Continuous flow microwave system heating uniformity analysis and system design method

Abstract

The application discloses a continuous flow microwave system heating uniformity analysis and system design method, and belongs to the microwave technology field.The method obtains fluid region power loss density distribution and velocity size distribution by constructing a continuous flow microwave heating system numerical model, calculates fluid region synchronization index and cumulative index based on the numerical solution results, and is used for further analysis of continuous flow microwave heating uniformity and energy utilization efficiency; the system heating uniformity is evaluated based on the cumulative index and the region related uniformity calculation method; the system energy utilization efficiency is evaluated based on the cumulative index or the synchronization index; in addition, the comprehensive cumulative index of a multi-element combination system can be further evaluated according to a power distribution coefficient, and a multi-element combination system with different uniformity and energy utilization efficiency demand proportions can be calculated and obtained. The application provides a specific and executable analysis method for the uniformity design of the continuous flow microwave heating system, and provides a reliable selection basis for the development of the continuous flow microwave heating system.

Description

Technical Field

[0001] This invention relates to heating uniformity analysis and system design methods for continuous flow microwave systems, belonging to the field of microwave technology. Background Technology

[0002] Microwaves refer to electromagnetic waves with frequencies ranging from 300MHz to 300GHz. Microwaves are widely used in modern radar and communication technologies. Besides communication applications, the heating properties of microwaves on dielectric materials make them a promising new technology in the processing field. Compared to traditional heating, microwave heating offers advantages such as rapid heating, fewer byproducts, and higher product purity. However, due to the limited penetration depth of electromagnetic waves in different media, the distribution of hot and cold spots is significant during microwave heating. At the commonly used operating frequency of 2450MHz, microwaves penetrate only a few centimeters into common liquid systems. Therefore, compared to static microwave heating methods such as household microwave ovens, continuous flow microwave heating technology can significantly improve heating uniformity, has high industrialization potential, and helps establish safe, efficient, and sustainable production processes.

[0003] The improvement in material uniformity by continuous flow microwave heating technology mainly lies in accelerating heat diffusion through fluid flow. Furthermore, in steady-state operation, the time it takes for a unit volume of liquid to flow through the microwave radiation region is constant, reducing the risk of heat accumulation at microwave hotspots. Therefore, the improvement in heating uniformity by continuous flow technology primarily relies on the fluid flow process. However, since heat generation is still related to the distribution of the electric field intensity within the material, there is still a risk of temperature inhomogeneity at the pipe outlet when the electric field intensity distribution is uneven, especially when the electric field intensity gradient differs from the fluid velocity gradient.

[0004] The development of existing continuous-flow microwave systems typically relies on S-parameters to evaluate system efficiency and performance. However, even with identical S-parameters, significant differences in heating effects persist. Furthermore, current methods lack an accurate assessment of heating uniformity in continuous-flow microwave systems, hindering system design and optimization and potentially leading to discrepancies between expected and actual results. To overcome these shortcomings, a method is needed to predict the heating uniformity of continuous-flow microwave systems and provide reliable insights for system optimization. Summary of the Invention

[0005] To address the problems of limited evaluation methods for continuous flow microwave heating systems (relying solely on S-parameters) and difficulty in effectively assessing outlet uniformity, this invention provides a method for analyzing heating uniformity and designing a continuous flow microwave system. The technical solution is as follows:

[0006] The first objective of this invention is to provide a method for analyzing the heating uniformity of a continuous flow microwave system, the method comprising:

[0007] Step 1: Establish the finite element model of the continuous flow microwave system;

[0008] Step 2: Numerically solve the finite element model of the continuous flow microwave system and obtain the electromagnetic power loss density and velocity in the fluid region from the results;

[0009] Step 3: Calculate the synchronicity index and the cumulative index;

[0010] The synchronization index is the actual electromagnetic power density distribution after eliminating the influence of velocity in the continuous flow region, and the calculation formula is as follows:

[0011]

[0012] Among them, Q e(x,y,z) V is the electromagnetic power loss density. (x,y,z) Let V be the fluid velocity, ∈ be the velocity calibration coefficient, ∈ be a natural number greater than 0, and Max(V) and Min(V) be the maximum and minimum velocity values, respectively.

