Sand dune imitating original surface heat exchanger and design method and preparation method thereof

Abstract

The invention relates to the technical field of heat exchanger design, in particular to a sand dune-imitated original surface heat exchanger and a design method and a preparation method thereof, and the flue gas side and / or cold air side pipe wall of the sand dune-imitated original surface heat exchanger adopts a surface rough microstructure; the surface rough microstructure comprises a plurality of flow guide strips; the multiple flow guide strips are arranged at intervals, and the length direction of the flow guide strips is arranged in the fluid flowing direction. A plurality of crescent-shaped sand dune imitating structures are arranged on each flow guide strip at intervals in the fluid flowing direction; a leeward slope is arranged at a notch of each crescent-imitated dune structure, a windward slope is arranged on the other side of the notch, the crescent-imitated dune structures are in the same direction, and the windward slopes are all opposite to the flowing direction of fluid. The heat exchange efficiency of the heat exchanger is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchanger design, and in particular to a heat exchanger with a surface imitating a dune original surface, and its design method and preparation method. Background Art

[0002] The original surface heat exchanger is a compact hot flue gas - cold air heat exchanger, which is widely used in various industrial and energy recovery systems; its main function is to achieve heat exchange between hot flue gas and cold air through surface heat transfer; due to its compact design and high heat transfer capacity, the original surface heat exchanger saves a large amount of space during the heat exchange process and improves energy efficiency at the same time.

[0003] With the improvement of energy conservation and environmental protection awareness, the heat exchange efficiency of heat exchangers has become a key performance indicator in design and application; however, there are certain limitations in the surface structure design of traditional heat exchangers, making it difficult to fully exploit the potential of materials and fluid flow. Specifically, the heat exchange capabilities of the flue gas side and the cold air side of existing heat exchangers are unbalanced during heat exchange, and it is difficult to synchronously improve the overall heat transfer performance of both sides' channels, resulting in a poor matching degree of heat exchange capabilities between the flue gas side and the cold air side, leading to a decrease in the heat exchange efficiency of traditional heat exchangers; therefore, how to avoid affecting the heat exchange capacity of the other side's channel when improving the heat exchange performance of one side's channel has always been a technical bottleneck in the design of heat exchangers. Summary of the Invention

[0004] The present invention provides a heat exchanger with a surface imitating a dune original surface, and its design method and preparation method, which are used to solve existing problems.

[0005] The object of the present invention can be achieved by the following technical solutions: In a first aspect of the present invention, a heat exchanger with a surface imitating a dune original surface is provided, and the tube walls on the flue gas side and / or the cold air side of the heat exchanger with a surface imitating a dune original surface adopt a surface rough microstructure. The surface rough microstructure includes a plurality of guiding strips; the plurality of guiding strips are arranged at intervals, and the length direction of the guiding strips is set along the fluid flow direction; a plurality of structures imitating crescent dunes are arranged at intervals along the fluid flow direction on each guiding strip. The notch of the structure imitating a crescent dune is the leeward slope, and the other side of the notch is the windward slope. The directions of the plurality of structures imitating crescent dunes are the same, and the windward slopes are all opposite to the fluid flow direction.

[0006] As a further improvement of the present invention, protrusions extend outward on both sides of the guiding strip where the structure imitating a crescent dune is located, and there is an arc transition between adjacent protrusions.

[0007] As a further improvement of the present invention, a dividing line is formed between the windward slope and the leeward slope of the crescent dune-like structure, the height of the dividing line gradually decreases towards the bottom of the windward slope, and a first arc is formed at the bottom of the windward slope; The dividing line is a second arc; The height of the dividing line gradually decreases towards the bottom of the leeward slope, and a third arc is formed at the bottom of the leeward slope; The centers of the first arc, the second arc, and the third arc are arranged on the same straight line, and the first arc, the second arc, and the third arc intersect at two endpoints at both ends.

[0008] As a further improvement of the present invention, the crescent dune-like structure is an axisymmetric structure, and the axis of symmetry is parallel to the fluid flow direction; The crescent dune-like structures on all the flow guiding strips are arranged in an array.

[0009] As a further improvement of the present invention, the crescent dune-like structure satisfies: the aspect ratio is 0.4 - 0.6; the angle of the windward slope is 10 - 16°, the angle of the leeward slope is 30 - 35°, and the width-height ratio is 10 - 18.

[0010] Wherein, the length refers to the horizontal distance from the front end of the windward slope to the top of the crescent dune-like structure, the width refers to the horizontal distance between the wing angles of the crescent dune-like structure, and the height refers to the vertical height from the top of the crescent dune-like structure to the base of the dune.

[0011] As a further improvement of the present invention, the morphology of the crescent dune-like structure is arranged on the straight section of the flue gas side and / or the cold air side tube wall of the dune-like primary surface heat exchanger; The morphology of the crescent dune-like structure is formed by laser etching.

[0012] The second aspect of the present invention is to provide a design method for a dune-like primary surface heat exchanger, including: Introducing a surface roughness microstructure with the morphology of the crescent dune-like structure; Determining the structural parameters included in the surface roughness microstructure of the crescent dune-like structure morphology, obtaining the range of the structural parameters and the range of the relationship between different structural parameters; According to the structural parameters, the range of the structural parameters, and the range of the relationship between different structural parameters, determining the optimal value of each structural parameter through an optimization algorithm; Manufacturing the surface roughness microstructure of the crescent dune-like structure morphology according to the optimal values of all the structural parameters.

[0013] Further, the structural parameters included in the surface rough microstructure of the crescent - shaped dune - like structure are: the vertical height h from the crest of the crescent - shaped dune - like structure to the base of the dune, the dune width w, the horizontal distance from the front end of the windward slope of the crescent - shaped dune - like structure to the crest, and the lengths la and lb of the two flanks of the crescent - shaped dune - like structure.

