Predictive complementary frequency selection microwave heating method and system

Abstract

The invention discloses a predictive complementary frequency selection microwave heating method and a predictive complementary frequency selection microwave heating system. The method comprises the following steps: providing an adjustable frequency in a range of 2.2 GHz to 3GHz by using a solid-state microwave source, and providing various frequency selections for material heating. An efficient frequency set of each heating stage is obtained through multi-physics field modeling, and switching is carried out according to needs in the heating process; meanwhile, the frequency is corrected in combination with experiments so as to make up for the simulation limitation. And determining and applying a corrected frequency sequence according to optimal frequency cycle data predicted by simulation and an energy reflection measurement result of the feed-in port during heating. According to the scheme, under the condition that a complex mechanical structure is not added, through advanced frequency selective heating, the heating uniformity is remarkably improved, hot spots and thermal runaway phenomena are reduced, the heating efficiency and the energy utilization rate are improved, and compared with fixed-frequency heating, heating is more efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave heating technology, in particular to a predictive complementary frequency selection method for microwave heating and a heating system. BACKGROUND

[0002] In the process of microwave heating, uniformity has always been a core problem that needs to be solved in the food industry. Traditional microwave heating systems based on magnetrons usually work at a frequency of 2.45 GHz, but this frequency may cause local overheating or cold spots during the heating process due to its unique standing wave effect, affecting the uniformity of heating. With the development of solid-state microwave source technology, new frequency selection methods have become an important direction to improve heating uniformity. Solid-state microwave sources provide a wider frequency bandwidth (such as 2.2 GHz to 3.0 GHz), allowing flexible selection of different frequencies for heating, thereby optimizing the electric field distribution and reducing the occurrence of hot and cold spots.

[0003] Currently, although there are heating methods based on frequency switching, there are still certain challenges. Frequency selection is not only affected by the dielectric properties of materials and electromagnetic wave propagation characteristics, but also needs to consider factors such as power, frequency, and time interval during the specific heating process. In this process, by comparing the heating effect and temperature distribution at different frequencies, more accurate frequency selection can be achieved, effectively avoiding the problem of too single electric field distribution, thereby significantly improving the uniformity of microwave heating. SUMMARY

[0004] Therefore, the present application provides a predictive complementary frequency selection microwave heating method and system to significantly improve heating uniformity and maintain heating efficiency.

[0005] The technical solution is as follows:

[0006] A predictive complementary frequency selection microwave heating method, characterized in that it comprises:

[0007] Establishing a microwave heating multi-physical field calculation model, the model couples electromagnetic field and thermodynamic field, and includes time-varying parameters of dielectric function, density, thermal conductivity, and specific heat capacity of the heated material and other materials;

[0008] According to the multi-physical field model, multi-physical field calculation is performed within the frequency range of 2.2-3GHz, and the temperature distribution complementary characteristics and energy absorption efficiency at each frequency are predicted to select a high-efficiency frequency set for each time period according to the electric field distribution;

[0009] Using the target frequency selected from the high-efficiency frequency set of the initial time period to act on the heating process;

[0010] For the subsequent time period, based on the predicted temperature field distribution at the end of the previous time period, the target frequency matching the complementary temperature distribution is selected from the corresponding set of efficient frequencies and acted upon.

[0011] During heating, the port power reflection is obtained by the measuring device, and the core computing device compares the obtained data with the simulation data to calibrate the complementary frequency sequence obtained by prediction.

[0012] Preferably, during the multi-physical field calculation, the dielectric function is a multi-parameter function with respect to temperature and frequency.

[0013] During the multi-physical field calculation, the frequency step is 0.01 GHz.

[0014] Preferably, when selecting the target frequency from the set of efficient frequencies to determine the heating frequency of the initial time period, it further includes:

[0015] According to the port reflected power, the power with large microwave energy reflection (port reflection greater than 25%) is removed, and the initial frequency is selected from the remaining efficient frequencies.

[0016] Preferably, when calculating the electric field distribution prediction temperature distribution complementary characteristics and energy absorption efficiency of each frequency to screen the efficient frequency of each time period, it further includes:

[0017] According to the port reflected power, first, the power with large microwave energy reflection (port reflection greater than 25%) is removed, and then the complementary frequency is selected from the remaining frequencies according to the temperature pattern of the current heating stage.

[0018] Preferably, after obtaining the set of efficient frequencies corresponding to each time period and the optimal frequency cycle according to the calculation results of each microwave frequency acting on the heated material, it further includes:

[0019] Display the frequency change and the optimal frequency cycle on the liquid crystal screen and prompt the end of the calculation.

