A metal tube inside film microwave heating system based on quasi-coaxial structure
By using a quasi-coaxial structure-based microwave heating system for thin films inside metal tubes, the problems of low energy absorption efficiency and heat loss of thin film materials are solved by utilizing TEM mode electromagnetic waves and hot air, thus achieving uniform heating and temperature stability of the thin films.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHENGDU FENYU ELECTRONIC TECH CO LTD
- Filing Date
- 2025-06-24
- Publication Date
- 2026-06-12
Smart Images
Figure CN224356299U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of microwave heating technology, and more specifically to the field of a metal tube thin-film microwave heating system based on a quasi-coaxial structure. Background Technology
[0002] Microwave heating utilizes the interaction between microwaves and the molecules of matter. When microwaves pass through a substance, they cause the molecules to vibrate, converting electromagnetic energy into heat energy. This heating method differs from traditional convection and conduction heating; it is faster and can achieve more uniform heating. With the continuous development of science and technology, microwave heating technology is constantly being improved. For example, by adjusting the microwave frequency and power distribution, heating uniformity can be improved; and by employing advanced sensors and control systems, precise control of the heating process can be achieved.
[0003] Microwave heating of thin films is the process of heating thin film materials using microwave heating technology. Microwave heating can rapidly transfer energy to the interior of the thin film material, thus achieving rapid heating. This is particularly important for thin films that require rapid processing in certain production processes, improving production efficiency. Microwave heating ensures uniform heating throughout the film, avoiding localized overheating or underheating caused by varying conductivity in traditional heating methods. This helps maintain consistent processing quality. Microwave heating only transfers energy to the film that needs heating, without releasing large amounts of heat into the surrounding environment, making it more energy-efficient. Microwave heating systems are typically equipped with advanced sensors and control systems that can monitor the temperature of the bar stock in real time and adjust the microwave power, thereby achieving precise control of the heating process.
[0004] The effectiveness of microwave heating depends on a material's ability to absorb microwave energy. However, thin film materials, such as thin rubber, have low energy absorption efficiency due to their thin-layer structure, making it difficult to quickly and effectively raise the temperature. Firstly, thin film materials have a high surface area to volume ratio, meaning that during heating, surface heat dissipation is more significant than the heat stored within their volume. Secondly, the high surface area of thin film materials increases heat exchange with the surrounding environment, leading to substantial heat loss. This heat dissipation effect further reduces heating efficiency, making it more difficult to maintain and raise the temperature of thin film materials. Utility Model Content
[0005] The purpose of this utility model is to provide a metal tube thin-film microwave heating system based on a quasi-coaxial structure in order to solve the above-mentioned technical problems.
[0006] To achieve the above objectives, this utility model specifically adopts the following technical solution:
[0007] This utility model provides a metal tube thin-film microwave heating system based on a quasi-coaxial structure, including a microwave generating system, a coaxial heating system, a gas flow meter, and a high-pressure gas cylinder; the coaxial heating system includes a gas inlet and a gas outlet, the high-pressure gas cylinder is connected to the gas inlet through a gas pipeline, the gas flow meter is installed on the gas pipeline, the high-pressure gas cylinder is filled with hot air, the microwave generating system is connected to the coaxial heating system, and the microwave generating system feeds microwaves into the coaxial heating system.
[0008] Specifically, such as Figure 1 The diagram shown is a theoretical system diagram for thin-film heating. Microwaves are fed into the coaxial heating cavity through a microwave generator system, thereby heating the thin-film load within the coaxial heating system. During the heating process, hot air is introduced into the coaxial heating system using a gas flow meter and a high-pressure gas cylinder to maintain the temperature of the thin film and prevent it from dissipating heat rapidly, thus making the measurement results more accurate.
[0009] In one embodiment, the microwave generating system includes a solid-state source, a circulator, a microwave power measuring device, and a waveguide-coaxial converter arranged sequentially. The solid-state source feeds microwaves into the coaxial heating system through the circulator, the microwave power measuring device, and the waveguide-coaxial converter. The other end of the circulator is connected to a water load for absorbing and reflecting microwaves and protecting the solid-state source. The microwave power measuring device includes a directional coupler, a microwave power meter, and a subsequently heated thin film sample.