[0014] Further, the optimal value of each structural parameter is determined through an optimization algorithm according to the structural parameters, the ranges of the structural parameters, and the ranges of the relationships between different structural parameters, including: Mesh the flue gas channel, air channel, and solid part in the heat exchanger, and determine the mesh encryption degree through mesh - independent verification. Generate an initial structural parameter evaluation table using the symmetric Latin hypercube design based on the mesh encryption degree. Construct a three - dimensional physical model according to the initial structural parameter evaluation table, and form a corresponding physical model library through the three - dimensional physical model; among them, the three - dimensional physical model includes the three - dimensional physical model of the flue gas channel and the three - dimensional physical model of the air channel. Set the air parameters, flue gas parameters, and periodic boundary conditions. Obtain the temperature - related parameters according to the three - dimensional physical model, air parameters, flue gas parameters, structural parameters, and periodic boundary conditions in the physical model library. Solve through CFD according to the temperature - related parameters to obtain the drag coefficient and heat transfer coefficient, and integrate the drag coefficient and heat transfer coefficient into the initial structural parameter evaluation table. Determine the optimal value of each structural parameter through an optimization algorithm according to the initial structural parameter evaluation table.

[0015] Further, the generation of the initial structural parameter evaluation table using the symmetric Latin hypercube design based on the mesh encryption degree includes: Construct a variable space according to the range variables corresponding to all structural parameters; among them, all range variables include: the windward slope angle, the leeward slope angle, and the ratio of the width and height of the dune. Use the symmetric Latin hypercube design method to uniformly sample the variable space based on the mesh encryption degree, generate design space sample points with a uniform distribution, and then uniformly select the initial parameters from the design space and integrate them to obtain the initial structural parameter evaluation table.

[0016] Further, the obtaining of the temperature - related parameters according to the three - dimensional physical model, air parameters, flue gas parameters, structural parameters, and periodic boundary conditions in the physical model library includes: According to the three - dimensional physical model in the physical model library, use periodic boundary conditions in the direction perpendicular to the flow to create a more realistic calculation model without boundary influence, and denote it as the temperature - related physical property model. The temperature-dependent parameter is calculated using the temperature-dependent physical property model based on the structural parameters, air parameters, and flue gas parameters.

[0017] Further, based on the initial structural parameter evaluation table, the optimal value of each structural parameter is determined through an optimization algorithm, including: Obtain the flow resistance friction coefficient and the heat transfer Nusselt number through empirical formulas; based on all the structural parameters, the flow resistance friction coefficient, and the heat transfer Nusselt number, obtain the heat transfer performance and the flow resistance through a response surface surrogate model. Based on the heat transfer performance and the flow resistance obtained through the response surface surrogate model, determine the objective function value according to the initial structural parameter evaluation table, the heat transfer performance, and the flow resistance. According to the objective function value, find the optimal solution through the TVH-DYCORS algorithm, and at the same time, dynamically update the response surface model through the newly added experimental data or simulation results to obtain the updated response surface model; then, through the updated response surface model, obtain the new objective function value, and optimize the solution through the TVH-DYCORS algorithm according to the new objective function value, and continue to update the response surface model; continue to iterate until all the iteration conditions are met and stop, and obtain the optimal value of each structural parameter when the last iteration stops.

[0018] Further, the process manufacturing of the surface rough microstructure of the crescent dune structure 3 morphology is carried out according to the optimal values of all the structural parameters, including the steps of: selecting materials, optimizing laser parameters, surface cleaning and pretreatment, laser etching processing, post-treatment, and quality inspection.

[0019] The third aspect of the present invention is to provide a manufacturing method for an imitation dune original surface heat exchanger, which is characterized by including: According to the working conditions of the heat exchanger, select stainless steel, copper alloy, or aluminum alloy materials for the workpiece; According to the characteristics and design requirements of the heat exchanger material, select the laser type and optimize parameters such as laser power, pulse width, and scanning speed; Clean the surface of the workpiece; Deposit an anti-oxidation mask on the surface of the workpiece through chemical vapor deposition; Use a laser beam to etch the surface of the workpiece. The laser beam forms a high-energy point on the material surface, and through the laser scanning system, the microstructure is etched along a predetermined path to gradually process the crescent dune morphology; After the laser etching is completed, blow the surface with air; and smooth the burrs on the microstructure surface through an ultra-fine powder fluidized bed.

[0020] Compared with the prior art, the beneficial effects of the present invention are: In the dune - like original surface heat exchanger of the present invention, by introducing a surface rough microstructure with the morphology of crescent - shaped dunes, and arranging a plurality of crescent - shaped dune structures on the flow - guiding strip, it can not only effectively enhance the perturbation effect of the fluid but also improve the heat exchange efficiency. The micro - structure with the dune morphology can effectively break the boundary layer of the fluid in the channel, prompting the fluid to generate more intense turbulence. The generation of turbulence not only increases the contact area between the fluid and the heat - exchange surface but also improves the efficiency of heat exchange.

[0021] In the design method of the present invention, determine the structural parameters included in the surface rough microstructure with the morphology of crescent - shaped dunes, obtain the range of the structural parameters and the range of the relationships between different structural parameters; reduce the optimization range to make the optimization process set smaller; according to the range of the structural parameters and the range of the relationships between different structural parameters, determine the optimal value of each structural parameter through an optimization algorithm to improve the accuracy of optimization; according to the optimal values of all structural parameters, carry out the process manufacturing of the surface rough microstructure with the morphology of crescent - shaped dunes to improve the heat exchange efficiency of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 Construct a three - dimensional physical model diagram for the evaluation table of the initial structure (i.e., the prior - art structure) parameters of the flue - gas channel; Figure 2 Side view of the crescent - shaped dune structure of the present invention; Figure 3 Top view of the crescent - shaped dune structure; Figure 4 Cross - sectional view of the crescent - shaped dune structure imitating the present invention; Figure 5 Overall view of the crescent - shaped dune structure imitating the present invention; Figure 6 Flowchart of the structure optimization method of the present invention; Figure 7 Processing flowchart of the present invention; Figure 8 Side view of the heat - exchange capacity on the flue - gas side and the air side of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] In the design and operation of existing surface heat exchangers, the matching degree of the heat transfer capabilities on the flue gas side and the cold air side is poor, which has always been an urgent problem to be solved. Specifically, when the existing heat exchanger design improves the heat transfer capacity on the flue gas side, the heat transfer efficiency on the cold air side often decreases due to structural design or changes in flow characteristics, and vice versa. This is because in the design, key parameters such as the ratio of the radius of the gas channel to the radius of the air channel and the ratio of the internal height to the radius of the air channel are not optimally matched. The improvement of these design parameters often only focuses on enhancing the heat transfer capacity of one-sided channels, and it is difficult to simultaneously improve the overall heat transfer performance of both channels, resulting in an imbalance in the heat exchange capacity of the system.

