A flow channel topology optimization design method for a power battery water cooling flow plate

Abstract

The present invention discloses a flow channel topology optimization design method for a water-cooled flow plate of a power battery, and relates to a technical field related to thermal fluid topology optimization. The present invention adopts the Darcy seepage model to equivalently describe the fluid flow behavior, and establishes a convection heat dissipation model based on this. Compared with the existing cooling channel topology optimization method based on a high-fidelity fluid model, the method disclosed in the present invention can significantly reduce the complexity of fluid simulation and sensitivity analysis, and improve the efficiency of topology optimization calculations. Compared with the regular flow channel layout commonly used in current power batteries, the two-dimensional planar cooling flow channel designed by the method disclosed in the present invention has better heat dissipation performance, and can also improve the efficiency of power battery product development.

Description

Technical Field

[0001] The present invention relates to the technical field related to thermal fluid topology optimization design, and in particular to a power battery water-cooling flow plate and a flow channel topology optimization design method thereof. Background Art

[0002] Water-cooled flow plates are widely used in the heat dissipation system of large-capacity, high-heat flux density new energy power batteries. In the design process of water-cooled flow plates, factors such as convective heat dissipation and flow pressure loss need to be considered. Water-cooled flow plates are mainly designed using a proxy model optimization method with flow channel size and position parameters as variables. This type of method requires the construction of a proxy model based on numerical simulation and thermal fluid experiments, replacing the more complex original physical model for optimization and solution, which reduces the size of the feasible solution set to a certain extent, and the optimization process is relatively complex, making it difficult to use for product conceptual design. Cooling channel topology optimization is a flow channel design method driven by thermal fluid simulation, which can fully consider the distribution of different battery cells and efficiently design water-cooled flow plates with excellent cooling performance.

[0003] In response to the flow channel design problem of water-cooled flow plates, Chinese patent CN 113094944 A discloses a microchannel radiator and a corresponding topology optimization design method. Based on the Naiver-Stokes equations with temperature equations, a forced convection physical model is established to simulate the flow and convection heat transfer behavior of the fluid in the flow channel, and a parameter level set topology optimization model is established accordingly. This design method can design the microscopic configuration of the microchannel to maximize the heat transfer efficiency of the radiator. However, the high-fidelity fluid model used in this method has high computational complexity, and the overall efficiency of the optimization method is low. In the early stage of the optimization design, the simulation may not converge due to the unformed flow channel, making it difficult to quickly obtain complex conformal cooling channels in the early stage of the design. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention aims to solve the technical problem of how to efficiently design the cooling channel of the water-cooled flow plate.

[0005] To achieve the above object, the present invention provides a flow channel topology optimization design method for a power battery water cooling flow plate, the method comprising the following steps:

[0006] Step 1: Determine the design space, boundary conditions and optimization parameter initialization;

[0007] Step 2: Build a thermal fluid finite element simulation model;

[0008] Step 3: Construct a parameterized representation model of the fluid unit;

[0009] Step 4: Topology optimization modeling;

[0010] Step 5: Design response solution;

[0011] Step 6: Sensitivity analysis;

[0012] Step 7: Optimize the solution;

[0013] Step 8: Convergence judgment;

[0014] Step 9: Post-processing of optimization results.

[0015] Furthermore, the step 1 is specifically as follows: according to the external dimensions of the water-cooled flow plate of the power battery, the flow channel design space is determined, and the structure to be designed is discretized into multiple finite units; according to the layout position and heating power of the battery cells, the heat flux density and its action position are determined, and the thermal boundary conditions are set; and the design variable x is set to indicate that the material is solid or fluid.

[0016] Furthermore, step 2 is specifically as follows: using the linear Darcy seepage model to predict the pressure field and velocity field of the water-cooled flow plate, based on the obtained velocity field, establishing a convection heat dissipation structure model suitable for the water-cooled flow plate of the power battery, and based on the model, solving the temperature field of the convection heat dissipation structure.

[0017] Further, the step 3 is specifically as follows: based on the solid isotropic material interpolation format (SIMP), the unit permeability matrix κ, the equivalent heat conduction matrix k, the density ρ, the specific heat c p The interpolation model.

[0018] Furthermore, step 4 is specifically as follows: taking minimizing the average temperature value of a given area as the optimization goal, taking unit density as the design variable, considering fluid volume, inlet and outlet pressure drop, and minimum size constraints, and establishing a topology optimization model for a water-cooled flow plate of a power battery.

[0019] Furthermore, the step 5 is specifically as follows: based on the unit density information in the current optimization iteration step, the pressure field, velocity field, and temperature field are solved, and the average temperature value in a given area, the fluid volume constraint value g1, the pressure drop constraint value g2, and the minimum characteristic size constraint value g3 are calculated.

