A cross-flow microchannel heat exchanger structure design and performance optimization method

Abstract

A method for the structural design and performance optimization of a cross-flow microchannel heat exchanger is described. This method establishes a countercurrent single-channel model to screen microchannel size, wall thickness, channel spacing, and cross-sectional shape. Based on the optimal structural parameters, a local model of the cross-flow microchannel heat exchanger is established. By determining the optimization order for the cross-flow microchannel heat exchanger's structural parameters and adjusting structural parameters such as cross-sectional shape and channel size, iterative optimization of heat transfer capacity and uniformity is performed to obtain a cross-flow microchannel heat exchanger core structure that meets both heat transfer capacity and thermal stress requirements. This method can reduce the amount of simulation computation required during the design and optimization of a cross-flow microchannel heat exchanger and optimize the uneven temperature distribution caused by the crossflow of hot and cold fluids, effectively reducing heat transfer non-uniformity within the cross-flow microchannel heat exchanger.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and in particular to a cross-flow microchannel heat exchanger structural design and performance optimization method. Background Art

[0002] Microchannel heat exchangers have the advantages of compact structure, high heat exchange efficiency, small heat transfer temperature difference, and strong temperature and pressure resistance. They are widely used in aerospace, petrochemical, nuclear power, refrigeration and other fields. In the future, they will also be applied on a large scale in supercritical carbon dioxide power generation and solar thermal power generation.

[0003] The structural design of microchannel heat exchangers is an important technical research direction at present. Due to the setting of the header structure, the core of the microchannel heat exchanger is often designed in a vertical cross arrangement of hot and cold fluid channels, such as the attached Figure 1 This causes uneven heat transfer, large differences in fluid temperature in each heat exchange channel, and reduces the overall heat transfer efficiency of the heat exchanger, as shown in the attached figure. Figure 2 In a steam generation system composed of a cross-flow microchannel heat exchanger, premature boiling or drying out may even occur in some channels, affecting the operating efficiency and safety of the heat exchange system. Therefore, structural optimization is required to reduce heat transfer unevenness.

[0004] The design of microchannel heat exchangers lacks mature and accurate thermodynamic calculation formulas. Using formulas such as the surface heat transfer coefficient of conventional-sized channels will result in large design errors. Flow heat transfer simulations are usually required to optimize the structure and verify the performance of the heat exchanger. However, in cross-flow heat exchangers where hot and cold fluids flow vertically, the temperature, flow rate, pressure and other parameters in each channel between the same plates are not equal. Therefore, the cross-flow heat exchanger cannot simplify the core model of the heat exchanger into a single-channel model with periodic boundaries like the counter-flow heat exchanger. This results in a large amount of flow heat transfer simulation calculations and difficulty in structural optimization, which in turn increases the difficulty of design optimization of cross-flow heat exchangers. Although cross-flow microchannel heat exchangers are currently widely used, there is still a lack of efficient and convenient structural optimization methods. Summary of the Invention

[0005] This disclosure provides a method for structural design and performance optimization of a cross-flow microchannel heat exchanger. The design targets include channel size, channel number, wall thickness, and cross-sectional shapes of the cold-side and hot-side channels within the cross-flow microchannel heat exchanger. This method screens structural parameters by establishing a countercurrent single-channel model. Based on the optimal countercurrent microchannel structure, a local model of the cross-flow microchannel heat exchanger is established to further optimize the channel structure and number to improve heat transfer performance and uniformity. Furthermore, the optimization sequence of the cross-flow microchannel heat exchanger structural parameters is prioritized to reduce the computational effort involved in iterative optimization.

[0006] The method mainly includes the following steps:

[0007] S1: Establish three-dimensional structural models of counterflow microchannels with different microchannel sizes, wall thicknesses, channel spacings, and cross-sectional shapes;

[0008] S2: Build flow and heat transfer models for microchannels with different structures and perform simulation calculations. Using comprehensive performance evaluation factor, Colburn factor, and surface area density as evaluation indicators, screen out the cold-side and hot-side microchannel structural parameters with the best performance under counterflow conditions.