[0013] The cumulative index is a linear superposition of the results of the same plane coordinate points on the flow path, and the calculation formula is: C(x,y)=∑ z S(x,y,z), where the z-direction represents the flow path direction;

[0014] Step 4: Perform heating uniformity analysis based on the cumulative index;

[0015] The cumulative exponent result is divided into several regions using concentric circles, with the radius of each circle following the binary exponent method 2. m Where m = 1, 2, 3, ..., M, M+1, and the pipe radius is r, there exist 2 M ≤r, at this time the outermost concentric circle region is the (M+1)th concentric circle, and its value range is 2. M ≤x 2 +y 2 ≤r, when 2 M When r = r, the value of the (M+1)th concentric circle is 0 and m = M;

[0016] The formula for calculating the heating uniformity is:

[0017]

[0018] Among them, C i (x,y) represents the cumulative index within the i-th concentric circle region. This represents the mean of the cumulative index across all calculation regions;

[0019] The smaller the calculated value of heating uniformity U, the better the system uniformity.

[0020] Step 5: Perform heating efficiency analysis based on the synchronization index and cumulative index;

[0021] The energy utilization efficiency of the continuous flow microwave system is E = ∑C(x,y).

[0022] The higher the calculated value of energy utilization efficiency E, the higher the system efficiency.

[0023] Optionally, step 1 includes: drawing a three-dimensional initial geometric model of the continuous flow microwave system in finite element analysis software, defining and determining the material parameters of each part in the geometric model, setting boundary conditions, and meshing the established continuous flow microwave system model.

[0024] Optionally, the three-dimensional initial geometric model includes, but is not limited to: waveguide, microwave cavity, heated material, and heated material container.

[0025] Optionally, the material parameters include, but are not limited to, electromagnetic property parameters, flow property parameters, and thermophysical parameters, and each parameter is defined as a function of temperature.

[0026] Optionally, the boundary conditions include, but are not limited to, physical fields such as electromagnetic fields, laminar or turbulent flow, and fluid heat transfer.

[0027] Optionally, the speed calibration coefficient can be between 0 and 1.

[0028] A second objective of this invention is to provide a design method for a continuous flow microwave heating system, the method comprising:

[0029] Step 1: Using any of the above-mentioned uniformity analysis methods, analyze multiple candidate continuous flow microwave systems to obtain the heating uniformity and energy utilization efficiency of each candidate system;

[0030] Step Two: Based on the heating uniformity and energy utilization efficiency of each candidate system, a combined design of the continuous flow microwave system is carried out. By adjusting the power output ratio of each system, continuous flow system designs with different uniformity and energy efficiency requirements are achieved. The specific design method is as follows:

[0031] Calculate the comprehensive score coefficient of the multivariate combination system based on the cumulative index of the alternative systems:

[0032]

[0033] Where P represents the comprehensive score coefficient, U(C(x,y)) and E(C(x,y)) are functions for calculating uniformity and energy efficiency, and C(x,y) = aC1(x,y) + bC2(x,y) + cC3(x,y) + ... + zC n(x,y), 1, 2, 3, ..., n represent n different candidate systems; a, b, c, ..., z represent the power allocation coefficients of each system, and a+b+c+...+z=1; Max(U) and Min(U) are the maximum and minimum values ​​of heating uniformity in the n candidate systems, respectively; Max(E) and Min(E) are the maximum and minimum values ​​of energy utilization efficiency in the n candidate systems, respectively; and k represents the uniformity allocation coefficient for dividing uniformity and energy efficiency weight ratio.

[0034] The optimal combination of n-element systems and power allocation method is achieved by calculating all possible power allocation coefficients and alternative system combinations through enumeration. When the calculated P value is minimized by adjusting the power allocation coefficients a, b, c, ..., z, the optimal combination of n-element systems and power allocation method is obtained.

