A microwave dynamic zoned heating method

Abstract

The application discloses a microwave dynamic partition heating method, characterized in that a plurality of adjustable electromagnetic resonance units are arranged on the surface of a heated material, and a microwave is radiated to the laminated structure of the adjustable electromagnetic resonance units and the heated material, so that the working frequency of each adjustable electromagnetic resonance unit is controlled by applying an external excitation, and microwave dynamic partition heating of the heated material is realized. The application can realize pixel-level heat control precision, and the size of a single pixel point is the structural size of the adjustable electromagnetic resonance unit.

Description

Technical Field

[0001] This invention relates to a microwave heating method, particularly a zoned heating method, and more specifically, a microwave dynamic zoned heating method. Background Technology

[0002] Microwaves are electromagnetic waves with frequencies ranging from 300 MHz to 300 GHz. Compared to traditional electric heating technologies, microwave heating technology offers significant advantages, including non-contact heating, rapid temperature response, fast heating rate, and low energy consumption. Achieving high-precision microwave dynamic zone heating plays a crucial role in areas such as material zone forming, thermal displays, and wearable devices, and may even spur the development of new material heat treatment technologies.

[0003] Currently, there are two main methods for achieving microwave zoned heating: controlling the electromagnetic properties of the highly conductive material itself or controlling the microwave beam. Regarding the method of controlling the material's electromagnetic properties, the literature (see Carbon 2021; 174:518-523) reports a method of spraying graphene solutions with different absorption rates onto the substrate surface to achieve fixed-zone microwave differential heating of the substrate. However, the absorption rate of the graphene solution during microwave heating cannot be controlled, thus preventing dynamic zoned heating of the substrate. Regarding the method of controlling the beam, Chinese patent CN210112318U proposes designing a phased array antenna and controlling the phase of the microwaves fed into the cavity, based on the principle of phase superposition, to achieve control over the distribution of electromagnetic wave energy at different locations on the material surface. However, the electromagnetic waves inside the microwave cavity are in a resonant state, posing a significant challenge to beam-directed control.

[0004] The applicant previously utilized a dielectric layer and subwavelength highly conductive patterns to form an electromagnetic resonant unit. High-power microwave radiation was then used to radiate this "electromagnetic resonant unit + heated material" stacked structure, achieving efficient heating of the heated material (authorization number CN112455048B). Further, by pre-designing electromagnetic resonant units with different frequency response characteristics and then using microwaves of various corresponding frequencies to heat the aforementioned stacked structure, a regionally fixed differentiated heating effect was achieved. However, this also failed to achieve dynamically zoned microwave heating. Based on this, after extensive theoretical analysis, simulation design, and experimental research, the applicant proposed introducing adjustable units that can sense external excitation inside or outside the electromagnetic resonant unit to form an adjustable electromagnetic resonant unit. This allows for dynamic, zoned microwave heating of the heated material using only a single-frequency microwave. Summary of the Invention

[0005] The purpose of this invention is to address the problem of inconvenient heating control, especially zoned heating control, in existing microwave heating methods, and to develop a dynamic zoned microwave heating method.

[0006] The technical solution of this invention is:

[0007] A microwave dynamic zone heating method is characterized by placing multiple adjustable electromagnetic resonant units on the surface of the material to be heated, using microwave irradiation of the above-mentioned "adjustable electromagnetic resonant unit + heated material" stacked structure, and controlling the operating frequency of each adjustable electromagnetic resonant unit by applying external excitation to achieve microwave dynamic zone heating of the heated material.

[0008] The adjustable electromagnetic resonance unit consists of an adjustable unit and an electromagnetic resonance unit.

[0009] The adjustable unit refers to a material or structure whose electromagnetic properties change significantly under external excitation.

[0010] More specifically, the adjustable unit refers to a material or structure whose resistance (R) and / or inductance (L) and / or capacitance (C) parameters change significantly under external excitation, and is installed inside or outside the electromagnetic resonant unit by physical or chemical methods.

[0011] The adjustable unit contacts the highly conductive geometric pattern, and the width w1 of the highly conductive pattern on the overlapping cross section and the width w2 of the active device on the cross section satisfy the following relationship:

[0012] 0 <w2≤w1≤2w2。

[0013] The electromagnetic resonance unit consists of a dielectric layer and a subwavelength highly conductive pattern attached to the dielectric layer.

[0014] The dielectric layer is made of one or more dielectric materials with a dielectric constant less than 16 and a dielectric loss less than 5; the highly conductive pattern refers to a pattern with a conductivity of not less than 10. 3 S·m -1 Patterns made from materials.

