and reduces the pressure in the capillary tube 30 into the low-temperature low-pressure liquid refrigerant. This part of the low-temperature low-pressure liquid refrigerant evaporates into a low-temperature low-pressure gas refrigerant in the third flow path 1415 and the fourth flow path 1416, and is then sucked again into the suction port 112 by the first compressor 11a, and enters the next refrigeration cycle.
Next, the defrosting method for the heat pump type drying system 1 according to the present invention will be described in detail with reference to the above-described embodiments of the heat pump type drying system 1.
Fig. 5 is a flow chart illustrating a defrosting method for a heat pump type drying system according to the present invention. As shown in fig. 5, when the condition for the heat pump type drying system 1 of the present invention to enter the defrost mode is satisfied, the first solenoid valve 16 and the second solenoid valve 17 of the heat pump type drying system 1 are controlled to be closed, and the third solenoid valve 23 is controlled to be opened (step S1). With the above arrangement, when the condition for entering the defrost mode is satisfied, a part of the high-temperature and high-pressure gaseous refrigerant discharged from the discharge port 111 of the compressor 11 can be transferred to the bottom coil 141 of the evaporator 14 through the defrost bypass pipe to defrost. In addition, the liquid refrigerant condensed in the bottom coil 141 can be expanded and decompressed through the capillary tube 30 and then continuously evaporated into a low-temperature low-pressure gaseous refrigerant, so that the compressor 11 is ensured to have enough suction pressure, and frequent start and stop caused by insufficient suction pressure are prevented.
Fig. 6 is a flow chart illustrating a first embodiment of a defrosting method for a heat pump type drying system according to the present invention. As shown in fig. 6, in one or more embodiments, after the defrosting method for the heat pump type drying system 1 of the present invention is started, step S10 is first performed, i.e., the temperature of the external environment is detected. The temperature of the external environment may be detected by a temperature sensor arranged in the external environment. Next, step S11 is executed to determine whether the temperature of the external environment is less than a preset temperature. In one or more embodiments, the preset temperature is 3 ℃ (degrees celsius). Alternatively, the preset temperature may be set to other suitable temperatures higher or lower than 3 ℃, for example, 2 ℃,4 ℃, etc. When the determination result is no, it is indicated that the temperature of the external environment is high at this time, and the possibility of frosting of the evaporator 14 is small. Therefore, the step S10 is repeatedly executed, and the temperature of the external environment is continuously detected. When the determination result is yes, it is indicated that the temperature of the external environment is low, and there is a possibility of frosting of the evaporator 14. But whether the evaporator 14 is frosted or has a high probability of frosting, further detection of the temperature of the coil of the evaporator 14 is required to determine. Accordingly, the defrosting method proceeds to step S12 of detecting the coil temperature of the evaporator 14 of the heat pump type drying system 1 and determining the difference of the outside environment temperature minus the coil temperature. The coil temperature of the evaporator 14 may be measured by a temperature sensor disposed on the evaporator 14. The type, number and arrangement position of the temperature sensors can be adjusted according to actual needs. Next, the defrosting method proceeds to step S13, and it is determined whether the difference is equal to or greater than a first preset difference. In one or more embodiments, the first predetermined difference is 3 ℃. Alternatively, the first preset difference may also be set to other suitable temperatures higher or lower than 3 ℃, e.g. 2 ℃,4 ℃, etc. If the determination result is yes, it is indicated that the temperature of the external environment is low, but the coil temperature is still high, and the possibility of frosting of the evaporator 14 is small, so that the step S10 is repeatedly executed, and the temperature of the external environment is continuously detected. When the determination is negative, it indicates that the temperature of the external environment is low and the coil temperature is also low, and the evaporator 14 is more likely to frost. Therefore, step S14 of controlling the first solenoid valve 16 and the second solenoid valve 17 of the heat pump type drying system 1 to be closed and controlling the third solenoid valve to be opened 23 is performed, thereby defrosting the evaporator 14.