[0020] Furthermore, the step 6 is specifically as follows: solving the sensitivity values ​​of the objective function and each constraint function to the design variable x in each optimization iteration step.

[0021] Furthermore, the step 7 specifically includes: solving the optimization model using a moving asymptote algorithm (MMA) and updating the design variable x.

[0022] Furthermore, the step 8 is specifically as follows: if the change rate of the objective function and the constraint function is less than 0.5% within 5 consecutive iterations, the optimization solution is considered to have converged; if the optimization does not meet the convergence condition, steps 5 to 8 are repeated.

[0023] Furthermore, the step 9 is specifically as follows: based on the dichotomy method, the optimization result is converted into a clear flow channel structure without gray units.

[0024] The present invention has the following technical effects:

[0025] (1) The present invention adopts the Darcy seepage model to equivalently describe the fluid flow behavior, which can significantly reduce the complexity of fluid simulation and sensitivity analysis and improve the efficiency of topology optimization calculation;

[0026] (2) Compared with the regular flow channel layout commonly used in current power batteries, the two-dimensional planar cooling flow channel designed using the method disclosed in the present invention has better heat dissipation performance and can also improve the efficiency of power battery product development.

[0027] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic flow chart of a flow channel topology optimization design method of a power battery water-cooling flow plate provided by the present invention;

[0029] Figure 2 Schematic diagram of the design space and heat flow load distribution of the water-cooling flow plate of the power battery according to an embodiment of the present invention;

[0030] Figure 3 yes Figure 2 Schematic diagram of the final flow channel topology configuration of the power battery water-cooling flow plate. DETAILED DESCRIPTION

[0031] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0032] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0033] Figure 1 The flowchart of an embodiment of the present invention is shown. According to the above process, the embodiment of the present invention is executed as follows:

[0034] Step 1: Create Figure 2The design space of the power battery water-cooled flow plate shown in the figure (the battery cells are arranged above the black area, representing the action area of ​​the heat flow load), the design domain height H = 500mm, width L = 1000mm, other dimensions L1 = 50mm, L2 = 100mm, L3 = 100mm, H1 = 50mm, H2 = 100mm, H3 = 50mm, 400 × 200 four-node finite elements are used to discretize the design domain; the "double inlet-double outlet" circulation method is adopted, and the fluid flows at v in =0.5m / s flows into the left area Γ1 and flows out of the right area Γ2. The pressure of this area is defined as 0Pa during the optimization process. The cell area is set as a volume heat source q = 2×10 7 W / m 3 ; The cooling fluid is water, and its physical parameters are: permeability κ f =2.5×10 -5 m 2 , thermal conductivity k f =0.6W / (m·K), density ρ f =1000kg / m 3 , specific heat capacity c f =0.46×10 3 J / (kg·K); the solid material is steel, and its physical property is permeability κ s =2.5×10 -11 m 2 , thermal conductivity k s =44W / (m·K), density ρ s =7.8×10 3 kg / m 3 , specific heat capacity c s =4.2×10 3 J / (kg·K); The optimization parameters are set as follows: The upper limit of fluid volume fraction V f =0.4, the upper limit of the inlet volume fraction V in =0.16, the upper limit of the outlet volume fraction V out =0.16; each finite element is assigned a design variable x i ∈[0,1](i=1,2,…,N e ), where N e Indicates the number of units.

[0035] Step 2: Use the linear Darcy seepage model to predict the pressure field and velocity field of the water-cooled flow plate. Its finite element form can be expressed as:

[0036] κ p P = f pin ,

[0037] where κ pand P represent the pressure field and permeability matrix of the water-cooled flow plate, respectively. pin represents the inlet pressure vector calculated from the inlet flow velocity; based on this model, the pressure field P is solved, and the velocity field u can be expressed as:

[0038]

[0039] Based on the obtained velocity field, a convection heat dissipation structure model suitable for the flat water-cooled flow plate of the power battery is established, and its finite element form can be expressed as:

[0040] (k t +c(p))T=f q ,

[0041] Where T represents the temperature field of the water-cooled flow plate, k t and c(p) represent the heat conduction matrix and convection matrix of the cold plate, respectively. q is a uniformly distributed volume heat source; based on this model, the temperature field T of the structure can be solved.

[0042] Step 3: Based on the solid isotropic material interpolation format (SIMP), the unit permeability matrix κ, equivalent heat conduction matrix k, density ρ, and specific heat c are established respectively. p Interpolation model:

[0043]

[0044]

[0045]

[0046]

[0047] where κ s , k s , ρ s , c s , γ s , κ f , k f , ρ w , c w , γ w are the permeability, thermal conductivity, density, specific heat and penalty parameter of solid and fluid respectively (subscripts s and f represent fluid and solid respectively), p κ =p γ =3, p k =p ρ =p w =1.