[0009] S3, based on the heat transfer capacity of the heat exchanger Design requirements for calculating heat exchange area : ,in is the total heat transfer coefficient of the hot and cold countercurrent microchannel, is the logarithmic mean temperature difference;

[0010] Set the heat transfer area margin coefficient , the heat transfer area of ​​the cross-flow microchannel heat exchanger is obtained : ;

[0011] Based on heat exchange area The number of channels per layer is given based on the space requirements and number of plates ;

[0012] S4, analyze the sensitivity of heat transfer performance and uniformity to structural parameters. According to the degree of sensitivity, iteratively adjust and optimize the structural parameters of the fixed cross-flow microchannel heat exchanger and perform simulation verification. When the heat transfer and thermal stress meet the requirements, the core structure of the cross-flow microchannel heat exchanger is output.

[0013] Furthermore, the step S1 specifically includes:

[0014] Based on space requirements, processing technology, impurity particle size, corrosion allowance, etc., the hot side and cold side microchannel sizes, channel center spacing and wall thickness ranges are preliminarily determined, and three-dimensional models of countercurrent microchannels with different microchannel sizes, wall thicknesses, channel center spacing and cross-sectional shapes are established respectively. Among them, the cold fluid and the hot fluid flow in opposite directions, and the outer wall is set as a periodic boundary.

[0015] Furthermore, the calculation formula of the evaluation index in step S2 includes:

[0016] Comprehensive performance factor:

[0017]

[0018] Among them, the Nusselt number , is the heat transfer coefficient, is the hydraulic diameter of the channel, is the average thermal conductivity of the fluid; Fanning friction coefficient , is the pressure drop at the inlet and outlet of the channel, is the channel length, is the average density of the fluid, is the average velocity of the fluid; is the Nusselt number of the control model, is the Fanning friction coefficient of the control model;

[0019] Colburn Factor:

[0020]

[0021] in, is the Reynolds number, is the Prandtl number;

[0022] Surface area density:

[0023]

[0024] in, is the heat exchange area, is the volume of the heat exchanger.

[0025] Furthermore, the step S4 specifically includes:

[0026] S41, analyze the sensitivity of heat transfer performance and uniformity to structural parameters, and determine the order and direction of structural parameter adjustment in cross-flow microchannel heat exchanger performance optimization;

[0027] S42, based on the order and direction of structural parameter optimization obtained in step S41, and on the basis of the obtained optimal counterflow microchannel structure, sequentially adjusting the structural parameters in the local three-dimensional model of the cross-flow microchannel heat exchanger, and performing flow heat transfer calculations to select a microchannel structure with better heat transfer capacity and uniformity that meets the set requirements;

[0028] S43, establishing a three-dimensional overall model of a single-layer cross-flow microchannel heat exchanger, and verifying whether the cross-flow microchannel heat exchanger meets the design requirements through flow and heat transfer simulation; if not, repeating steps S3, S42, and S43 for iterative adjustment and optimization; if it meets the design requirements, performing thermal stress analysis;

[0029] S44: When the maximum thermal stress exceeds the allowable stress of the material, the number of single-layer channels is adjusted first. and the number of channel layers , to improve the uniformity of temperature distribution, and repeat steps S43 and S44 for verification and iterative optimization; when both the heat exchange amount and the thermal stress meet the requirements, the cross-flow microchannel heat exchanger core structure is output.

[0030] Furthermore, the step S41 specifically includes:

[0031] A local three-dimensional model of the cross-flow microchannel heat exchanger is established to carry out flow and heat transfer calculations. The channel cross-section structural parameters are further adjusted through orthogonal experiments or uniformity test methods, and the influence of each parameter on the heat transfer performance and uniformity is analyzed. Combined with range analysis or regression analysis, the sensitivity of heat transfer performance and uniformity to the structural parameters is obtained, and the order and direction of structural parameter adjustment in the performance optimization of the cross-flow microchannel heat exchanger are determined.