[0035] in, A smaller value indicates better system uniformity. The larger the value, the higher the system efficiency, therefore, The smaller the value, the higher the system efficiency; therefore, the smaller the P value, the better the system performance. When the P value is optimized to the minimum, the power allocation coefficients a, b, c, ..., z and the system combination are in the optimal combination state.

[0036] Optionally, the step size δ of the uniformity distribution coefficient k can be set to 0.1.

[0037] Optionally, the step size σ of the power allocation factor can be set to 0.01.

[0038] A third object of the present invention is to provide an electronic device, including a memory and a processor;

[0039] The memory is used to store computer programs;

[0040] The processor is configured to, when executing the computer program, implement the method as described in any of the preceding descriptions.

[0041] The beneficial effects of this invention are:

[0042] This invention proposes a method for analyzing the heating uniformity and designing a system for continuous flow microwave systems. Compared with existing methods for evaluating the performance of such systems, this method can obtain a system design scheme with specified uniformity and energy efficiency requirements based on a thorough assessment of the energy interaction between microwaves and food materials. The synchronization index and accumulation index proposed in this invention are targeted evaluation indicators for continuous flow reaction systems under microwave fields, which can eliminate the problem of microwave energy absorption differences caused by velocity differences in the fluid region. This method has important guiding significance for the design of advanced continuous flow microwave reactors and can be used in the development of microwave chemical reactors, microwave sterilization and disinfection devices, to target and improve the energy efficiency and uniformity of microwave reactors. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the electric field distribution of ten continuous flow microwave heating systems provided in the embodiments of the present invention.

[0045] Figure 2 This is a schematic diagram illustrating the differences in heating efficiency and heating uniformity of ten continuous flow microwave heating systems provided in this embodiment of the invention.

[0046] Figure 3 This is a schematic diagram of the S-parameters of ten continuous flow microwave heating systems provided in the embodiments of the present invention.

[0047] Figure 4 This is a schematic diagram of the synchronization index of ten continuous flow microwave heating systems provided in the embodiments of the present invention.

[0048] Figure 5 This is a schematic diagram of the cumulative index of ten continuous flow microwave heating systems provided in the embodiments of the present invention.

[0049] Figure 6 This is a schematic diagram of the region-related uniformity division rules provided in an embodiment of the present invention.

[0050] Figure 7 This is a schematic diagram illustrating the reliability analysis of the energy efficiency and uniformity evaluation method provided in this embodiment of the invention.

[0051] Figure 8 This is a schematic diagram of a binary system combination scheme based on ten existing continuous flow microwave heating systems under different energy efficiency and uniformity requirements, provided by an embodiment of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0053] Example 1:

[0054] This embodiment provides a method for analyzing the heating uniformity of a continuous flow microwave system. The method uses multiphysics simulation software to numerically simulate the continuous flow microwave heating system and solve for the electromagnetic power loss density distribution and velocity magnitude distribution within the fluid region.

[0055] This embodiment lists ten continuous flow microwave heating systems with different electric field distribution characteristics. Figure 1 Furthermore, the fluid samples processed by these ten systems exhibit different heating efficiencies and heating uniformities. Figure 2 The differentiated heating efficiency and heating uniformity were both obtained through numerical model calculations. Heating efficiency was obtained by evaluating the average temperature at the pipe outlet, and heating uniformity was obtained by calculating the plane temperature data at the pipe outlet using the covariance method. The covariance calculation formula is as follows:

[0056]

[0057] Among them, T i and T a These represent the grid point temperature (K) and the average temperature (K) of the selected region, respectively; n is the total number of grid points.

[0058] The analysis method proposed in this invention will be described in detail below based on ten continuous flow microwave heating systems with significant differences in microwave performance constructed in this embodiment.

[0059] The heating uniformity analysis method in this embodiment includes the following steps:

[0060] (1) Establish the finite element model of the continuous flow microwave heating system, including the following steps:

[0061] In the finite element analysis software COMSOL Multiphysics, a three-dimensional initial geometric model of the continuous flow microwave heating system was drawn, and the material parameters were set. The dielectric property of air was set to 1, the dielectric property of the fluid pipeline region was set to 2.04, and the dielectric property of the fluid region was set to 60-15j.

