Eccentric rotating microwave heating method and device

Abstract

The invention relates to an eccentric rotating microwave heating method and device, and belongs to the technical field of microwave high-flux high-temperature heating. The device comprises a rectangular multi-mold cavity, a turntable in the cavity and a storage table arranged on the turntable according to a certain eccentric distance, wherein the rectangular multi-mold cavity, the turntable and the storage table jointly form a core heating cavity. Microwaves are fed into the cavity through the WR340 standard waveguide, and the non-metal turntable drives the object placing table to eccentrically rotate around the central shaft. By adjusting the eccentric distance, the heated object covers more electromagnetic field distribution areas in the cavity, so that the utilization efficiency of microwave energy is optimized, and the heating uniformity and speed are remarkably improved. The device is suitable for materials with different dielectric properties, and the heating effect and adaptability can be further improved through real-time monitoring and dynamic adjustment functions. The device has the characteristics of high efficiency, energy conservation, safety and reliability, is widely applied to the fields of food processing, chemical engineering, material treatment and the like, and solves the problems of insufficient uniformity and low efficiency of traditional microwave heating.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave high-flux high-temperature heating, and in particular relates to a microwave heating method and device with an eccentric rotation mode. Background Art

[0002] Traditional heating methods usually conduct heat from an external source to the inside gradually, which means that the surface of the material or the surrounding environment is heated first, and then the internal temperature of the material is gradually increased through heat conduction. This heating method has problems such as low efficiency and poor heating uniformity, and it is difficult to meet the needs of efficient and high-quality heating.

[0003] Microwave heating utilizes the dielectric properties of the material itself. Under the action of an external alternating electric field, the polar molecules inside the material are rapidly polarized and frequently change direction with the electric field, thereby directly generating heat inside the material. This heating method does not require heat conduction and can heat the inside and outside of the material at the same time. Compared with traditional methods, it has significantly improved efficiency and better heating uniformity.

[0004] Due to its significant advantages such as rapidity, selectivity and high efficiency, microwave heating technology has been widely used in many fields such as food engineering and chemical engineering. However, as the heating process proceeds, microwave heating may still cause hot spots due to factors such as material properties and electromagnetic field distribution, thus affecting the overall heating uniformity. Therefore, how to further improve the uniformity of microwave heating has become one of the main technical bottlenecks limiting its wider application.

[0005] To solve the above problems, researchers have proposed a variety of improvement methods, such as adding moving elements (such as turntables, conveyor belts, etc.) to the microwave heating cavity; achieving variable frequency heating by changing the microwave frequency; inserting regularly arranged metal rods into the cavity based on the Bragg scattering characteristics to construct a photonic crystal microwave reaction cavity, etc. The core of these methods is to optimize the distribution of the electromagnetic field in the cavity to improve the uniformity of heating. Among them, rotating the turntable is one of the most common means of implementation.

[0006] However, the current mainstream rotating turntable design usually rotates around the central axis of the cavity, so that the turntable is always in the center area of ​​the cavity XY plane. However, the center of the cavity is not the best heating position. This design easily causes microwave energy waste and reduces heating efficiency. Therefore, there is an urgent need for a new microwave heating method and device that can optimize the heating position, make full use of microwave energy, and rotate with a certain eccentricity to significantly improve heating efficiency and uniformity. Summary of the invention

[0007] The purpose of the present invention is to provide a microwave heating method and device using an eccentric rotation method, which can optimize the utilization efficiency of microwave energy, significantly improve the uniformity of heating by adjusting the movement trajectory of the material in the heating chamber, and solve the problems of low heating efficiency and insufficient uniformity in the traditional rotation method. At the same time, the present invention can also reduce the generation of microwave hot spots, thereby improving the heating effect, and is suitable for industrial and scientific research fields with high-throughput and high-temperature heating requirements.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a microwave heating method and device using eccentric rotation, the device mainly comprising a rectangular multi-mode cavity, a turntable inside the cavity, and a storage table fixed on the turntable at a certain eccentric distance. The three together constitute a heating cavity, and microwaves are fed into the cavity through a WR340 standard waveguide connected to the heating cavity, thereby realizing the eccentric rotation microwave heating function.

[0009] The rectangular multimode cavity is made of metal material (usually aluminum) or other materials with high conductivity, such as copper or silver-plated metal plates, to ensure the electromagnetic shielding performance of the cavity and efficient microwave transmission. The interior of the cavity is designed to support the coexistence of multiple modes, which can form a complex electromagnetic field distribution and provide basic conditions for improving heating uniformity.