[0027] Therefore, the present invention proposes a design method and device for an original surface heat exchanger imitating sand dunes, which has important practical significance in avoiding affecting the heat transfer capacity of the other side channel when improving the heat transfer performance of one side channel.

[0028] In order to break through the limitations of the traditional heat exchanger surface design, such as Figure 1 As shown, the internal structure of the existing heat exchanger consists of a gas channel and an air channel. The widest part of the channel is about 1.1 mm, and the structure is a micro-structure. The present invention proposes a micro-structure design for the heat exchanger surface imitating the sand dune morphology, and it is manufactured by laser surface etching technology.

[0029] Specifically, as Figures 2 to 5As shown, the flue gas side and / or the cold air side tube wall 1 of the sand dune-like original surface heat exchanger of the present invention has a rough microstructure; the surface rough microstructure includes a plurality of guide strips 2; the plurality of guide strips 2 are arranged at intervals, and the length direction of the guide strip 2 is set along the fluid flow direction; a plurality of sand dune-like crescent structures 3 are arranged at intervals along the fluid flow direction on each guide strip 2; the notch of the sand dune-like crescent structure 3 is the leeward slope, and the other side of the notch is the windward slope, the directions of the plurality of sand dune-like crescent structures 3 are the same, and the windward slopes are all opposite to the fluid flow direction.

[0030] Furthermore, protrusions 4 extend outward on both sides of the guide strip 2 where the sand dune-like crescent structure 3 is located, and there is an arc transition between adjacent protrusions.

[0031] Specifically, a dividing line is formed between the windward slope and the leeward slope of the sand dune-like crescent structure 3, the height of the dividing line gradually decreases towards the bottom of the windward slope, and a first arc 7 is formed at the bottom of the windward slope; the dividing line is a second arc; the height of the dividing line gradually decreases towards the bottom of the leeward slope, and a third arc is formed at the bottom of the leeward slope; the centers of the first arc 7, the second arc 6, and the third arc 5 are arranged on the same straight line, and the first arc 7, the second arc 6, and the third arc 5 intersect at two end points 8 at both ends. More specifically, the arc lengths of the first arc 7, the second arc 6, and the third arc 5 decrease in sequence.

[0032] Among them, the arc design of the sand dune-like crescent structure 3 can effectively target the heat transfer performance of the microstructure of the original surface heat exchanger.

[0033] More specifically, through the geometric characteristics of its three-dimensional curved surface, the arc structure induces the generation of multi-scale vortices during the fluid flow process, and these vortices can significantly enhance the turbulence intensity of the fluid. Windward slope effect: The arc curved surface forms a gradually shrinking channel in the fluid incoming flow direction (windward slope), accelerating the fluid and generating axial vortices, promoting the mixing of hot and cold fluids. Leeward slope optimization: Different from the traditional sand dune structure, the arc leeward slope reduces the area of the recirculation zone through the gradual change of curvature, avoiding heat accumulation caused by ineffective vortices. Tangential perturbation: The transverse curvature of the arc causes the fluid to generate spiral flow in the flow direction (tangential), further destroying the thermal boundary layer and improving the convective heat transfer efficiency. Experimental verification: When the height of the sand dune-like crescent is 8 mm, the gas vortex coverage area formed by the cooling medium under the action of the arc curved surface increases by 40% compared with the flat plate structure, and the cooling efficiency is increased by 26.62%.

[0034] After verification, sand dune-like crescents of other shapes cannot meet the requirement of improving the heat transfer performance of the microstructure of the original surface heat exchanger, and other shapes such as ellipse, straight line, wavy line, etc. Sharp broken line structure: It is easy to generate flow separation at the corner, forming a low-energy fluid area and weakening heat transfer.

[0035] Based on the above solution, the present invention introduces a surface rough microstructure imitating the crescent dune morphology, which can not only effectively enhance the perturbation effect of the fluid, but also improve the heat transfer efficiency. The microstructure with dune morphology can effectively break the boundary layer of the fluid in the channel, prompting the fluid to generate more intense turbulence. The generation of turbulence not only increases the contact area between the fluid and the heat transfer surface, but also improves the efficiency of heat exchange. In addition, the surface structure with dune morphology can promote the countercurrent and vortex effects of the fluid, further enhancing the heat transfer process. In terms of improving the heat transfer capacity on the flue gas side and the air side, this microstructure has good adaptability. By precisely designing the size and layout of the dune morphology, the heat transfer capacity of both channels can be improved more balancedly, avoiding the problem of unilateral enhancement in traditional designs. The introduction of the surface roughness imitating the dune morphology can not only change the fluid flow pattern, but also reduce the energy consumption by reducing the flow resistance. The formation of the microstructure makes the heat transfer surface have more heat exchange points, and the fluid distributes heat more evenly when flowing through, thus improving the efficiency of the entire heat exchange process.

[0036] As a specific preferred solution, the crescent dune-like structure 3 is an axisymmetric structure, and the axis of symmetry is parallel to the fluid flow direction; the crescent dune-like structures 3 on all the guide bars 2 are arranged in an array.

[0037] More specifically, the crescent dune-like structure 3 is arranged along a line both horizontally and vertically, in the same direction and at intervals.

