Control method for a drying system and drying system

Abstract

The present application relates to a control method for a drying system and the drying system. The drying system comprises an interconnected compressor, a three-way valve, a four-way valve, a one-way electromagnetic valve, an indoor heat exchanger and an outdoor heat exchanger. The control method comprises: after the compressor is stopped, a preset downtime of the compressor is obtained; the preset downtime is compared with a downtime threshold; when the preset downtime is greater than or equal to the downtime threshold, a first outlet is controlled to be opened, a second outlet is controlled to be closed, and the four-way valve is controlled to allow the drying system to enter a refrigeration mode; and when the preset downtime is less than the downtime threshold, the first outlet is controlled to be closed, the second outlet is controlled to be opened, so that the refrigerant in the indoor heat exchanger is blocked by the one-way electromagnetic valve and cannot flow back to the compressor. The control method can avoid the liquid refrigerant in the indoor heat exchanger flowing back to the exhaust port of the compressor, and improve the service life of the compressor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air conditioning, in particular to a control method for a drying system and the drying system. BACKGROUND

[0002] The drying system refers to a combination of equipment for drying treatment of materials with high water content by using heat energy. According to the form of heat energy generation, the drying system can be divided into electric heating type, gas type, oil type, coal type, heat pump type and other types. Compared with the traditional fuel type drying system, the heat pump type drying system has the advantages of energy saving, high efficiency, environmental friendliness and low operation cost, and is widely used in tobacco processing, grain storage, metallurgy and chemical industry and many other fields.

[0003] The heat pump type drying system usually includes components such as compressor, condenser, expansion device and evaporator connected in sequence by refrigerant pipeline to form a refrigeration circuit allowing refrigerant (such as R34a, etc.) to circulate therein. According to the different dehumidification modes, the heat pump type drying system can be divided into open type drying system and closed type drying system. Among them, the open type drying system is provided with a new air inlet and a dehumidification outlet in the heating chamber, and when dehumidifying, the new air of the external environment enters the drying room from the new air inlet and drives the hot and humid air in the drying room to be discharged from the dehumidification outlet. The closed type drying system is provided with a special dehumidification component in the heating chamber (without opening the new air inlet and the dehumidification outlet), and when dehumidifying, the hot and humid air flows through the dehumidification component to condense and dehumidify.

[0004] Whether it is an open type drying system or a closed type drying system, the compressor (mostly a fixed frequency compressor) exists the phenomenon of frequent start and stop during the whole drying process. Taking tobacco drying as an example, the compressor needs to be started and stopped more than 1000 times during the drying process of about 7 days. Since the condenser (also known as "indoor heat exchanger") in the heating chamber is arranged at a high position, there is a large height difference between it and the compressor. In addition, the exhaust pipe between the compressor and the indoor heat exchanger is also relatively thick. Therefore, when the compressor stops, the liquid refrigerant in the condenser is easily returned to the exhaust port of the compressor along the exhaust pipe under the action of its own gravity, which causes the compressor to need a very large torque to start normally when it starts again, which will inevitably cause damage to the compressor.

[0005] Therefore, there is a need in the art for a new technical solution to solve the above problems. SUMMARY

[0006] To solve the technical problem of compressor exhaust port backflow of liquid in the prior art, the present application provides a control method for a drying system. The drying system comprises a compressor, a three-way valve, a four-way valve, a one-way electromagnetic valve, an indoor heat exchanger and an outdoor heat exchanger connected with each other, wherein the indoor heat exchanger is located higher than the compressor, the outdoor heat exchanger is located flush with the compressor, and during the heating of the drying system, the control method comprises: after the compressor is stopped, obtaining a preset stop time of the compressor; comparing the preset stop time with a stop time threshold; when the preset stop time is greater than or equal to the stop time threshold, controlling the first outlet of the three-way valve to open, controlling the second outlet of the three-way valve to close, and controlling the four-way valve to allow the drying system to enter a cooling mode; and when the preset stop time is less than the stop time threshold, controlling the first outlet to close and the second outlet to open, so that the refrigerant in the indoor heat exchanger is blocked by the one-way electromagnetic valve and cannot flow back to the compressor.