[0032] Furthermore, in step S42, the uniformity is determined by the unevenness evaluate:

[0033]

[0034] in, is the temperature or heat transfer coefficient; the smaller the non-uniformity value, the better the uniformity.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1) A complete cross-flow microchannel heat exchanger structural design and performance optimization method was established;

[0037] 2) A counterflow single-channel model was established to screen microchannel size, wall thickness, channel spacing, and cross-sectional shape. Based on the optimal structural parameters, a local model of a cross-flow microchannel heat exchanger was established. The cross-sectional shape and channel size were further adjusted to optimize heat transfer capacity and uniformity, reducing the computational resources consumed in direct screening of cross-flow microchannel heat exchanger structural parameters.

[0038] 3) Prioritize the optimization order of the cross-flow microchannel heat exchanger structural parameters to reduce the amount of calculation required for parameter adjustment during iterative optimization of the cross-flow microchannel heat exchanger;

[0039] 4) Optimizing the uneven temperature distribution caused by the cross flow of hot and cold fluids can effectively reduce the heat transfer unevenness in the cross flow microchannel heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0041] Figure 1 Schematic diagram of the cross-flow microchannel heat exchanger core;

[0042] Figure 2 is the difference in heat transfer coefficient and heat transfer capacity under cross-flow and counter-flow conditions;

[0043] Figure 3 The present invention provides a method for structural design and performance optimization of a cross-flow microchannel heat exchanger.

[0044] Figure 4 Schematic diagram of the optimal design parameters for countercurrent microchannels;

[0045] Figure 5 The water side outlet temperature and heat transfer in the cross-flow microchannel heat exchanger structural parameter optimization;

[0046] Figure 6 Heat transfer non-uniformity in cross-flow microchannel heat exchanger structural parameter optimization;

[0047] Figure 7 Local model of channel heat exchanger for counterflow and crossflow. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] The present disclosure provides a cross-flow microchannel heat exchanger structure design and performance optimization method. According to an exemplary embodiment of the present disclosure, the process is as shown in the attached figure. Figure 3 As shown, the specific steps include:

[0050] Step 1: Preliminarily determine the hot side and cold side microchannel dimensions based on space requirements, processing technology, impurity particle size, corrosion margin, etc. ( d )、Channel center distance( w ) and wall thickness ( δ ) range, and established three-dimensional counterflow microchannel models with different microchannel sizes, wall thicknesses, channel spacing, and cross-sectional shapes. The cold and hot fluids flow in opposite directions, and the outer wall is set as a periodic boundary.

[0051] Step 2: Use the finite volume method to establish the flow and heat transfer model of microchannels with different structures and perform simulation calculations. PEC )、Colburn factor( ) and surface area density ( ) evaluates the combined performance of heat transfer and compactness of microchannel heat exchangers, selecting structural parameters such as cold-side and hot-side microchannel dimensions and wall thickness that provide optimal performance under counterflow conditions. The calculation formula is as follows.

[0052] Comprehensive performance factor:

[0053]

[0054] Among them, the Nusselt number , is the heat transfer coefficient, is the hydraulic diameter of the channel, is the average thermal conductivity of the fluid. Fanning friction coefficient , is the pressure drop at the inlet and outlet of the channel, is the channel length, is the average density of the fluid, is the average velocity of the fluid. is the Nusselt number of the control model, is the Fanning friction coefficient of the control model.

[0055] Colburn Factor:

[0056]

[0057] in is the Reynolds number, is the Prandtl number.

[0058] Surface area density:

[0059]

[0060] in is the heat exchange area, is the volume of the heat exchanger.

[0061] Step 3: Based on the heat transfer capacity of the heat exchanger ( ) Design requirements for calculating heat exchange area ( ), ,in is the total heat transfer coefficient of the hot and cold countercurrent microchannel, is the logarithmic mean temperature difference. Since the heat exchange capacity of the counterflow microchannel heat exchanger is stronger than that of the cross-flow microchannel heat exchanger of equal area, the heat exchange area margin coefficient ( ), the heat transfer area of ​​the cross-flow microchannel heat exchanger is obtained ( ), . Based on heat exchange area Combined with the space requirements, the number of channels per layer is given ( ) and the number of plates ( ).