[0038] The morphology of the crescent dune-like structure 3 is arranged on the straight section 10 of the tube wall 1 on the flue gas side and / or the cold air side of the heat exchanger with a dune-like original surface; the morphology of the crescent dune-like structure 3 is formed by laser etching.

[0039] Based on the above solution, the present invention provides a crescent dune-like structure 3 that realizes the synergistic effect of drag reduction and flow rectification through fluid mechanics optimization. The axis of symmetry of the dune is parallel to the fluid direction, simulating the streamlined profile of a natural crescent dune, which can significantly inhibit the fluid separation phenomenon. It also has the flow rectification effect of the array guide bars 2. The guide bars 2 and the dune array form periodic perturbations, similar to the principle of the dimples on the surface of a golf ball, redistributing the turbulent energy.

[0040] Furthermore, the heat transfer performance is enhanced, and the roughness of the microstructure is enhanced. The micron-scale dune texture formed by laser etching can break the thermal boundary layer and promote the perturbation of the fluid near the wall surface. The dune morphology can increase the heat transfer surface area, realizing the miniaturization of the "fin effect". Heat is transferred through multiple channels via the bifurcated flow path, and the temperature field uniformity coefficient is improved.

[0041] The present invention also provides a specific embodiment, where the crescent - dune - like structure 3 satisfies the following: the aspect ratio is 0.4 - 0.6, preferably 0.5; the windward slope angle is 10 - 16°, the leeward slope angle is 30 - 35°, the width - to - height ratio is 10 - 18, and the height is 20 - 50 μm. Herein, the length refers to the horizontal distance from the front end of the windward slope to the crest of the crescent - dune - like structure 3, the width refers to the horizontal distance between the wing angles of the crescent - dune - like structure 3, and the height refers to the vertical height from the crest of the crescent - dune - like structure 3 to the base of the dune.

[0042] Based on the above - mentioned solution, in this specific embodiment, through precise control of the geometric parameters of the crescent - dune - like structure 3, the collaborative optimization of flow resistance and heat transfer performance is achieved. The drag - reduction mechanism with a low windward slope angle (10 - 16°), where the windward slope angle is less than 18 - 22° of traditional sand dunes, reduces the momentum loss when the fluid impacts the sand dune. The wake - flow optimization of the leeward slope angle (30 - 35°), with a steeper leeward slope accelerating the fluid to separate from the sand - dune surface, shortens the length of the wake - flow region by about 40%. The streamline compression effect with an aspect ratio of 0.4 - 0.6 compresses in the length direction, causing the fluid to form a local acceleration region at the top of the sand dune, thus increasing the flow velocity. The laterally - extended wing - angle structure increases the effective heat - transfer area.

[0043] Among them, the ratios and ranges in this embodiment are determined by experience. In this embodiment, the ratios and ranges are not specifically limited, and the implementer can determine according to specific circumstances.

[0044] The design method of the present invention is described as follows, which specifically includes the following steps: Step S001: Introduction of the surface rough microstructure of the crescent - dune - like structure 3.

[0045] It should be noted that since existing heat exchangers can only centrally improve the heat - transfer capacity of one - side channels and it is difficult to simultaneously improve the overall heat - transfer performance of both - side channels, the heat - exchange capacity of the system is unbalanced.

[0046] Specifically, in order to break through the limitations of the surface design of traditional heat exchangers, a surface microstructure design of a heat exchanger in the shape of a sand dune, that is, the surface rough microstructure of the crescent - dune - like structure 3, is proposed. Among them, this structure is manufactured by laser surface etching technology.

[0047] Furthermore, it should be noted that by introducing the surface rough microstructure with the morphology of the crescent - like dune structure 3, it can not only effectively enhance the perturbation effect of the fluid, but also improve the heat transfer efficiency. The surface rough microstructure with the morphology of the crescent - like dune structure 3 can effectively break the boundary layer of the fluid in the channel, prompting the fluid to generate more intense turbulence. The generation of turbulence not only increases the contact area between the fluid and the heat transfer surface, but also improves the efficiency of heat exchange. In addition, the surface rough microstructure with the morphology of the crescent - like dune structure 3 can promote the counter - flow and vortex effect of the fluid, further enhancing the heat transfer process. In terms of improving the heat transfer capacity on the flue gas side and the cold air side, the surface rough microstructure with the morphology of the crescent - like dune structure 3 has good adaptability.

[0048] Step S002: Determine the structural parameters included in the surface rough microstructure with the morphology of the crescent - like dune structure 3, and obtain the range of the structural parameters and the range of the relationships between different structural parameters.

[0049] The structural parameters included in the surface rough microstructure with the morphology of the crescent - like dune structure 3 are: h, w, l, la, lb; where h represents the vertical height from the crest of the crescent - like dune structure 3 to the base of the dune, w represents the horizontal distance between the wing angles of the crescent - like dune structure 3, that is, the width of the dune; l represents the horizontal distance from the front end of the windward slope of the crescent - like dune structure 3 to the crest, that is, the length of the dune, and la and lb respectively represent the lengths of the two flanks of the crescent - like dune structure 3.

[0050] Step S003: According to the structural parameters, the range of the structural parameters, and the range of the relationships between different structural parameters, determine the optimal value of each structural parameter through an optimization algorithm.

[0051] The first step is grid division; Meshes are generated for the flue gas channel, the air channel, and the solid part respectively, and then all the meshes are merged together. The computational domain is discretized using non - structured elements such as prisms, pyramids, and tetrahedrons. In order to reduce the influence of mesh quality on the numerical simulation results, the corners and the regions adjacent to the inner surfaces of the flue gas and air and the joint surfaces are refined to meet the requirements of the wall function method. Among them, the grid independence verification is carried out to determine the degree of grid encryption, so as to select a suitable grid density.

[0052] Among them, the grid independence verification and the wall function method are well - known technologies and will not be specifically elaborated here.