[0007] As can be understood by those skilled in the art, in the control method for the drying system of the present application, the drying system comprises a compressor, a three-way valve, a four-way valve, a one-way electromagnetic valve, an indoor heat exchanger and an outdoor heat exchanger connected with each other. The indoor heat exchanger is located higher than the compressor in the height direction, and the outdoor heat exchanger is located flush with the compressor in the height direction. During the heating of the drying system, the control method for the drying system of the present application comprises the following steps: after the compressor is stopped, obtaining a preset stop time of the compressor; then, comparing the preset stop time with a stop time threshold. When the preset stop time is greater than or equal to the stop time threshold, it indicates that the compressor has been stopped for a long time, and the liquid refrigerant in the indoor heat exchanger is easy to flow back to the exhaust port of the compressor under the action of its own gravity, so the first outlet of the three-way valve is controlled to open, the second outlet of the three-way valve is controlled to close, and the four-way valve is controlled to allow the drying system to enter a cooling mode. In other words, the four-way valve is switched from a state satisfying the heating mode to a state satisfying the cooling mode. In this way, the indoor heat exchanger originally serving as a condenser is converted into an evaporator, and the outdoor heat exchanger originally serving as an evaporator is converted into a condenser. Since the outdoor heat exchanger is flush with the compressor, there is no obvious height difference between the two, and thus the above-mentioned arrangement can prevent the liquid refrigerant from flowing back to the exhaust port of the compressor. In addition, when the preset stop time is less than the stop time threshold, it indicates that the compressor has been stopped for a short time, so the first outlet of the three-way valve is controlled to close and the second outlet of the three-way valve is controlled to open, so that the liquid refrigerant in the indoor heat exchanger is blocked by the one-way electromagnetic valve and cannot flow back to the exhaust port of the compressor. Further, the above-mentioned arrangement can also prevent the four-way valve from being damaged due to frequent switching in a short time, thereby prolonging the service life of the components.

[0008] In the preferred technical solution of the control method for the drying system, when the preset shutdown time length is greater than or equal to the shutdown time length threshold, the control method further comprises: when the start-up condition of the compressor is met, controlling the compressor to start up so that the drying system enters the refrigeration mode; detecting the exhaust pressure of the compressor; comparing the exhaust pressure with an exhaust pressure threshold; when the exhaust pressure is greater than or equal to the exhaust pressure threshold, controlling the four-way valve so that the drying system switches to the heating mode. Through the above setting, the compressor can have a larger exhaust pressure before switching to the heating mode, thereby ensuring the smooth operation of the drying system.

[0009] In the preferred technical solution of the control method for the drying system, the exhaust pressure threshold ranges from 1.5 MPa to 2 MPa. Through the above setting, the exhaust pressure threshold has a moderate numerical range.

[0010] In the preferred technical solution of the control method for the drying system, the one-way electromagnetic valve is configured to have a one-way cut-off function when powered off and an open pipeline function when powered on. Through the above setting, the one-way electromagnetic valve has both the one-way cut-off and open pipeline functions to meet the design needs under different working conditions.

[0011] In the preferred technical solution of the control method for the drying system, when the preset shutdown time length is less than the shutdown time length threshold, the control method further comprises: when the compressor is in a shutdown state, controlling the one-way electromagnetic valve to be powered off, so that the refrigerant in the indoor heat exchanger cannot flow back to the compressor through the one-way electromagnetic valve. When the preset shutdown time length is less than the shutdown time length threshold, the one-way electromagnetic valve is controlled to be powered off in the compressor shutdown state, so that the refrigerant in the indoor heat exchanger is blocked by the one-way electromagnetic valve and cannot flow back to the compressor, thereby avoiding the liquid return at the exhaust port of the compressor.

[0012] In the preferred technical solution of the control method for the drying system, the control method further comprises: when the start-up condition of the compressor is met, controlling the compressor to start up; after a preset time period, controlling the one-way electromagnetic valve to be powered on, so that the refrigerant discharged from the compressor can flow to the indoor heat exchanger through the one-way electromagnetic valve. After the compressor is started up, the one-way electromagnetic valve is controlled to be powered on to open the pipeline between the compressor and the indoor heat exchanger, thereby reducing the resistance of the refrigerant passing through the one-way electromagnetic valve and improving the operating efficiency of the compressor. In addition, the one-way electromagnetic valve is controlled to be powered on after a preset time period after the compressor is started up, so that the compressor has a higher exhaust pressure, thereby ensuring the smooth operation of the drying system.

