A fluid heating device combining high frequency resistance heat and induction heat

Abstract

The application discloses a fluid heating device combining high-frequency resistance heat and induction heat, which comprises a high-frequency AC power supply for generating high-frequency AC power with an alternating frequency of f0; and a heating body for constructing a current path; the high-frequency AC power supply has two output ends, and the AC power with the alternating frequency of f0 output between the two output ends is far greater than a commercial power frequency; the heating body is arranged in a flow channel of the fluid to be heated; and the two ends of the heating body are connected with the two output ends of the high-frequency AC power supply and kept in electrical conduction. Compared with the prior art, the fluid heating device combining high-frequency resistance heat and induction heat provided in the application has the advantages of simple structure, small size, long service life, long-time stable work without burning loss, and convenient application in a wide range of industrial hot air, industrial hot water, domestic hot water and other fluid heating application occasions.

Description

Technical Field

[0001] This invention belongs to the field of industrial heating technology, and specifically relates to a fluid heating device. Background Technology

[0002] In both industrial applications and daily life, there are frequent scenarios requiring the heating of fluids such as gases or liquids. For example, in the printing industry, liquid ink needs to be heated to a certain temperature before being sprayed onto a substrate to form text or images. Similarly, common household appliances such as water heaters, hot air blowers, and steam boilers for heating drinking water all essentially utilize heating methods to obtain fluids at a specific temperature. Fluid heating processes are widely used in industrial processes such as welding, pharmaceuticals, printing, packaging, cleaning, and heat treatment, as well as in everyday scenarios like boiling water and air conditioning heating.

[0003] Fluid heating processes require a corresponding fluid heater to execute. Existing fluid heaters often use resistance wires as the heating element to provide a heat source for the fluid. For example, Chinese patent application CN202021988075.2 provides a fluid heater that explicitly describes: a resistance heating element comprising a resistance wire; the resistance wire having a heating resistance wire and a temperature-controlling resistance wire, the heating resistance wire including a thin resistance wire and a thick resistance wire; a fluid heating container comprising a body and a cover; the body and cover forming a cavity, the cover having a fluid inlet, and the body having a fluid outlet near the cover; and an electrical control system including a heating element temperature detection circuit; wherein the resistance heating element is located within the cavity inside the fluid heating container.

[0004] The technical solution described in the aforementioned patent employs a "heating resistance wire," which is the most common and typical implementation of fluid heating devices in the prior art. This implementation is widely used in existing fluid heating devices. After constructing the heating component in the fluid heating device in the above manner, the heating component will have a certain resistance value R at the electrical level. In actual processing, a direct current or power frequency alternating current with a certain current amplitude needs to be passed through the "heating resistance wire." This "heating resistance wire" is based on P=I 2 Only by understanding the principle of R can heat be generated.

[0005] In existing technologies, a resistance wire is used as the heating element, and current is passed through the resistance wire, based on P=I 2 When the principle of R generates heat, to improve heating efficiency, the resistance R of the resistance wire or the magnitude of the current I flowing through the resistance wire should be increased as much as possible. According to the formula for calculating the resistance of the resistance wire: R = ρl, where ρ is the resistance of the resistance wire...

[0006] s

[0007] Resistivity, l is the effective length of the resistance wire connected in the circuit, and s is the cross-sectional area of ​​the largest connected resistance wire. It can be clearly seen from the above formula that if the resistance value of the resistance wire needs to be increased, it can be achieved by selecting a material with higher resistivity to prepare the resistance wire, or by connecting a resistance wire that is as long and thin as possible.

[0008] It should be pointed out that when the above-mentioned methods of increasing the current in the resistance wire and increasing the resistance wire's own resistance value are applied to specific fluid heating devices, there will be obvious drawbacks: On the one hand, increasing the current in the resistance wire will pose challenges to the performance of both the power supply and the resistance wire itself. Not only will the power supply equipment need to output a larger current to meet the requirements, but the components of the power supply equipment itself and the resistance wire itself will also need to be configured with corresponding devices or materials that can withstand a larger current, which will significantly increase the manufacturing difficulty and cost of the entire fluid heating device; On the other hand, in the existing technology, in order to increase the resistance value of the resistance wire used in fluid heating devices, thin resistance wires with high resistivity, long length, and small wire diameter are usually selected and repeatedly wound into the desired shape on a mold. After the entire thin resistance wire is connected to the circuit, the resistance wire heats up. Because the resistance wire itself has a small wire diameter, it is very easy to melt after prolonged heating. For fluid heating devices, once the resistance wire, which is the core heating component, melts, the entire fluid heating device will lose its effectiveness, which brings great difficulties to the smooth progress of the fluid heating process. Summary of the Invention

[0009] To address the aforementioned problems, the present invention aims to provide a fluid heating device that utilizes the dual thermal effects of resistance heating and induced heating of a conductor in a high-frequency alternating current environment to generate a large amount of heat in the conductor.