[0010] The turntable inside the cavity is made of non-metallic materials (usually glass or other materials with low dielectric loss, such as quartz or high-performance plastics) to reduce interference with the microwave distribution in the cavity. The turntable can rotate around the central axis, and the storage table is fixed on the turntable with a certain eccentricity. The eccentricity can be adjusted according to the cavity size and microwave distribution characteristics, so that the heated object experiences an asymmetric motion trajectory in the cavity.

[0011] Microwaves are provided by an external microwave generator, and the operating frequency can be selected as 915MHz, 2.45GHz or 5.8GHz, which are all microwave frequency bands licensed in the industrial, scientific and medical (ISM) fields. Microwaves are fed into the cavity through the WR340 standard waveguide to form a standing wave field.

[0012] The object to be heated is placed on the table and moved around the center of the turntable by eccentric rotation. In this process, the object to be heated is not limited to the center of the cavity, but moves in the cavity based on the eccentric distance, entering the area with better microwave electromagnetic field distribution, thereby significantly improving the heating uniformity and efficiency.

[0013] Furthermore, in order to enter the area with better microwave electromagnetic field distribution, the Maxwell equations can be used to obtain the electromagnetic field distribution in the multi-mode cavity. The mode distribution of the electromagnetic field in the cavity can be expressed as:

[0014]

[0015] Where: a, b, c are the geometric dimensions of the cavity; m, n, p are the mode numbers of the mode; A mnp is the mode coefficient, which is determined by the cavity boundary conditions and the fed power. The electromagnetic field intensity distribution inside the cavity is analyzed to provide theoretical support for the optimization of eccentricity and rotation trajectory.

[0016] Furthermore, by setting the eccentricity, the heated object constantly changes its position inside the cavity, dynamically adjusting the dielectric distribution inside the cavity, thereby to a certain extent, uniformizing the electromagnetic field distribution inside the cavity and reducing the probability of hot spots. The selection of the eccentricity is based on the electromagnetic field distribution and the dielectric properties of the heated object, as shown below:

[0017]

[0018] Wherein: ropt is the optimal eccentric radius; E(r,t) represents the electromagnetic field intensity distribution in the cavity; T is the rotation period; V is the volume where the heated object is located; by optimizing the electromagnetic field distribution in the cavity, the heated object is placed in a more optimal energy-intensive area, thereby maximizing the heating uniformity.

[0019] Experiments have shown that as the eccentricity increases, the uniformity of the heating object is significantly improved, thereby greatly optimizing the heating effect. Users can precisely adjust the eccentricity through the dial on the device or the electronic control interface to adapt to different heating requirements.

[0020] Furthermore, the electromagnetic field distribution monitoring module installed in the cavity collects electric field strength data in real time, and combines the heat distribution feedback from the temperature sensor to dynamically adjust the eccentricity and speed using a closed-loop control algorithm:

[0021] Δr=K p (T target -T current )

[0022] Where: Δr is the adjustment amount of eccentricity; T target is the target temperature; T current is the currently measured temperature; K p It is a proportional control parameter, which is set according to the actual application requirements. The system can dynamically adjust the rotation speed and eccentricity of the turntable to ensure that the heating process is carried out under optimal conditions.

[0023] Furthermore, in order to further verify the effectiveness of the cavity design and the eccentric rotation method, the temperature distribution of the heated object can be predicted by simulation. The temperature change of the heated object is as follows:

[0024]

[0025] Where: ρ is the material density; c is the specific heat capacity; k is the thermal conductivity; Q is the power density of microwave heating: Q = σ|E| 2 ;σ is the dielectric loss factor of the material; |E| 2 is the square of the electromagnetic field strength. This formula is used to evaluate heating uniformity and guide the adjustment of eccentricity and cavity design.

[0026] Furthermore, in order to ensure the safety and reliability of the equipment operation, multiple safety measures are designed outside the cavity, including a microwave leakage detection device and a cavity locking mechanism. The microwave leakage detection device can quickly cut off the power supply when a microwave leakage is detected, and issue an audible and visual alarm to remind the operator to check in time. The cavity locking mechanism prevents the cavity from being accidentally opened during the operation of the equipment, ensuring safety during use.

[0027] Furthermore, in order to improve energy efficiency, the device automatically enters standby mode when no operation is detected for a long time, and reduces energy waste through the intelligent control module. In addition, the power switch of the device is equipped with an indicator light, which can reflect the operating status of the device in real time, making it easier for operators to control the use of the device.

[0028] The beneficial effects of the present invention are:

[0029] Improve the uniformity of microwave heating: The present invention sets a certain eccentricity so that the heated object rotates in a non-central trajectory in the cavity, so that it can cover more electromagnetic field areas. This method effectively solves the problem of local overheating or non-heating caused by uneven distribution of electromagnetic fields during microwave heating, and significantly improves heating uniformity.

