Electric heating device and heating method

Abstract

The present application relates to the technical fields of electric heater, and discloses an electric heating device and a heating method, the electric heating device comprises a shell and a heating module, the shell forms a heating chamber with an air inlet and an air outlet, the heating module is arranged in the heating chamber, and multiple heating modules are arranged at intervals along the airflow direction; wherein the heating module comprises a support frame, a support rod and a resistance wire, multiple support rods are arranged at intervals on the support frame, the support rod extends along the direction perpendicular to the airflow direction, and the resistance wire is spirally sleeved on the support rod; the resistance wire is used for connecting high-voltage power supply, the electric heating device of the present application can improve the heating power of the electric heating device on the one hand by using high-voltage connection of the resistance wire, on the other hand, the resistance wire can directly exchange heat with air during the heating process, which can effectively improve the heating rate of air and reduce the surface temperature of the resistance wire, and the resistance wire is arranged in the direction perpendicular to the airflow direction, thereby improving the service life of the resistance wire.

Description

Technical Field

[0001] This invention relates to the field of electric heater technology, and more specifically to electric heating devices and heating methods. Background Technology

[0002] Electric heating devices are devices that convert electrical energy into heat energy to heat the air. They have advantages such as convenient energy supply, compact structure, easy installation and maintenance, and no pollution, and have been widely used in industrial production, commercial places, and agriculture.

[0003] To achieve higher heating power, high voltage needs to be connected to the electric heating device. However, the heating element commonly used in related technologies is an electric heating tube, which mainly consists of an external protective sheath, an internal heating resistance wire, and protective insulation magnesium oxide powder. The use of the sheath and magnesium oxide powder increases the thermal resistance of the resistance wire. When the heating power is high and the air velocity outside the heating tube is low, the large surface heat load can easily cause the resistance wire to melt, affecting the use of the equipment. Summary of the Invention

[0004] In view of this, the present invention provides an electric heating device and heating method to solve the problem of resistance wire melting under high heating power.

[0005] In a first aspect, the present invention provides an electric heating device, comprising a housing and a heating module. The housing forms a heating chamber having an air inlet and an air outlet. The heating module is disposed in the heating chamber, and a plurality of the heating modules are arranged at intervals along the airflow direction. Each heating module includes a support frame, support rods, and resistance wires. A plurality of support rods are arranged at intervals on the support frame, extending in a direction perpendicular to the airflow direction. The resistance wires are spirally sleeved on the support rods and are used to connect to a high-voltage power supply.

[0006] Beneficial effects: Gas flows from the inlet to the outlet, forming a directional airflow within the heating chamber. The resistance wire heats the surrounding gas under high voltage, converting electrical energy into heat energy. The low-temperature gas entering from the inlet is transformed into high-temperature gas that meets temperature requirements through multiple heating modules and then delivered to downstream users. On one hand, the high-voltage connection of the resistance wire increases the heating power of the electric heating device, which is conducive to large-scale promotion. On the other hand, the resistance wire directly exchanges heat with the air during the heating process, which can effectively increase the heating rate of the air and reduce the surface temperature of the resistance wire through airflow, thus reducing the risk of resistance wire melting. The resistance wire is arranged perpendicular to the airflow direction, which helps to make the surface temperature of the resistance wire uniform, reducing the risk of damage and thus improving the service life of the resistance wire.

[0007] In one alternative implementation, the heating power of the heating module is configured to decrease sequentially along the airflow direction.

[0008] Beneficial effects: On the side near the air inlet, the gas temperature is relatively low, and using higher heating power helps to convert more electrical energy into heat energy. On the side near the air outlet, the gas temperature is close to or reaches the target temperature, so only lower heating power is needed. By rationally distributing the heating power of the electric heating device, the gas can be heated more efficiently.

[0009] In one optional embodiment, the resistance wire is divided into three groups, and the three groups of resistance wires are respectively used to connect to phase A, phase B and phase C of the high voltage power supply, and the resistance wires in the same group are connected in series.

