Preheating device and method for electric heater

Abstract

The invention relates to the technical field of molten salt equipment preheating, in particular to a preheating device and method for an electric heater, and the preheating device comprises a base, a hot air module and a control module. Wherein the hot air module comprises a fan, a heating piece and a connecting pipe which are connected in sequence, and the connecting pipe is used for being detachably connected with the electric heater; the control module comprises a temperature and humidity sensor, a pressure sensor and an operation table comprising a power supply unit and a control terminal; the temperature and humidity sensor and the pressure sensor are electrically connected with the control terminal and used for being assembled at an air outlet of the electric heater. An inlet of the switch valve is connected with an air outlet of the electric heater. By means of the preheating device independent of the electric heater, preheating of the electric heater in the shutdown state can be achieved in an external connection mode, a molten salt system is not needed, one set of preheating device can be used for preheating and moisture removal of all the electric heaters on a project site, the same preheating device can be reused, the utilization rate of the preheating device is greatly increased, and the cost is reduced. The cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preheating of molten salt equipment, in particular to a preheating device and method for an electric heater. BACKGROUND

[0002] The molten salt heat storage system plays an important role in the development of new energy field in China, and the electric heater is the core equipment of the molten salt heat storage system. Before the molten salt heat storage system starts, if the electric heater has been placed for a long time, the electric heater itself is at room temperature, and moisture will accumulate inside the electric heater. This results in that the insulation resistance of the electric heater under the hot state cannot be measured before the electric heater is used, and if the molten salt heat storage system is started directly at this time, the system temperature is lower than the freezing point of the heat conducting medium, which will cause the medium to freeze, the electric heater to heat up sharply, the thermal stress to concentrate, and the service life of the electric heater to be affected. In addition, the contact between the moisture and the molten salt increases the water content of the molten salt, which may cause problems such as equipment corrosion, reduction of heat transfer performance of the molten salt, local overheating or boiling of the molten salt, etc.

[0003] Therefore, it is often necessary to preliminarily heat the electric heater which has been placed for a long time before the molten salt heat storage system starts, so as to realize preheating and moisture removal of the electric heater.

[0004] The existing preheating device is mostly integrated into the molten salt heat storage system as a part of the system, and uses the energy output of the molten salt system to output hot air to warm up the core equipment or pipeline of the system. The hot air becomes cold air after heat exchange, and is then recycled into the preheating device to absorb the heat of the heat storage system again. In this way, the air is circulated in a closed loop. However, this results in a very complex molten salt heat storage system, and the pipeline valve of the preheating device needs to be closed when the molten salt system is running normally, otherwise there is a risk of leakage. Moreover, the closed loop form makes the preheating work dependent on the energy of the molten salt system, and the system cannot be preheated when the molten salt system is completely shut down. In addition, since each molten salt heat storage system needs its own dedicated preheating device, in other words, the same preheating device can only be connected to a dedicated molten salt system, the universality is low, and the preheating device cannot be used for preheating different molten salt systems or different electric heater modules. If there are multiple molten salt systems or electric heater modules on the project site, multiple preheating devices need to be provided correspondingly, resulting in a significant increase in cost. SUMMARY

[0005] In view of the defects of the existing preheating method of the electric heater, the present application provides a preheating device and method for an electric heater. The preheating device is independent of the electric heater, and can realize preheating of the electric heater in a state of shutdown in an external connection form. The preheating device does not need to depend on the energy of the molten salt system, avoids the complex design of the molten salt system, and can be used for preheating and moisture removal of all electric heaters on the project site. The same preheating device can be reused, which greatly improves the utilization rate of the preheating device and reduces the cost.

[0006] The technical solution provided by this invention is as follows: a preheating device for an electric heater, comprising: a base, wherein a movable part is provided at the bottom of the base; a hot air module, wherein the hot air module is disposed on the base, the hot air module comprising a fan, a heating element and a connecting pipe connected in sequence, the heating element being used to heat the air generated by the fan into hot air, and the connecting pipe being used to detachably connect to the air inlet of the electric heater; a control module, wherein the control module is disposed on the base, the control module comprising a temperature and humidity sensor, a pressure sensor, an operating table, and a power supply unit and a control terminal located within the operating table, the power supply unit being electrically connected to the control terminal, the fan and the heating element, and being used to supply power to the heating element of the electric heater; the temperature and humidity sensor and the pressure sensor being installed at the air outlet of the electric heater, and the temperature and humidity sensor and the pressure sensor being electrically connected to the control terminal; and a switching valve, wherein the switching valve is used to connect to the air outlet of the electric heater.

[0007] Optionally, the base is provided with a cabinet, the cabinet including a functional cavity on the lower side and a storage cavity on the upper side, and the hot air module is located in the functional cavity.

[0008] Optionally, a space is provided between the cabinet and the worktable.