[0048] Step 4, Step 5: Taking minimizing the average temperature value of a given area as the optimization goal, taking the unit density as the design variable, considering the fluid volume, inlet and outlet pressure drop, and minimum size constraints, a topology optimization model for the water-cooled flow plate of the power battery is established:

[0049] find: x

[0050] min:φ

[0051] stg j ≤0,j=1,2,3

[0052]

[0053]

[0054] 0≤x i ≤1,i=1,2,…,N e

[0055] Among them, the objective function φ can be expressed as:

[0056]

[0057] in and N1 represent the given area Ω * The area and total number of nodes, L1 is the indicator vector of the temperature field;

[0058] The fluid volume constraint g1 can be expressed as:

[0059]

[0060] Where V f represents the upper limit of fluid volume fraction;

[0061] The pressure drop constraint function g2 can be expressed as:

[0062]

[0063] Where N2 represents the total number of nodes in the inlet area, L2 is the indicator vector of the pressure field, and P0 represents the upper limit of the pressure drop constraint;

[0064] g3 is the minimum feature size constraint to avoid the optimization result showing a flow channel design that is too small to be processed;

[0065] Based on the unit density information of the current optimization iteration step, the Darcy seepage model and convection heat dissipation model are solved to obtain the pressure field, velocity field, and temperature field, and calculate the objective function and the values ​​of each constraint function.

[0066] Step 6: Solve the sensitivity values ​​of the objective function (average temperature value in a given area) and each constraint function (fluid volume constraint g1, pressure drop constraint g2, minimum characteristic size constraint g3) to the design variable x in each optimization iteration step.

[0067] Step 7, Step 8: Use the moving asymptote algorithm (MMA) to solve the optimization model and update the design variable x. If the objective function meets the convergence condition, the optimization is completed and the optimization result is output.

[0068] Step 9: Use the dichotomy method to transform the optimization results into a clear structure, such as Figure 3 shown.

[0069] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A flow channel topology optimization design method for a power battery water cooling flow plate, characterized in that: The method comprises the following steps: Step 1: Determine the design space, boundary conditions and optimization parameter initialization; specifically: determine the flow channel design space according to the external dimensions of the power battery water-cooling flow plate, and discretize the structure to be designed into multiple finite units; determine the heat flux density and its action position according to the cell layout position and heating power, and set the thermal boundary conditions; set the design variable x to indicate whether the material is solid or fluid; Step 2: Build a thermal fluid finite element simulation model; specifically: use the linear Darcy seepage model to predict the pressure field and velocity field of the water-cooled flow plate, and based on the obtained velocity field, establish a convection heat dissipation structure model suitable for the power battery water-cooled flow plate. Based on this model, solve the temperature field of the convection heat dissipation structure; Step 3: Construct a parameterized representation model of the fluid unit; specifically, based on the solid isotropic material interpolation format (SIMP), establish the unit permeability matrix κ, equivalent heat conduction matrix k, density ρ, specific heat c p Interpolation model of Step 4: Topology optimization modeling; specifically: taking minimizing the average temperature value of a given area as the optimization goal, taking unit density as the design variable, considering fluid volume, inlet and outlet pressure drop, and minimum size constraints, a topology optimization model of the power battery water cooling flow plate is established; Step 5: Design response solution; specifically: based on the unit density information in the current optimization iteration step, solve the pressure field, velocity field, and temperature field, and calculate the average temperature value, fluid volume constraint value g1, pressure drop constraint value g2, and minimum characteristic size constraint value g3 in a given area; Step 6: Sensitivity analysis; specifically: solving the sensitivity values ​​of the objective function and each constraint function to the design variable x in each optimization iteration step; Step 7: Optimization solution; specifically: using the moving asymptote algorithm (MMA) to solve the optimization model and update the design variable x; Step 8: Convergence judgment; Step 9: Post-processing of optimization results.

2. The flow channel topology optimization design method of the power battery water cooling flow plate according to claim 1, characterized in that: The step 8 is specifically as follows: if the change rates of the objective function and the constraint function are both lower than 0.5% in 5 consecutive iterations, the optimization solution is considered to have converged; if the optimization does not meet the convergence conditions, steps 5 to 8 are repeated.

3. The flow channel topology optimization design method of the power battery water cooling flow plate according to claim 2, characterized in that: The step 9 specifically includes: based on the dichotomy method, converting the optimization result into a clear channel structure without grayscale units.

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