[0010] Another objective of this invention is to provide a fluid heating device that combines high-frequency resistance heating and induction heating. This device is compact, generates a large amount of heat, has a long service life, is low in cost, and is suitable for widespread application.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows:

[0012] A fluid heating device combining high-frequency resistance heating and induction heating, the heating device comprising:

[0013] A high-frequency AC power supply used to generate high-frequency alternating current with an alternating frequency of f0;

[0014] And, a heating element used to construct a current path;

[0015] The high-frequency AC power supply has two output terminals, and the AC power output between the two output terminals has a variable frequency of f0, which is much greater than the mains frequency; the heating element is placed in the flow channel of the heated fluid; the two ends of the heating element are connected to the two output terminals of the high-frequency AC power supply and maintain electrical conduction.

[0016] When applied to specific fluid heating scenarios, the heating element is made of a conductive material with good conductivity, high resistivity, and good heat resistance. The inherent resistance of the heating element is denoted as R. dc That is, the heating element will exhibit resistive behavior under DC conditions, and its DC resistance value is R. dc The alternating frequency of the AC current output between the two output terminals of the high-frequency AC power supply is f0. After connecting the two ends of the heating element to the high-frequency AC power supply, this alternating frequency of f0 AC current will be applied to the heating element. At this time, due to the skin effect and proximity effect of AC current in the conductor, the heating element will exhibit "AC resistance" characteristics that are completely different from its own natural resistance value. In the technical solution provided in this application, the AC resistance of the heating element in the AC environment with an alternating frequency of f0 is denoted as R. ac That is, the heating element exhibits resistive behavior at the electrical level under AC conditions, and its AC resistance is R. ac At this point, R exists. ac =R dc (1+γ s +γ p ), where γ s This represents the resistance change factor caused by the skin effect of current under the current alternating current environment, where γ is... p This represents the resistance change factor caused by the proximity effect of the current under the current alternating current environment; γ s With γ p Both are positively correlated with f0; the larger f0 is, the greater γ is. s With γ p All of these will increase accordingly.

[0017] In the technical solution provided in this application, a high-frequency AC power supply is set up. After the alternating current output from the high-frequency AC power supply is applied to the heating element, on the one hand, due to the skin effect and proximity effect of AC current, the heating element will exhibit AC resistance characteristics that are significantly greater than the DC resistance value of the heating element at the electrical level. The higher the alternating frequency of the AC current output from the high-frequency AC power supply, the greater the AC resistance exhibited by the heating element at the electrical level, the higher the heating power of the heating element, the greater the heat generation in the same time length, and the higher the heating efficiency of the heating element. On the other hand, the heating element is made of a conductor with good conductivity, high resistivity, and good heat resistance. After being combined with the high-frequency AC power supply, it can form a complete and continuous current path. When AC current is passed through a conductor, it is easy to infer that an alternating magnetic field will be generated near that conductor. The magnetic fields of adjacent conductors affect each other. After the magnetic field generated by the previous conductor covers the next conductor, the magnetic field generated by the previous conductor will induce heating in the next conductor, further increasing the heat generation on the heating element and improving the heating efficiency of the heating element.

[0018] Therefore, it can be said that by placing a heating element in the flow channel of the heated body and applying high-frequency AC power to the heating element, on the one hand, based on the skin effect and proximity effect of AC power, the heating element itself will exhibit AC resistance characteristics that are significantly greater than its DC resistance. The heating element will exhibit excellent resistance heating characteristics at the electrical level, with higher heating power and significantly improved heating efficiency. On the other hand, based on the principle of electromagnetic induction, an alternating magnetic field is generated around the heating element to which AC power is applied. The alternating magnetic field will induce heating in the adjacent section of the heating element, further increasing the heat generated on the heating element. Thus, compared with the existing technology that uses thin resistance wires and relies on the DC resistance characteristics of the resistance wires to generate resistance heat to heat the fluid, the technical solution provided in our application uses a combination of high-frequency AC resistance heat and induction heat to generate heat. After the fluid flows through the heating element, it comes into direct contact with the surface of the heating element, and the fluid molecules exchange heat with the heating element, significantly improving the heating efficiency.