[0013] In the preferred technical scheme of the control method for the drying system, the one-way electromagnetic valve comprises a housing, a valve seat arranged in the housing, a valve hole being provided on the valve seat to allow the refrigerant to pass therethrough, a valve body having a closed position abutting on the valve seat to seal the valve hole and an open position away from the valve seat to open the valve hole, an electromagnetic coil configured to attract the valve body when energized so that the valve body moves from the closed position to the open position, and a reset member connected with the housing and the valve body respectively and capable of causing the valve body to reset from the open position to the closed position when the electromagnetic coil is de-energized. With the above arrangement, the one-way electromagnetic valve has a simple structure and is easy to process.

[0014] In the preferred technical scheme of the control method for the drying system, the preset time period ranges from 1s to 2s. With the above arrangement, the preset time period has an appropriate numerical range.

[0015] In the preferred technical scheme of the control method for the drying system, the shutdown duration threshold ranges from 8min to 12min. With the above arrangement, the shutdown duration threshold has an appropriate numerical range.

[0016] To solve the technical problem of the compressor exhaust port backflow of liquid in the prior art, the present application provides a drying system. The control method for the drying system according to any one of the above is performed in the drying system. By adopting the control method for the drying system according to any one of the above, the drying system of the present application can avoid the liquid refrigerant of the indoor heat exchanger flowing back to the exhaust port of the compressor, thereby improving the service life of the compressor. BRIEF DESCRIPTION OF DRAWINGS

[0017] The preferred embodiments of the present application will be described below with reference to the accompanying drawings, in which:

[0018] Figure 1 is a structural schematic diagram of an embodiment of the drying system of the present application;

[0019] Figure 2 is a structural schematic diagram of an embodiment of the heat pump system of the drying system of the present application;

[0020] Figure 3 is a first structural schematic diagram of an embodiment of the one-way electromagnetic valve of the drying system of the present application;

[0021] Figure 4 is a second structural schematic diagram of an embodiment of the one-way electromagnetic valve of the drying system of the present application;

[0022] Figure 5 is a flow schematic diagram of the control method for the drying system of the present application;

[0023] Figure 6 is a flowchart of an embodiment of the control method for the drying system of the present application.

[0024] List of reference signs:

[0025] 100, drying system; 110, curing barn; 111, first temperature sensor; 120, inner machine chamber; 121, air inlet; 122, air outlet; 123, auxiliary heater; 130, outer machine chamber; 131, second temperature sensor; 132, containing space; 140, heat pump system; 141, compressor; 141a, exhaust port; 141b, suction port; 142, four-way valve; 142a, first port; 142b, second port; 142c, third port; 142d, fourth port; 143, indoor heat exchanger; 144, expansion device; 145, outdoor heat exchanger; 146, refrigerant pipeline; 147, three-way valve; 147a, inlet; 147b, first outlet; 147c, second outlet; 148, one-way electromagnetic valve; 481, housing; 481a, inlet end; 481b, outlet end; 482, valve seat; 4821, valve hole; 483, valve body; 484, electromagnetic coil; 485, reset member; 149, gas-liquid separator. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that the embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0027] It should be noted that, in the description of the present application, the terms "first", "second" are only for the purpose of description, and should not be understood as indicating or implying relative importance. The terms "mounting", "setting", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0028] In order to solve the technical problem of compressor exhaust backflow in the prior art drying system, the present application provides a control method for a drying system 100. The drying system 100 comprises an interconnected compressor 141, a three-way valve 147, a four-way valve 142, a one-way electromagnetic valve 148, an indoor heat exchanger 143 and an outdoor heat exchanger 145, wherein the indoor heat exchanger 143 is located higher than the compressor 141, the outdoor heat exchanger 145 is located flush with the compressor 141, and during the heating of the drying system 100, the control method comprises: after the compressor 141 is stopped, a preset stop time of the compressor 141 is obtained (step S1); the preset stop time is compared with a stop time threshold (step S2); when the preset stop time is greater than or equal to the stop time threshold, the first outlet 147b of the three-way valve 147 is opened, the second outlet 147c of the three-way valve 147 is closed, and the four-way valve 142 is controlled to allow the drying system 100 to enter a cooling mode (step S3); and when the preset stop time is less than the stop time threshold, the first outlet 147b is closed and the second outlet 147c is opened, so that the refrigerant in the indoor heat exchanger 143 is blocked by the one-way electromagnetic valve 148 and cannot flow back to the compressor 141 (step S4).