[0010] Beneficial effects: The three-phase connection method makes the heating module suitable for connection to a three-wire high-voltage AC power supply, meeting the requirements for the electric heating device to operate under high voltage. The resistance wires of the same phase are connected in series, which can reduce the heating power of a single resistance wire and reduce the risk of the resistance wire melting under high voltage.

[0011] In an optional embodiment, a heat storage module is further included, which is disposed between two adjacent heating modules and has a flow-through hole extending along the airflow direction.

[0012] Beneficial effects: After being heated by the upstream heating module, the gas flows through the flow hole to the next heating module. First, the heat storage module can absorb some heat from the gas and reverse-heat the gas when the heating module fluctuates or malfunctions, thus acting as a buffer and helping to maintain the stability of the gas temperature at the outlet. Second, the heat storage module also acts as an insulator, enhancing the insulation performance between adjacent heating modules and helping to ensure the reliability of the electric heating device under high pressure. Finally, the flow hole also acts as a guide, making the air flowing to the next heating module more uniform.

[0013] In one alternative implementation, the heat storage capacity of the heat storage module gradually increases along the airflow direction.

[0014] Beneficial effects: During the heating process, the temperature of the gas gradually increases along the airflow direction. By rationally allocating the heat storage capacity and placing more heat storage capacity in the area where the gas temperature is relatively high, the heat storage capacity of the electric heating device can be enhanced, which helps the heat storage module to better play its buffering role.

[0015] In one alternative embodiment, an insulating base is further included, the number of which corresponds to the number of heating modules disposed on the insulating base.

[0016] Beneficial effects: The insulating foundation can ensure the insulation requirements of the heating module to the ground. By equipping each heating module with an individual insulating foundation, the insulation requirements between heating modules can be guaranteed, thereby improving the safety of the electric heating device.

[0017] In an alternative embodiment, an insulating layer is further included, the insulating layer being disposed on the inner wall of the housing.

[0018] Beneficial effects: By also providing insulation on the inner wall of the casing, the insulation performance of the electric heating device can be enhanced, thereby improving the safety of the electric heating device.

[0019] In one optional implementation, the system further includes flow equalization modules, with two flow equalization modules respectively disposed at the air inlet and the air outlet.

[0020] Beneficial effects: The flow equalization module enables the airflow to flow more evenly to each resistance wire on the heating module, thereby ensuring that the resistance wire is fully heated and improving the heating effect of the electric heating device.

[0021] Secondly, the present invention also provides a heating method using the electric heating device provided by the present invention, the heating method comprising: introducing air to be heated into the heating chamber; activating the heating module to heat the air; and delivering the heated air to a user.

[0022] Beneficial effects: The heating method uses an electric heating device, and therefore also has the beneficial effects brought by the electric heating device, which will not be elaborated here.

[0023] In an optional implementation, the starting and stopping of each of the heating modules is dynamically adjusted according to the power capacity and the heat load; wherein, when the heat load or the power capacity decreases, the heating modules are sequentially shut down according to the airflow direction until the heating power of the electric heating device matches the current heat load and the power capacity.

[0024] Beneficial effects: By prioritizing the shutdown of heating modules near the air inlet and keeping heating modules near the air outlet in operation, the temperature of the heat storage module near the air outlet is maintained, heat loss is reduced, and the emergency buffering capacity of the electric heating device is ensured. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of an electric heating device according to an embodiment of the present invention;

[0027] Figure 2 for Figure 1 Schematic diagram of the sectional view of section AA in the middle;