[0019] The heating element provided in this application utilizes high-frequency AC resistance heating and induced heating principles. Increasing the frequency of the output AC power supply effectively enhances the heat generation and efficiency of AC resistance heating and induced heating. The heating element no longer needs to be elongated to achieve higher DC resistance. Therefore, in specific applications, those skilled in the art can use conductors with larger cross-sections, higher conductivity, and better heat resistance to manufacture the heating element, eliminating the need for repeated winding of thin resistance wires. Furthermore, because the heating element is made with conductors that have larger cross-sections, higher conductivity, and better heat resistance, its current resistance and heat resistance are stronger in specific applications. The heating element's structure is simpler, allowing it to withstand prolonged high-temperature heating without melting. This further extends the overall service life of the heating device and improves its stability during operation.

[0020] Furthermore, the heating element includes a first heating element and a second heating element; both the first and second heating elements are disposed in the flow channel of the fluid being heated; the first heating element is disposed on one side of the second heating element, one end of the first heating element is connected to one output terminal of a high-frequency AC power supply, the other end of the first heating element is connected to one end of the second heating element, and the other end of the second heating element is connected to the other output terminal of the high-frequency AC power supply. The first and second heating elements are connected in series sequentially, so the DC resistance of the entire heating element will be the sum of the DC resistances of the first and second heating elements, according to the R... ac =R dc (1+γ s +γ p Increasing the overall DC resistance of the heating element will help to further increase the overall AC resistance of the heating element, thereby helping the heating element to obtain a larger AC resistance and further improve its fluid heating effect.

[0021] Furthermore, the first heating element is placed within the magnetic field range of the second heating element. The first heating element is positioned on the side closer to the center of the flow channel of the heated fluid; the second heating element is positioned on the other side farther from the center of the flow channel of the heated fluid. By placing the first heating element on the center side of the flow channel of the heated fluid and keeping it within the magnetic field range of the second heating element, when alternating current with an alternating frequency of f0 provided by the high-frequency AC power supply is applied to the first and second heating elements, the second heating element will generate an alternating magnetic field around it. This alternating magnetic field will induce eddy currents on the surface of the first heating element within the magnetic field range, thus inducing heating of the first heating element and further increasing the temperature at the surface of the first heating element. When the heated fluid flows along the flow channel, the fluid molecules fully contact it, resulting in a better fluid heating effect.

[0022] Furthermore, the minimum thickness of the first heating element's cross-section is not less than the penetration depth of the current in the first heating element under the current AC environment; the minimum thickness of the second heating element's cross-section is also not less than the penetration depth of the current in the second heating element under the current AC environment. If the minimum thickness of the first heating element's cross-section and the minimum thickness of the second heating element's cross-section are equal to their respective penetration depths, then under the current AC environment, after the AC current output between the two output terminals of the high-frequency AC power supply enters the first and second heating elements, the entire cross-section of the first and second heating elements will participate in current transmission, and the first and second heating elements will be fully utilized. If the minimum thickness at the cross-section of the first heating element and the minimum thickness at the cross-section of the second heating element are both greater than their respective penetration depths, then under the current AC power environment, after the AC power output from the two output terminals of the high-frequency AC power supply enters the first and second heating elements, the surface layer of the first and second heating elements participates in current transport, while the current density in the deeper layers is sparse and the heat generation is not significant. At this time, they will play more of a structural support and heat conduction role, thereby improving the structural stability and heat resistance of the first and second heating elements and ensuring that the first and second heating elements can work stably for a long time without melting.

[0023] The advantages of this invention are as follows: Compared with the prior art, the fluid heating device combining high-frequency resistance heating and induction heating provided in this invention has a simple structure, small size, long service life, and can work stably for a long time without burning out. It is convenient to be applied to a wide range of fluid heating applications such as industrial hot air, industrial hot water, and domestic hot water. Attached Figure Description

[0024] Figure 1 This is a circuit diagram of a hot air device combining high-frequency resistance heating and induction heating, provided in Specific Embodiment 1.

[0025] Figure 2 This is a first-view overall structural diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 1.

[0026] Figure 3 This is a second-view overall structural diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 1.

[0027] Figure 4 This is a cross-sectional view of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 1.

[0028] Figure 5 This is a first-view overall structural diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 2.

[0029] Figure 6This is a second-view overall structural schematic diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 2.