[0030] Accelerate heating speed: By optimizing the eccentricity, the heated object can make fuller use of the high electromagnetic field intensity area in the cavity, which significantly improves the energy absorption efficiency during the heating process, thereby accelerating the heating speed. This design can more efficiently meet the rapid heating needs in the industrial, food or chemical fields.

[0031] Adapt to the heating needs of various materials: Since different materials have different dielectric properties and loss factors, the present invention can flexibly adapt to various heated objects by adjusting the eccentricity and rotation speed. This adaptability enables the device to meet the heating needs of different materials in a wide range of application scenarios.

[0032] Reduce energy consumption and improve energy utilization efficiency: The present invention optimizes the cavity design and eccentric rotation method to concentrate microwave energy on the effective area of ​​the heated object, reduce useless energy scattering and loss, significantly improve energy utilization efficiency, and thus reduce operating costs and environmental impact.

[0033] Reduce the complexity of heat distribution simulation: By combining the heat conduction equation and electromagnetic field distribution analysis, the present invention simplifies the modeling and prediction of heat distribution in the cavity. The dynamic adjustment algorithm further improves the automation of the equipment, reduces the need for manual intervention, and provides an efficient and reliable solution for precise control. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the geometric model of the present invention;

[0035] Figure 2 This is the electric field distribution diagram in the cavity during traditional central rotation heating;

[0036] Figure 3 This is the temperature distribution diagram of potatoes heated in a traditional central rotating heating chamber;

[0037] Figure 4 This is the electric field distribution diagram in the cavity when the eccentricity is 10 mm;

[0038] Figure 5 This is the temperature distribution diagram of potatoes heated in the cavity when the eccentricity is 10 mm;

[0039] Figure 6 This is the electric field distribution diagram in the cavity when the eccentricity is 20 mm;

[0040] Figure 7 This is the temperature distribution diagram of potatoes heated in the cavity when the eccentricity is 20 mm;

[0041] Figure 8 This is the electric field distribution diagram in the cavity when the eccentricity is 30 mm;

[0042] Fig. 9 This is the temperature distribution diagram of potatoes heated in the cavity when the eccentricity is 30 mm.

[0043] The numbers in the figure are: 1. WR340 standard waveguide, 2. rectangular multi-mode resonator, 3. thermocouple, 4. sealing device, 5. tray, 6. potato, 7. electromagnetic sensor, 8. eccentricity adjustment switch, 9. glass turntable. DETAILED DESCRIPTION

[0044] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0045] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0046] In the present invention, unless otherwise specified, the directions used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directions are not used to limit the present invention.

[0047] Reference Figure 1 The present invention proposes an eccentrically rotating microwave heating method and device. The basic structure of the device includes a rectangular multi-mode cavity, a turntable in the cavity, and a storage table arranged on the turntable at a certain eccentric distance, and the three together constitute the core cavity structure of microwave heating. The rectangular multi-mode cavity is made of a metal material with high conductivity (such as aluminum), and its outer shell is connected to the microwave generator through a WR340 standard waveguide. The example size is set to 291×291×186mm, which can be adjusted according to actual needs; the microwave generator provides microwaves with a frequency of 2.45GHz, which are fed into the cavity in TE10 mode. A glass turntable is set at the bottom of the cavity, and the turntable is made of a low dielectric loss material (such as glass or quartz) to minimize interference with the microwave electromagnetic field distribution. The turntable is driven by a motor and can rotate around the central axis. Its size can be adjusted according to specific application requirements. The size of this embodiment is R120×10mm. Potato slices are placed on the glass turntable and fixed at a certain eccentric distance. The eccentricity is defined as the distance between the center of the platform and the rotation center of the turntable. By adjusting the eccentricity, the motion trajectory of the heated object in the cavity can be changed. In this embodiment, the eccentricity is set to 10mm, 20mm and 30mm respectively to experimentally evaluate the heating uniformity.

[0048] The heating object is potato slices, which are placed on the storage table. The potato slices have a high dielectric loss factor and can significantly absorb microwave energy. During the eccentric rotation process, the potato slices move eccentrically around the center of the turntable, and their positions are constantly changing, thereby covering more electromagnetic field distribution areas in the cavity.