[0009] A preheating method for an electric heater, based on the preheating device for an electric heater as described above, the method comprising: a preparation stage: moving the preheating device to the vicinity of the air inlet of the electric heater and connecting a connecting pipe to the air inlet of the electric heater, the air inlet being located above one end of the electric heater; placing a pressure sensor and a temperature and humidity sensor at the air outlet of the electric heater and electrically connecting them to a control terminal; installing a switching valve at the air outlet of the electric heater, the air outlet being located below the other end of the electric heater; and electrically connecting a power supply unit to the junction boxes at both ends of the electric heater via cables, respectively for preheating the area on the side where the air inlet is located within the electric heater. The power supply unit powers the heating element on the side where the air outlet is located. During startup: the switch valve at the air outlet is opened, and the power supply unit powers the hot air module, which then supplies hot air into the electric heater through the connecting pipe. Simultaneously, the power supply unit powers the heating element on the side where the air outlet is located within the electric heater, causing it to heat up. The startup phase ends when the temperature and humidity sensor detects that the air outlet temperature reaches 80℃. During transition: at the end of the startup phase, the switch valve at the air outlet is closed, and the power supply unit continues to power the hot air module, which then supplies hot air into the electric heater through the connecting pipe. Simultaneously, the power supply unit... The unit supplies power to the junction boxes at both ends of the electric heater to ensure that the heating elements inside the heater are heated evenly, enabling pressurized heat exchange within the heater. The pressure inside the heater is kept below a threshold pressure by adjusting the opening and closing of the switching valve. When the switching valve is open, a temperature and humidity sensor detects the temperature at the air outlet. When the temperature at the air outlet stabilizes at 80°C after fluctuating, the switching valve is closed, ending the transition phase. In the steady-state phase, the power supply unit continues to supply power to the hot air module, which delivers hot air to the electric heater through connecting pipes. Simultaneously, the power supply unit supplies power to the junction boxes at both ends of the electric heater to ensure that the heating elements are heated evenly. All heating elements inside the heater generate heat; the electric heater continuously heats up, and the switching valve is continuously or intermittently open to ensure that the pressure inside the electric heater is less than the threshold pressure during continuous heating; when the switching valve is open, the temperature and humidity values ​​at the air outlet are detected by temperature and humidity sensors. When the temperature value at the air outlet changes from fluctuating to stabilizing at 300℃, and the humidity value continues to decrease to a stable value, the steady-state phase ends; End phase: the control module automatically performs a PID temperature control program, dynamically adjusts the power of the fan and heating elements in the hot air module to maintain the temperature at the air outlet of the electric heater at the set value, and records the running time, indicating that the electric heater preheating is complete.

[0010] Optionally, during the transition phase, when pressurized heat exchange occurs in the electric heater, the opening of the switch valve is adjusted to 10%–20%, and the fan outputs an air pressure of 9 kPa–11 kPa; or, the switch valve is fully opened, and the fan provides an air pressure of 4 kPa–6 kPa to continuously input hot air into the electric heater, and ensures that the pressure inside the electric heater is less than the threshold pressure during pressurized heat exchange.

[0011] Optionally, during the transition phase, when the electric heater is pressurized and heat exchanged, the switch valve is kept closed, and the hot air module continuously supplies hot air into the electric heater. When the pressure displayed by the pressure sensor reaches the warning pressure, the switch valve is intermittently opened, or the switch valve is opened to a specific degree to release pressure.

[0012] Optionally, the warning pressure is less than the threshold pressure.

[0013] Optionally, during the steady-state phase, when the electric heater is continuously heating up, the opening of the switch valve is adjusted to 10%-20%, and the fan outputs a wind pressure of 9 kPa-11 kPa; or, the opening of the switch valve is adjusted to more than 50% or fully open, and the fan provides a wind pressure of 4 kPa-6 kPa to continuously input hot air into the electric heater and ensure that the pressure inside the electric heater is less than the threshold pressure.

[0014] Optionally, during the steady-state phase, while the electric heater is continuously heating up, the switching valve remains closed. When the pressure sensor detects that the pressure value reaches 8 kPa, a pressure relief operation is performed. This pressure relief operation involves intermittently opening the switching valve or opening the switching valve to a specific degree to relieve pressure. When the pressure sensor detects that the pressure value reaches 4 kPa, a pressurization operation is performed. This pressurization operation involves closing the switching valve again to allow the pressure to rise back to 8 kPa. The pressure relief and pressurization operations are repeated until the temperature at the air outlet changes from fluctuating to stabilizing at 300°C, and the humidity value continuously decreases to a stable value.

[0015] Optionally, the threshold pressure is 2 MPa.

[0016] Compared with the prior art, the technical solution provided by this invention has the following advantages: Addressing the shortcomings of existing electric heater preheating methods, this invention provides a preheating device and method for electric heaters. This preheating device, independent of the electric heater itself, can be detachably connected to different electric heaters for preheating and dehumidification, eliminating reliance on the energy of the molten salt system and avoiding its complex design. It is highly versatile; even with multiple molten salt systems or electric heater modules on-site, only one preheating device is needed to preheat and dehumidify all molten salt systems or electric heater modules, significantly reducing system costs and ensuring safety before the electric heater is put into operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a preheating device for an electric heater proposed in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram illustrating an embodiment of the preheating device for an electric heater proposed in this invention. Detailed Implementation

[0019] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. The terms "first," "second," etc., used in this invention are for the convenience of describing the technical solutions of the invention and have no specific limiting effect; they are all general terms and do not constitute a limitation on the technical solutions of the invention. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, not to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Multiple technical solutions in the same embodiment, as well as multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions that do not contradict or conflict, all of which are within the scope of protection claimed by this invention.