[0030] Figure 7 This is a cross-sectional view of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 2.

[0031] Figure 8 This is a first-view overall structural diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 3.

[0032] Figure 9 This is a second-view structural schematic diagram of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 3.

[0033] Figure 10 This is a cross-sectional view of the hot air device combining high-frequency resistance heating and induction heating provided in Specific Embodiment 3.

[0034] Figure 11 It is a partial structure of two adjacent heating elements in the hot air device that combines high-frequency resistance heating and induction heating provided in Specific Embodiment 3. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] To achieve the above objectives, the technical solution of the present invention is as follows: Specific Implementation Example 1

[0038] Please see Figure 1-4 .

[0039] This specific embodiment provides a fluid heating device that combines high-frequency resistance heating and induction heating, the device comprising:

[0040] A high-frequency AC power supply E used to generate high-frequency alternating current with an alternating frequency of f0;

[0041] And, a heating element L used to construct the current path;

[0042] The high-frequency AC power supply E has two output terminals, and the AC current U output between the two output terminals has a variable frequency of f0. ac f0 is much greater than the mains frequency; the heating element L is placed in the flow channel of the heated fluid; the two ends of the heating element L are connected to the two output terminals of the high-frequency AC power supply and remain electrically conductive.

[0043] Furthermore, in this specific embodiment, the fluid heating device also includes a resonant capacitor C for engaging with the heating element L to form a resonant structure, and a housing S for constraining the flow direction and flow range of the fluid. The heating element L and the resonant capacitor C are both disposed inside the housing S. The resonant capacitor C is disposed near the position where the fluid flows into the housing S, and the heating element L is disposed near the position where the fluid flows out of the housing S. The resonant capacitor C and the heating element L are both connected to the housing S.

[0044] Furthermore, in this specific embodiment, the resonant capacitor C includes at least one capacitor C1, a first water-cooled copper foil C2, a second water-cooled copper foil C3, and a water-cooling pipe C4; the first water-cooled copper foil C2 is in close contact with one of the plates of capacitor C1 and is conductive thereto, and the second water-cooled copper foil C3 is in close contact with the other plate of capacitor C1 and is conductive thereto; the water-cooling pipe C4 is coiled around the first water-cooled copper foil C2 and / or the second water-cooled copper foil C3; the water-cooling pipe C4 is connected to an external cooling water source. The two output terminals of the high-frequency AC power supply E are respectively connected to and conductive to the first water-cooled copper foil C2 and the second water-cooled copper foil C3; the first water-cooled copper foil C2 is also connected to one end of the heating element L and is conductive thereto; the second water-cooled copper foil C3 is also connected to the other end of the heating element L and is conductive thereto.

[0045] Furthermore, in this specific embodiment, the heating element L includes a first heating element L1 and a second heating element L2; both the first heating element L1 and the second heating element L2 are disposed in the flow channel of the heated fluid; the first heating element L1 is disposed on one side of the second heating element L2, one end of the first heating element L1 is connected to the first water-cooled copper sheet C2, the other end of the first heating element L1 is connected to one end of the second heating element L2, and the other end of the second heating element L2 is connected to the second water-cooled copper sheet C3.

[0046] Furthermore, in this specific embodiment, the first heating element L1 is placed within the magnetic field range of the second heating element L2. The first heating element L1 is disposed on the side closer to the center of the flow channel of the heated fluid; the second heating element L2 is disposed on the other side away from the center of the flow channel of the heated fluid.

[0047] Furthermore, in this specific embodiment, the minimum thickness at the cross-section of the first heating element L1 is not less than the penetration depth of the current in the first heating element L1 under the current AC power environment; the minimum thickness at the cross-section of the second heating element L2 is also not less than the penetration depth of the current in the second heating element L2 under the current AC power environment.

[0048] Furthermore, in this specific embodiment, the first heating element L1 extends from the direction close to the capacitor C1 to the direction away from the capacitor C1 and is continuously coiled into a solenoid shape, and the second heating element L2 extends from the direction away from the capacitor C1 to the direction close to the capacitor C1 and is continuously coiled into a solenoid shape surrounding the first heating element L1.