[0020] Preferably, after obtaining the set of efficient frequencies corresponding to each time period and the optimal frequency cycle according to the calculation results of each microwave frequency acting on the heated material, it further includes:

[0021] Store the heating frequency calculation results and the optimal frequency cycle.

[0022] A core computing device includes:

[0023] A memory for storing a computer program for predicting complementary frequency selection microwave heating method, dielectric properties of heated material, port reflected power, and temperature data.

[0024] A processor is configured to execute the computer program to implement the steps of the method for predicting complementary frequency selection microwave heating, thereby realizing the method for predicting complementary frequency selection microwave heating according to any one of the preceding embodiments.

[0025] Preferably, the method further comprises:

[0026] An input component is configured to input the dielectric constant and thermodynamic parameters of the heating material through the input component.

[0027] An output component is configured to input the frequency sequence to the frequency control device through the output component.

[0028] A variable-frequency microwave heating system comprises the core computing device, the frequency control device, the measuring device, the microwave feeding device and the heating cavity provided with the microwave feeding device.

[0029] The frequency control device is configured to drive the microwave feeding device to feed the microwave frequency matching the frequency sequence obtained by the method to each reaction time period under the control of the core computing device.

[0030] The microwave feeding device is configured to stably feed the microwave signal generated by the frequency control device into the heating cavity.

[0031] The heating cavity is configured to place the heating material and form a closed metal space. The electromagnetic field signal transmitted by the microwave feeding device forms a stable standing wave in the metal cavity, so that the microwave heating can be smoothly performed.

[0032] The measuring device 35 is configured to measure the port reflection power and transmit the information to the core computing device, and the core computing device corrects the frequency sequence.

[0033] The present application realizes a dynamic frequency selection method based on multi-physical field simulation calculation and actual measurement correction mechanism through the programmable frequency control capability of the solid-state microwave source in a wide frequency band. The multi-physical field simulation is used to predict efficient frequencies and form a sequence for microwave heating. The simulation deviation is corrected by combining measurement calibration, which makes up for the calculation error in a wide frequency band. The double-threshold frequency screening mechanism with the best uniformity and high energy efficiency is used to eliminate local hot spots while maintaining the energy absorption efficiency > 80%. The optimal cycle frequency sequence is used to efficiently utilize microwave energy to achieve uniform heating. The technology is conducive to promoting the dynamic uniformity optimization of microwave heating technology and provides a new solution for the microwave heating application fields of food, chemical industry and the like. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The present application is a whole method flowchart;

[0035] Figure 2Temperature distribution diagram of the embodiment of the present application;

[0036] Figure 3 Temperature mean value change diagram of the embodiment of the present application;

[0037] Figure 4 Schematic diagram of the core computing device of the present application;

[0038] Figure 5 Schematic diagram of the heating system of the present application. Specific implementation method

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0040] The present application provides a technical solution: a complementary frequency selection microwave heating method for prediction, comprising the following steps:

[0041] S1 According to the geometric size and dielectric constant of the microwave heating device and the heated material, and other parameters, a multi-physical field model is established in the finite element analysis software. The model of the multi-physical field includes geometric model, material parameters, physical field setting, boundary condition, partial differential equation, solver setting, etc. All parameters can be called existing parameters or input through external input devices. Then, through the internal setting of the finite element software, the input parameters and equations can be repeatedly called and modified.

[0042] S2 Based on the established heating model, the calculation strategy and stopping condition of the model are formulated by controlling the initial conditions and solving parameters to carry out simulation analysis, and the temperature change in the heating process and the electromagnetic field change in the cavity are given, and the frequency sequence under the given conditions is obtained.

[0043] When the frequency sequence is obtained by the multi-physical field model calculation, the initial frequency, i.e. the initial condition of the calculation, is input by a person through an external input device. After the heating result of the first frequency is calculated, the dielectric constant inside the model is updated. The power reflection of the port at each frequency is calculated, and all frequencies with a reflection greater than 80% of the input power are regarded as low-efficiency frequencies, and the rest are regarded as high-efficiency frequencies that can be used. Then, the electric field distribution and temperature change distribution prediction of all high-efficiency frequencies under the current temperature distribution are calculated. The predicted temperature distribution at each frequency is superimposed and combined with the existing temperature distribution, and the frequency corresponding to the minimum variation coefficient of the temperature data, i.e. the best uniformity, is calculated and saved as the next frequency in the sequence. In this way, the next frequency is repeatedly calculated and saved through prediction and calculation until the termination condition of the calculation is triggered, and the frequency sequence under the calculation condition of the model is obtained.