[0015] The frequency of the microwave is not lower than 430MHz and not higher than 6000MHz.

[0016] The power density of the microwave is not less than 5mW / cm². 2 .

[0017] The beneficial effects of this invention are:

[0018] 1. The present invention can achieve pixel-level thermal control precision, with the size of a single pixel being the structural size of an adjustable electromagnetic resonant unit.

[0019] 2. The absorption rate of the adjustable electromagnetic resonance unit designed in this invention can be continuously adjusted within the range of (0%, 100%).

[0020] 3. This invention can be implemented with only a single-frequency microwave heating system. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the device used in this invention.

[0022] Figure 2 This is a schematic diagram of the adjustable electromagnetic resonance unit of the present invention.

[0023] Figure 3 The absorption performance of the adjustable electromagnetic resonance unit designed in this invention under different electromagnetic wave incident angles and direction angles is shown in the following figures: (a) Schematic diagram of the adjustable electromagnetic resonance unit arrangement; (b) Polarization sensitivity; (c) Incident angle sensitivity.

[0024] Figure 4 The manufactured adjustable electromagnetic resonant unit and its absorption performance are: (a) multiple adjustable electromagnetic resonant units; (b) absorption performance testing system; (c) simulation results of absorption performance under different control voltages; (d) test results of absorption performance under different control voltages.

[0025] Figure 5 The results of the spatiotemporal microwave dynamic partitioned heating experiment of carbon fiber composite material are as follows: (a) temperature curves of three regions; (b) control voltage of three regions at different stages; (c) infrared map of temperature distribution on the material at different times; (d) simulation results of energy loss on the material at different times.

[0026] Figure 6 These are the experimental results of digital display.

[0027] In the diagram: 1 Magnetron, 2 Microwave transmission line, 3 Microwave resonant cavity, 4 Stage, 5 Heated material, 6 Dielectric layer, 7 Subwavelength high conductivity pattern, 8 Adjustable unit, 9 Wire, 10 DC power supply. Detailed Implementation

[0028] The method solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the protection scope of the present invention.

[0029] like Figure 1 As shown.

[0030] A microwave dynamic zone heating method is characterized by placing a dielectric layer 6, a subwavelength highly conductive pattern 7, and an adjustable unit 8 on the surface of the material to be heated 5. The aforementioned stacked structure and a support stage 4 are placed in a microwave heating cavity 3 for heating. Simultaneously, a DC power supply 10 is connected to an adjustable electromagnetic resonant unit via wires 9 to provide control voltage. The schematic diagram is shown below. Figure 1 As shown.

[0031] In this invention, as a specific embodiment, the heated material is described as a carbon fiber composite material, but the heated material is by no means limited to carbon fiber composite materials. The dielectric layer is made of one or more of the following: polymer, polymer composite material, ceramic, ceramic composite material, ferrite material, ferroelectric material, and ferromagnetic material. Preferably, materials with good dielectric properties such as glass fiber composite, polyimide, and polytetrafluoroethylene are selected. As a specific embodiment, the dielectric layer is described as a flexible polyimide film, but the dielectric layer material is by no means limited to polyimide. The subwavelength high conductivity pattern has a conductivity of not less than 10. 3 S·m -1 The material is preferably made of an electrical conductivity of 10. 5 S·m -1 The materials mentioned above include metals such as copper, aluminum, silver, gold, and zinc. As a specific embodiment, the subwavelength high conductivity pattern is described using copper, but it is by no means limited to copper. The subwavelength high conductivity pattern can be elliptical, fan-shaped, square, or some combinations thereof. The form of the pattern is not the core of this invention. Through reasonable design of the dielectric layer material, thickness, and the material, shape, size, and arrangement of the subwavelength high conductivity pattern, the desired wave impedance or wave impedance distribution can be ultimately obtained. As a specific embodiment, the subwavelength high conductivity pattern used in this invention is as follows: Figure 2 As shown.

[0032] The adjustable unit can be composed of devices whose resistance (R) and / or inductance (L) and / or capacitance (C) parameters can be controllably varied with a control signal. As a specific embodiment, the adjustable control element is described using a varactor diode (whose capacitance varies with the control voltage), but it is by no means limited to varactor diodes. The capacitance value C of the adjustable unit and the absorption rate A of the "adjustable electromagnetic resonant unit + heated material" satisfy the following relationship:

[0033] When A > 20%, C < 1pF.