[0053] The second step is to generate an initial structural parameter evaluation table using the symmetric Latin - hypercube design according to the degree of grid encryption; Construct a variable space according to the range variables corresponding to all structural parameters; among them, all range variables include: the windward slope angle, the leeward slope angle, and the ratio of the width to the height of the dune; The variable space is uniformly sampled by using the symmetric Latin hypercube design method according to the grid encryption degree to generate sample points of the design space with a uniform distribution. Then, initial parameters are uniformly selected from the design space, and an initial structure parameter evaluation table is obtained through integration. Among them, the symmetric Latin hypercube design method is a well-known technology and will not be specifically elaborated here.

[0054] In the third step, a physical model library is constructed through the initial structure parameter evaluation table. Three-dimensional physical models are constructed according to the initial structure parameter evaluation table to form a corresponding physical model library. Among them, the three-dimensional physical models include a three-dimensional physical model of the flue gas channel and a three-dimensional physical model of the air channel. Among them, the flue gas channel is coupled with the air channel through the surface, and the heat exchanger is simplified to a coupled heat transfer model containing only two channels.

[0055] In the fourth step, air parameters, flue gas parameters, and periodic boundary conditions are set. According to the structure parameters, air parameters, flue gas parameters, periodic boundary conditions, and three-dimensional physical models, temperature correlation parameters are obtained. Relevant parameters at the flue gas inlet are set, that is, flue gas parameters; relevant parameters at the air inlet are set, that is, air parameters; periodic boundary conditions are set. Among them, according to the three-dimensional physical model in the physical model library, periodic boundary conditions are adopted in the direction perpendicular to the flow to create a calculation model closer to the actual situation without boundary influence, which is denoted as the temperature-correlated physical property model. Temperature correlation parameters are calculated and obtained by using the temperature-correlated physical property model according to the air parameters and flue gas parameters.

[0056] In the fifth step, the drag coefficient and heat transfer coefficient are obtained through CFD solution according to the temperature correlation parameters, and the drag coefficient and heat transfer coefficient are integrated into the initial structure parameter evaluation table. The drag coefficient and heat transfer coefficient are obtained through CFD (Computational Fluid Dynamics) solution according to the temperature correlation parameters. The drag coefficient and heat transfer coefficient after CFD solution are counted and placed in the initial structure parameter evaluation table. Among them, CFD solution is a well-known technology and will not be specifically elaborated here.

[0057] Among them, in the process of CFD solution, all control equations are discretized by using the finite volume method. A high-resolution advection scheme is adopted to provide better accuracy in the boundary layer of the unstructured grid. Both the fluid time scale control and the solid time scale control adopt the automatic time scale option. The RMS (Root Mean Square) residual target and the conservation target are both set to The model is solved using a segregated solution method. The SIMPLEC (Semi-Implicit Method for Pressure-Linked Equations–Consistent) is used to solve the pressure-velocity coupling problem, and the second-order upwind scheme is used for equation discretization; Among them, in this embodiment, the setting of the residual target and the conservation target is not specifically limited, and the implementer can determine according to the specific situation; among them, the finite volume method, the high-resolution advection scheme, the segregated solution method, SIMPLEC, and the second-order upwind scheme are all well-known technologies, and no specific elaboration will be made here.

[0058] Step 6: According to the initial structure parameter evaluation table, determine the optimal value of each structure parameter through an optimization algorithm; Obtain the flow resistance friction coefficient and the heat transfer Nusselt number through empirical formulas; according to all the structure parameters, the flow resistance friction coefficient, and the heat transfer Nusselt number, obtain response values such as heat transfer performance and flow resistance through a response surface surrogate model.

[0059] It should be noted that in the optimization of the dune-like micro-structure, the goal is to improve the heat exchange efficiency while minimizing the flow resistance as much as possible. The micro-structure of the crescent dune-like structure 3 can increase the turbulence of the fluid through its irregular surface morphology, thereby enhancing the heat exchange. However, the design process of the micro-structure usually involves multiple optimization goals, such as reducing the flow resistance, increasing the heat exchange efficiency, and improving the manufacturing feasibility. These problems are usually high-dimensional, non-linear, and computationally intensive, so efficient optimization methods need to be adopted.

[0060] Specifically, according to the response values such as heat transfer performance and flow resistance obtained through the response surface surrogate model, determine the objective function value according to the initial structure parameter evaluation table, the heat transfer performance, and the flow resistance. According to the objective function value, use the variable hyperparameter DYCORS (TVH-DYCORS, Time-Varying Hybrid Dynamic Response Surface Method for Optimization and Reliability) algorithm to find the optimal solution, and at the same time dynamically update the response surface model through the newly added experimental data or simulation results to obtain the updated response surface model; then through the updated response surface model, obtain the new objective function value, and use the TVH-DYCORS algorithm to optimize the solution according to the new objective function value, and continue to update the response surface model; continue to iterate until all the iteration conditions are met and then stop, and obtain the optimal value of each structure parameter when the last iteration stops. Among them, the response surface surrogate model and the TVH-DYCORS algorithm are all well-known technologies, and no specific elaboration will be made here.

[0061] So far, the optimal values of all structural parameters are obtained.

[0062] The following combines specific embodiments to elaborate in detail on the design method and manufacturing method of the present invention.

[0063] First, carry out structural design and manufacturing process design, specifically including: The present invention adopts a method for optimizing the size and layout of the micro-structure of the sand dune imitation based on the response surface surrogate model and the variable hyperparameter DYCORS (TVH-DYCORS) algorithm.

[0064] More specifically, in the optimization of the sand dune imitation micro-structure, the goal is to improve the heat exchange efficiency while minimizing the flow resistance as much as possible. The micro-structure of the crescent sand dune imitation can increase the turbulence of the fluid through its irregular surface morphology, thereby enhancing heat exchange. However, the design process of the micro-structure usually involves multiple optimization goals, such as reducing the flow resistance, increasing the heat exchange efficiency, and improving the manufacturing feasibility, etc. These problems are usually high-dimensional, non-linear, and computationally intensive, so an efficient optimization method is required.

