Anti-freezing shallow underground water monitoring system and method

Abstract

The invention discloses an anti-freezing shallow groundwater monitoring system and method.The anti-freezing shallow groundwater monitoring system comprises a heat preservation water tank, a detection mechanism and a temperature control mechanism, a heat preservation layer is arranged on the outer side of the heat preservation water tank, and the top of the heat preservation water tank is connected with a water supply pipeline; the detection mechanism comprises a water quality analyzer, a carbon dioxide sensor, a first temperature sensor and a liquid level sensor, and a probe of the water quality analyzer, the carbon dioxide sensor, the temperature sensor and the liquid level sensor are arranged in the water tank and used for detecting underground water; the temperature control mechanism comprises a heating piece arranged at the bottom of the heat preservation water tank, a controller and a second temperature sensor arranged on the inner wall of the water tank, and the controller is electrically connected with the heating piece and the second temperature sensor to control the temperature of the heat preservation water tank. The anti-freezing shallow groundwater monitoring system provided by the invention has the advantages of adaptability to severe cold weather, low energy consumption and high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of groundwater monitoring, and in particular to a freezing-proof shallow groundwater monitoring device. BACKGROUND

[0002] At present, especially in the northern low-temperature area, the shallow groundwater monitoring device is prone to freezing in the winter low-temperature environment, which can easily cause equipment damage, data interruption and high energy consumption, and cannot realize continuous and stable monitoring of groundwater throughout the year, thereby bringing negative effects to production and research activities. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, the embodiments of the present application provide a freezing-proof shallow groundwater monitoring system, which has the advantages of adapting to severe cold weather, low energy consumption and high reliability.

[0004] The freezing-proof shallow groundwater monitoring system according to the embodiments of the present application comprises a heat-insulating water tank, a detection mechanism and a temperature control mechanism, the outer side of the heat-insulating water tank is provided with a heat-insulating layer, the top of the heat-insulating water tank is connected with a water supply pipeline, an electromagnetic valve is arranged on the water supply pipeline, the detection mechanism comprises a water quality analyzer, a carbon dioxide sensor, a first temperature sensor and a liquid level sensor, etc., the probe of the water quality analyzer and the carbon dioxide sensor, the temperature sensor and the liquid level sensor are arranged in the water tank to detect groundwater, the temperature control mechanism comprises a heating sheet arranged at the bottom of the heat-insulating water tank, a controller and a second temperature sensor arranged on the inner wall of the water tank, and the controller is electrically connected with the heating sheet and the second temperature sensor to control the temperature of the heat-insulating water tank.

[0005] The freezing-proof shallow groundwater monitoring system according to the embodiments of the present application has the advantages of adapting to severe cold weather, low energy consumption and high reliability. The present application has the following advantages: the heat-insulating water tank cooperates with the temperature control mechanism to cope with the winter low-temperature environment through the heat-insulating layer, so as to ensure that the annual monitoring of the shallow groundwater is not affected, and the data sufficiency is improved.

[0006] In some embodiments, a support is further included, the support comprises a receiving seat and a plurality of supporting feet, the receiving seat is detachably connected with the bottom of the heat-insulating water tank, and the supporting feet are connected with the receiving seat.

[0007] In some embodiments, the temperature control mechanism further comprises a heating sheet arranged on the outer wall of the heat-insulating water tank, and the heating sheet is arranged between the heat-insulating water tank and the heat-insulating layer in the circumferential direction.

[0008] In some embodiments, a stirrer is further included, and the stirrer is arranged in the heat-insulating water tank to disturb the water body.

[0009] In some embodiments, the heat preservation water tank is a spherical water tank, and the stirrer is arranged at the bottom of the spherical water tank and at a distance from the central axis of the spherical water tank.

[0010] In some embodiments, a drain pipeline is arranged at the bottom of the heat preservation water tank, and a drain pump and a solenoid valve are arranged on the drain pipeline, and the solenoid valve and the drain pump are electrically connected with the controller.

[0011] In some embodiments, a reflective heat insulation film is further arranged between the heat preservation layer and the heat preservation water tank.

[0012] In some embodiments, the thickness of the heat preservation layer at the top and bottom of the heat preservation water tank is greater than the thickness of the heat preservation layer at other positions of the heat preservation water tank.

[0013] In some embodiments, a heat preservation structure is arranged on the water supply pipeline, and the heat preservation structure comprises a polyurethane heat preservation pipe and a protective shell, which are sequentially arranged outside the water supply pipeline.