[0029] Figure 1 is a structural schematic diagram of an embodiment of the drying system of the present application. As shown in Figure 1 In one or more embodiments, the drying system 100 of the present application is a one-piece drying system. Alternatively, the drying system 100 can also be an open drying system, a closed drying system or other suitable drying system, etc. The drying system comprises a drying room 110, an indoor unit chamber 120, an outdoor unit chamber 130 and a heat pump system 140. The drying room 110 encloses a space for placing the articles to be dried. The articles to be dried can be, but are not limited to, tobacco, grains, medicinal materials, etc. A first temperature sensor 111 is arranged in the drying room 110 to detect the dry-bulb temperature and the wet-bulb temperature of the drying room 110, thereby providing a data basis for controlling the drying system 100. The first temperature sensor 111 can be a thermal resistance sensor, a thermal couple sensor or other suitable sensor. The number and arrangement position of the first temperature sensor 111 can also be adjusted according to actual needs to more accurately obtain the real-time temperature and humidity of the drying room 110.

[0030] As shown in Figure 1 In one or more embodiments, the indoor unit chamber 120 is arranged adjacent to the drying room 110 to shorten the length of the air duct. An air inlet 121 and an air outlet 122 are arranged on the side wall (not labeled in the figure) of the indoor unit chamber 120 adjacent to the drying room 110, and are spaced apart from each other, so that the indoor unit chamber 120 and the drying room 110 are in air communication. Alternatively, the indoor unit chamber 120 can also be arranged spaced apart from the drying room 110 and connected by an air duct to form air communication. Based on Figure 1As shown, the air inlet 121 is located at the upper part of the indoor unit compartment 120, while the air outlet 122 is located at the lower part of the indoor unit compartment 120. In one or more embodiments, an indoor unit fan (not shown) is provided at the top of the indoor unit compartment 120 near the air inlet 121 to regulate the airflow speed between the indoor unit compartment 120 and the drying oven 110. In one or more embodiments, an auxiliary heater 123 is also provided in the indoor unit compartment 120 between the air inlet 121 and the air outlet 122 to flexibly select the method for heating the drying air delivered to the drying oven 110. In other words, the auxiliary heater 123 can be used alone or shared with the indoor heat exchanger 143 of the heat pump system 140. The auxiliary heater 123 can be, but is not limited to, an electric heater, an infrared heater, an electromagnetic heater, etc.

[0031] like Figure 1 As shown, in one or more embodiments, the outdoor unit compartment 130 and the indoor unit compartment 120 are arranged adjacent to each other, giving the drying system 100 a compact structure and reducing space occupation. A second temperature sensor 131 is provided in the outdoor unit compartment 130 to detect the real-time temperature inside the outdoor unit compartment 130. The second temperature sensor 131 can be a resistance temperature detector (RTD), a thermocouple, or other suitable sensor. The number and arrangement of the second temperature sensors 131 can be adjusted according to actual needs. The outdoor unit compartment 130 encloses a receiving space 132. This receiving space 132 provides suitable space for the compressor 141 of the heat pump system 140, the outdoor heat exchanger 145, and other components. In one or more embodiments, the receiving space 132 is isolated from the external environment. For example, the outdoor unit compartment 130 is a closed glass room made of transparent glass to utilize sunlight from the external environment to heat the receiving space 132. A shading device (not shown) is also provided inside the glass room to block sunlight, so as to adjust the degree of sunlight entering the receiving space 132 according to actual needs. Alternatively, the outdoor unit compartment 130 can also be made of other suitable materials. Suitable insulation materials can also be installed inside the outdoor unit compartment 130 to improve the temperature stability within the housing space 132.