[0062] In this embodiment, the purpose of setting the dielectric properties of the fluid region to a constant value is to ensure that the S11 parameters of different systems remain constant during the fluid heating process, thereby eliminating the influence of S11 parameter fluctuations on heating efficiency and heating uniformity.

[0063] The parameters of ten systems were optimized using the built-in parametric scanning and optimization modules in COMSOL Multiphysics software, ensuring that the S11 parameter values ​​of all ten systems remained within the range of -10 ± 0.1 dB. The final S-parameters of the ten systems constructed in this implementation are as follows: Figure 3 As shown.

[0064] After the system is built, the electromagnetic power loss density Q in the fluid region of each model is extracted from the numerical model. e(x,y,z) and speed magnitude V (x,y,z) For further calculation and analysis.

[0065] Based on the electromagnetic power loss density Q of each system e(x,y,z) and speed magnitude V(x,y,z) Calculate the synchronization index:

[0066]

[0067] In this embodiment, the speed calibration coefficient is 0.3.

[0068] A schematic diagram of the synchronization index of the ten system fluid regions after calculation is shown below. Figure 4 As shown, the synchronization index can be used to analyze the actual electromagnetic power loss state in each region of the fluid after excluding the influence of velocity.

[0069] Superimpose the calculation results along the flow path, C(x,y)=∑ z S(x,y,z) yields the cumulative exponent results for each system. Based on the cumulative exponent data, a cumulative exponent diagram is plotted, such as... Figure 5 As shown.

[0070] The uniformity of the cumulative exponent of each system is evaluated using the regional correlation uniformity partitioning method. The regional correlation uniformity partitioning rules are as follows: Figure 6 As shown, in the current system, the pipeline radius is 8mm, and the radii of the divided areas are 2mm, 4mm, and 8mm respectively.

[0071] The regional correlation homogeneity is calculated based on the cumulative value results within each concentric circle region.

[0072] The energy utilization efficiency of each system, E = ∑C(x,y), is calculated based on the results of the synchronization index and the cumulative index.

[0073] To confirm the accuracy of the evaluation method proposed in this invention, the system uniformity and energy utilization efficiency scores obtained by the above method are compared with the heating efficiency and heating uniformity results obtained by the numerical model. Figure 2 A trend comparison was performed, and the normalized comparison results are as follows: Figure 7 As shown in the figure. The results demonstrate that the uniformity and energy utilization efficiency evaluation method proposed in this invention has good accuracy and reliability.

[0074] Example 2:

[0075] This embodiment provides a design method for a continuous flow microwave heating system. Based on the ten systems constructed in Embodiment 1, a binary system combination design is performed to obtain combinations with different heating efficiency and heating uniformity requirements.

[0076] In this embodiment, the uniformity allocation coefficient k step size δ used to divide the uniformity and energy efficiency weight ratio is set to 0.1.

[0077] In this embodiment, the power allocation coefficient l step size σ used to divide the power ratio of the two systems is set to 0.01.

[0078] For a binary combinatorial system, C(x,y)=lC i (x,y)+(1-l)C j (x,y) calculates the cumulative index of the combined system, where i and j represent two identical but different alternative systems.

[0079] Cumulative index calculation based on binary combinatorial systems:

[0080]

[0081] Where P represents the comprehensive score coefficient, the smaller the P value, the more ideal the system performance. U(C(x,y)) and E(C(x,y)) are functions for calculating uniformity and energy efficiency, C(x,y) = lC i (x,y)+(1-l)C j (x,y). Max(U) and Min(U) are the maximum and minimum values ​​of heating uniformity in the ten candidate systems, respectively, and Max(E) and Min(E) are the maximum and minimum values ​​of energy utilization efficiency in the ten candidate systems, respectively.