[0014] The anti-freezing type shallow groundwater monitoring method according to the embodiment of the present application comprises the following steps: starting the second temperature sensor to detect the temperature of the water tank and recording, opening the solenoid valve, and supplying water to the water tank through the water supply pipeline; opening the detection mechanism, and detecting the liquid level height in the water tank by the liquid level sensor, and stopping water supply by closing the solenoid valve when the liquid level height is greater than a predetermined range; opening the water quality analyzer to analyze various indexes of water quality, and respectively detecting and recording by the carbon dioxide sensor and the first temperature sensor; opening the heating sheet if the temperature of the water tank is lower than a target range, and not opening the heating sheet if the temperature of the water tank is higher than the target range, and discharging water through the drain pipeline when the temperature of the water tank falls into the target range; continuing to heat by the heating sheet for a certain period of time, keeping the water in the water tank discharged, and closing the heating sheet. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structural schematic diagram of an anti-freezing type shallow groundwater monitoring system according to the embodiment of the present application.

[0016] Mark: 1, heat preservation water tank; 11, heat preservation layer; 2, water supply pipeline; 21, solenoid valve; 3, water quality analyzer; 4, support; 41, receiving seat; 42, supporting foot; 5, drain pipeline. DETAILED DESCRIPTION

[0017] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0018] The anti-freezing type shallow groundwater monitoring system according to the embodiment of the present application comprises a heat-preservation water tank 1, a detection mechanism and a temperature control mechanism. The heat-preservation water tank 1 is provided with a heat-preservation layer 11 on the outside. The heat-preservation water tank 1 is connected with a water supply pipeline 2 at the top. An electromagnetic valve 21 is arranged on the water supply pipeline 2. The detection mechanism comprises a water quality analyzer 3, a carbon dioxide sensor, a first temperature sensor and a liquid level sensor. The probe of the water quality analyzer 3 and the carbon dioxide sensor, the first temperature sensor and the liquid level sensor are arranged in the water tank to detect the underground water. The temperature control mechanism comprises a heating sheet arranged at the bottom of the heat-preservation water tank 1, a controller and a second temperature sensor arranged on the inner wall of the water tank. The controller is electrically connected with the heating sheet and the second temperature sensor to control the temperature of the heat-preservation water tank 1. The heat-preservation layer 11 can be made of polyurethane foaming material and closely adheres to the outer wall of the heat-preservation water tank 1 to reduce heat loss and effectively slow down the heat exchange between the underground water in the water tank and the external environment. In the outdoor environment below zero, the water temperature in the water tank can be maintained at a certain temperature. Optionally, the water temperature is maintained above 4℃ to avoid damage to the sensor caused by ice formation. Through the automatic opening and closing of the electromagnetic valve 21, the water supply cycle can be preset (for example, the water supply cycle is 1 time every 4-6 hours, and each time the water supply is 2 / 3 of the water tank volume) to avoid the tediousness of frequent manual water supply and prevent the water tank from overflowing (the electromagnetic valve 21 is automatically closed when the water level reaches the upper limit under the cooperation of the sensor), which is especially suitable for unattended monitoring points. The intermittent water supply controlled by the electromagnetic valve 21 can reduce the energy consumption of the temperature control mechanism. The detection mechanism detects various indicators of water through the water quality analyzer 3 and multiple sensors. The water quality analyzer 3 has a conductivity probe, an optical dissolved oxygen probe, a turbidity probe, a pH and ORP two-in-one probe, which are respectively used to test the temperature, conductivity (salinity), dissolved oxygen, turbidity, pH value and oxidation-reduction potential of water. The carbon dioxide sensor can measure the atmospheric temperature and carbon dioxide concentration, and is arranged outside the water tank. The temperature control mechanism heats the water tank through the heating sheet arranged at the bottom of the heat-preservation water tank 1 to ensure the temperature in the water tank and avoid the difficulty of discharging the water condensed into ice in the water tank after detection.

[0019] In some embodiments, a support 4 is further included, which comprises a receiving seat 41 and multiple supporting legs 42. The receiving seat 41 is detachably connected with the bottom of the heat-preservation water tank 1, and the supporting legs 42 are connected with the receiving seat 41.

[0020] Specifically, the receiving seat 41 is used to support and limit the heat preservation water tank 1 to avoid movement of the heat preservation water tank 1, and the supporting feet 42 support the heat preservation water tank 1 upward away from the ground to reduce heat conduction between the ground and the heat preservation water tank 1, and form a certain heat insulation through air. The number of the supporting feet 42 can be three, four or more, and three supporting feet 42 form a stable triangular structure, and four supporting feet 42 are suitable for a larger diameter water tank. The four supporting feet 42 can be inclined to the center of gravity to play a better supporting role. The supporting feet 42 can evenly disperse the weight of the device to the ground to avoid tilting of the device caused by single-point force. If the water tank has a water leakage fault, the support 4 does not need to be moved, and the heat preservation water tank 1 can be separated from the receiving seat 41 to replace it.