[0062] Step 4: Build a local 3D model of the cross-flow microchannel heat exchanger and perform flow and heat transfer calculations. Through orthogonal and uniformity testing, further adjust structural parameters such as channel cross-sectional shape and dimensions. Analyze the impact of each parameter on heat transfer performance and uniformity. Combined with range analysis and regression analysis, determine the sensitivity of heat transfer performance and uniformity to structural parameters. This helps determine the order and direction of structural parameter adjustments for cross-flow microchannel heat exchanger performance optimization. This step is performed only once during iterative optimization.

[0063] Step 5: Since the heat transfer performance and uniformity of the cross-flow microchannel heat exchanger are worse than those of the counter-flow microchannel heat exchanger with the same structure, the channel structure and number of the cross-flow microchannel heat exchanger are further adjusted on the basis of the optimal design of the counter-flow microchannel heat exchanger to reduce the differences in heat transfer performance and heat transfer uniformity under cross-flow and counter-flow conditions, thereby improving the heat transfer capacity. According to the optimization order and direction of the structural parameters obtained in step 4, on the basis of the obtained optimal counter-flow microchannel structure, the channel size, cross-sectional shape and number in the local three-dimensional model of the cross-flow microchannel heat exchanger are adjusted in turn, and flow heat transfer calculations are carried out to screen microchannel structures with strong heat transfer capacity and good uniformity. Uniformity is determined by the unevenness ( ), evaluate, The smaller the non-uniformity value, the better the uniformity. Since the cross flow does not cause the pressure drop to increase inhomogeneity, the pressure drop change caused by the cross flow is not considered in the optimization process.

[0064] Step 6: Build a 3D overall model of the single-layer cross-flow microchannel heat exchanger and perform flow and heat transfer simulations to obtain the heat transfer rates on the hot and cold sides, as well as the outlet temperatures and pressures, to verify whether the cross-flow microchannel heat exchanger meets design requirements. If not, repeat Steps 3 and 5. If it does, perform a thermal stress analysis.

[0065] Step 7: For the overall cross-flow microchannel heat exchanger, due to the uneven temperature distribution, there may be a situation where the local maximum thermal stress exceeds the allowable stress. After steps 1, 2, 4 and 5, the optimal cross-flow heat exchange channel structure has been obtained. Therefore, when the maximum thermal stress exceeds the allowable stress of the material, the number of single-layer channels should be adjusted first. and the number of channel layers , to improve the uniformity of temperature distribution, and repeat steps six and seven; when the heat transfer and thermal stress meet the requirements, output the cross-flow microchannel heat exchanger core structure.

[0066] The above steps 4 to 7 can also be independently used as a performance optimization method for the cross-flow microchannel heat exchanger that has been designed.

[0067] In this embodiment, a complete cross-flow microchannel heat exchanger structural design and performance optimization method is established; by establishing a countercurrent single-channel model, preliminary screening of structural parameters such as channel cross-sectional shape, size, center spacing and wall thickness is carried out, and based on the optimal structural parameters, a local model of the cross-flow microchannel heat exchanger is established, and the channel structure and number are adjusted to achieve optimization of the heat transfer performance and uniformity of the cross-flow heat exchanger, thereby reducing the computing resources consumed in the direct screening of the cross-flow microchannel heat exchanger structural parameters; and determining the optimization order of the cross-flow microchannel heat exchanger structural parameters to reduce the computational complexity increased by parameter adjustment in the iterative optimization of the cross-flow microchannel heat exchanger.

[0068] Application Examples

[0069] A cross-flow microchannel heat exchanger, used in a solar thermal power generation system, was designed based on its operating conditions. The hot-side fluid is molten salt, with an inlet temperature of 618.15K, a pressure of 0.5 MPa, and a mass flow rate of 1.2 kg / s. The cold-side fluid is water, with an inlet temperature of 257.70K, a pressure of 14.7 MPa, and a mass flow rate of 0.214 kg / s.