With continued reference to fig. 6, after step S14 is completed, the defrost method proceeds to step S15, where after a first preset period of time, the temperature of the external environment and the coil temperature are re-detected. In one or more embodiments, the first preset time period is 5s (seconds). Alternatively, the first preset time period may be set to other suitable times longer or shorter than 5s, for example, 4s, 6s, etc. Next, step S16 is performed to determine the difference between the current external environment temperature minus the coil temperature. Then, it is determined whether the current difference is equal to or greater than a first preset difference (step S17). If the determination is yes, it is indicated that the coil temperature is still low, step S18 is performed to control the expansion device 13 to decrease the second opening degree. It is noted that the "expansion device 13" referred to herein refers only to the first expansion device 13a in the same refrigeration circuit as the defrost bypass line 20, and does not include the second expansion device 13b in a different refrigeration circuit than the defrost bypass line 20. In one or more embodiments, the second opening is 50 steps. Alternatively, the second opening degree may be set to other suitable step numbers larger or smaller than 50 steps. By decreasing the expansion device by the second opening degree, the amount of refrigerant flowing into the defrost bypass pipe 20 can be increased accordingly, thereby improving defrost efficiency. After the step S18 is completed, the defrosting method repeatedly performs the step S15, that is, the temperature of the external environment and the temperature of the coil are re-detected after the first preset period of time.
With continued reference to fig. 6, after step S17 is performed, when the determination result is no, step S19 is performed, i.e., whether the current difference is greater than the second preset difference and less than the first preset difference is determined. In one or more embodiments, the second preset difference is 0 ℃. Alternatively, the second preset difference may also be set to other suitable values higher or lower than 0 ℃, for example 0.5 ℃, -1 ℃ and the like. When the determination is yes, indicating that the coil temperature has started to decrease at this time, step S20 is performed, i.e., the current opening degree of the expansion device 13 is maintained, so as to continue defrosting the evaporator 14. After the step S20 is performed, the defrosting method repeatedly performs the step S15, that is, the temperature of the external environment and the coil temperature are re-detected after the first preset period of time.
With continued reference to fig. 6, after step S19 is performed, when the determination result is no, it is indicated that the current difference is less than or equal to the second preset difference, and step S21 is performed to obtain the duration. Next, it is determined whether the duration is less than a second preset time period (step S22). In one or more embodiments, the second preset time period is 5 minutes. Alternatively, the second preset time period may be set to other suitable times longer or shorter than 5 minutes. When the result of the interpretation is yes, step S20 is performed, i.e., the current opening degree of the expansion device 13 is maintained. After step S20 is completed, step S15 is repeatedly performed, that is, after the first preset period of time has elapsed, the temperature of the external environment and the temperature of the coil are re-detected. When the judgment result is no, the coil temperature is higher and the duration time is longer, the current opening degree of the expansion device 13 is kept, the third electromagnetic valve 23 is controlled to be closed, and the first electromagnetic valve 16 and the second electromagnetic valve 17 are controlled to be opened. When step S23 is completed, the defrosting process is ended.
Fig. 7 is a flow chart illustrating a defrosting method for a heat pump type drying system according to a second embodiment of the present invention. As shown in fig. 7, in one or more embodiments, in the defrosting method for the heat pump type drying system 1 of the present invention, after step S19 is completed, if the result of the determination is yes, step S24 is performed, that is, the expansion device 13 is controlled to reduce the first opening degree, wherein the second opening degree is greater than the first opening degree. In one or more embodiments, the first opening is 5 steps. Alternatively, the first opening degree may be set to other suitable step numbers larger or smaller than 5 steps, for example, 4 steps, 6 steps, or the like. By appropriately reducing the opening degree of the expansion device 13, the amount of refrigerant flowing into the defrost bypass pipe 20 can be appropriately increased, thereby improving the defrost efficiency. It should be noted that the parts not mentioned in the second embodiment may be configured identically to the first embodiment, and will not be described here again.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will fall within the scope of the present invention.