[0010] Specifically, such as Figure 2 The diagram shown is of a coaxial heating system. Figure 2 (a) shows the structure of each part of the experimental system. First is the microwave generation system, where a solid-state source feeds microwaves into a coaxial heating cavity via a waveguide-coaxial converter and a circulator. The other end of the circulator is connected to a water load to absorb reflected microwaves and protect the solid-state source. The microwave power measurement equipment includes a directional coupler, a microwave power meter, and the subsequently heated thin film sample.
[0011] In one embodiment, the coaxial heating system includes a coaxial heating cavity connected to a waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. A thin film sample is disposed between the aluminum shell and the copper core. The thin film sample is attached to the inner wall of the aluminum shell and there is a gap between it and the copper core. The gap is filled with hot air.
[0012] Specifically Figure 2 (b) and Figure 2 (c) shows the impedance matching structure and material distribution of the coaxial heating cavity. The impedance matching structure is achieved using a wedge-shaped coaxial structure. The materials of each part of the heating element from the outside to the inside are: aluminum as the outer conductor, thin film dielectric, thin film sample, and copper. HD represents the thickness of the thin film.
[0013] In one embodiment, the coaxial heating system includes a coaxial heating cavity connected to a waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. A thin film sample is disposed between the aluminum shell and the copper core. The thin film sample is wrapped around the outside of the copper core and there is a gap between it and the aluminum shell. The gap is filled with hot air.
[0014] In one embodiment, the thin film sample is made of polytetrafluoroethylene.
[0015] In one embodiment, the thin film sample is attached to an aluminum shell to form a thin film structure with a ring-shaped cross-section, and the thin film structure and the aluminum shell are coaxially arranged.
[0016] Specifically, during the heating of the thin film sample, the thin film sample and the aluminum shell are regarded together as an external conductor, thus forming a quasi-coaxial structure, which excites stable TEM mode electromagnetic waves and achieves in-situ uniform heating.
[0017] In one embodiment, the thickness of the thin film structure is 0.2 mm to 0.4 mm.
[0018] In one embodiment, the cavity cross-sectional diameter of the thin film structure is 24mm-28mm.
[0019] In one embodiment, the thin film structure has an electrical conductivity of 1100 S / m to 3100 S / m.
[0020] The beneficial effects of this utility model are as follows:
[0021] 1. Existing microwave heating methods rely on the material's ability to absorb microwave energy. However, thin film materials, such as thin rubber, have low energy absorption efficiency due to their thin-layer structure, making it difficult to quickly and effectively raise the temperature. Firstly, thin film materials have a high surface area to volume ratio, meaning that surface heat dissipation is more significant than heat storage within their volume during heating. Secondly, the high surface area of thin film materials increases heat exchange with the surrounding environment, leading to substantial heat loss. This heat dissipation effect further reduces heating efficiency, making it more difficult to maintain and raise the temperature of the thin film material. Therefore, this invention designs a coaxial microwave heating cavity operating at 2.45 GHz, utilizing a TEM mode electric field to uniformly heat the thin film, thereby solving the problem of traditional multimode cavities failing to uniformly heat rod materials.
[0022] 2. There has been no research or attempt to use strip wire for heating continuous bar stock. This design not only solves the limitations of microwave heating of continuous bar stock, but also provides new possibilities for the industrial development of microwave heating. Attached Figure Description
[0023] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.
[0024] Figure 1 This is a schematic diagram of a thin-film microwave heating system for metal tubes based on a quasi-coaxial structure.
[0025] Figure 2 This is a schematic diagram of a thin-film microwave heating system in a metal tube based on a quasi-coaxial structure.
[0026] Figure 3 A schematic diagram of the boundary settings and electric field distribution for traveling wave heating.
[0027] Figure 4 A schematic diagram of the boundary setting and electric field distribution for standing wave heating.
[0028] Figure 5 This is a graph showing the heating efficiency analysis.
[0029] Figure 6 The diagrams show the heating efficiency analysis for different dielectrics: (a) for standing wave heating and (b) for traveling wave heating.
[0030] Figure 7 This is a temperature distribution diagram.
[0031] Figure 8 This is a temperature distribution diagram for films of different thicknesses.