[0065] The response surface surrogate model and the variable hyperparameter DYCORS (TVH-DYCORS) algorithm adopted by the present invention are powerful tools commonly used in multi-objective optimization at present. Combining the response surface method (RSM) with the DYCORS algorithm can effectively optimize the size and layout of the sand dune imitation micro-structure and quickly find the best design scheme.

[0066] The following is the specific method for optimizing the sand dune imitation micro-structure based on the response surface surrogate model and the variable hyperparameter DYCORS algorithm. See Figure 6 .

[0067] Step 1, simplify the structural characteristic parameters of the crescent sand dune imitation; The main structural and geomorphic characteristic parameters of the crescent sand dune imitation are: h refers to the vertical height from the top of the crescent sand dune imitation structure 3 to the base of the sand dune, w refers to the horizontal distance between the wing angles of the crescent sand dune imitation structure 3, that is, the width of the sand dune, l refers to the horizontal distance from the front end of the windward slope of the crescent sand dune imitation structure 3 to the top of the dune, and la and lb respectively refer to the lengths of the two sides of the crescent sand dune imitation structure 3.

[0068] Step 2, preferably, in this embodiment, the length / width of the crescent sand dune imitation structure is selected to be 0.4 - 0.6; the range of the windward slope angle is between 10 - 16°, the leeward slope angle is 30 - 35°, and the width-to-height ratio is 10 - 18.

[0069] Step 3, use the symmetric Latin hypercube design to generate an initial structural parameter evaluation table; Use the Latin hypercube design method to generate sample points with a uniform distribution in the variable space of step 2, and uniformly select the initial parameters in the design space to avoid the aggregation or non-uniformity of sample points. The basic steps of the symmetric Latin hypercube design are as follows: 3-1 Determine the number of sampling points: Usually, the number of sampling points 10-20 is selected according to the complexity of the problem and the required accuracy.

[0070] 3-2 Allocate the parameter intervals: Divide the value interval of each parameter into equal-spacing intervals equal to the number of sampling points.

[0071] 3-3 Randomly generate sampling points: Generate a random sample point within the interval of each dimension to ensure that the samples in each dimension are uniformly distributed within their intervals.

[0072] 3-4 Maintain symmetry: Ensure that the arrangement of sampling points in each dimension is as symmetric as possible, so that each sample point is uniformly distributed in the entire design space.

[0073] Step 4, construct a physical model library; Specifically, construct a three-dimensional physical model according to the initial structure parameter evaluation table in step 3 to form a corresponding physical model library. Physical models of a flue gas channel and an air channel, where periodic boundary conditions are adopted in the direction perpendicular to the flow. The flue gas channel is coupled with the air channel through surface D, and the heat exchanger is simplified to a coupled heat transfer model with only two channels.

[0074] Step 5, mesh generation; Specifically, generate meshes for the flue gas channel, air channel, and solid part respectively, and then merge all the meshes together. Use unstructured elements such as prisms, pyramids, and tetrahedrons to discretize the computational domain. To reduce the influence of mesh quality on the numerical simulation results, the corners and regions adjacent to the inner surfaces of the flue gas and air and the joint surfaces are refined to meet the requirements of the wall function method. Determine the mesh encryption degree through mesh independence verification.

[0075] Step 6. Set parameters and boundary conditions; Specifically, in this embodiment, the flue gas inlet (temperature, pressure, and flow rate), air inlet (temperature, pressure, flow rate), and periodic boundary are designed, and the temperature-dependent property model is used to calculate the air and flue gas parameters.

[0076] Step 7. Perform CFD solution; Specifically, in this embodiment, all control equations are discretized using the finite volume method. A high-resolution advection scheme is adopted to provide better accuracy in the boundary layer of the unstructured mesh. Both the fluid time scale control and the solid time scale control adopt the automatic time scale option. The RMS residual target and the conservation target are both set to 10 -5The model is solved using a segregated solution method, with the SIMPLEC pressure-velocity coupling algorithm, and the equations are discretized using a second-order upwind scheme.

[0077] Step 8. Statistically analyze the database of drag coefficients and heat transfer coefficients; Specifically, statistically analyze the drag coefficients and heat transfer coefficients calculated in Step 7, fill them into the structural parameter sample table created in Step 3, and integrate the parameters and results of each sampling point into an evaluation table.

[0078] Step 9. Construct a surrogate model based on the response surface method; Specifically, based on the database of drag coefficients and heat transfer coefficients obtained in Step 8, use the response surface method and a polynomial regression model to approximate the surrogate model of the flow resistance and heat transfer coefficient of the heat exchanger unit channels. Relate the structural parameters (the vertical height from the top to the base of the crescent-shaped dune structure 3, the dune width, the horizontal distance from the front end of the windward slope to the top of the crescent-shaped dune structure 3, and the lengths of the two wings of the crescent-shaped dune structure 3) to the flow resistance friction coefficient and the heat transfer Nusselt number, and approximate the response values such as the actual heat transfer performance and flow resistance with less computational cost, thereby accelerating the optimization process. Conduct an optimization search on the response surface and use a time-varying perturbation strategy. Establish a criterion / metric for the optimization search and use a time-varying weight pattern strategy. Determine whether to stop the iterative process prematurely according to at least one criterion. The specific method is as follows: Step 9-1. Use the variable hyperparameter DYCORS algorithm to accelerate the tuning of the response surface surrogate model; Specifically, the DYCORS algorithm is an evolution strategy based on covariance matrix adaptation (CMA-ES), which can perform optimization in a high-dimensional complex space and has good global search capabilities. The variable hyperparameter DYCORS (TVH-DYCORS) introduces variable hyperparameters on the basis of the traditional DYCORS algorithm, including (1) the time-varying weight pattern strategy, which introduces a more balanced weight pattern for the search of candidate points, and (2) the time-varying perturbation strategy to accelerate the convergence rate of the algorithm. This dynamic adjustment can better handle the optimization process at different stages, especially for global search in the early stage and local fine search in the later stage, improving the efficiency and accuracy of the search. TVH-DYCORS adjusts the hyperparameters continuously, enabling the search process to change according to the current optimization situation, thereby improving global convergence and reducing the possibility of falling into local optimal solutions.