[0070] Refer to the attached Figure 3 The main steps are as follows:

[0071] (1) The structural design of the microchannel heat exchanger is carried out based on the processing technology, operating conditions and simulation results.

[0072] Specifically, the microchannels are processed using an etching process or capillary microchannels, and the microchannels are determined to have either a rectangular or circular structure. Taking into account the possibility of clogging by impurity particles during actual operation of the microchannel heat exchanger, combined with the minimum filtration size and etching depth of the molten salt filter, the minimum size of the microchannel on the molten salt side is 1-2 mm. Considering that molten salt and water are corrosive at high temperatures, the thickness of the solid domain between channels (wall thickness) should not be less than the corrosion margin of the service life. For heat exchangers made of 347H metal, the wall thickness on the molten salt side and the water side should be greater than 0.2 mm.

[0073] On this basis, a three-dimensional countercurrent single-channel model with different microchannel dimensions, wall thickness and other structural parameters was established, and flow and heat transfer simulation was performed using ANSYS Fluent software to calculate the comprehensive performance evaluation factors ( PEC )、Colburn factor( ) and surface area density ( The molten salt side channel is a rectangular channel with a size of 2.5mm×1.4mm and a wall thickness of 0.3mm; the water side channel is a circular channel with a diameter of 2mm and a wall thickness of 0.5mm. The center spacing of the channels on the molten salt side and the water side is 3.5mm. The structural parameters of the countercurrent microchannel are shown in the attached figure. Figure 4 As shown, this structure is the best design for microchannel under countercurrent conditions. ) Calculate the heat transfer area of ​​the heat exchanger ( ), and based on the heat transfer area margin coefficient ( ) and space requirements give the cross-flow microchannel heat exchanger with 40 layers of hot and cold fluid channels each, and 60 channels in a single layer.

[0074] (2) Determine the optimization order of the structural parameters of the cross-flow microchannel heat exchanger based on flow and heat transfer simulation.

[0075] Specifically, a local model of a single-layer cross-flow microchannel heat exchanger was established. The length and width of the heat exchange core were 350 mm respectively. There were 10 channels on the molten salt side and the water side. The cross-sectional shapes of the channels on the molten salt side and the water side were circular / rectangular, rectangular / circular, circular / circular and rectangular / rectangular respectively. The channel sizes were 0.9 times, 1.0 times and 1.1 times the optimal countercurrent microchannel size. Based on the optimal countercurrent microchannel structure, a core model with 8, 10 or 12 channels on the molten salt side and the water side was established to explore the influence of the channel cross-sectional shape, size and number on the performance of the cross-flow microchannel heat exchanger. The total heat transfer of the core, the outlet temperature of the water side and the heat transfer unevenness were obtained through flow heat transfer simulation, and the attached Figure 5 and attached Figure 6 The calculation results are shown.

[0076] According to the attached Figure 5 It can be seen that reducing the channel size helps improve the water-side outlet temperature and heat transfer rate. When the channel size is reduced by 0.9 times from its original size, the water-side outlet temperature and heat transfer rate increase by 0.65K and 10.03J / s, respectively. Rectangular channels on the molten salt side can also improve the water-side outlet temperature and heat transfer rate, compared to circular channels on the molten salt side. The heat transfer performance is strongest when both the molten salt side and the water side have rectangular channels. Increasing the number of channels significantly increases the outlet temperature and heat transfer rate. When the number of channels increases from 10 to 12, the water-side outlet temperature and heat transfer rate increase by 5.33K and 70.44J / s, respectively.

[0077] According to the attached Figure 6It can be seen that due to differences in physical properties and inlet parameters, the heat transfer nonuniformity of the hot and cold fluids varies. Increasing the channel size reduces the heat transfer nonuniformity on the molten salt side, while the water side nonuniformity increases from 0.125 to 0.135. Rectangular molten salt channels increase the heat transfer nonuniformity on the molten salt side by 0.010 and 0.039, respectively, compared to circular molten salt channels. The change in water-side nonuniformity is related to the cross-sectional shape of both channels. Increasing the number of channels increases the heat transfer nonuniformity, which is more pronounced on the molten salt side. When the number of channels increases from 10 to 12, the nonuniformity on the molten salt side increases by 0.022.