[0021] Example 1 Combined with appendix Figure 1This embodiment proposes a preheating device for an electric heater, including a base 20, a hot air module 21, and a control module 22. A movable part 201 is provided at the bottom of the base 20. The hot air module 21 is mounted on the base 20 and includes a fan, a heating element, and a connecting pipe connected in sequence. The heating element heats the air generated by the fan into hot air, and the connecting pipe is detachably connected to the air inlet of the electric heater. The control module 22 includes a temperature and humidity sensor, a pressure sensor, an operating console, and a power supply unit and a control terminal located within the operating console. The power supply unit is electrically connected to the control terminal, the fan, and the heating element, and is used to supply power to the heating element 11 of the electric heater. The temperature and humidity sensor and the pressure sensor are installed at the air outlet of the electric heater and are electrically connected to the control terminal. A switching valve 13 is connected to the air outlet of the electric heater, and the outlet of the switching valve 13 is used to communicate with the external environment.

[0022] In this embodiment, both the hot air module 21 and the control module 22 are mounted on the base 20. The base 20 serves as a support platform. The hot air module 21 is used to provide hot air, and the control module 22 is used to supply power to the hot air module 21, supply power to the junction box 12 of the electric heater, and also functions as a control cabinet.

[0023] Specifically, the bottom of the base 20 is provided with rollers and other structures as a moving part 201. The rollers and other moving parts 201 enable the base 20 to move flexibly to adjust the relative position of the hot air module 21 and the control module 22 with the electric heater. This facilitates the connection of pipelines and cables between the hot air module 21 and the control module 22 and the electric heater, and allows the preheating device to be moved freely on the project site. This allows the preheating device to be used to preheat multiple sets of electric heaters in succession, as well as the entry and exit of the preheating device itself, making it convenient for operators to use.

[0024] In the hot air module 21, the outlet of the fan is connected to the heating element, which is connected to a high-temperature resistant connecting pipe. The connecting pipe is used to detachably connect to the air inlet of the electric heater. The air provided by the fan is turned into hot air by the heating element and then transported into the electric heater through the connecting pipe to preheat and dehumidify the electric heater.

[0025] Preferably, a cabinet 202 is provided on the base 20, the cabinet 202 includes a functional cavity on the lower side and a storage cavity on the upper side, and the hot air module 21 is located in the functional cavity. Furthermore, a cabinet door is provided on the cabinet 202 to close the storage cavity and the functional cavity.

[0026] In this implementation, the storage cavity is used to store the connecting pipes and cables connected to the control module 22, which are only removed when in use. The preheating device in this embodiment is an external device to the molten salt system. When not in use, the air supply connecting pipes and cables can be disassembled from the molten salt system, and the preheating device can be moved away from the site for long-term storage. Therefore, the cabinet 202 is used to store the connecting pipes and cables. This design improves the convenience of the preheating device, facilitates the storage of related components, reduces the occupation of plant space, protects the connecting pipes and cables, and facilitates operation by personnel.

[0027] In this implementation, the hot air module 21 is located below the storage cavity, which allows the heavier fan and heating element to be located at the bottom, thereby lowering the center of gravity, improving stability, ensuring safety, and making the weight mainly supported by the base 20, reducing the pressure on the cabinet 202, and thus reducing the structural strength requirements of the cabinet 202.

[0028] Generally, the openings of the storage cavity and the functional cavity face the side opposite to the control module 22, that is, outward, for easy operation.

[0029] The control module 22 includes an operating console, a power supply unit, a temperature and humidity sensor, and a pressure sensor. The operating console contains a control terminal, which is connected to the temperature and humidity sensor and the pressure sensor via cables to obtain various real-time data from the electric heater. The power supply unit supplies power to the hot air module 21 via cables (the cables can be routed from the base module 20). The power supply unit can also connect to the junction box 12 of the electric heater via cables (with clamps at the ends) to provide low-voltage electricity (380V) to the heating element 11.

[0030] Furthermore, in this embodiment, the switching valve 13 is located at the air outlet of the electric heater.

[0031] Furthermore, in a further embodiment, a space 203 is provided between the cabinet 202 and the operating table. Generally, the hot air module 21 and the control module 22 are located on the left and right sides of the base 20 in the width direction, respectively, forming a space 203 between them. The hot air module 21 and the control module 22 being arranged on both sides of the base 20 allows the center of gravity of the preheating device to be adjusted to the middle, improving stability, and also makes the cabinet door facing outwards of the hot air module 21 and the operating table facing outwards of the control module 22 closer to the outer edge, facilitating operation.