[0034] The adjustable unit contacts the subwavelength highly conductive pattern and can be placed between patterns or inside a pattern; the width w1 of the subwavelength highly conductive pattern on the overlapping cross section and the width w2 of the adjustable unit on the cross section satisfy the following relationship:

[0035] 0 <w2≤w1≤2w2。

[0036] In a specific embodiment, the adjustable unit is placed between subwavelength high conductivity patterns, and the width w1 of the subwavelength high conductivity pattern at the overlapping cross section and the width w2 of the adjustable unit on the cross section satisfy the following:

[0037] w2 = w1

[0038] Adjustable electromagnetic resonance unit form and size such as Figure 2 As shown, the structural shape, dimensions, layout, and materials in the figure were all determined using the finite element method. The adjustable electromagnetic resonant unit can achieve strong robustness to electromagnetic wave polarization angles and incident angles through its arrangement design, such as... Figure 3 As shown, the highly conductive geometric pattern is etched and attached to the dielectric layer by means of etching, electroplating, photolithography, electron / ion etching, molding, chemical etching, etc.

[0039] After the tunable electromagnetic resonant unit was fabricated, the absorption curves of the "tunable electromagnetic resonant unit + heated material" stacked structure under different control voltages were further tested using a vector network analyzer (VNA). The "tunable electromagnetic resonant unit + heated material" stacked structure, the testing system, and the corresponding simulation and test results are as follows: Figure 4 As shown, the test results and simulation results show good consistency. Furthermore, at the heating frequency (2.45 GHz), the sample absorbance can be continuously varied from 11.2% to 99.6% by controlling the voltage. It should be noted that this absorbance adjustment range can be further expanded by using / designing a larger diode capacitance variation range.

[0040] Example 1.

[0041] Achieving dynamic, zoned microwave heating of carbon fiber composite materials across the spatiotemporal dimensions. This is achieved using carbon fiber reinforced resin matrix composite materials [0 / 90]. 10 Its dimensions are 200 (length) × 60 (width) × 2 (height) mm. 3 The material is divided into three regions, each containing five adjustable electromagnetic resonant units with identical control voltages. The control voltages for the three regions are independent of each other. By applying different control voltages to the three regions sequentially (29V for high absorption rate and 0V for low absorption rate), dynamic microwave zonal heating of the carbon fiber composite material in the spatiotemporal dimension is achieved. Figure 5 As shown, it can be seen that at each moment, the region with high absorption rate heats up at a significantly higher rate than the region with low absorption rate, demonstrating the invention's ability to independently control the temperature of each region in real time. Simultaneously, it can be seen that the energy distribution within the region is relatively uniform, demonstrating the good practicality of this method. Figure 5 As shown.

[0042] Example 2.

[0043] Digital thermal display experiment. Seven independently controllable adjustable electromagnetic resonant units were placed on the surface of a carbon fiber composite material, arranged in the shape of the number "8". By activating the adjustable electromagnetic resonant units on different sides, different thermal display patterns were constructed, such as... Figure 6As shown in the figure, digital thermal display can be achieved through different voltage distribution controls; some numbers, such as "2", "5", "8", "3", "6", and "9", are shown in the figure. This experiment demonstrates that the smallest unit of thermal control achievable by this invention is a single adjustable electromagnetic resonant unit, verifying the advantages of this invention in temperature control accuracy. Figure 6 As shown.

[0044] All parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A microwave dynamic zonal heating method, characterized by: A plurality of adjustable electromagnetic resonance units are placed on the surface of the heated material, the adjustable electromagnetic resonance units and the heated material form a laminated structure, the laminated structure is irradiated by microwaves, the working frequency of each adjustable electromagnetic resonance unit is controlled by applying external excitation, and dynamic partition heating of the heated material by microwaves is realized; the adjustable electromagnetic resonance unit is composed of an adjustable unit and an electromagnetic resonance unit; the adjustable unit refers to a material or structure whose electromagnetic performance will change significantly under external excitation; the electromagnetic resonance unit is composed of a dielectric layer and a subwavelength high-conductivity pattern attached to the dielectric layer; the adjustable unit and the subwavelength high-conductivity pattern are in contact, or are placed between patterns, or are placed inside the pattern; the width of the subwavelength high-conductivity pattern on the overlapping cross section w 1 and the width of the adjustable unit on the cross section w 2 satisfy the following relationship:

2. The method of claim 1, wherein: The medium layer is made of one or more dielectric materials with dielectric constant less than 16 and dielectric loss less than 5; the high conductive pattern refers to a pattern made of materials with electric conductivity not less than 10 3 S·m -1 .

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