[0079] Step 9-2. Determine the convergence criterion; Specifically, the convergence criteria of the surrogate response surface model: Criterion (a): The number of iterations exceeds the maximum number of evaluations; Criterion (b): The maximum allowed time is reached; Criterion (c): The results converge and it is difficult to continue to improve; Criterion (d): For example, the relative error between the calculation results of the surrogate model and the results in the flow resistance and heat transfer coefficient database is less than 5%.

[0080] Step 10: Apply the surrogate model and the TVH-DYCORS optimization algorithm to optimize the design of the dune microstructure size; specifically including: Step 10-1 Optimization objective; The optimization objective is designed to maximize the heat transfer coefficient and minimize the favorable probability of flow resistance.

[0081] Step 10-2: Use the TVH-DYCORS algorithm for multi-objective optimization to search for the optimal design of the size and layout of the barchan dune microstructure. The TVH-DYCORS algorithm dynamically adjusts the search hyperparameters according to the prediction results of the surrogate model to improve the optimization efficiency. This algorithm can globally search in a complex design space and, after obtaining an effective convergence solution, finely adjust the parameters to avoid falling into local optimal solutions.

[0082] Step 10-3 Verification of the processability of the optimized structure. If the optimization results do not meet the processing expectations, iterative optimization can be continued by sample points, updating the surrogate model or adjusting the optimization strategy. Finally, the optimized results of the barchan dune microstructure are obtained.

[0083] Among them, based on the above optimization results, this embodiment gives the design method of the heat exchanger surface structure with barchan dune morphology and the processing technology of laser surface etching technology, which will be described in detail below.

[0084] 1. Design method of the surface structure with barchan dune morphology. In the present invention, the design of the barchan dune morphology, the characteristics of this morphology of the barchan dune are to form a semi-spherical structure similar to a crescent moon, which can form a stronger vortex effect when the fluid passes through. It is suitable for occasions where large-area fluid disturbance and high heat transfer requirements are needed. The design of these morphologies takes into account the material properties, fluid flow characteristics and their roles in the heat exchange process, so it can take into account the dual requirements of reducing resistance and enhancing heat transfer.

[0085] 2. Processing technology of laser surface etching technology, specifically see Figure 7 Laser surface etching technology, as a non-contact and high-precision surface treatment method, is widely used in microstructural processing. The present invention uses laser surface etching technology to process the heat exchanger surface with barchan dune morphology. The specific steps are as follows: 2.1 Select materials; According to the working conditions of the heat exchanger, materials such as stainless steel, copper alloy, and aluminum alloy should have good thermal conductivity, corrosion resistance and processing stability.

[0086] 2.2 Laser parameter optimization: According to the characteristics and design requirements of the heat exchanger material, select an appropriate laser type (such as a pulsed laser or a fiber laser), and optimize parameters such as laser power, pulse width, and scanning speed. Reasonable laser parameters can ensure the accuracy and stability of the microstructures during the processing.

[0087] 2.3 Surface cleaning and pretreatment: Before laser etching, clean the surface of the workpiece to remove oil stains, oxide layers, and impurities to ensure the precise action of the laser beam.

[0088] 2.4 Laser etching processing: Use a laser beam to etch the surface of the workpiece. The laser beam forms high-energy points on the material surface and etches the microstructures along a predetermined path through a laser scanning system. According to the design requirements, during the laser etching process, a crescent-shaped dune morphology is gradually processed.

[0089] 2.5 Post-processing and quality inspection: After laser etching, there may be laser processing residues or tiny heat-affected zones on the surface of the workpiece. It is necessary to blow the surface with air flow. Subsequently, smooth the burrs on the surface of the microstructures through an ultra-fine powder fluidized bed to ensure that the structure size, shape, and surface roughness meet the design standards.

[0090] Through the above steps, the laser surface etching technology of the present invention can accurately manufacture the microstructures on the surface of the heat exchanger in the shape of dunes, which not only enhances the heat exchange performance but also realizes good fluid flow performance, solving the problem of matching the heat exchange capabilities on the flue gas side and the cold air side in the traditional heat exchanger design. Figure 8 It shows that the addition of the microstructures can simultaneously improve the heat exchange capabilities on both the flue gas side and the air side, with the improvement amplitude reaching 20% (the Nusselt number increases by 20%).

[0091] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the specific implementation manners of the present invention or make equivalent replacements. Any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A dune-like original surface heat exchanger, characterized in that: The flue gas side and / or cold air side tube wall of the dune-simulating original surface heat exchanger has a rough surface microstructure; The surface roughness microstructure comprises a plurality of guide strips; the plurality of guide strips are arranged at intervals, and the length direction of the guide strips is arranged along the fluid flow direction; a plurality of imitation crescent-shaped sand dune structures are arranged at intervals along the fluid flow direction on each guide strip; The gap of the imitation crescent-shaped sand dune structure is a leeward slope, and the other side of the gap is a windward slope. The multiple imitation crescent-shaped sand dune structures have the same direction, and the windward slopes are opposite to the fluid flow direction.

2. The dune-like original surface heat exchanger according to claim 1, characterized in that: Both sides of the guide strip where the imitation crescent-shaped sand dune structure is located extend outwards to form protrusions, and arc transitions are provided between adjacent protrusions.

3. The dune-like original surface heat exchanger according to claim 1, characterized in that: A dividing line is formed between the windward slope and the leeward slope of the imitation crescent-shaped sand dune structure, the dividing line gradually decreases in height toward the bottom of the windward slope, and a first arc is formed at the bottom of the windward slope; The dividing line is the second arc; The dividing line gradually decreases in height toward the bottom of the leeward slope, and a third arc is formed at the bottom of the leeward slope; The centers of the first arc, the second arc, and the third arc are arranged on the same straight line, and the first arc, the second arc, and the third arc intersect at two endpoints at both ends.