[0032] Figure 2 This is a schematic diagram of the structure of an embodiment of the heat pump system of the drying system of the present invention. Figure 2As shown, in one or more embodiments, the heat pump system 140 includes a compressor 141, a three-way valve 147, a four-way valve 142, a one-way electromagnetic valve 148, an indoor heat exchanger 143, an expansion device 144, and an outdoor heat exchanger 145, etc. The components are connected by refrigerant pipelines 146 to form a refrigeration circuit allowing refrigerant (e.g. R34a, R30a, etc.) to circulate therein. In one or more embodiments, the compressor 141 is a fixed frequency compressor to reduce component cost. Alternatively, the compressor 141 can also be a variable frequency compressor. The compressor 141 can be, but is not limited to, a screw compressor, a piston compressor, a scroll compressor, etc. The compressor 141 has opposite discharge port 141a and suction port 141b. The three-way valve 147 has an inlet 147a, a first outlet 147b, and a second outlet 147c. The four-way valve 142 has a first port 142a, a second port 142b, a third port 142c, and a fourth port 142d. The one-way electromagnetic valve 148 has an inlet end 481a and an outlet end 481b. The inlet 147a of the three-way valve 147 is connected to the discharge port 141a of the compressor 141, the first outlet 147b of the three-way valve 147 is connected to the first port 142a of the four-way valve 142, and the second outlet 147c of the three-way valve 147 is connected to the inlet end 481a of the one-way electromagnetic valve 148. The second port 142b of the four-way valve 142 is connected to the suction port 141b of the compressor 141, the third port 142c of the four-way valve 142 is connected to the indoor heat exchanger 143, and the fourth port 142d of the four-way valve 142 is connected to the outdoor heat exchanger 145. The outlet end 481b of the one-way electromagnetic valve 148 is connected to the indoor heat exchanger 143. The expansion device 144 is arranged between the indoor heat exchanger 143 and the outdoor heat exchanger 145. In one or more embodiments, the heat pump system 140 further includes a gas-liquid separator 149. The gas-liquid separator 149 is arranged between the compressor 141 and the four-way valve 142. Specifically, one end of the gas-liquid separator 149 is connected to the suction port 141b of the compressor 141, and the other end of the gas-liquid separator 149 is connected to the second port 142b of the four-way valve 142.

[0033] Continuing to refer to Figure 1 , the indoor heat exchanger 143 is arranged in the indoor unit chamber 120, and the compressor 141 and the outdoor heat exchanger 145 are arranged in the outdoor unit chamber 130. The indoor heat exchanger 143 is higher than the compressor 141 in the height direction, and the outdoor heat exchanger 145 is substantially flush with the compressor 141. The structures of the indoor heat exchanger 143 and the outdoor heat exchanger 145 are not limited, and can be, but are not limited to, plate heat exchangers, finned coil heat exchangers, etc. In addition, the structure of the expansion device 144 can also be adjusted according to actual needs, for example, the expansion device 144 can be, but is not limited to, an electronic expansion valve, a thermal expansion valve, a capillary tube, etc.

[0034] Figure 3is a first structural schematic view of an embodiment of the one-way electromagnetic valve of the drying system of the present application; Figure 4 is a second structural schematic view of an embodiment of the one-way electromagnetic valve of the drying system of the present application. As shown in Figure 3 and Figure 4 , in one or more embodiments, the one-way electromagnetic valve 148 has a housing 481, a valve seat 482, a valve body 483, an electromagnetic coil 484 and a reset member 485, etc. In one or more embodiments, the housing 481 has a substantially cylindrical shape. Alternatively, the housing 481 can also be provided in other suitable shapes, such as a square column, etc. The housing 481 has opposite inlet end 481a and outlet end 481b. The valve seat 482 is arranged in the housing 481. The valve seat 482 is provided with a valve hole 4821 allowing the refrigerant to pass therethrough. The valve body 483 is movably arranged in the housing 481. The valve body 483 has a closed position (see Figure 3 ) abutting against the valve seat 482 and closing the valve hole 4821, and an open position (see Figure 4 ) away from the valve seat 482 to open the valve hole 4821. One end of the reset member 485 is fixed to the valve body 483, and the other end is fixed to the housing 481. The reset member 485 can be a spring or other suitable component. The reset member 485 applies a pre-pressing force to the valve body 483 so as to firmly abut the valve body 483 against the valve seat 482. The electromagnetic coil 484 is configured to cooperate with the valve body 483. When the electromagnetic coil 484 is energized, the electromagnetic coil 484 can apply a sufficient attractive force to the valve body 483 to overcome the pressure exerted thereon by the reset member 485, so that the valve body 483 moves towards the direction away from the valve seat 482. At this time, the one-way electromagnetic valve 148 has the function of opening the pipeline. When the electromagnetic coil 484 is de-energized, the attractive force exerted on the valve body 483 by the electromagnetic coil 484 is removed, and the valve body 483 abuts against the valve seat 482 again under the action of the reset member 485. At this time, the one-way electromagnetic valve 148 has the function of one-way cut-off. The refrigerant in the indoor heat exchanger 143 cannot pass through the valve hole 4821 on the valve seat 482 from the outlet end 481b, achieving effective blocking of the refrigerant and avoiding backflow of the refrigerant to the exhaust port 141a of the compressor 141.