[0032] The intermediate space 203 can serve as a heat dissipation space. The heat generated by the operation of the hot air module 21 and the control module 22 can be transferred to the intermediate space 203 (heat dissipation inward), thereby preventing the heat from spreading outward and burning the operator.

[0033] Furthermore, the wiring between the hot air module 21 and the control module 22 is preferably routed through the base 20 module to hide the wiring between the hot air module 21 and the control module 22, and is not routed through the partition space 203 to reduce the adverse effects of heat on the cables.

[0034] Additionally, a handrail can be provided on the base 20 for the operator to push. The handrail is preferably located on one side of the base 20 along its length. When the operator moves the preheating device using the handrail, the hot air module 21 and the control module 22 are located on the left and right sides in front of the operator, respectively. A heat insulation baffle can be installed between the handrail and the corresponding partition space 203 to prevent heat from the partition space 203 from affecting the operator.

[0035] When in use, the preheating device and the electric heater need to be combined and installed as follows: the connecting pipe at the outlet of the hot air module 21 is connected to the air inlet of the electric heater, and the temperature and humidity sensor, pressure sensor and switch valve 13 are installed at the air outlet of the electric heater.

[0036] Furthermore, the power supply unit of the control module 22 is connected to the junction boxes 12 at both ends of the electric heater via a power supply cable, supplying power to the heating elements 11 on both sides of the electric heater. The power supply cable is generally equipped with a high-current cable clamp at the end, making the connection simple and efficient, without the need to disassemble the power cord.

[0037] During preheating, hot air can be injected into the electric heater using the hot air module 21 to replace or heat the cold air inside the heater. Simultaneously, the power supply unit can supply power to the heating element 11 inside the electric heater for auxiliary heating. It should be noted that if the heating element 11 is heated only by supplying low-voltage electricity without hot air, there is a risk of overheating because there is no medium around the heating element 11 to carry away the heat. Therefore, the preheating device in this embodiment primarily uses hot air preheating, with power supply to the heating element 11 for self-heating as an auxiliary method.

[0038] Example 2 Combined with appendix Figure 1 To be continued Figure 2 This embodiment proposes a preheating method for an electric heater, based on the preheating device for an electric heater described in the technical solution of Embodiment 1, to preheat the electric heater.

[0039] Before describing the preheating method, the main structure of the electric heater to be preheated will be explained first: the electric heater includes a shell 10, an inlet pipe 101, an outlet pipe 102, and heating elements 11. The inlet pipe 101 and outlet pipe 102 are used for the inflow and outflow of molten salt into and out of the electric heater. The inlet pipe 101 is located on the lower side of one end of the shell 10 and serves as an air outlet during preheating; the outlet pipe 102 is located on the upper side of the other end of the shell 10 and serves as an air inlet during preheating. Both ends of the electric heater are equipped with junction boxes 12, which are respectively connected to two sets of heating elements 11 inside the shell 10 to supply power to both. The two sets of heating elements 11 are responsible for heating the area on one side where the air inlet is located and the area on the other side where the air outlet is located within the shell 10, respectively.

[0040] For electric heaters in energy storage systems, there may also be pipe fittings for connecting different electric heaters, but this embodiment does not involve them and will not be described in detail.

[0041] When the preheating device is connected to the electric heater in the manner described in Example 1, the electric heater can be preheated, specifically including a preparation stage, a start-up stage, a transition stage, a steady-state stage, and an end stage.

[0042] The preparation stage includes: moving the preheating device to the vicinity of the air inlet of the electric heater and connecting the connecting pipe to the air inlet of the electric heater; setting the pressure sensor and temperature and humidity sensor at the air outlet of the electric heater and maintaining an electrical connection with the control terminal via wired or wireless means; installing the switch valve 13 at the air outlet of the electric heater; and electrically connecting the power supply unit to the junction boxes 12 at both ends of the electric heater via cables to supply power to the heating element 11 on the side where the air inlet is located and the heating element 11 on the side where the air outlet is located, respectively.

[0043] During the preparation phase, moving the preheating device near the air inlet of the electric heater can reduce the path of the high-temperature connecting pipe, thereby reducing heat loss from the hot air.

[0044] The advantage of choosing the outlet pipe 102 of the electric heater as the air inlet for introducing hot air is that hot air tends to rise. After entering the electric heater through the air inlet, it can first gather in the upper region of the electric heater, suppressing the tendency of hot air to quickly leave the electric heater through the lower air outlet, reducing airflow short-circuiting, increasing the residence time of hot air in the electric heater, and allowing the hot air to gradually diffuse from top to bottom. Therefore, on the one hand, it can reduce dead zones within the electric heater and improve preheating uniformity; on the other hand, it can improve the heat exchange effect of hot air within the electric heater, thus improving the preheating effect. During the preparation stage, no temperature or humidity treatment is performed inside the electric heating tube; the temperature and humidity are the same as the site environment.