[0021] In some embodiments, the temperature control mechanism further comprises a heating sheet arranged on the outer wall of the heat preservation water tank 1, and the heating sheet is arranged between the heat preservation water tank 1 and the heat preservation layer 11 in the circumferential direction.

[0022] Specifically, the heating sheet is a flexible silicone rubber heating sheet, which has strong flexibility and can closely fit the curved surface of the outer wall of the water tank. The heating sheet is arranged in the circumferential direction along the horizontal direction of the outer wall of the heat preservation water tank 1, and the spacing between adjacent heating sheets is equal. The outer wall circumferential heating sheet can uniformly heat from the side of the water tank, and form a three-dimensional heating mode of the bottom and the side with the bottom heating sheet, so that the water temperature distribution in the water tank is more uniform, the risk of local icing at the top or side wall is eliminated, the entire water body in the water tank is ensured to be in a flowing state, and the probe is prevented from being damaged by being soaked in the iced water body. The flexible characteristic of the outer wall circumferential heating sheet can closely fit the curved surface, avoid heating dead angles caused by shape limitations, and improve the overall temperature control effect.

[0023] In some embodiments, a stirrer is further included, and the stirrer is arranged in the heat preservation water tank 1 to disturb the water body.

[0024] Specifically, the size of the blade of the stirrer is adapted according to the size of the water tank, and the edge of the blade is arc-shaped to prevent scratching the inner wall of the water tank or the probe of the sensor. The stirrer can be a submersible magnetic stirrer suitable for use in water. The stirrer is at a certain distance from the bottom of the water tank to avoid abrasion caused by the collision of the blade with the bottom of the deposited large particles during stirring. The axis of the stirrer is offset from the central axis of the water tank by a distance, which can be 100-1500 mm, so that the sensor and the like can be avoided. The installation position of the stirrer avoids the area of the sensor probe to prevent the direct impact of the stirred water flow on the probe from causing fluctuations in the measurement data. The stirrer can be set to stir at a certain time, and the stirring at a certain time in cold weather prevents the water body in the water tank from freezing. The stirrer can homogenize the water body in the water tank to ensure accurate data collection.

[0025] In some embodiments, the heat preservation water tank 1 is a spherical water tank, and the stirrer is arranged at a distance from the central axis of the spherical water tank.

[0026] Specifically, the heat dissipation surface area of the spherical water tank is smaller than that of a cuboid, a cylinder or the like, so that heat dissipation of the water tank can be reduced. The offset direction of the stirrer is towards the water inlet side of the water tank, and the included angle between the stirrer and the water inlet can be controlled to be 30°-60°, and the preferred angle is 45°. By using the superposition effect of the water inlet flow and the stirring flow, the disturbance range is expanded, and the stirring effect of the stirrer is improved. The offset of the stirrer can avoid the formation of a central dead zone at low speed, and can make the water flow generated by the stirring blade flow along the inner wall of the sphere. The water flow flows upward from the bottom offset position, climbs along the inner wall to the top, and then falls back to the bottom from the central area, forming a complete circulation path and reducing the blind area.

[0027] In some embodiments, a drain pipeline is arranged at the bottom of the heat preservation water tank 1, a drain pump and a solenoid valve 21 are arranged on the drain pipeline, and the solenoid valve 21 and the drain pump are electrically connected with the controller.

[0028] Specifically, the drain port is arranged at the bottom of the heat preservation water tank 1, and when the water tank is a spherical water tank, the lowest point of the bottom is selected to ensure that the water in the water tank can be completely drained without residual water. The drain pump is controlled by the controller to start draining the water tank, and the residual water in the water tank and the drain pipeline is drained to avoid blockage caused by low temperature icing. The solenoid valve 21 is used to open and close the drain pipeline to prevent the water in the water tank from entering the drain pipeline and being frozen at low temperature.

[0029] In some embodiments, a reflective heat insulation film is further arranged between the heat preservation layer 11 and the heat preservation water tank 1.

[0030] Specifically, the reflective heat insulation film can be arranged on the surface of the water tank, and the heat insulation film has good ductility to tightly adhere to the outer wall of the water tank, reducing the heat dissipation of the heat preservation water tank 1. The high reflectivity (≥95%) of the reflective heat insulation film can prevent the heat in the water tank from being dissipated outward in the form of thermal radiation. The reflective heat insulation film cooperates with the heat preservation layer 11 to form double protection of reflection and heat preservation, and cooperates to reduce heat loss, thereby reducing the heat required by the temperature control mechanism to maintain the temperature, reducing the maintenance cost, and ensuring stable heat insulation for a long time.