[0035] Next, embodiments of the control method for the drying system 100 of the present application will be described in detail with reference to Figure 5 and Figure 6 . It should be noted that the control method can be executed in any of the above embodiments of the drying system 100.

[0036] Figure 5 is a flowchart of the control method for the drying system of the present application. As shown in Figure 5As shown, in one or more embodiments, when the control method of the present application is used in the drying system 100, first, step S1 is performed, i.e. when the compressor 141 is stopped during the heating of the drying system 100, the preset stop time of the compressor 141 is obtained. The preset stop time can be designed according to the actual needs of the drying process. For example, when the drying process is in the constant temperature stage, the preset stop time of the compressor 141 can be set to 8 min, 10 min, 12 min, 14 min, or other suitable time. When the drying process is in the dehumidification stage or the temperature rising stage, the preset stop time of the compressor 141 can be set to 1 min, 2 min, 3 min, or other suitable time. Then, the control method performs step S2, compares the preset stop time with the stop time threshold. In one or more embodiments, the stop time threshold ranges from 8 min to 12 min. For example, the stop time threshold can be 8 min, 10 min, or 12 min, etc. When the preset stop time is greater than or equal to the stop time threshold, the first outlet 147b is controlled to be opened, the second outlet 147c is controlled to be closed, and the four-way valve 142 is controlled to allow the drying system 100 to enter the refrigeration mode (i.e. step S3). When the preset stop time is greater than or equal to the stop time threshold, it means that the compressor 141 stops for a long time this time, and the liquid refrigerant in the indoor heat exchanger 143 is easy to flow back to the exhaust port 141a of the compressor 141 under the action of its own gravity along the refrigerant pipeline 146, therefore, by controlling the first outlet 147b of the three-way valve 147 to be opened, controlling the second outlet 147c of the three-way valve 147 to be closed, and controlling the four-way valve 142 to allow the drying system 100 to enter the refrigeration mode, the indoor heat exchanger 143 originally serving as a condenser can be converted into an evaporator, and the outdoor heat exchanger 145 originally serving as an evaporator can be converted into a condenser. Since the outdoor heat exchanger 145 is roughly flush with the compressor 141, there is no obvious height difference between the two, so the above setting can prevent the liquid refrigerant from flowing back to the exhaust port 141a of the compressor 141.

[0037] Continuing to refer to Figure 5 When the preset stop time is less than the stop time threshold, the first outlet 147b is controlled to be closed, and the second outlet 147c is controlled to be opened, wherein the refrigerant in the indoor heat exchanger 143 is blocked by the one-way electromagnetic valve 148 and cannot flow back to the compressor 141 (i.e. step S4). When the preset stop time is less than the stop time threshold, it means that the compressor 141 stops for a short time this time, then the first outlet 147b of the three-way valve 147 is controlled to be closed, and the second outlet 147c of the three-way valve 147 is controlled to be opened, so that the liquid refrigerant in the indoor heat exchanger 143 is blocked by the one-way electromagnetic valve 148 and cannot flow back to the exhaust port 141a of the compressor 141. Further, through the above setting, it can also prevent the four-way valve 142 from frequently reversing in a short time and causing damage, prolonging the service life of the components.

[0038] Figure 6 is a flowchart of an embodiment of the control method for a drying system of the present application. As shown in Figure 6 one or more embodiments, when the control method for a drying system 100 of the present application starts, first, step S10 is performed, i.e., when the compressor 141 stops during the heating period of the drying system 100, the preset stop time length of the compressor 141 is obtained. Then, step S20 is performed, i.e., whether the preset stop time length is less than or equal to the stop time length threshold value is determined. When the determination result is yes, it indicates that the compressor 141 stops for a short time, in order to avoid the frequent switching of the four-way valve 142, the control method proceeds to step S30, i.e., the first outlet 147b of the three-way valve 147 is controlled to be closed, and the second outlet 147c of the three-way valve 147 is controlled to be opened. When step S30 is completed, the control method performs step S31, i.e., whether the start-up condition of the compressor 141 is satisfied is determined. In one or more embodiments, when the actual stop time length of the compressor 141 is equal to the preset stop time length, the start-up condition of the compressor 141 is satisfied. When the determination result is no, it indicates that the compressor 141 is still in the stop state, then the one-way electromagnetic valve 148 is controlled to be powered off (i.e., step S34). When the one-way electromagnetic valve 148 is powered off, the one-way electromagnetic valve 148 has the function of one-way cut-off, so that the liquid refrigerant in the indoor heat exchanger 143 cannot flow back to the exhaust port 141a of the compressor 141 through the one-way electromagnetic valve 148. When step S34 is completed, the control method repeatedly performs step S31, i.e., whether the start-up condition of the compressor 141 is satisfied is continuously determined.

