A collaborative optimization method for flow channels and inlets and outlets of a power battery water-cooling flow plate

Abstract

The present invention discloses a method for collaborative optimization of flow channels and inlets and outlets of a water-cooled flow plate of a power battery, and relates to the technical field related to thermal fluid topology optimization. The present invention adopts the Darcy seepage model to equivalently describe the flow behavior of the fluid. Compared with the steady-state incompressible Naiver‑Stokes model, the model improves the simulation efficiency and the robustness of the optimization; the present invention adopts a boundary-based penalty format to achieve collaborative design of cooling channels and fluid inlets and outlets. Compared with the existing design method for fixed fluid inlet and outlet channels, the fluid flow and heat exchange behavior between the fluid inlet and outlet and the flow channel can be better matched.

Description

Technical Field

[0001] The present invention relates to the technical field related to thermal fluid topology optimization design, and in particular to a method for collaboratively optimizing flow channels and inlets and outlets of a water-cooled flow plate of a power battery. Background Art

[0002] Water-cooling channels are widely used in the heat dissipation system of large-capacity, high-heat flux density batteries. Efficient cooling channel design can extend the service life of power batteries, ensure their stable performance and safety, and is of great significance for the innovative design of electric vehicle batteries. The design of traditional regular water-cooling channels relies on the experience of designers, and requires repeated trial and error based on numerical simulation and convection heat dissipation test results. The design cycle is long, and the cooling performance of the designed channels is limited. Cooling channel topology optimization is a channel design method driven by thermal fluid simulation. It can fully consider the coupling effect between different design elements such as the flow channel and the layout of fluid inlet and outlet, and quickly design water-cooling channels with excellent cooling performance. The present invention can realize the coordinated design of water-cooling channels and fluid inlets and outlets of power batteries.

[0003] In response to the design problem of water-cooling flow channels, Chinese patent CN 112380652A discloses a design method for cooling microchannels, which uses a high-fidelity fluid model to describe fluid flow, and establishes a convection heat transfer model and a variable density topology optimization model based on this. This design method can reduce the flow resistance and heat transfer resistance of the flow channel, and the cooling performance is significantly improved compared with the reference design. However, this method only targets the flow channel structure of the predefined fluid inlet and outlet, and it is difficult to achieve the coordinated design of the water-cooling flow channel and the fluid inlet and outlet of the power battery. In addition, it is necessary to repeatedly solve highly nonlinear differential equations during the optimization process, and the optimization efficiency is low.

[0004] The prior art has the following problems:

[0005] (1) At present, most of the research on water-cooling channels of power batteries at home and abroad focuses on heat dissipation tests and numerical simulations. However, there are many factors that affect the active heat dissipation performance of the channel, such as channel width and layout, fluid inlet and outlet position and size, etc. It is difficult to quickly achieve the coordinated design of cooling channels and fluid inlets and outlets using traditional methods.

[0006] (2) Although the high-fidelity fluid model can simulate the fluid flow behavior more accurately, the corresponding thermal-fluid coupling simulation has high computational complexity. The cooling channel topology optimization method based on the high-fidelity fluid model has low overall optimization efficiency, and in the early stage of the optimization process, since the structure has not yet been formed, the CFD simulation is prone to non-convergence problems, which leads to the failure of the overall optimization process.

[0007] (3) As part of the flow channel, the fluid inlet and outlet will affect its cooling performance and the layout of the flow channel. However, the existing cooling channel topology optimization methods are mostly aimed at cold plate structures with predefined fluid inlets and outlets, and have not achieved the coordinated design of fluid inlets and outlets and internal flow channels. Summary of the invention

[0008] In view of the above-mentioned defects of the prior art, the present invention aims to solve the technical problem of how to achieve the coordinated optimization design of the flow channel and the inlet and outlet of the water-cooling flow plate of the power battery.

[0009] To achieve the above object, the present invention provides a method for collaboratively optimizing the flow channel and inlet and outlet of a water-cooled flow plate of a power battery, the method comprising the following steps:

[0010] Step 1: Determine the load and boundary conditions according to the design requirements; define the design domain and non-design domain of the structure to be designed, discretize the structure to be designed into multiple macro units; assign an initial relative density value to each macro unit;

[0011] Step 2: Establish the Darcy linear seepage model to solve the velocity field of the structure to be designed;

[0012] Step 3: Establish a convection heat dissipation model to solve the temperature field of the structure to be designed;

[0013] Step 4: Establish an interpolation format based on the SIMP method. On the basis of the above interpolation format, establish a topology optimization model for realizing the coordinated design of the water cooling channel and the fluid inlet and outlet;

[0014] Step 5: Use the moving asymptote algorithm to optimize and update the design variables and determine whether it converges; if not, go to step 2; if converged, output the optimization results.