[0031] In some embodiments, the thickness of the heat preservation layer 11 at the top and bottom of the heat preservation water tank 1 is greater than the thickness of the heat preservation water tank 1 at other positions.

[0032] Specifically, no matter the shape of the heat preservation water tank 1 is a cuboid, a sphere or a cylinder, the top and the bottom of the water tank are places where heat is easily lost, the probe of the detection mechanism enters from the top of the water tank, and the top is easily impacted by cold air convection, so more heat is lost. The bottom is conducted and lost by heat by the receiving seat 41 of the support 4, so the heat preservation layer 11 of the top and the bottom is thickened to help reduce heat loss. The heat preservation layer 11 can be made of polyurethane foam and be made by model shaping. The top is thickened and wrapped in a ring shape to wrap the entrance of the detection mechanism, and the bottom is wrapped in a ring shape to wrap the water inlet and the water outlet, so as to avoid the gap connected with the pipeline from becoming a heat loss channel.

[0033] In some embodiments, the inner wall of the heat preservation water tank 1 is sprayed with a nano antibacterial coating to inhibit the breeding of microorganisms.

[0034] Specifically, for the iron bacteria, sulfate-reducing bacteria, algae and other microorganisms that may be contained in the water in the groundwater detection scene, a nano-silver antibacterial coating is selected for microbial control. Nano-silver can damage the cell membrane of microorganisms, prevent their respiration and reproduction, and avoid water pollution caused by the large-scale reproduction of microorganisms. The breeding of microorganisms can cause corrosion to the inner wall of the spherical water tank and the equipment components, and the nano antibacterial coating can prevent microorganisms from adhering to these key parts and reduce the risk of corrosion. In addition, the use of a hydrophobic coating can reduce the deposition of impurities (such as silt and organic debris) on the inner wall of the water tank.

[0035] In some embodiments, a heat preservation structure is arranged on the water delivery pipeline 2, and the heat preservation structure comprises a polyurethane heat preservation pipe and a protective shell, which are sequentially arranged outside the water delivery pipeline 2.

[0036] Specifically, the protective shell is arranged outside the polyurethane heat preservation pipe, the polyurethane heat preservation pipe is arranged outside the water delivery pipeline 2, the protective shell extends out of the heat preservation pipe by a certain distance at both ends, and the low thermal conductivity and high closed pore rate of the polyurethane heat preservation pipe can effectively block the heat exchange between the water in the pipeline and the outside. The protective shell has the functions of wind and rain and snow prevention, ensuring that the groundwater can be smoothly injected into the water tank and avoiding monitoring interruption caused by pipeline icing. The protective shell is made of an aluminum plastic protective shell, which has excellent impact resistance and corrosion resistance, and can avoid being bitten by animals and being eroded by rainwater and ultraviolet rays.

[0037] The anti-freezing type shallow groundwater monitoring method according to the embodiments of the present application comprises the following steps: The second temperature sensor detects the temperature of the water tank and records it, the electromagnetic valve is turned on, and the water delivery pipeline delivers water into the water tank; the second temperature sensor detects the temperature of the water tank to detect the current temperature in the water tank and record it, which is convenient for judging the influence of the temperature of the water tank on the water in the water tank in the later period, and can be compared with the environmental temperature value detected by the first temperature sensor.

[0038] The opening detection mechanism, the liquid level sensor detects the liquid level height in the water tank, when the liquid level height is greater than the predetermined range, the electromagnetic valve is closed to stop water supply; according to the detection result of the liquid level sensor, the total amount of water injected into the water tank is judged, so as to control the liquid level height in the water tank, avoid excessive water inflow and cause equipment short circuit. When the liquid level sensor does not detect the liquid level rising in a period of time, the alarm can be triggered to inform the personnel to check the fault, such as pipeline blockage.

[0039] The water quality analyzer is opened to analyze various indexes of water quality, and the carbon dioxide sensor and the first temperature sensor are detected and recorded respectively; the equipment of the detection mechanism is carried out in the order of liquid level reaching standard, stirring homogenization and detection starting. The ambient temperature and carbon dioxide concentration can be detected by the carbon dioxide sensor and the first temperature sensor, and the related data of the water body can be compared and analyzed.