[0082] in, A smaller value indicates better system uniformity. The larger the value, the higher the system efficiency, therefore, A smaller P-value indicates higher system efficiency; therefore, a smaller P-value indicates better system performance. When the P-value is optimized to its minimum, the power allocation coefficient l and the system combination C are at their lowest values. i and C j This represents the optimal combination.

[0083] Assign a value k based on the system uniformity requirement. For example, if the system uniformity requirement is 80%, substitute k = 0.8 into the P-value calculation formula.

[0084] All possible power allocation coefficients and alternative system combinations are calculated using an enumeration method until the obtained P value is minimized. When the calculated P value is minimized by adjusting the power allocation coefficient l, the binary system combination and power allocation method are optimal.

[0085] Based on the above calculation method, binary combination system schemes with uniformity requirement ratios of 100%, 90%, 80%, ..., 10%, and 0 are obtained, and the combination results are as follows: Figure 8 As shown.

[0086] Example 3:

[0087] This embodiment provides a design method for a continuous flow microwave heating system, which combines n systems into an n-element system design to obtain combinations with different heating efficiencies and heating uniformity requirements (n≥2 and n is a positive integer).

[0088] In this embodiment, the uniformity allocation coefficient k step size δ used to divide the uniformity and energy efficiency weight ratio is set to 0.1.

[0089] In this embodiment, the power allocation coefficient step size σ used to divide the power ratio of the two systems is set to 0.01.

[0090] For an n-ary combinatorial system, C(x,y) = aC1(x,y) + bC2(x,y) + cC3(x,y) + ... + zC n (x,y) calculates the cumulative index of the combined system; 1, 2, 3, ..., n represent n different alternative systems; a, b, c, ..., z represent the power allocation coefficients of each system, and a+b+c+...+z=1.

[0091] Cumulative exponent calculation based on n-ary combinatorial systems:

[0092]

[0093] Where P represents the comprehensive score coefficient, the smaller the P value, the more ideal the system performance. U(C(x,y)) and E(C(x,y)) are functions for calculating uniformity and energy efficiency, C(x,y)=aC1(x,y)+bC2(x,y)+cC3(x,y)+…+zC n (x,y). Max(U) and Min(U) are the maximum and minimum values ​​of heating uniformity in the n candidate systems, respectively, and Max(E) and Min(E) are the maximum and minimum values ​​of energy utilization efficiency in the n candidate systems, respectively.

[0094] The process involves enumerating all possible power allocation coefficients and alternative system combinations until the obtained P value is minimized. In other words, the optimal n-element system combination and power allocation method is achieved when the calculated P value is minimized by adjusting the power allocation coefficients a, b, c, ..., z.

[0095] The analytical method proposed in this invention not only accurately evaluates the uniformity and efficiency of a continuous flow microwave heating system while eliminating the influence of velocity magnitude, but also provides a reliable basis and effective data for the development of combined systems with different uniformity and energy efficiency requirements. In practical applications, the analytical method proposed in this invention can also be extended to the combined design of multi-element (>2) systems and can also be applied to situations with complex and variable flow paths.

[0096] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the heating uniformity of a continuous flow microwave system, characterized in that, The method includes: Step 1: Establish the finite element model of the continuous flow microwave system; Step 2: Numerically solve the finite element model of the continuous flow microwave system and obtain the electromagnetic power loss density and velocity in the fluid region from the results; Step 3: Calculate the synchronicity index and the cumulative index; The synchronization index is the actual electromagnetic power density distribution after eliminating the influence of velocity in the continuous flow region, and the calculation formula is as follows: Among them, Q e(x,y,z) V is the electromagnetic power loss density. (x,y,z) Let V be the fluid velocity, ∈ be the velocity calibration coefficient, ∈ be a natural number greater than 0, and Max(V) and Min(V) be the maximum and minimum velocity values, respectively. The cumulative index is a linear superposition of the results of the same plane coordinate points on the flow path, and the calculation formula is: C(x,y)=∑ z S(x,y,z), where the z-direction represents the flow path direction; Step 4: Perform heating uniformity analysis based on the cumulative index; The cumulative exponent result is divided into several regions using concentric circles, with the radius of each circle following the binary exponent method 2. m Where m = 1, 2, 3, ..., M, M+1, and the pipe radius is r, there exist 2 M ≤r, at this time the outermost concentric circle region is the (M+1)th concentric circle, and its value range is 2. M ≤x 2 +y 2 ≤r, when 2 M When r = r, the value of the (M+1)th concentric circle is 0; The formula for calculating the heating uniformity is: Among them, C i (x,y) represents the cumulative index within the i-th concentric circle region. This represents the mean of the cumulative index; Step 5: Perform heating efficiency analysis based on the synchronization index and cumulative index; The energy utilization efficiency of the continuous flow microwave system is E = ∑C(x,y).