[0028] Figure 3 This is a schematic diagram of the electrical connection of an electric heating device according to an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] 101. Housing; 102. Heating module; 1021. Support frame; 1022. Support rod; 1023. Resistance wire; 103. Heat storage module; 104. Insulation base; 105. Insulation layer; 1061. Guide plate; 1062. Air distribution plate; 107. Electrical control unit. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a," "an," and "comprising" as used herein may also mean including the plural forms. The terms "comprising," "including," and "having" are inclusive and therefore indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0033] Although terms such as "first," "second," etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Furthermore, in the description of this application, unless otherwise expressly specified and limited, the terms "set up" and "connected" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a direct connection or an indirect connection via an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0034] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "end," "length," "inner," "outer," etc. Such spatial relative terms are intended to include different orientations of the mechanism in use or operation, in addition to those depicted in the figure. For example, if the mechanism in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented as "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The mechanism may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0035] Electric heating devices are devices that convert electrical energy into heat energy to heat the air. In some fields, high-power electric heating devices are required to meet the heating needs of downstream users. For this reason, some related technologies connect high-voltage electricity (greater than or equal to 1kV) to the electric heating device, but this also puts higher demands on the reliability of the electric heating device.

[0036] Specifically, in some related technologies, the heating resistance wire 1023 does not directly contact the outside air, but indirectly heats the air through an external sleeve. This increases the thermal resistance of the resistance wire 1023. When the outside air velocity is low, heat dissipation is not timely, and the large surface heat load can easily cause the resistance wire 1023 to melt, affecting equipment operation. To prevent the resistance wire 1023 from melting, it is necessary to control the heating power of the resistance wire 1023 in real time according to the operating conditions. However, the power adjustment technology under high voltage is not mature and is costly, making large-scale application impossible.

[0037] The following is combined Figures 1 to 3The following describes embodiments of the present invention.

[0038] Reference Figure 1 and Figure 2 According to an embodiment of the present invention, an electric heating device is provided, including a housing 101 and a heating module 102. The housing 101 forms a heating chamber with an air inlet and an air outlet. The heating module 102 is disposed in the heating chamber, and a plurality of heating modules 102 are arranged at intervals along the airflow direction. The heating module 102 includes a support frame 1021, a support rod 1022, and a resistance wire 1023. A plurality of support rods 1022 are arranged at intervals on the support frame 1021. The support rods 1022 extend in a direction perpendicular to the airflow direction. The resistance wire 1023 is spirally sleeved on the support rod 1022 and is used to connect to a high-voltage power supply.

[0039] In use, the gas flows from the air inlet to the air outlet, thus forming a directional airflow in the heating chamber. The resistance wire 1023 heats the surrounding gas under high pressure, converting electrical energy into heat energy. The low-temperature gas entering from the air inlet is transformed into high-temperature gas that meets the temperature requirements through the step-by-step heating of multiple heating modules 102, and then delivered to downstream users.

[0040] First, the high-voltage connection of the resistance wire 1023 increases the heating power of the electric heating device, which is beneficial for large-scale promotion. Second, the resistance wire 1023 directly exchanges heat with the air during the heating process, which can effectively increase the heating rate of the air and improve the heat exchange efficiency. This helps to reduce the surface temperature of the resistance wire 1023 through airflow, avoiding excessive surface heat load under high heating power and reducing the risk of the resistance wire 1023 melting. Finally, the resistance wire 1023 is arranged perpendicular to the airflow direction, so that different positions of the same resistance wire 1023 have similar ambient temperatures. This helps to make the surface temperature of the resistance wire 1023 uniform, reducing the risk of damage and thus improving the service life of the resistance wire 1023.

[0041] In addition, since the electric heating device is equipped with multiple heating modules 102, the heating power of the electric heating device can be adjusted by selectively shutting down some of the heating modules 102. When the power supply changes (for example, the power capacity of the factory where the electric heating device is located decreases due to production expansion), the heating power can be adjusted to ensure the normal operation of the electric heating device.

[0042] In this invention, the support frame 1021 and the support rod 1022 need to be made of insulating materials. For example, the material of the support frame 1021 and the support rod 1022 can be ceramic. Ceramic is a commonly used insulating material in the field of high voltage power transmission and distribution, and has good high voltage insulation performance. Specifically, the ceramic can be silicon carbide, silicon nitride, aluminum oxide, etc.