[0049] Furthermore, in this specific embodiment, the first heating element L1 and the second heating element L2 are made of a circular wire coarse conductor with a diameter greater than the penetration depth of the current under the current alternating current environment. Specific Implementation Example 2

[0051] Please see Figure 5-7 ;

[0052] This specific embodiment provides a fluid heating device that combines high-frequency resistance heating and induction heating, the device comprising:

[0053] A high-frequency AC power supply E (not shown in the figure) used to generate high-frequency alternating current with an alternating frequency of f0;

[0054] And, a heating element L used to construct the current path;

[0055] The high-frequency AC power supply E has two output terminals, and the AC current U output between the two output terminals has a variable frequency of f0. ac f0 is much greater than the mains frequency; the heating element L` is placed in the flow channel of the heated fluid; the two ends of the heating element L` are connected to the two output terminals of the high-frequency AC power supply and remain electrically conductive.

[0056] Furthermore, in this specific embodiment, the fluid heating device also includes a resonant capacitor C' for engaging with the heating body L' to form a resonant structure. The resonant capacitor C' is disposed on one side of the heating body L' and is connected to the heating body L'.

[0057] Furthermore, in this specific embodiment, the resonant capacitor C' includes at least one capacitor C1', a first water-cooled copper foil C2', a second water-cooled copper foil C3', and a water-cooling pipe C4'; the first water-cooled copper foil C2' is in close contact with one of the plates of capacitor C1' and is conductive thereto, and the second water-cooled copper foil C3' is in close contact with the other plate of capacitor C1' and is conductive thereto; the water-cooling pipe C4' is coiled around the first water-cooled copper foil C2' and / or the second water-cooled copper foil C3'; the water-cooling pipe C4' is connected to an external cooling water source. The two output terminals of the high-frequency AC power supply E are respectively connected to and conductive to the first water-cooled copper foil C2' and the second water-cooled copper foil C3'; the first water-cooled copper foil C2' is also connected to one end of the heating element L' and is conductive thereto; the second water-cooled copper foil C3' is also connected to the other end of the heating element L' and is conductive thereto.

[0058] The heating element L' includes a first heating element L1' and a second heating element L2'; both the first heating element L1' and the second heating element L2' are disposed in the flow channel of the heated fluid; the first heating element L1' is disposed on one side of the second heating element L2', one end of the first heating element L1' is connected to the first water-cooled copper sheet C2', the other end of the first heating element L1' is connected to one end of the second heating element L2', and the other end of the second heating element L2' is connected to the second water-cooled copper sheet C3'.

[0059] Furthermore, in this specific embodiment, the first heating element L1' is placed within the magnetic field range of the second heating element L2'. The first heating element L1' is disposed on the side closer to the center of the heated fluid flow channel; the second heating element L2' is disposed on the other side away from the center of the heated fluid flow channel.

[0060] Furthermore, in this specific embodiment, the minimum thickness at the cross-section of the first heating element L1' is not less than the penetration depth of the current in the first heating element L1' under the current AC power environment; the minimum thickness at the cross-section of the second heating element L2' is also not less than the penetration depth of the current in the second heating element L2' under the current AC power environment.

[0061] Furthermore, in this specific embodiment, the first heating element L1' extends from the direction close to the capacitor to the direction away from the capacitor and is continuously coiled into a solenoid shape, and the second heating element L2' extends from the direction away from the capacitor to the direction close to the capacitor and is continuously coiled into a solenoid shape surrounding the first heating element L1'.

[0062] Furthermore, in this specific embodiment, the first heating element L1` and the second heating element L2` are made of a wide and flat strip-shaped thick conductor with a thickness greater than the penetration depth of the current under the current alternating current environment. Specific Implementation Example 3

[0064] Please see Figure 8-11 .

[0065] This specific embodiment provides a fluid heating device that combines high-frequency resistance heating and induction heating, the device comprising:

[0066] A high-frequency AC power supply E (not shown in the figure) used to generate high-frequency alternating current with an alternating frequency of f0;

[0067] And, a heating element L`` used to construct the current path;

[0068] The high-frequency AC power supply E has two output terminals, and the AC current U output between the two output terminals has a variable frequency of f0. ac f0 is much greater than the mains frequency; the heating element L`` is placed in the flow channel of the heated fluid; the two ends of the heating element L`` are connected to the two output terminals of the high-frequency AC power supply and remain electrically conductive.

[0069] Furthermore, in this specific embodiment, the fluid heating device also includes a resonant capacitor C`` for engaging with the heating element L`` to form a resonant structure. The resonant capacitor C`` is disposed near the fluid inflow position, and the heating element L`` is disposed near the fluid outflow position; the resonant capacitor C`` is connected to the heating element L``.