[0078] Overall, the number of channels has the greatest impact on the heat transfer performance of a cross-flow microchannel heat exchanger, while channel size has a smaller impact. Rectangular channels are beneficial for improving heat transfer performance. Therefore, the order for optimizing the heat exchanger structure is as follows: first, ensure that both the molten salt side and the water side have rectangular channels; then, adjust the number of channels to ensure that the heat transfer performance and compactness meet the design requirements; and then, appropriately reduce the channel size to further improve heat transfer performance.

[0079] (3) The structure of the cross-flow microchannel heat exchanger is optimized based on the optimal design of the counter-flow microchannel heat exchanger.

[0080] A local model of a single-layer counter-flow microchannel heat exchanger under the optimal design is established, with the length and width both being 1 / 6 of the heat exchanger core. A local model of a single-layer cross-flow microchannel heat exchanger with the same size and structural parameters is established, with the length and width also being 1 / 6 of the heat exchanger core, as shown in the attached figure. Figure 7 As shown, optimization is performed based on these structural parameters. According to the above steps, the cross-sectional shapes of the molten salt side and water side channels are both selected as rectangular, the number of single-layer channels can be adjusted within a range of 60-70 (the adjustment range is selected based on space requirements), and the channel size can be adjusted within a range of 0.7-1.0 times.

[0081] Flow heat transfer simulation was carried out for each model, and the heat transfer was calculated respectively ( ) and heat transfer unevenness ( Based on the calculation results of the local model of the counterflow microchannel heat exchanger under the optimal design, the appropriate selection ranges of the heat transfer and heat transfer unevenness of the local model of the cross-flow microchannel heat exchanger are given, such as heat transfer ≥ 360 J / s and heat transfer unevenness ≤ 0.15. The structural parameters that meet the conditions are screened and the optimal values ​​are selected.

[0082] (4) Establish an overall model of a single-layer cross-flow microchannel heat exchanger, conduct heat transfer analysis and stress analysis, and verify the rationality of the design.

[0083] Based on the optimized structural parameters, a three-dimensional overall model of a single-layer cross-flow microchannel heat exchanger is established, and flow heat transfer simulation is carried out to obtain the heat transfer capacity and the outlet temperatures and pressures of the hot and cold sides. Verify whether the flow heat transfer performance of the cross-flow microchannel heat exchanger meets the design requirements. If it does not meet the required heat transfer design requirements, adjust the heat transfer area margin coefficient ( ), recalculate the number of single-layer channels of the cross-flow microchannel heat exchanger and the number of channel layers , and re-optimize the structure of the cross-flow microchannel heat exchanger. This step is repeated until the heat transfer capacity of the cross-flow microchannel heat exchanger meets the design requirements.

[0084] On this basis, the thermal stress analysis is carried out using the overall model of a single-layer cross-flow microchannel heat exchanger. Since the above steps have obtained the current optimal cross-flow microchannel heat exchanger structure, when the local maximum thermal stress exceeds the allowable stress of the material, the number of single-layer channels is adjusted first. and the number of channel layers To improve the uniformity of temperature distribution, the flow heat transfer analysis and thermal stress analysis were re-performed. When both the heat transfer and thermal stress met the requirements, the cross-flow microchannel heat exchanger core structure was output.

[0085] The above technical solutions are only exemplary embodiments of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and are not limited to the methods described in the above specific embodiments of the present invention. Therefore, the methods described above are only preferred and do not have a restrictive meaning.