[0043] It is understandable that the high-voltage power source is the power grid or other upstream power supply facilities, and the resistance wire 1023 is not suitable for direct connection to the high-voltage power source. Therefore, referring to... Figure 3 In some embodiments, the electric heating device may also include an electronic control unit 107, where high-voltage electricity from the upstream power supply facility first enters the electronic control unit 107 and is then supplied to the resistance wire 1023 of the heating module 102 under the control of the electronic control unit 107.

[0044] For example, refer to Figure 3 In some embodiments, the resistance wire 1023 is divided into three groups, which are respectively used to connect to phase A, phase B, and phase C of the high-voltage power supply. The resistance wires 1023 in the same group are connected in series. The three-phase connection makes the heating module 102 suitable for connection to a three-wire high-voltage AC power supply, meeting the requirements for the electric heating device to operate under high voltage. The series connection of the resistance wires 1023 in the same phase can reduce the heating power of a single resistance wire 1023 and reduce the risk of the resistance wire 1023 melting under high voltage.

[0045] Continue to refer to Figure 3 The resistance wire 1023 can be connected in a star configuration, meaning that the resistance wires 1023 of each phase are ultimately connected to the same neutral point.

[0046] In some embodiments, each heating module 102 is equipped with an independent electronic control unit 107, thereby facilitating flexible control of the start and stop of each heating module 102.

[0047] Optionally, the resistance wire 1023 is made of an electrothermal alloy, and the surface of the resistance wire 1023 is coated with a high-temperature resistant, thermally conductive, and corrosion-resistant coating to extend the service life of the resistance wire 1023 exposed to the environment.

[0048] In some embodiments, the heating power of the heating module 102 is configured to decrease sequentially along the airflow direction. Near the air inlet, the gas temperature is relatively low, and using a higher heating power helps convert more electrical energy into heat energy, thus raising the gas temperature. Near the air outlet, the gas temperature is close to or reaches the target temperature, so only a lower heating power is needed to meet the requirements for heating or maintaining the temperature. By rationally allocating the heating power of the electric heating device, the gas can be heated more efficiently under a given heating power, improving the performance of the electric heating device.

[0049] In some embodiments, the electric heating device further includes a heat storage module 103, which is disposed between two adjacent heating modules 102, and the heat storage module 103 has a flow hole extending along the airflow direction.

[0050] The gas, heated by the upstream heating module 102, flows through the flow-through hole to the next heating module 102. First, the heat storage module 103 can absorb some heat from the gas and reverse-heat the gas when the heating module 102 experiences fluctuations or malfunctions, thus acting as a buffer and helping to maintain the stability of the gas temperature at the outlet. Second, the heat storage module 103 also acts as an insulator, enhancing the insulation performance between adjacent heating modules 102 and helping to ensure the reliability of the electric heating device under high pressure. Finally, the flow-through hole also acts as a guide, making the air distribution to the next heating module 102 more uniform.

[0051] It is understandable that the heat storage module 103 needs to be made of materials with high thermal conductivity and good insulation. For example, the material of the heat storage module 103 can be ceramic. Ceramic is a commonly used insulating material in the field of high voltage power transmission and distribution, and has good high voltage insulation performance. Specifically, ceramic can be silicon carbide, silicon nitride, alumina, etc.

[0052] Optionally, in some embodiments, the heat storage module 103 and the heating module 102 are spaced apart. The gas leaving the heating module 102 first mixes in the heating chamber before colliding with the heat storage module 103 and being guided by the flow orifice. This gas mixing process makes the gas temperature more uniform, preventing damage to the downstream resistance wire 1023 due to uneven temperature. Furthermore, the spaced arrangement utilizes the insulating properties of air to ensure the reliability of the electric heating device under high pressure.

[0053] Optionally, in some embodiments, the heat storage capacity of the heat storage module 103 gradually increases along the airflow direction.