[0039] Continuing to refer to Figure 6 , when step S31 is performed and the determination result is yes, it indicates that the start-up condition of the compressor 141 is satisfied, then step S32 is performed, i.e., the compressor 141 is controlled to be started. Then, the control method proceeds to step S33, after a preset time period, the one-way electromagnetic valve 148 is controlled to be powered on. When the one-way electromagnetic valve 148 is powered on, the one-way electromagnetic valve 148 has the function of opening the pipeline, so that the gaseous refrigerant discharged by the compressor 141 can smoothly pass through the one-way electromagnetic valve 148 along the refrigerant pipeline 146, the refrigerant can smoothly pass through without needing to overcome the pressure of the reset member in the one-way electromagnetic valve 148, which reduces the resistance when the refrigerant flows, and ensures the operation efficiency of the compressor 141. In one or more embodiments, the preset time period ranges from 1s to 2s. After the compressor 141 is started and the one-way electromagnetic valve 148 is powered on after the preset time period, the compressor 141 has a larger exhaust pressure, so as to smoothly transport the liquid refrigerant on the outlet end 481b side of the one-way electromagnetic valve 148 back to the indoor heat exchanger 143, and not to flow back to the compressor 141. When step S33 is completed, the control method ends.

[0040] Continuing to refer to Figure 6 After step S20 is performed, when the result of the determination is no, it indicates that the compressor 141 has been stopped for a long time, and the liquid refrigerant in the indoor heat exchanger 143 is prone to flow back to the discharge port 141a of the compressor 141 under the action of its own gravity. Therefore, the first outlet 147b of the three-way valve 147 is controlled to be open, the second outlet 147c of the three-way valve 147 is controlled to be closed, and the four-way valve 142 is controlled to allow the drying system 100 to enter the refrigeration mode (step S40). In other words, the four-way valve 142 is switched from the state originally satisfying the heating mode (the first port 142a and the third port 142c are connected, and the second port 142b and the fourth port 142d are connected) to the state satisfying the refrigeration mode (the first port 142a and the fourth port 142d are connected, and the second port 142b and the third port 142c are connected). In this way, the indoor heat exchanger 143 originally serving as a condenser is converted into an evaporator, and the outdoor heat exchanger 145 originally serving as an evaporator is converted into a condenser. On the one hand, since the outdoor heat exchanger 145 is flush with the compressor 141 in the height direction, the refrigerant in the outdoor heat exchanger 145 will not flow back to the discharge port 141a of the compressor 141; on the other hand, after being reversed by the four-way valve 142, even if part of the refrigerant remaining in the indoor heat exchanger 143 flows back to the compressor 141 along the refrigerant pipeline 146, it will only flow to the suction port 141b of the compressor 141, and since the gas-liquid separator 149 is arranged near the suction port 141b, the liquid refrigerant cannot flow back to the suction port 141b.

[0041] Continuing to refer to Figure 6 After step S40 is performed, the control method proceeds to step S41, that is, whether the start-up condition of the compressor 141 is satisfied is determined. When the result of the determination is no, the control method repeats step S40, that is, the first outlet 147b is controlled to be open, the second outlet 147c is controlled to be closed, and the four-way valve 142 is controlled to allow the drying system 100 to enter the refrigeration mode. When the result of the determination is yes, the compressor 141 is controlled to start up so that the drying system 100 enters the refrigeration mode (i.e., step S42). Then, step S43 is performed, that is, the discharge pressure of the compressor 141 is detected. Then, whether the discharge pressure is greater than or equal to the discharge pressure threshold value is determined (i.e., step S43). In one or more embodiments, the discharge pressure threshold value ranges from 1.5 MPa to 2 MPa (i.e., megapascal). If the result of the determination is no, it indicates that the discharge pressure of the compressor 141 is still small at this time, and step S43 is repeated, that is, the discharge pressure of the compressor 141 is continuously monitored. If the result of the determination is yes, it indicates that the discharge pressure of the compressor 141 is already large at this time, and step S45 is performed, that is, the four-way valve 142 is controlled so that the drying system 100 is switched to the heating mode, thereby ensuring the smooth operation of the drying system 100. After step S45 is completed, the control method ends.