Claims

1. A cross-flow microchannel heat exchanger structure design and performance optimization method, characterized in that: The following steps are involved: S1: Establish three-dimensional structural models of counterflow microchannels with different microchannel sizes, wall thicknesses, channel spacings, and cross-sectional shapes; S2: Build flow and heat transfer models for microchannels with different structures and perform simulation calculations. Using comprehensive performance evaluation factor, Colburn factor, and surface area density as evaluation indicators, screen out the cold-side and hot-side microchannel structural parameters with the best performance under counterflow conditions. S3, based on the heat transfer capacity of the heat exchanger Design requirements for calculating heat exchange area : ,in is the total heat transfer coefficient of the hot and cold countercurrent microchannel, is the logarithmic mean temperature difference; Set the heat transfer area margin coefficient , the heat transfer area of ​​the cross-flow microchannel heat exchanger is obtained : ; Based on heat exchange area The number of channels per layer is given based on the space requirements and number of plates ; S4, analyzing the sensitivity of heat transfer performance and uniformity to structural parameters. According to the degree of sensitivity, the structural parameters of the cross-flow microchannel heat exchanger are iteratively adjusted and optimized and simulated and verified. When the heat transfer and thermal stress meet the requirements, the core structure of the cross-flow microchannel heat exchanger is output; The step S4 specifically includes: S41, analyze the sensitivity of heat transfer performance and uniformity to structural parameters, and determine the order and direction of structural parameter adjustment in cross-flow microchannel heat exchanger performance optimization; S42, based on the order and direction of structural parameter optimization obtained in step S41, and on the basis of the obtained optimal counterflow microchannel structure, sequentially adjusting the structural parameters in the local three-dimensional model of the cross-flow microchannel heat exchanger, and performing flow heat transfer calculations to select a microchannel structure with better heat transfer capacity and uniformity that meets the set requirements; S43, establishing a three-dimensional overall model of a single-layer cross-flow microchannel heat exchanger, and verifying whether the cross-flow microchannel heat exchanger meets the design requirements through flow and heat transfer simulation; if not, repeating steps S3, S42, and S43 for iterative adjustment and optimization; if it meets the design requirements, performing thermal stress analysis; S44: When the maximum thermal stress exceeds the allowable stress of the material, the number of single-layer channels is adjusted first. and the number of channel layers , to improve the uniformity of temperature distribution, and repeat steps S43 and S44 for verification and iterative optimization; when both the heat exchange amount and the thermal stress meet the requirements, the cross-flow microchannel heat exchanger core structure is output.

2. The method according to claim 1, characterized in that The step S1 specifically includes: Based on space requirements, processing technology, impurity particle size, and corrosion allowance, the hot and cold side microchannel sizes, channel center spacing, and wall thickness ranges are preliminarily determined, and three-dimensional models of countercurrent microchannels with different microchannel sizes, wall thicknesses, channel center spacing, and cross-sectional shapes are established. The cold fluid and the hot fluid flow in opposite directions, and the outer wall is set as a periodic boundary.

3. The method according to claim 1, characterized in that The calculation formula of the evaluation index in step S2 includes: Comprehensive performance factor: Among them, the Nusselt number , is the heat transfer coefficient, is the hydraulic diameter of the channel, is the average thermal conductivity of the fluid; Fanning friction coefficient , is the pressure drop at the inlet and outlet of the channel, is the channel length, is the average density of the fluid, is the average velocity of the fluid; is the Nusselt number of the control model, is the Fanning friction coefficient of the control model; Colburn Factor: in, is the Reynolds number, is the Prandtl number; Surface area density: in, is the heat exchange area, is the volume of the heat exchanger.

4. The method according to claim 1, wherein The step S41 specifically includes: A local three-dimensional model of the cross-flow microchannel heat exchanger is established to carry out flow and heat transfer calculations. The channel cross-section structural parameters are adjusted through orthogonal experiments or uniformity test methods, and the influence of each parameter on the heat transfer performance and uniformity is analyzed. Combined with range analysis or regression analysis, the sensitivity of heat transfer performance and uniformity to the structural parameters is obtained, and the order and direction of structural parameter adjustment in the performance optimization of the cross-flow microchannel heat exchanger are determined.

5. The method according to claim 1, characterized in that In step S42, the uniformity is determined by the unevenness evaluate: in, is the temperature or heat transfer coefficient; the smaller the non-uniformity value, the better the uniformity.

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