[0054] During the heating process, the temperature of the gas gradually increases along the airflow direction. By rationally allocating the heat storage capacity and setting more heat storage capacity in the area where the gas temperature is relatively high, the heat storage capacity of the electric heating device can be enhanced, which helps the heat storage module 103 to better play its buffering role.

[0055] In some embodiments, the electric heating device further includes an insulating base 104, the number of which corresponds to the number of heating modules 102, and the heating modules 102 are disposed on the insulating bases 104. The insulating bases 104 can ensure the insulation requirements of the heating modules 102 to ground. By equipping each heating module 102 with a separate insulating base 104, the insulation requirements between the heating modules 102 can be guaranteed, thereby improving the safety of the electric heating device.

[0056] It is understandable that, such as Figure 1As shown, the support rod 1022 extends horizontally at this time, and multiple support rods 1022 are spaced apart on the support frame 1021 along the height direction. The resistance wire 1023 is spirally wound on the support rod 1022 along the horizontal axis.

[0057] In related technologies, the orientation of the heating element (axis direction) of the heating element does not affect the heating performance of the resistance wire 1023 provided in the form of a heating tube. However, in the present invention, the exposed resistance wire 1023, if placed vertically, will deform under gravity due to the lack of a protective sleeve and the support of magnesium oxide powder, resulting in a pitch that is larger at the top and smaller at the bottom, leading to uneven heating of the gas. When placed horizontally, the horizontal support rod 1022 supports the resistance wire 1023, and the weight of the resistance wire 1023 will not generate a component force along the horizontal axis, thus overcoming this defect and preventing the resistance wire 1023 from changing its pitch under its own weight, which would affect the uniformity of heating.

[0058] Optionally, in some embodiments, the electric heating device further includes an insulating layer 105, which is disposed on the inner wall of the housing 101. By also providing insulation on the inner wall of the housing 101, the insulation performance of the electric heating device can be enhanced, thereby improving the safety of the electric heating device.

[0059] In some embodiments, the electric heating device further includes flow equalization modules, with two flow equalization modules respectively disposed at the air inlet and air outlet. The flow equalization modules enable the airflow to flow more evenly to each resistance wire 1023 on the heating module 102, thereby ensuring that the resistance wire 1023 is fully heated and improving the heating effect of the electric heating device.

[0060] For example, refer to Figure 1 The flow equalization module is arranged in a funnel shape at both the air inlet and outlet. The cross-sectional area of ​​the flow equalization module at the air inlet gradually increases along the airflow direction. The flow equalization module may include a guide plate 1061 and a distribution plate 1062. The guide plate 1061 is located upstream of the distribution plate 1062 and extends inclined downstream from the air inlet. The airflow from the air inlet is dispersed and expanded under the action of the guide plate 1061. The distribution plate 1062 has an array of holes, allowing the airflow to be uniformly distributed. The cross-sectional area of ​​the flow equalization module at the air outlet gradually decreases along the airflow direction, and this flow equalization module may consist only of the distribution plate 1062.

[0061] According to an embodiment of the present invention, in another aspect, a heating method is also provided. The heating method uses the electric heating device provided by the present invention. The heating method includes: introducing air to be heated into the heating chamber; activating the heating module 102 to heat the air; and delivering the heated air to the user.

[0062] On the one hand, the heating method uses an electric heating device, and therefore also has the beneficial effects brought by the electric heating device. On the other hand, by introducing air and generating airflow before starting the heating module 102, excessive surface heat load can be avoided in the resistance wire 1023 under high voltage and low surface airflow, ensuring the safe and stable operation of the electric heating device.

[0063] In some embodiments, the heating method further includes dynamically adjusting the start and stop of each heating module 102 according to the power capacity and heat load.

[0064] In other words, during normal heating, the low-temperature air to be heated is evenly distributed into the heating module 102 through the guide plate 1061 and the air distribution plate 1062 in the flow equalization module. Each heating module 102 is in working condition. The electrical energy from green electricity or off-peak electricity is connected to the three-phase resistance wires 1023 of each heating module 102 through the three-phase leads of the electronic control unit 107. The resistance wires 1023 convert electrical energy into heat energy. The air is heated step by step by each heating module 102 along the horizontal flow until the air is heated to the target temperature and then discharged from the air outlet for user use.