[0044] S3After the frequency sequence of the multi-physical field model calculation is obtained, a commonly used radio frequency test instrument, i.e. a vector network analyzer, is used in the real physical environment for waveguide calibration. Then, the port energy reflection of the microwave heating system is tested by the device, and the actual measured data is stored. According to the comparison and analysis of the S parameter data in the simulation and the S parameter obtained by the actual measurement, the shifted resonance peak frequency is adjusted. For example, if 2.45 GHz is the frequency determined in the simulation, it is shifted to 2.44 GHz in the experiment, then the corresponding value in the sequence is updated to 2.44 GHz.

[0045] S4After obtaining the complete and corrected frequency sequence, it can be applied to the actual heating process. In specific implementation, the corresponding frequency sequence is preset in the storage, and then the core calculation device controls the frequency regulation device to realize the automatic switching of the microwave heating frequency according to the determined sequence. When using, the core calculation device is sent a start signal through the input device, and the core calculation device controls the frequency regulation device to output a signal for frequency change until the preset heating time ends.

[0046] The comprehensive evaluation of the heating effect is a key step to ensure the effectiveness, operability and practical application value of the method. The comprehensive evaluation of the heating effect needs to consider multiple factors, such as heating uniformity and heating efficiency. The heating effect is generally characterized by professional detection equipment such as optical fiber thermometers and thermal imagers.

[0047] The following is the experimental heating object with the use of K-Carrageenan, which can be proportionally adjusted as the basic material of various food models, and has wide representativeness. In the present embodiment, the frequency range is 2.2 GHz-3 GHz, and the change step is 0.01 GHz, covering 2.45 GHz commonly used in household and industrial microwave ovens. The preparation process of K-Carrageenan is as follows: 1% by weight of K-Carrageenan powder is poured into deionized water, at which time the solution is in a suspended state. Then the solution with K-Carrageenan powder is stirred and heated to 90°C to ensure that the powder is completely dissolved, forming a transparent flowing solution state. Then 0.17% ionic concentration of anhydrous calcium chloride is added to form a hard and stable colloid. The sample is tested by using the conventional 2.45 GHz fixed frequency heating and the proposed variable frequency heating method respectively, and the heating time is 120 seconds and the power is 30 W. When the method proposed in the present application is used, the frequency sequence is switched every 10 seconds. After the foregoing steps, the final frequency sequence used is [2.44 GHz, 2.26 GHz, 2.44 GHz, 2.26 GHz, 2.72 GHz, 2.26 GHz, 2.44 GHz, 2.26 GHz, 2.44 GHz, 2.26 GHz, 2.72 GHz, 2.26 GHz]. During the heating process, a thermal imager is used, and the upper surface temperature is recorded every 60 s, and the initial temperature is 20°C.

[0048] The temperature measurement results of the present embodiment refer to Figure 2 and Figure 3 . Figure 2 The upper three graphs are the temperature distribution of the conventional method, and the lower three graphs are the temperature distribution of the method provided by the present application. The energy is obviously concentrated in the four corners under the conventional method heating, resulting in obvious temperature difference, and the obviously uneven temperature change seriously affects the food heating quality. In the method provided by the present application, the thermal imaging picture color is obviously more uniform, and the temperature difference at different positions is smaller. The heating results of the two methods are statistically compared by the coefficient of variation, and the uniformity is increased by 75%. Figure 3 In the present embodiment, the temperature rises slowly when the conventional method is used, and is obviously faster when the method provided by the present application is used, and the final surface average temperature is increased by 54%. After comparison, the temperature uniformity and average temperature of the method of the present application are obviously better than those of the conventional method when the input power is kept consistent.

[0049] By comparing with the traditional fixed frequency heating method, it can be clearly observed that the proposed frequency adjustment method has significant advantages in improving heating uniformity, improving heating efficiency and improving energy utilization rate. The traditional fixed frequency heating method often cannot avoid the hot spots and cold spots generated during the heating process, resulting in uneven temperature distribution, affecting the quality of the final product. And the method of the application can significantly reduce the phenomenon of uneven temperature distribution through the frequency adjustment strategy, and ensure the uniformity of heating and the quality of the product.

[0050] Through the implementation of the scheme of the application, the temperature uniformity in each heating cycle is significantly improved, thereby greatly improving the heating efficiency, reducing energy waste, and ensuring the safety and stability of the microwave heating process. The optimized frequency switching strategy not only can significantly improve the temperature uniformity, but also can improve the energy utilization rate, so that each link in the heating process can fully utilize the microwave energy and maximize the heating effect.

[0051] The embodiment of the application further provides a core computing device, and a structural schematic diagram thereof is shown in Figure 4 may include:

[0052] The input component 21 is used to input the dielectric constant, thermodynamic parameters of the heating material through the input component;

[0053] The memory 22 is used to store the computer program of the microwave heating frequency selection method, the dielectric properties of the heating material, the port reflection power and the temperature data;

[0054] The output component 23 is used to input the frequency sequence to the frequency regulation device through the output component;

[0055] The processor 24 is used to execute the microwave heating frequency selection method according to the computer program, so as to realize the steps of the microwave heating frequency selection method according to any one of the above.