[0070] Furthermore, in this specific embodiment, the resonant capacitor C`` includes at least one capacitor C1``, a first water-cooled copper foil C2``, a second water-cooled copper foil C3``, and a water-cooling pipe C4``; the first water-cooled copper foil C2` is in close contact with one of the plates of capacitor C1`` and is conductive thereto, and the second water-cooled copper foil C3` is in close contact with the other plate of capacitor C1`` and is conductive thereto; the water-cooling pipe C4` is coiled around the first water-cooled copper foil C2`` and / or the second water-cooled copper foil C3``; the water-cooling pipe C4` is connected to an external cooling water source. The two output terminals of the high-frequency AC power supply E are respectively connected to and conductive to the first water-cooled copper foil C2`` and the second water-cooled copper foil C3``; the first water-cooled copper foil C2` is also connected to one end of the heating element L`` and is conductive thereto; the second water-cooled copper foil C3` is also connected to the other end of the heating element L` and is conductive thereto.

[0071] The heating element L`` includes a first heating element L1`` and a second heating element L2``; both the first heating element L1`` and the second heating element L2`` are disposed in the flow channel of the heated fluid; the first heating element L1`` is disposed on one side of the second heating element L2``, one end of the first heating element L1`` is connected to the first water-cooled copper sheet C2``, the other end of the first heating element L1`` is connected to one end of the second heating element L2``, and the other end of the second heating element L2`` is connected to the second water-cooled copper sheet C3``.

[0072] Furthermore, in this specific embodiment, the first heating element L1`` is placed within the magnetic field range of the second heating element L2``. The first heating element L1`` is disposed on the side closer to the center of the flow channel of the heated fluid; the second heating element L2`` is disposed on the other side away from the center of the flow channel of the heated fluid.

[0073] Furthermore, in this specific embodiment, the minimum thickness at the cross-section of the first heating element L1` is not less than the penetration depth of the current in the first heating element L1` under the current AC power environment; the minimum thickness at the cross-section of the second heating element L2` is also not less than the penetration depth of the current in the second heating element L2` under the current AC power environment.

[0074] Furthermore, in this specific embodiment, several heating elements L`` are provided. The first heating element L1`` and the second heating element L2`` in each heating element L`` are made of a wide and flat strip-shaped straight thick conductor with a thickness greater than the penetration depth of the current under the current AC environment. In the first heating element L``, one end of the first heating element L1`` is connected to the first water-cooled copper sheet C2``. The second heating element L2`` is located outside the first heating element L1`` and parallel to the first heating element L1``. The other end of the first heating element L1`` is connected to and conducts through one end of the corresponding second heating element L2``. The first heating element L1`` and the second heating element L2`` form a structure similar to a rectangular frame. The other end of the second heating element L2`` is connected to one end of the first heating element L1`` in the next heating element L``, and so on, until the second heating element L2`` in the last heating element L` is connected to and conducts through the second water-cooled copper sheet C3`. Several heating elements L`` keep their respective first heating elements L1` close to the central axis of the flow of the heated fluid, and their respective second heating elements L2` are arranged in a centrally converging multi-fin structure according to the central axis of the heated fluid.

[0075] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fluid heating device combining high-frequency resistance heating and induction heating, characterized in that, The heating device includes: A high-frequency AC power supply used to generate high-frequency alternating current with an alternating frequency of f0; And, a heating element used to construct a current path; The high-frequency AC power supply has two output terminals, and the AC power output between the two output terminals has a variable frequency of f0, which is much greater than the mains frequency; the heating element is disposed in the flow channel of the fluid being heated; the two ends of the heating element are connected to the two output terminals of the high-frequency AC power supply and maintain electrical conductivity. The heating element includes a first heating element and a second heating element; both the first heating element and the second heating element are disposed in the flow channel of the fluid being heated; the first heating element is disposed on one side of the second heating element, one end of the first heating element is connected to one output terminal of the high-frequency AC power supply, the other end of the first heating element is connected to one end of the second heating element, and the other end of the second heating element is connected to the other output terminal of the high-frequency AC power supply. The first heating element is placed within the magnetic field range of the second heating element; The first heating element is located on the side close to the center of the flow channel of the heated fluid; the second heating element is located on the other side away from the center of the flow channel of the heated fluid.

2. The fluid heating device combining high-frequency resistance heating and induction heating as described in claim 1, characterized in that, The minimum thickness at the cross-section of the first heating element is not less than the penetration depth of the current in the first heating element under the current AC environment; the minimum thickness at the cross-section of the second heating element is also not less than the penetration depth of the current in the second heating element under the current AC environment.

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