[0042] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.

Claims

1. A control method for a drying system, characterized by, The drying system comprises a compressor, a three-way valve, a four-way valve, a one-way electromagnetic valve, an indoor heat exchanger and an outdoor heat exchanger, wherein the indoor heat exchanger is located higher than the compressor, the three-way valve has an inlet connected with an exhaust port of the compressor, a first outlet connected with a first port of the four-way valve and a second outlet connected with an inlet end of the one-way electromagnetic valve, a second port of the four-way valve is connected with a suction port of the compressor, a third port of the four-way valve is connected with the indoor heat exchanger, a fourth port of the four-way valve is connected with the outdoor heat exchanger, and an outlet end of the one-way electromagnetic valve is connected with the indoor heat exchanger; and during heating of the drying system, the control method comprises: acquiring a preset shutdown duration of the compressor after the compressor is shut down; comparing the preset shutdown duration with a shutdown duration threshold; when the preset shutdown duration is less than the shutdown duration threshold, controlling the first outlet of the three-way valve to be closed and the second outlet of the three-way valve to be opened, so that the refrigerant in the indoor heat exchanger is blocked by the one-way electromagnetic valve and cannot flow back to the compressor.

2. The control method for a drying system according to claim 1, wherein The outdoor heat exchanger is located flush with the compressor, and the control method further comprises: when the preset shutdown duration is greater than or equal to the shutdown duration threshold, controlling the first outlet of the three-way valve to be opened, the second outlet of the three-way valve to be closed, and the four-way valve to allow the drying system to enter a cooling mode.

3. The control method for a drying system according to claim 2, wherein when the preset shutdown duration is greater than or equal to the shutdown duration threshold, the control method further comprises: controlling the compressor to start when a starting condition of the compressor is met, so that the drying system enters the cooling mode; detecting an exhaust pressure of the compressor; comparing the exhaust pressure with an exhaust pressure threshold; when the exhaust pressure is greater than or equal to the exhaust pressure threshold, controlling the four-way valve so that the drying system switches to a heating mode.

4. The control method for a drying system according to claim 3, wherein The exhaust pressure threshold ranges from 1.5 MPa to 2 MPa.

5. The control method for a drying system according to claim 1, wherein The one-way electromagnetic valve is configured to have a one-way blocking function when powered off and an open pipeline function when powered on.

6. The control method for a drying system according to claim 5, wherein when the preset shutdown duration is less than the shutdown duration threshold, the control method further comprises: when the compressor is in a shutdown state, controlling the one-way electromagnetic valve to be powered off, so that the refrigerant in the indoor heat exchanger cannot flow back to the compressor through the one-way electromagnetic valve.

7. The control method for a drying system according to claim 6, wherein The control method further comprises: controlling the compressor to start when a starting condition of the compressor is met; after a preset time period, controlling the one-way electromagnetic valve to be powered on, so that the refrigerant discharged from the compressor can flow to the indoor heat exchanger through the one-way electromagnetic valve.

8. The control method for a drying system according to any one of claims 5 to 7, characterized in that, The one-way electromagnetic valve comprises: a housing; a valve seat arranged in the housing, wherein a valve hole allowing the refrigerant to pass therethrough is provided on the valve seat; a valve body having a closed position abutting on the valve seat to seal the valve hole and an open position away from the valve seat to open the valve hole; An electromagnetic coil configured to attract the valve body when energized, such that the valve body moves from the closed position to the open position; and A reset member connected with the housing and the valve body respectively, and the reset member can urge the valve body to reset from the open position to the closed position when the electromagnetic coil is de-energized.

9. The control method for a drying system according to claim 7, wherein The preset time period ranges from 1s to 2s.

10. The control method for a drying system according to claim 1, wherein The shutdown time threshold ranges from 8min to 12min.

11. A drying system, characterized by The control method for the drying system according to any one of claims 1-10 is performed in the drying system.

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