4. The dune-like original surface heat exchanger according to claim 1, characterized in that: The imitation crescent-shaped sand dune structure is an axisymmetric structure, and the axis of symmetry is parallel to the fluid flow direction; The imitation crescent-shaped sand dune structures on all the guide strips are arranged in an array.

5. The dune-like original surface heat exchanger according to claim 1, characterized in that: The imitation crescent-shaped sand dune structure meets the following requirements: aspect ratio of 0.4-0.6; windward slope angle of 10-16°, leeward slope angle of 30-35°, aspect ratio of 10-18, and height of 20-50um; Among them, the length refers to the horizontal distance from the front end of the windward slope of the barchan dune structure to the top of the dune, the width refers to the horizontal distance between the wing corners of the barchan dune structure, and the height refers to the vertical height from the top of the barchan dune structure to the base of the dune.

6. The dune-like original surface heat exchanger according to claim 1, characterized in that: The simulated crescent-shaped sand dune structure is arranged on the straight section of the flue gas side and / or cold air side tube wall of the simulated sand dune original surface heat exchanger; The imitation crescent-shaped sand dune structure is formed by laser etching.

7. A method for designing a dune-like original surface heat exchanger according to any one of claims 1 to 6, characterized in that: include: The surface roughness microstructure that simulates the structure morphology of crescent-shaped sand dunes is introduced; Determine the structural parameters contained in the surface roughness microstructure of the simulated crescent-shaped sand dune structure morphology, obtain the range of structural parameters and the range of the relationship between different structural parameters; According to the structural parameters, the range of the structural parameters and the range of the relationship between different structural parameters, the optimal value of each structural parameter is determined by an optimization algorithm; The surface roughness microstructure imitating the crescent-shaped sand dune structure morphology is manufactured according to the optimal values ​​of all structural parameters.

8. The design method of the dune-like original surface heat exchanger according to claim 7 is characterized in that: The method of determining the optimal value of each structural parameter by an optimization algorithm based on the structural parameters, the range of the structural parameters and the range of the relationship between different structural parameters includes: Mesh the flue gas channel, air channel and solid part in the heat exchanger, and determine the mesh encryption degree through mesh independence verification; The initial structural parameter evaluation table is generated by using the symmetric Latin hypercube design according to the degree of mesh refinement; A three-dimensional physical model is constructed according to the initial structural parameter evaluation table, and a corresponding physical model library is formed through the three-dimensional physical model; wherein the three-dimensional physical model includes a three-dimensional physical model of a flue gas channel and a three-dimensional physical model of an air channel; Set air parameters, flue gas parameters and periodic boundary conditions, and obtain temperature-related parameters based on the three-dimensional physical model, air parameters, flue gas parameters, structural parameters and periodic boundary conditions in the physical model library; The resistance coefficient and heat transfer coefficient are obtained by CFD solution according to the temperature correlation parameters, and the resistance coefficient and heat transfer coefficient are integrated into the initial structural parameter evaluation table; According to the initial structural parameter evaluation table, the optimal value of each structural parameter is determined through the optimization algorithm.

9. The design method of the dune-like original surface heat exchanger according to claim 8, characterized in that: The initial structural parameter evaluation table is generated by using a symmetric Latin hypercube design according to the degree of mesh refinement, including: The variable space is constructed based on the range variables corresponding to all structural parameters; wherein all range variables include: windward slope angle, leeward slope angle and the ratio of dune width to height; The variable space is uniformly sampled by using the symmetric Latin hypercube design method according to the degree of grid density to generate design space sample points with uniform distribution, and then the initial parameters are uniformly selected from the design space to obtain the initial structural parameter evaluation table through integration; Preferably, the temperature-related parameters are obtained according to the three-dimensional physical model, air parameters, flue gas parameters, structural parameters and periodic boundary conditions in the physical model library, including: According to the three-dimensional physical model in the physical model library, a periodic boundary condition is used in the direction perpendicular to the flow to create a computational model that is closer to reality and has no boundary influence, which is recorded as a temperature-dependent physical property model; The temperature-related parameters are obtained by using the temperature-related physical property model according to the structural parameters, air parameters and flue gas parameters; Preferably, determining the optimal value of each structural parameter by an optimization algorithm according to the initial structural parameter evaluation table includes: The flow resistance friction coefficient and heat transfer Nusselt number are obtained through empirical formulas; based on all structural parameters, flow resistance friction coefficient and heat transfer Nusselt number, the heat transfer performance and flow resistance are obtained through the response surface proxy model; The heat transfer performance and flow resistance obtained by the response surface proxy model are used to determine the objective function value according to the initial structural parameter evaluation table, heat transfer performance and flow resistance. The TVH-DYCORS algorithm is used to find the optimal solution based on the objective function value. At the same time, the response surface model is dynamically updated through the newly added experimental data or simulation results to obtain an updated response surface model. Then, a new objective function value is obtained through the updated response surface model. The solution is optimized through the TVH-DYCORS algorithm based on the new objective function value, and the response surface model is continued to be updated. The iteration is continued until all iteration conditions are met and the optimal value of each structural parameter when the last iteration stops is obtained.

10. A method for manufacturing a dune-simulating original surface heat exchanger according to any one of claims 1 to 7, characterized in that: include: According to the working conditions of the heat exchanger, choose stainless steel, copper alloy or aluminum alloy materials for the workpiece; According to the characteristics of the heat exchanger material and design requirements, select the laser type and optimize the laser power, pulse width, scanning speed and other parameters; Clean the surface of the workpiece; Depositing an anti-oxidation mask on the workpiece surface by chemical vapor deposition process; The workpiece surface is etched with a laser beam. The laser beam is focused on the material surface to form a high-energy point. The microstructure is etched along a predetermined path through a laser scanning system, and a crescent-shaped dune morphology is gradually processed. After laser etching is completed, the surface is swept by air flow; and the burrs on the microstructure surface are smoothed by an ultrafine powder fluidized bed.

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