2. The method for analyzing the heating uniformity of a continuous flow microwave system according to claim 1, characterized in that, Step 1 includes: drawing a three-dimensional initial geometric model of the continuous flow microwave system in finite element analysis software, defining and determining the material parameters of each part in the geometric model, setting boundary conditions, and meshing the established continuous flow microwave system model.

3. The method for analyzing the heating uniformity of a continuous flow microwave system according to claim 2, characterized in that, The initial three-dimensional geometric model includes, but is not limited to: waveguide, microwave cavity, heated material, and heated material container.

4. The method for analyzing the heating uniformity of a continuous flow microwave system according to claim 2, characterized in that, The material parameters include, but are not limited to, electromagnetic property parameters, flow property parameters, and thermophysical parameters, and each parameter is defined as a function of temperature.

5. The method for analyzing the heating uniformity of a continuous flow microwave system according to claim 2, characterized in that, The boundary conditions include, but are not limited to, physical fields such as electromagnetic fields, laminar or turbulent flow, and fluid heat transfer.

6. The method for analyzing the heating uniformity of a continuous flow microwave system according to claim 1, characterized in that, The speed calibration coefficient ∈ takes a value between 0 and 1.

7. A design method for a continuous flow microwave heating system, characterized in that, The method includes: Step 1: Using the uniformity analysis method described in any one of claims 1-6, analyze multiple candidate continuous flow microwave systems to obtain the heating uniformity and energy utilization efficiency of each candidate system; Step Two: Based on the heating uniformity and energy utilization efficiency of each candidate system, a multi-component combination design of the continuous flow microwave system is carried out. By adjusting the power output ratio of each system, continuous flow system designs with different uniformity and energy efficiency requirements are achieved. The specific design method is as follows: Calculate the comprehensive score coefficient of the multivariate combination system based on the cumulative index of the alternative systems: Where P represents the comprehensive score coefficient, U(C(x,y)) and E(C(x,y)) are functions for calculating uniformity and energy efficiency, and C(x,y) = aC1(x,y) + bC2(x,y) + cC3(x,y) + ... + zC n (x,y), 1, 2, 3, ..., n represent n different candidate systems; a, b, c, ..., z represent the power allocation coefficients of each system, and a+b+c+...+z=1; Max(U) and Min(U) are the maximum and minimum values ​​of heating uniformity in the n candidate systems, respectively; Max(E) and min(E) are the maximum and minimum values ​​of energy utilization efficiency in the n candidate systems, respectively; and k represents the allocation coefficient for dividing uniformity and energy efficiency weight ratios. The optimal combination of n-element systems and power allocation method is achieved by calculating all possible power allocation coefficients and alternative system combinations through enumeration. When the calculated P value is minimized by adjusting the power allocation coefficients a, b, c, ..., z, the optimal combination of n-element systems and power allocation method is obtained.

8. The design method of the continuous flow microwave heating system according to claim 7, characterized in that, The step size δ of the allocation coefficient k is set to 0.

1.

9. The design method of the continuous flow microwave heating system according to claim 7, characterized in that, The step size σ of the power allocation coefficient is set to 0.

01.

10. An electronic device, characterized in that, Including memory and processor; The memory is used to store computer programs; The processor is configured to implement the method as described in any one of claims 1 to 9 when executing the computer program.

Images