[0045] Then, the startup phase begins: the switch valve 13 at the air outlet is opened, the power supply unit supplies power to the hot air module 21, and the hot air module 21 delivers hot air into the electric heater through the connecting pipe; at the same time, the power supply unit supplies power to the electric heating tube 11 on the side where the air outlet is located in the electric heater, so that the electric heating tube 11 on the side where the air outlet is located in the electric heater heats up; when the temperature and humidity sensor detects that the air outlet temperature reaches 80°C, the startup phase ends.

[0046] When no power is supplied to the heating element 11 on the side where the air outlet is located inside the electric heater to generate heat, the internal temperature of the electric heater is low during the start-up phase, containing raw cold air. Therefore, the hot air cools down quickly after entering, resulting in the area near the air inlet being the hot end and the area near the air outlet being the cold end inside the electric heater during this phase. For ease of description, please refer to the appendix. Figure 2 As shown in the diagram, the side with the air inlet is the left side of the electric heater, and the side with the air outlet is the right side. Hot air travels from the hot end to the cold end, releasing heat and cooling down, and finally exits from the air outlet. Obviously, the temperature of the electric heater is uneven on both sides, and as the air continues to be discharged after releasing heat and cooling down, it is difficult to achieve uniform temperature on both sides even over time.

[0047] Therefore, during the startup phase, the control module 22 only supplies power to the left junction box 12, causing the heating element 11 on the side where the air outlet is located inside the electric heater to self-heat. After the hot air releases heat and cools down in the right half of the electric heater, the right end of the electric heater becomes the hot end, while the left half becomes the cold end. The cooled air moves to the left, and at this time, the heating element 11 on the left reheats the cold air into hot air. As the air moves to the left, the hot air acts as a medium to diffuse heat to all parts of the left side of the electric heater.

[0048] This accelerates the achievement of temperature uniformity on both sides of the electric heater. Based on the temperature measurement at the lower air outlet on the left side (cold end), when this temperature reaches 80℃, it is considered that the electric heater has initially achieved a state of temperature uniformity on both sides, and the operation of the electric heater with the left and right ends clearly resembling the hot and cold ends has ended, marking the end of the start-up phase. During the start-up phase, the humidity change trend is basically consistent with the temperature change trend, and the humidity decrease rate is relatively fast.

[0049] After the start-up phase, the electric heater initially achieves a state of temperature uniformity at both ends, meaning there are no longer significant (large areas) of cold air inside. However, currently, only the temperatures of the left and right parts are roughly similar, resulting in low uniformity and potentially numerous dead zones. Therefore, it is necessary to eliminate these insufficiently heated dead zones and further improve the temperature uniformity inside the electric heater, allowing the preheating state to transition to a steady state.

[0050] After the start-up phase ends, the transition phase begins: At the end of the start-up phase, the switch valve 13 at the air outlet is closed, and the power supply unit continues to supply power to the hot air module 21. The hot air module 21 delivers hot air into the electric heater through the connecting pipe. At the same time, the power supply unit supplies power to the junction boxes 12 at both ends of the electric heater so that the heating elements 11 in the electric heater are heated. The electric heater undergoes pressurized heat exchange, and the pressure inside the electric heater is kept below the threshold pressure during pressurized heat exchange by adjusting the opening or closing of the switch valve 13. When the switch valve 13 is open, the temperature value at the air outlet is detected by the temperature and humidity sensor. When the temperature value at the air outlet changes from fluctuating to stabilizing at 80°C, the switch valve 13 is closed, and the transition phase ends.

[0051] During the transition phase, valve 13 is initially temporarily closed. Because valve 13 is closed, the hot air entering the electric heater is not immediately exhausted but instead diffuses fully within the heater. This allows the heat emitted by the heating element 11 to be diffused throughout the heater using the reheated air as a medium, eliminating dead zones and further improving temperature uniformity within the heater. It also accelerates the transition from preheating to a steady state. Clearly, since hot air is continuously supplied to the heater while valve 13 is closed, the primary heat exchange mechanism during this phase is pressurized heat exchange. The relatively high pressure accelerates heat exchange, thereby improving preheating efficiency. Furthermore, during the transition phase, humidity decreases, and the rate of humidity reduction gradually slows compared to the start-up phase.

[0052] However, continuously supplying hot air without exhausting the air outlet may cause pressure overload within the electric heater. Therefore, it is necessary to adjust the opening or closing of the switch valve 13 to ensure that the pressure inside the electric heater is less than the threshold pressure during pressurized heat exchange. The threshold pressure is generally designed to be 2 MPa.

[0053] To avoid pressure overload during the transition phase, in a preferred embodiment, during the transition phase, when the electric heater is pressurized for heat exchange, the opening of the switch valve 13 is adjusted to 10%-20%, and the fan outputs an air pressure of 9 kPa-11 kPa; or, the switch valve 13 is fully opened, and the fan provides an air pressure of 4 kPa-6 kPa to continuously input hot air into the electric heater, and to ensure that the pressure inside the electric heater is less than the threshold pressure during the pressurized heat exchange.