Claims (9)
1. A heat pump type drying system, characterized in that the heat pump type drying system comprises:
The refrigeration main loop comprises a compressor, a condenser, an expansion device and an evaporator which are sequentially connected through a refrigerant pipeline, wherein a bottom coil is arranged at the bottom of the evaporator, the bottom coil is provided with an inlet end connected with the expansion device and an outlet end connected with an air suction port of the compressor, a first electromagnetic valve capable of being opened and closed is arranged between the inlet end and the expansion device, and a second electromagnetic valve capable of being opened and closed is arranged in the bottom coil;
A defrosting bypass pipe, which is provided with a first end connected with the exhaust port of the compressor and a second end connected with the inlet end, and is also provided with a third electromagnetic valve which can be opened and closed; and
A capillary line configured to be disposed in the bottom coil in parallel with the second solenoid valve, and
When the heat pump type drying system enters a defrosting mode, the first electromagnetic valve and the second electromagnetic valve are in a closed state, and the third electromagnetic valve is in an open state,
The bottom coil comprises a first flow path, a second flow path, a third flow path and a fourth flow path which are sequentially connected end to end, the tail ends of the first flow path and the fourth flow path are respectively an inlet end and an outlet end, and the second electromagnetic valve and the capillary pipeline are mutually parallel and arranged between the second flow path and the third flow path.
2. The heat pump drying system of claim 1, wherein the refrigerant line includes an exhaust pipe between the exhaust port and the condenser, the exhaust pipe having a first inner diameter, the defrost bypass pipe having a second inner diameter, wherein the first inner diameter is greater than the second inner diameter.
3. A defrosting method for a heat pump type drying system, characterized in that the defrosting method is performed in a heat pump type drying system according to any one of claims 1-2, comprising:
when the condition that the heat pump type drying system enters the defrosting mode is satisfied, the first electromagnetic valve and the second electromagnetic valve of the heat pump type drying system are controlled to be closed, and the third electromagnetic valve is controlled to be opened.
4. The defrosting method for a heat pump type drying system according to claim 3, characterized in that the defrosting method further comprises:
Detecting the temperature of the external environment;
Comparing the measured temperature of the external environment with a preset temperature;
Detecting a coil temperature of an evaporator of the heat pump type drying system when the temperature of the external environment is less than the preset temperature, and determining a difference value of the temperature of the external environment minus the coil temperature;
Comparing the difference value with a first preset difference value;
And when the difference value is greater than or equal to the first preset difference value, the condition for entering the defrosting mode is satisfied.
5. The defrosting method for a heat pump type drying system according to claim 4, wherein after "controlling the first solenoid valve and the second solenoid valve of the heat pump type drying system to be closed and controlling the third solenoid valve to be opened", the defrosting method comprises:
Re-detecting the temperature of the external environment and the temperature of the coil after a first preset period of time;
determining a current temperature of the external environment minus the coil temperature;
comparing the current difference value with the first preset difference value and the second preset difference value;
adjusting the opening degree of an expansion device of the heat pump type drying system based on the comparison result,
Wherein the second preset difference is smaller than the first preset difference.
6. The defrosting method for a heat pump type drying system according to claim 5, wherein,
And when the current difference value is larger than the second preset difference value and smaller than the first preset difference value, maintaining the current opening of the expansion device.
7. The defrosting method for a heat pump type drying system according to claim 5, wherein the expansion device is controlled to decrease the first opening degree when the current difference is greater than the second preset difference and less than the first preset difference.
8. The defrosting method for a heat pump type drying system according to claim 7, wherein when the current difference is equal to or larger than the first preset difference, the expansion device is controlled to decrease a second opening degree, wherein the second opening degree is larger than the first opening degree.
9. The defrosting method for a heat pump type drying system according to claim 5, wherein,
And when the current difference value is smaller than or equal to the second preset difference value and is kept for a second preset time period, keeping the current opening of the expansion device, controlling the third electromagnetic valve to be closed, and controlling the first electromagnetic valve and the second electromagnetic valve to be opened.
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| CN215898848U (en) * | 2021-06-07 | 2022-02-25 | 山东朗进科技股份有限公司 | Air source heat pump drying unit and tobacco flue-curing house |
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