[0049] Reference Figure 2 To Attachment Fig. 9 : Attached Figure 2 and attached Figure 3 The figure shows the electromagnetic field distribution in the cavity and the temperature distribution of potato slices under the traditional central rotation heating method. It can be seen that the electromagnetic field distribution is relatively concentrated, the temperature distribution is uneven, and there are obvious hot spots in some parts. Figure 4 To Attachment Fig. 9The electromagnetic field distribution and corresponding temperature distribution in the cavity are shown when the eccentricity is 10mm, 20mm and 30mm respectively. As the eccentricity increases, the heated object can cover more electromagnetic field area, the overall heating uniformity is significantly improved, and the local hot spots are gradually weakened.

[0050] In this embodiment, the movement trajectory of the heated object and the utilization rate of the electromagnetic field in the cavity are optimized by adjusting the eccentricity, so that the heating speed and uniformity are significantly improved.

[0051] In addition, the device of the present invention is also equipped with a temperature monitoring module and an eccentricity adjustment mechanism:

[0052] Temperature monitoring module: It can detect the surface and internal temperature distribution of the heated object in real time, and provide data support for adjusting microwave power and eccentricity.

[0053] Eccentricity adjustment mechanism: manual or electric adjustment is adopted to accurately set the optimal eccentricity according to the physical characteristics of the heated object and the heating requirements.

[0054] In summary, the present invention optimizes the uniformity of microwave heating through the eccentric rotation method, while significantly improving the heating efficiency and the flexibility of use of the device, and has high practical application value.

[0055] It should be emphasized that although the present invention describes the technical solution in detail through multiple embodiments, those skilled in the art should understand that the technical solution in the embodiments can be modified or replaced by equivalents without departing from the spirit of the present invention. These modifications or replacements will not change the core technical content and innovation of the present invention. Therefore, the protection scope of the present invention shall be subject to the claims.

Claims

1. An eccentrically rotating microwave heating method and device, characterized in that: The device includes: (1) The rectangular multi-mode cavity is made of highly conductive metal materials and has a cavity structure that supports multi-mode coexistence. The microwave generator is connected to the outside through a WR340 standard waveguide. (2) a turntable, disposed inside the cavity, made of non-metallic material, and capable of rotating around a central axis; (3) a storage table, fixed on the turntable and arranged at a certain eccentricity, for placing the heated object; (4) a microwave generator, used to provide microwaves with a frequency of 915 MHz, 2.45 GHz or 5.8 GHz and feed them into the cavity in TE10 mode; (5) a temperature monitoring module, used to detect the temperature distribution of the heated object in real time; (6) An eccentricity adjustment mechanism is used to adjust the distance between the center of the storage table and the center of the turntable to optimize heating uniformity.

2. The device according to claim 1, characterized in that The turntable is made of glass, quartz or other low dielectric loss materials to reduce interference with microwave field distribution.

3. The device according to claim 1, characterized in that The rectangular multi-mode cavity is made of aluminum or copper material, and has a conductive coating on the surface to further reduce energy loss.

4. The device according to claim 1, characterized in that The eccentricity adjustment mechanism adopts an electronic control method and combines with a motor to achieve precise adjustment of the eccentricity.

5. The device according to claim 1, characterized in that The temperature monitoring module includes a plurality of temperature sensors, which can simultaneously monitor the surface and internal temperature distribution of the heated object.

6. An eccentrically rotating microwave heating method and device, characterized in that: The method includes: (1) The microwave generator feeds microwaves into a rectangular multimode cavity through a WR340 standard waveguide to form a multimode standing wave field; (2) The object to be heated is placed on a storage table, and the storage table is driven to rotate around the central axis at a certain eccentric distance by a turntable; (3) By adjusting the eccentricity, the heated object covers more electromagnetic field area in the cavity; (4) Monitor the temperature distribution of the heated object in real time and dynamically adjust the eccentricity and turntable speed based on the feedback information; (5) Achieve uniform heating of the heated object under the condition of optimizing the electromagnetic field distribution.

7. The method according to claim 6, characterized in that The adjustment of the eccentricity is calculated based on the following formula: Wherein: ropt is the optimal eccentric radius; E(r,t) represents the electromagnetic field intensity distribution in the cavity; T is the rotation period; V is the volume where the heated object is located; by optimizing the electromagnetic field distribution in the cavity, the heated object is placed in a more optimal energy-intensive area, thereby maximizing the heating uniformity.

8. The method according to claim 6, characterized in that The temperature change in the cavity is described by the following heat conduction equation: Where: ρ is the material density; c is the specific heat capacity; k is the thermal conductivity; Q is the power density of microwave heating: Q = σ|E| 2 ;σ is the dielectric loss factor of the material; |E| 2 is the square of the electromagnetic field strength.

9. The method according to claim 6, characterized in that The device can automatically enter standby mode when no operation is detected for a long time, and reduce energy waste through the intelligent control module.

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