[0065] When there are significant changes in power capacity and heat load, only some heating modules 102 are activated to heat the air, depending on the specific circumstances. That is, the power of the heating module 102 is dynamically adjusted and matched with the power capacity and heat load to ensure that the electric heating device is in normal working condition. If a heating module 102 fails, it can be shut down by the control unit 107, and the remaining heating modules 102 can be put into normal use, thereby ensuring a continuous and stable supply of heat to the outside world.

[0066] Furthermore, in some embodiments, when the heat load or power capacity decreases, the heating module 102 is shut off sequentially according to the airflow direction until the heating power of the electric heating device matches the current heat load and power capacity.

[0067] This specific heating method is for an electric heating device with a heat storage module 103. When a sudden power outage or malfunction causes the heating module 102 to malfunction and the gas temperature does not reach the target temperature, the heat stored in the heat storage module 103 inside the electric heating device is used to heat the air, ensuring the continuous and stable heating of the production process in emergency situations.

[0068] In this situation, when the power capacity and heat load change, by prioritizing the shutdown of the heating module 102 near the air inlet and keeping the heating module 102 near the air outlet in operation, it helps to maintain the temperature of the heat storage module 103 near the air outlet, reduce heat loss, and ensure the emergency buffering capacity of the electric heating device.

[0069] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electric heating device, characterized in that include: The housing (101) forms a heating chamber having an air inlet and an air outlet; A heating module (102) is disposed in the heating chamber, and a plurality of heating modules (102) are arranged at intervals along the airflow direction; The heating module (102) includes a support frame (1021), a support rod (1022), and a resistance wire (1023). A plurality of support rods (1022) are spaced apart on the support frame (1021). The support rods (1022) extend in a direction perpendicular to the airflow direction. The resistance wire (1023) is spirally sleeved on the support rod (1022). The resistance wire (1023) is used to connect to a high-voltage power supply. The heating power of the heating module (102) is configured to decrease sequentially along the airflow direction; It also includes a heat storage module (103), which is disposed between two adjacent heating modules (102), and the heat storage module (103) has a flow hole that runs through the airflow direction; The heat storage capacity of the heat storage module (103) gradually increases along the airflow direction; The voltage of the high-voltage power supply is greater than or equal to 1kV; The resistance wire (1023) exchanges heat directly with the air during the heating process; The support rod (1022) extends horizontally, and multiple support rods (1022) are spaced apart along the height direction on the support frame (1021). The resistance wire (1023) is spirally wound around the support rod (1022) along the horizontal axis.

2. The electric heating device according to claim 1, characterized in that The resistance wire (1023) is divided into three groups. The three groups of resistance wires (1023) are respectively used to connect to phase A, phase B and phase C of the high voltage power supply. The resistance wires (1023) in the same group are connected in series.

3. The electric heating device of claim 1, wherein, It also includes insulating bases (104), the number of which corresponds to the number of heating modules (102), which are disposed on the insulating bases (104).

4. The electric heating device of claim 1, wherein, It also includes an insulating layer (105) disposed on the inner wall of the housing (101).

5. The electric heating device of claim 1, wherein, It also includes flow equalization modules, with two flow equalization modules respectively disposed at the air inlet and the air outlet.

6. A heating method characterized by, The heating method uses the electric heating device according to any one of claims 1 to 5, and the heating method includes: Air to be heated is introduced into the heating chamber; The heating module (102) is activated to heat the air; The heated air is then delivered to the user; The start and stop of each heating module (102) are dynamically adjusted according to the power capacity and heat load; When the heat load or the power capacity decreases, the heating module (102) is shut down sequentially according to the airflow direction until the heating power of the electric heating device matches the current heat load and the power capacity.

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