[0054] In this embodiment, by adjusting the switching valve 13 to a smaller opening (10%-20%) while the fan provides a larger air pressure (10 kPa); or by fully opening the switching valve 13 while the fan provides a smaller air pressure (4 kPa-6 kPa), hot air can be continuously supplied to the electric heater, effectively avoiding pressure overload.

[0055] Furthermore, in this implementation, based on the characteristic that hot air enters from the air inlet and initially accumulates in the upper region, the cooled and de-heated air inside the electric heater can be gradually compressed downwards and discharged through the lower air outlet. The cold air in the dead zone left during the start-up phase is either heated and becomes hot air, or it is similarly compressed downwards by the hot air and merges into the remaining cold air before being discharged. Therefore, this implementation can solve the problem of pressure overload within the electric heater while eliminating the dead zone, ensuring a safe preheating stage.

[0056] During this process, due to the continuous or intermittent discharge of cold air from the outlet, the outlet temperature, which had reached a relatively stable state during the startup phase, begins to fluctuate significantly again. Therefore, the outlet temperature can be used to determine whether the transition phase has ended. Specifically, when the outlet temperature changes from frequent fluctuations to gradually stabilizing and reaching 80°C, the transition phase is considered to have ended, the dead zone has been basically eliminated, and the electric heater has basically reached a steady state.

[0057] In addition to the aforementioned methods, to avoid pressure overload during the transition phase, another preferred implementation is as follows: during the transition phase, when the electric heater is pressurized and heat exchanged, the switch valve 13 is kept closed, and the hot air module 21 continuously supplies hot air into the electric heater. When the pressure displayed by the pressure sensor reaches the warning pressure, the switch valve 13 is intermittently opened, or the switch valve 13 is opened to a specific degree to release pressure.

[0058] In this implementation, a warning pressure is manually determined, which is lower than a threshold pressure. This warning pressure is typically set based on the specific characteristics of the electric heater. When the pressure sensor detects that the pressure has reached the warning value, the switch valve 13 is intermittently opened or opened to a certain degree to release some air and relieve pressure.

[0059] At this point, with the continuous input of hot air, the cooled air inside the electric heater is compressed and expelled. The cold air in the dead zone left during the start-up phase is either heated and becomes hot air, or it is similarly compressed downwards by the hot air and merges into the remaining cold air before being expelled. Therefore, in this embodiment, a situation similar to the previous embodiment will occur, namely, fluctuations in the temperature value detected by the temperature and humidity sensor. Therefore, the end of the transition phase can be determined based on the outlet temperature. Consistent with the previous embodiment, when the temperature value detected by the temperature and humidity sensor changes from frequent fluctuations to gradually stabilizing and reaching 80°C, the transition phase is considered to be over, the dead zone is essentially eliminated, and the electric heater has essentially reached a steady state. The advantage of this embodiment is that by first mixing the hot and cold air to reach a high pressure value, and then releasing the pressure to expel the cooled air, the rate of cold air expulsion is high due to the high internal pressure, thus improving efficiency.

[0060] After the transition phase, the electric heater reaches a basic steady state, which is considered to be the steady-state stage. However, it is still necessary to continuously strengthen the steady-state process to achieve continuous and sufficient preheating and dehumidification of the electric heater. Before the steady-state stage, the cold air has been exhausted and the dead zone has been eliminated, and the electric heater is filled with relatively uniform hot air at a high temperature, allowing for sufficient heat exchange between the hot air and the electric heater.

[0061] Specifically, during the steady-state phase, the power supply unit continues to supply power to the hot air module 21, which delivers hot air to the electric heater through the connecting pipe. Simultaneously, the power supply unit supplies power to the junction boxes 12 at both ends of the electric heater, so that the heating elements 11 inside the electric heater are heated. The electric heater continues to heat up, and the switching valve 13 is continuously or intermittently open to ensure that the pressure inside the electric heater is less than the threshold pressure during continuous heating. When the switching valve 13 is open, the temperature and humidity values ​​at the air outlet are detected by the temperature and humidity sensor. When the temperature value at the air outlet changes from fluctuating to stabilizing at 300°C, and the humidity value continues to decrease to a stable value, the steady-state phase ends.

[0062] In short, during the steady-state phase, the input of hot air continues, and the self-heating of the electric heating tubes on both sides of the electric heater is maintained, thus reheating the hot air.

[0063] Since the switching valve 13 is closed before entering the steady-state stage, there is a risk of overpressure and overload after entering the steady-state stage. To avoid pressure overload during the transition stage, in one embodiment, during the steady-state stage when the electric heater is continuously heating up, the opening of the switching valve 13 is adjusted to 10%-20%, and the fan outputs a wind pressure of 9Kpa-11Kpa; or, the opening of the switching valve 13 is adjusted to more than 50% or fully opened, and the fan provides a wind pressure of 4kPa-6kPa to continuously input hot air into the electric heater to ensure that the pressure inside the electric heater is less than the threshold pressure.