[0032] Figure 9 Temperature distribution diagrams for films of different sizes. Detailed Implementation
[0033] To make the technical problems, technical solutions, and technical effects of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0035] Example 1
[0036] This embodiment provides a metal tube-based thin-film microwave heating system based on a quasi-coaxial structure, including a microwave generating system, a coaxial heating system, a gas flow meter, and a high-pressure gas cylinder. The coaxial heating system includes a gas inlet and a gas outlet. The high-pressure gas cylinder is connected to the gas inlet through a gas pipeline. The gas flow meter is installed on the gas pipeline. The high-pressure gas cylinder is filled with hot air. The microwave generating system is connected to the coaxial heating system, and the microwave generating system feeds microwaves into the coaxial heating system.
[0037] Specifically, such as Figure 1 The diagram shown is a theoretical system diagram for thin-film heating. Microwaves are fed into the coaxial heating cavity through a microwave generator system, thereby heating the thin-film load within the coaxial heating system. During the heating process, hot air is introduced into the coaxial heating system using a gas flow meter and a high-pressure gas cylinder to maintain the temperature of the thin film and prevent it from dissipating heat rapidly, thus making the measurement results more accurate.
[0038] Example 2
[0039] This embodiment is a further optimization based on Embodiment 1, specifically:
[0040] The microwave generation system includes a solid-state source, a circulator, a microwave power measurement device, and a waveguide-coaxial converter arranged in sequence. The solid-state source feeds microwaves into the coaxial heating system through the circulator, the microwave power measurement device, and the waveguide-coaxial converter. The other end of the circulator is connected to a water load for absorbing and reflecting microwaves and protecting the solid-state source. The microwave power measurement device includes a directional coupler, a microwave power meter, and a subsequently heated thin film sample.
[0041] Specifically, such as Figure 2 The diagram shown is of a coaxial heating system. Figure 2 (a) shows the structure of each part of the experimental system. First is the microwave generation system, where a solid-state source feeds microwaves into a coaxial heating cavity via a waveguide-coaxial converter and a circulator. The other end of the circulator is connected to a water load to absorb reflected microwaves and protect the solid-state source. The microwave power measurement equipment includes a directional coupler, a microwave power meter, and the subsequently heated thin film sample.
[0042] The coaxial heating system includes a coaxial heating cavity connected to a waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. The thin film sample is placed between the aluminum shell and the copper core. The thin film sample is wrapped around the outside of the copper core and there is a gap between it and the aluminum shell. The gap is filled with hot air.
[0043] Example 3
[0044] This embodiment is a further optimization based on Embodiment 1, specifically:
[0045] The microwave generation system includes a solid-state source, a circulator, a microwave power measurement device, and a waveguide-coaxial converter arranged in sequence. The solid-state source feeds microwaves into the coaxial heating system through the circulator, the microwave power measurement device, and the waveguide-coaxial converter. The other end of the circulator is connected to a water load for absorbing and reflecting microwaves and protecting the solid-state source. The microwave power measurement device includes a directional coupler, a microwave power meter, and a subsequently heated thin film sample.
[0046] Specifically, such as Figure 2 The diagram shown is of a coaxial heating system. Figure 2 (a) shows the structure of each part of the experimental system. First is the microwave generation system, where a solid-state source feeds microwaves into a coaxial heating cavity via a waveguide-coaxial converter and a circulator. The other end of the circulator is connected to a water load to absorb reflected microwaves and protect the solid-state source. The microwave power measurement equipment includes a directional coupler, a microwave power meter, and the subsequently heated thin film sample.
[0047] The coaxial heating system includes a coaxial heating cavity connected to a waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. The thin film sample is placed between the aluminum shell and the copper core. The thin film sample is attached to the inner wall of the aluminum shell and there is a gap between it and the copper core. The gap is filled with hot air.
[0048] Specifically Figure 2 (b) and Figure 2 (c) shows the impedance matching structure and material distribution of the coaxial heating cavity. The impedance matching structure is achieved using a wedge-shaped coaxial structure. The materials of each part of the heating element from the outside to the inside are: aluminum as the outer conductor, thin film dielectric, thin film sample, and copper. HD represents the thickness of the thin film.
[0049] The thin film sample is made of polytetrafluoroethylene.
[0050] The thin film sample is attached to the aluminum shell to form a thin film structure with a ring-shaped cross-section, and the thin film structure and the aluminum shell are coaxially arranged.