[0056] The embodiment of the application further provides a variable-frequency microwave heating system, and a structural schematic diagram thereof is shown in Figure 5 may include: a core computing device 31, a frequency regulation device 32, a microwave feeding device 33, a heating cavity 34 provided with the microwave feeding device 33, and a measuring device 35, wherein:

[0057] The frequency regulation device 32 is used to accept the signal of the core computing device and output the microwave signal of the specified frequency;

[0058] The microwave feeding device 33 is used to stably feed the microwave signal generated by the frequency regulation device into the heating cavity;

[0059] A measuring device 35 is used to measure the port reflected power and to transfer information to the core computing device which corrects the frequency sequence.

[0060] The above merely describes the preferred embodiments of the present application, but not other forms of the present application, any skilled person in the art can use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes applied to other fields, but any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution content of the present application, according to the technical essence of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for predicting complementary frequency selective microwave heating, characterized in that: include: Construct a multi-physics calculation model based on the dielectric properties of the heated material and the geometric structure dimensions of the heating cavity; Perform multi-physics calculations within a given microwave frequency range at a preset frequency step size, and obtain the port energy reflection and corresponding predicted temperature distribution at each frequency. Selecting a target frequency with the best performance from the frequency set corresponding to the first heating stage, and applying the target frequency to the first heating stage; In the subsequent heating stage, the body temperature distribution of the heated material at the end of the previous heating stage of the current heating stage is obtained, and the matching frequency that matches the predicted temperature distribution is obtained from the high-efficiency frequency set corresponding to the current heating stage, and the matching frequency is applied to the current heating stage.

2. The predicted complementary frequency selective microwave heating method according to claim 1, characterized in that: When selecting the target frequency with the best performance from the high-efficiency frequency set corresponding to the first heating stage, it also includes: From the frequency set corresponding to the first heating stage, a microwave frequency with low reflection of the port feed energy and high uniformity of heating the material is selected; When matching the target frequency from the set of efficient frequencies corresponding to the current heating stage, it also includes: The microwave frequencies whose energy absorption by the currently heated material is less than 80% are excluded from the frequency set corresponding to the current heating stage.

3. The predicted complementary frequency selective microwave heating method according to claim 1, characterized in that: Obtain a matching frequency that matches the measured reflected power and temperature from a set of efficient frequencies corresponding to the current heating stage, including: A matching frequency that matches the best uniformity is obtained from the relationship between each microwave frequency, the temperature of the heating object and the energy reflection of the port in a pre-established high-efficiency frequency set corresponding to the current heating stage.

4. The predicted complementary frequency selective microwave heating method according to claim 1, characterized in that: The dielectric properties are multi-parameter functions of temperature and microwave frequency.

5. The predicted complementary frequency selective microwave heating method according to claim 1, characterized in that: After predicting the frequency set corresponding to each heating stage based on the calculation result of each microwave frequency acting on the heated material, the method further includes: The frequency sequence of the optimal cycle is calculated and displayed on the LCD screen.

6. The predicted complementary frequency selective microwave heating method according to claim 5, characterized in that: After obtaining the high-efficiency frequency set and the optimal cycle frequency sequence corresponding to each heating stage according to the calculation results of each microwave frequency acting on the heated material at each heating stage, the method further includes: The obtained frequency sequence is stored.

7. A core computing device, characterized in that: include: a memory for storing a computer program for predicting a complementary frequency selective microwave heating method, dielectric properties of a heated material, port reflected power, and temperature data; A processor, configured to execute the predicted complementary frequency selective microwave heating method according to the computer program, thereby realizing the functions as claimed in any one of claims 1 to 6.

8. The core computing device according to claim 7, characterized in that: Also includes: An input component is used to input the dielectric properties of the heating material, the port reflected power and the temperature data required by the core calculation method into the core calculation method through the input component. The output component is used to input the frequency sequence to the frequency control device through the output component.

9. A microwave heating system, characterized in that: The device comprises a core computing device, a frequency control device, a measuring device, a microwave feeding device, and a heating cavity provided with the microwave feeding device as claimed in claim 7 or 8, wherein: The frequency control device is used to drive the microwave feeding device to feed microwave frequencies capable of forming a complementary temperature pattern into the microwave heating cavity under the control of the core computing device; The measuring device is used to measure the surface temperature of the heated material and the reflected power of the port in real time, and send them to the core computing device, which reads the reflected power of the feed port and the surface temperature of the heated material.

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