[0064] This implementation involves opening the switch valve 13 at the appropriate time after the transition phase ends to maintain a continuous and stable flow of hot air inside the electric heater (continuous input and output) for sufficient heat exchange, thereby achieving sufficient preheating and dehumidification.

[0065] Specifically, when the opening of the switch valve 13 is large (adjusted to more than 50% or fully open), it is paired with a medium-low pressure air pressure (4kPa-6kPa); or when the opening of the switch valve 13 is small (10%-20%), it is paired with a higher pressure air pressure (9Kpa-11Kpa). This can ensure the residence time of hot air in the electric heater, reduce the airflow short-circuit effect, and ensure the preheating effect, while also ensuring a certain flow rate and preheating efficiency, thus achieving a balance between preheating efficiency and effect.

[0066] In addition to the above-described implementation, another implementation can avoid the risk of overpressure and overload during the steady-state phase. Specifically, during the steady-state phase, when the electric heater is continuously heating up, the switch valve 13 remains closed. When the pressure sensor detects a pressure value of 8 kPa, a pressure relief operation is performed. This involves intermittently opening the switch valve 13 or opening it to a specific degree to relieve pressure. When the pressure sensor detects a pressure value of 4 kPa, a pressurization operation is performed. This involves closing the switch valve 13 again to restore the pressure to 8 kPa. The pressure relief and pressurization operations are repeated until the temperature at the air vent stabilizes at 300°C, and the humidity continuously decreases to a stable value.

[0067] In short, this implementation method allows the input hot air to be fully reheated and diffused, enhancing the steady state, during which the air pressure inside the electric heater gradually increases.

[0068] When the pressure value detected by the pressure sensor reaches the warning value of 8 kPa, the switch valve 13 is continuously or intermittently opened at a certain opening degree to release pressure. At this time, the electric heater is filled with hot air. Hot air is continuously input into the air inlet and continuously discharged from the air outlet (the temperature is reduced after heat exchange). That is, the electric heater maintains a steady flow of hot air, thereby achieving continuous and stable preheating of the electric heater.

[0069] When the pressure value detected by the pressure sensor drops to 4 kPa, it is considered that the diffusion effect of hot air inside the electric heater is poor, and much hot air is expelled before it can fully diffuse and release heat. At this time, it is necessary to close the switch valve 13 again to allow the air pressure to rise. This cycle repeats throughout the entire steady-state stage, thereby ensuring that good and sufficient preheating and dehumidification effects are achieved during the steady-state stage.

[0070] Regardless of the method used to avoid pressure overload, the temperature inside the electric heater continues to rise during the steady-state phase. Correspondingly, the temperature at the air outlet will also fluctuate. When the temperature at the air outlet changes from fluctuating to stabilizing at 300℃, and the humidity continues to decrease to a stable value, the steady-state phase ends, and the phase ends.

[0071] In the final stage, the control module 22 automatically executes a PID temperature control program, dynamically adjusting the power of the fan and heating element in the hot air module 21 to maintain the temperature at the outlet of the electric heater at the set value, and records the running time, indicating that the preheating of the electric heater is complete. The PID temperature control program is a conventional temperature control program, and its temperature control logic is as follows: compare the difference between the set temperature and the actual temperature, and then dynamically adjust the temperature by adjusting the power of the fan and heating element in the hot air module 21, and / or the opening degree of the switching valve 13, etc.

[0072] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A preheating device for an electric heater, characterized in that, The utility model relates to a kind of preheating device for electric heater, including: Base (20), the bottom of the base (20) is provided with moving part (201); Hot air module (21), hot air module (21) is located on the base (20), and the hot air module (21) includes fan, heating piece and connecting pipe connected in sequence, the heating piece is used to heat the wind generated by fan as hot air, and the connecting pipe is used to be detachably connected with the air inlet of electric heater; Control module (22), the control module (22) is located on the base (20), and the control module (22) includes temperature and humidity sensor, pressure sensor, operation platform and power supply unit and control terminal in the operation platform, the power supply unit is electrically connected with the control terminal, fan and heating piece, and is used to supply power to the electric heating tube (11) of electric heater;Temperature and humidity sensor and pressure sensor are used to be installed at the air outlet of electric heater, and temperature and humidity sensor and pressure sensor are electrically connected with the control terminal; Switch valve (13), the switch valve (13) is used to be connected with the air outlet of electric heater.

2. A preheating device for an electric heater according to claim 1, characterized in that The base (20) is provided with cabinet (202), and the cabinet (202) includes functional cavity located at lower side and storage cavity located at upper side, and the hot air module (21) is located in the functional cavity.

3. A preheating device for an electric heater according to claim 2, characterized in that The interval space (203) is arranged between the cabinet (202) and the operation platform.