[0051] Specifically, during the heating of the thin film sample, the thin film sample and the aluminum shell are regarded together as an external conductor, thus forming a quasi-coaxial structure, which excites stable TEM mode electromagnetic waves and achieves in-situ uniform heating.
[0052] The thickness of the thin film structure is 0.2mm-0.4mm.
[0053] The cavity cross-sectional diameter of the thin-film structure is 24mm-28mm.
[0054] The conductivity of the thin film structure is 1100 S / m-3100 S / m.
[0055] Feasibility analysis of efficient and uniform heating in this embodiment:
[0056] Quasi-coaxial structure: During the heating of the thin film sample, the thin film sample and the aluminum shell are regarded together as the outer conductor, thus forming a quasi-coaxial structure, which excites stable TEM mode electromagnetic waves and achieves in-situ uniform heating.
[0057] Two heating methods: traveling wave heating and standing wave heating, as detailed below:
[0058] Both heating methods have an input power of 100W and a frequency of 2.45GHz.
[0059] Traveling wave heating: Figure 3 The boundary setting and electric field distribution for traveling wave heating, wherein Figure 3 (a) is the boundary setting, with the right side of the cavity being port 2 by default, but no microwaves are fed into port 2. Figure 3 (b) shows the electric field distribution of traveling wave heating, which is stable and uniform.
[0060] Standing wave heating: Figure 4 The boundary setting and electric field distribution for standing wave heating, wherein Figure 4 (a) To set the boundary, the right side of the cavity is set as an ideal electrical conductor. Figure 4 (b) shows the electric field distribution of standing wave heating. The electric field modulus exhibits a periodic distribution. Although the electric field distribution is not as uniform as that of traveling wave heating in the longitudinal direction, the electric field modulus is significantly increased. This means that the energy radiated to the thin film load is significantly increased, thus improving the energy utilization rate of heating.
[0061] Figure 5 The heating analysis diagrams under different parameters are shown, taking dielectric 10-j as an example. Figure 5 (a) shows the effect of film thickness on heating efficiency. Figure 5 (b) shows the effect of film length on heating efficiency. Figure 5In (a), the efficiency changes of the two heating methods were analyzed when the film thickness changed from 2 mm to 10 mm. It can be found that the heating efficiency of the film in both heating methods is positively correlated with the film thickness. Figure 5 In (b), the efficiency changes of the two heating methods were analyzed when the film length varied from 20 cm to 80 cm. It was found that both heating methods were positively correlated with the film length, and the standing wave heating was more effective than the traveling wave heating. Comparing the effects of the two parameters, the film thickness had a significantly greater impact on the heating efficiency than the film length.
[0062] Figure 6 The heating analysis diagrams under different dielectrics are shown, taking a thin film with a length of 30 cm and a thickness of 2 mm as an example. When the real part of the dielectric varies in the range of 10-80 and the imaginary part varies in the range of 0.1-0.5, the efficiency of standing wave heating is significantly higher than that of traveling wave heating.
[0063] Based on the above analysis, it is easy to see that the effect of standing wave heating is better than that of traveling wave heating. The following analysis will focus on the efficiency and temperature distribution under standing wave heating.
[0064] Uniformity analysis of microwave heating:
[0065] The effect of electrical conductivity on heating:
[0066] Figure 7 The temperature distribution under standing wave heating is shown, using a thin film with a length of 40 cm and a thickness of 0.3 mm as an example. The dielectric is distributed on the inner wall of the outer conductor and heated by a magnetic field. Since there is no magnetic loss, the dielectric is then set as a metallic thin film, heated by microwave current coupled to the inner wall of the cavity. The effects are shown for thin film conductivity ranging from 100 to 9000 S / m, with a heating time of 10 s.
[0067] Figure 7 The electrical conductivity values in the graphs, from left to right, are 100 S / m, 1100 S / m, 2100 S / m, 3100 S / m, 4100 S / m, 5100 S / m, 6100 S / m, 7100 S / m, and 8100 S / m. Heating is more effective within the conductivity range of 1100 S / m to 3100 S / m. The highest heating temperature is achieved at a conductivity of 2100 S / m, but this also results in the largest COV. Therefore, the conductivity can be optimized.