[0040] If the water tank temperature is lower than the target range, the heating sheet is opened, if the water tank temperature is higher than the target range, the heating sheet does not need to be opened, and when the water tank temperature falls into the target range, the drain pipeline is opened to drain water; the water after completing the detection can be drained, the water amount stored in the water tank is reduced, and the working load of the heating sheet is reduced.

[0041] The heating sheet continues to heat for a certain period of time, the water in the water tank is kept drained, and the heating sheet is closed. The water can be drained to avoid ice or microorganisms from being left in the water.

[0042] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0043] In addition, the terms "first", "second" are only for description purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0044] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", "fixedly connected", "connection", "fixedly connected", "connected", "fixed", and the like should be construed broadly, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be electrical connection or communication with each other; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. 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.

[0045] In the present application, unless specifically defined otherwise, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0046] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0047] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Changes, modifications, replacements and variations of the above embodiments made by those skilled in the art are within the scope of the present application.

Claims

1. A freeze-proof type shallow groundwater monitoring system, characterized by, It comprises: a heat preservation water tank, an outer side of which is provided with a heat preservation layer, a top of the heat preservation water tank is connected with a water supply pipeline, and an electromagnetic valve is arranged on the water supply pipeline; a detection mechanism, which comprises a water quality analyzer, a carbon dioxide sensor, a first temperature sensor and a liquid level sensor, a probe of the water quality analyzer and the carbon dioxide sensor, the temperature sensor and the liquid level sensor are arranged in the water tank to detect underground water; a temperature control mechanism, which comprises a heating sheet arranged at a bottom of the heat preservation water tank, a controller and a second temperature sensor arranged on an inner wall of the water tank, the controller is electrically connected with the heating sheet and the second temperature sensor to control a temperature of the heat preservation water tank.

2. The frost protected shallow groundwater monitoring system of claim 1, wherein, It further comprises a support, which comprises a receiving seat and a plurality of supporting legs, the receiving seat is detachably connected with the bottom of the heat preservation water tank, and the supporting legs are connected with the receiving seat.

3. The frost protected shallow groundwater monitoring system of claim 1, wherein, The temperature control mechanism further comprises a heating sheet arranged on an outer wall of the heat preservation water tank, and the heating sheet is arranged between the heat preservation water tank and the heat preservation layer in a circumferential direction.

4. The frost protected shallow groundwater monitoring system of claim 1, wherein, It further comprises a stirrer arranged in the heat preservation water tank to disturb water.

5. The frost protected shallow groundwater monitoring system of claim 4, wherein, The heat preservation water tank is a spherical water tank, the stirrer is arranged at a bottom of the spherical water tank and is at a distance from a central axis of the spherical water tank.

6. The frost protected shallow groundwater monitoring system of claim 1, wherein, A drain pipeline is arranged at the bottom of the heat preservation water tank, a drain pump and an electromagnetic valve are arranged on the drain pipeline, and the electromagnetic valve and the drain pump are electrically connected with the controller.

7. The frost protected shallow groundwater monitoring system of claim 1, wherein, It further comprises a reflective heat insulation film arranged between the heat preservation layer and the heat preservation water tank.

8. The frost protected shallow groundwater monitoring system of claim 1, wherein, The thickness of the heat preservation layer at the top and the bottom of the heat preservation water tank is greater than the thickness of the heat preservation layer at other positions of the heat preservation water tank.

9. The frost protected shallow groundwater monitoring system of claim 1, wherein, A heat preservation structure is arranged on the water supply pipeline, and the heat preservation structure comprises a polyurethane heat preservation pipe and a protective shell, which are sequentially arranged outside the water supply pipeline.

10. A method for monitoring the shallow ground water in a freezing condition, using the monitoring system for monitoring the shallow ground water in a freezing condition according to any one of claims 1 to 9, wherein It comprises the following steps: a second temperature sensor is started to detect a temperature of the water tank and record, an electromagnetic valve is turned on, and the water supply pipeline supplies water into the water tank; the detection mechanism is turned on, a liquid level sensor detects a liquid level height in the water tank, and when the liquid level height is greater than a predetermined range, the electromagnetic valve is turned off to stop water supply; a water quality analyzer is turned on to analyze various indexes of water quality, and a carbon dioxide sensor and a first temperature sensor are respectively detected and recorded; if the temperature of the water tank is lower than a target range, the heating sheet is turned on, if the temperature of the water tank is higher than the target range, the heating sheet is not needed to be turned on, and when the temperature of the water tank falls into the target range, a drain pipeline is turned on to drain water; the heating sheet continues to heat for a certain period of time, the water in the water tank is kept drained, and the heating sheet is turned off.

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