4. A preheating method for an electric heater, characterized by, Based on the preheating device for electric heater according to any one of claims 1-3, the method comprises: Preparation stage: the preheating device is moved to the air inlet of electric heater, and the connecting pipe is connected with the air inlet of electric heater, and the air inlet is located above one end of electric heater; Temperature and humidity sensor and pressure sensor are arranged at the air outlet of electric heater, and are electrically connected with the control terminal, and the switch valve (13) is installed at the air outlet of electric heater, and the air outlet is located below the other end of electric heater;Power supply unit is electrically connected with terminal box (12) of electric heater through cable, to be used for respectively supplying power to electric heating tube (11) of the side area where air inlet is located in electric heater and electric heating tube (11) of the side where air outlet is located; Start-up stage: open the switch valve (13) at the air outlet, and the power supply unit supplies power to the hot air module (21), and the hot air module (21) transports hot air into electric heater through the connecting pipe;Meanwhile, the power supply unit supplies power to the electric heating tube (11) of the side where air outlet is located in electric heater, so that the electric heating tube (11) of the side where air outlet is located in electric heater generates heat;When temperature and humidity sensor detects that the temperature value of air outlet reaches 80 DEG C, the start-up stage ends. The transition phase: when the start-up phase ends, the switch valve (13) at the air outlet is closed, the power supply unit continues to supply power to the hot air module (21), and the hot air module (21) delivers hot air into the electric heater through the connecting pipe; at the same time, the power supply unit supplies power to the terminal box (12) at both ends of the electric heater, so that the electric heater (11) in the electric heater generates heat, the pressure in the electric heater is increased, and heat exchange is performed; the opening and closing or opening degree of the switch valve (13) is adjusted to ensure that the pressure in the electric heater is less than the threshold pressure when the heat exchange is increased; when the switch valve (13) is opened, the temperature value at the air outlet is detected by the temperature and humidity sensor, and when the temperature value at the air outlet changes from fluctuation to stability and reaches 80℃, the switch valve (13) is closed, and the transition phase ends. The steady state phase: the power supply unit continues to supply power to the hot air module (21), and the hot air module (21) delivers hot air into the electric heater through the connecting pipe; at the same time, the power supply unit supplies power to the terminal box (12) at both ends of the electric heater, so that the electric heater (11) in the electric heater generates heat; the electric heater is continuously heated, and the switch valve (13) is continuously opened or intermittently opened to ensure that the pressure in the electric heater is less than the threshold pressure when the temperature is continuously increased; when the switch valve (13) is opened, the temperature and humidity values at the air outlet are detected by the temperature and humidity sensor, and when the temperature value at the air outlet changes from fluctuation to stability and reaches 300℃, and the humidity value continuously decreases to a stable value, the steady state phase ends. The end phase: the control module (22) automatically performs the PID temperature control program, dynamically adjusts the power of the fan and the heating element in the hot air module (21), maintains the temperature at the air outlet of the electric heater at the set value, and records the running time, and the preheating of the electric heater is completed.

5. A preheating method for an electric heater according to claim 4, wherein In the transition phase, when the electric heater is subjected to pressure increase and heat exchange, the opening degree of the switch valve (13) is adjusted to 10%-20%, and the fan outputs a wind pressure of 9Kpa-11Kpa; or the switch valve (13) is completely opened, and the fan gives a wind pressure of 4kPa-6kPa, so as to continuously input hot air into the electric heater and ensure that the pressure in the electric heater is less than the threshold pressure when the pressure increase and heat exchange are performed.

6. A preheating method for an electric heater according to claim 4, wherein In the transition phase, when the electric heater is subjected to pressure increase and heat exchange, the switch valve (13) is kept closed, the hot air module (21) continuously delivers hot air into the electric heater, and when it is detected that the pressure displayed by the pressure sensor reaches the warning pressure, the switch valve (13) is intermittently opened or opened to a certain opening degree for pressure relief.

7. A preheating method for an electric heater according to claim 6, wherein The warning pressure is less than the threshold pressure.

8. A preheating method for an electric heater according to claim 4, wherein In the steady state phase, when the electric heater is continuously heated, the opening degree of the switch valve (13) is adjusted to 10%-20%, and the fan outputs a wind pressure of 9Kpa-11Kpa; or the opening degree of the switch valve (13) is adjusted to more than 50% or completely opened, and the fan gives a wind pressure of 4kPa-6kPa, so as to continuously input hot air into the electric heater and ensure that the pressure in the electric heater is less than the threshold pressure.

9. A preheating method for an electric heater according to claim 4, wherein In the steady state stage, the electric heater is continuously heated, the switch valve (13) is kept closed, when the pressure sensor detects that the pressure value reaches 8 kPa, a pressure relief operation is performed, which is intermittently opening the switch valve (13) or opening the switch valve (13) to a certain opening degree to relieve pressure; When the pressure sensor detects that the pressure value reaches 4 kPa, a pressurization operation is performed, which is closing the switch valve (13) again to make the pressure rise to 8 kPa; The pressure relief operation and the pressurization operation are repeated until the temperature value at the tuyere changes from fluctuation to stability to reach 300℃, and the humidity value continuously decreases to a stable value.

10. A preheating method for an electric heater according to claim 4, wherein The threshold pressure is 2 MPa.

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