[0068] The effect of film thickness on heating:
[0069] like Figure 8 The figure shows the heating temperature distribution of films with different thicknesses, taking a film with a length of 40 cm and a conductivity of 2100 S / m as an example. The film thickness varies from 0.1 mm to 0.9 mm. The heating time is 10 s. Figure 8The film thicknesses in the figures, from left to right, are 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, and 0.9 mm. Films that are too thin or too thick cannot heat effectively. A film thickness of 0.2 mm to 0.4 mm results in better heating, and the COV of the heated film is positively correlated with the film thickness; the thinner the film, the more uniform the heating.
[0070] The effect of thin film cross-sectional dimensions on heating:
[0071] Analyzing the relationship between cavity size and heating effect—equivalent to changing the cross-sectional size of the metal film. For example... Figure 9 The figure shows the heating temperature distribution of thin films of different sizes, taking a 40cm long film with a conductivity of 2100 S / m and a thickness of 0.3mm as an example. The cavity cross-sectional diameter changes from 24mm to 40mm, and the change in cavity size is equivalent to the change in film size. The heating time is 10s. Figure 9 The cross-sectional dimensions of the cavities in the figures, from left to right, are 24mm, 26mm, 28mm, 30mm, 32mm, 34mm, 36mm, 38mm, and 40mm. The heating effect is better when the cross-sectional dimensions are between 24mm and 28mm, demonstrating that compressing the cavity size leads to a more concentrated electric field and improved heating efficiency. Furthermore, the COV of thin-film heating is negatively correlated with the film size; smaller films are easier to heat but exhibit poorer uniformity. Therefore, it is necessary to optimize the film size appropriately.
Claims
1. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure, characterized in that, The system includes a microwave generating system, a coaxial heating system, a gas flow meter, and a high-pressure gas cylinder. The coaxial heating system includes a gas inlet and a gas outlet. The high-pressure gas cylinder is connected to the gas inlet via a gas pipeline. The gas flow meter is installed on the gas pipeline. The high-pressure gas cylinder is filled with hot air. The microwave generating system is connected to the coaxial heating system and feeds microwaves into the coaxial heating system.
2. The metal tube thin-film microwave heating system based on a quasi-coaxial structure according to claim 1, characterized in that, The microwave generating system includes a solid-state source, a circulator, a microwave power measuring device, and a waveguide-coaxial converter arranged in sequence. The solid-state source feeds microwaves into the coaxial heating system through the circulator, the microwave power measuring device, and the waveguide-coaxial converter. The other end of the circulator is connected to a water load for absorbing and reflecting microwaves and protecting the solid-state source. The microwave power measuring device includes a directional coupler, a microwave power meter, and a subsequently heated thin film sample.
3. The metal tube thin-film microwave heating system based on a quasi-coaxial structure according to claim 2, characterized in that, The coaxial heating system includes a coaxial heating cavity connected to the waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. The thin film sample is disposed between the aluminum shell and the copper core. The thin film sample is attached to the inner wall of the aluminum shell and there is a gap between it and the copper core. The gap is filled with hot air.
4. The metal tube thin-film microwave heating system based on a quasi-coaxial structure according to claim 2, characterized in that, The coaxial heating system includes a coaxial heating cavity connected to the waveguide coaxial converter. The coaxial heating cavity includes an impedance matching structure, which includes an outer aluminum shell as an outer conductor and an inner copper core as an inner conductor. The copper core is located on the center line of the aluminum shell. The thin film sample is disposed between the aluminum shell and the copper core. The thin film sample is wrapped around the outside of the copper core and has a gap with the aluminum shell. The gap is filled with hot air.
5. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure according to claim 3, characterized in that, The thin film sample is made of polytetrafluoroethylene.
6. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure according to claim 5, characterized in that, The thin film sample is attached to the aluminum shell to form a thin film structure with a ring-shaped cross-section, and the thin film structure and the aluminum shell are coaxially arranged.
7. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure according to claim 6, characterized in that, The thickness of the thin film structure is 0.2mm-0.4mm.
8. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure according to claim 6, characterized in that, The cavity cross-sectional diameter of the thin film structure is 24mm-28mm.
9. A metal tube-based thin-film microwave heating system based on a quasi-coaxial structure according to claim 6, characterized in that, The thin film structure has an electrical conductivity of 1100 S / m-3100 S / m.