[0015] Further, the step 2 is specifically as follows: the finite element discretization form of the Darcy linear seepage model is expressed as:

[0016]

[0017] Where P represents the pressure field of the structure, κ p represents the permeability matrix of the structure, κ pγ is the pressure field penalty matrix, f pγin and f pγout are the pressure penalty vectors acting on the inlet and outlet boundaries of the structure respectively; the unit form of the above matrix and vector is expressed as:

[0018]

[0019]

[0020] Where κ is the permeability of the material, μ is the dynamic viscosity of the material, N t is the unit shape function matrix, is the shape function gradient matrix, are the permeability matrix in unit form, the pressure field penalty matrix, and the pressure penalty vector of the inlet and outlet respectively; γ is a maximum value, which can restore the pressure of the fluid inlet and outlet to the specified inlet pressure p in and outlet pressure p out Γ1 and Γ2 represent the inlet boundary and outlet boundary, respectively. In addition, the continuous interpolation format related to the design is used in the optimization process to obtain the fluid inlet and outlet matching the flow channel layout. Based on the obtained pressure field, the velocity field of the structure can be obtained:

[0021]

[0022] Further, the step 3 is specifically as follows: the finite element form of the convection heat dissipation model is expressed as:

[0023]

[0024] Where T represents the temperature field of the structure, k t represents the heat conduction matrix of the structure, c(p) is the convection matrix of the structure, and k tγ is the temperature field penalty matrix, f tγ is the temperature penalty vector acting on the structure inlet boundary, f q is a uniformly distributed volume heat source; the unit form of the above matrix and vector is expressed as:

[0025]

[0026]

[0027] Among them, γ is a maximum value, k,ρ,c p are the thermal conductivity, density and specific heat capacity of the material, q is the volume heat source, T A is the ambient temperature, c(p) e , are the heat conduction matrix, heat convection matrix, temperature field penalty matrix, temperature penalty vector, heat flow load vector in unit form, respectively. e is the unit flow rate, and the upwind format stability term It is expressed as:

[0028]

[0029] in h e Indicates the unit size.

[0030] Further, the step 4 is specifically as follows: based on SIMP interpolation, the permeability κ, thermal conductivity k, density ρ, specific heat c of the unit are respectively calculated. p The following interpolation format is established with the import and export boundary penalty term γ

[0031]

[0032] where κ s , k s , ρ s , C s , γ s , κ f , k f , ρ f , c f , γ f are the permeability, thermal conductivity, density, specific heat and penalty parameter of solid and fluid respectively (subscripts s and f represent solid and fluid respectively), p κ =p γ =3, p k =p ρ =p f =1;

[0033] Based on the above interpolation format, the topology optimization model used to realize the coordinated design of water cooling channel and fluid inlet and outlet can be expressed as:

[0034] find: x

[0035] min:φ

[0036] sth j ≤0,j=1,2,…,M

[0037]

[0038] 0≤x i ≤1,i=1,2,…,N e

[0039] Where x is the design variable field, N e represents the number of design variables, M represents the number of constraints, and the objective function φ is to minimize the target heat source area Ω * The average temperature is calculated by the following formula:

[0040]

[0041] in and N1 represent the area and total number of nodes of the region, respectively, and L1 is the indicator vector;

[0042] The fluid volume constraint h1 is calculated by the following formula:

[0043]

[0044] Where V f represents the upper limit of fluid volume fraction;

[0045] The fluid inlet volume constraint h2 and outlet volume constraint h3 are calculated by the following two formulas:

[0046]

[0047] Where V in and V out Respectively represent the upper limit of the inlet and outlet volume fractions, N in and N out They represent the number of cells at the inlet boundary Γ1 and the outlet boundary Γ2 respectively;

[0048] The adjoint method is used to calculate the sensitivity of the objective function and constraint function with respect to the design variables.

[0049] 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, fluid volume constraint value h1, pressure drop constraint value h2, and minimum characteristic size constraint value h3 in a given area are calculated.

[0050] Furthermore, the power battery water-cooling flow plate is designed by the above-mentioned flow channel and inlet and outlet coordinated optimization method of the power battery water-cooling flow plate.

[0051] Another aspect of the present invention provides a power battery, which includes the above-mentioned power battery water-cooling flow plate.

[0052] Another aspect of the present invention provides a power battery module, comprising a plurality of the above-mentioned power batteries.

[0053] Another aspect of the present invention provides a power battery pack, comprising a plurality of the above-mentioned power battery modules.

[0054] Another aspect of the present invention provides a device using a power battery, comprising the above-mentioned power battery, wherein the power battery is used to provide electrical energy.

[0055] The present invention has the following technical effects:

[0056] (1) Darcy's permeation law is used to describe the flow behavior of the fluid. Compared with the steady-state incompressible Naiver-Stokes model, this model improves the simulation efficiency and the robustness of the optimization.

[0057] (2) The cooling channel and the fluid inlet and outlet can be designed in coordination. Compared with the existing design method for fixed fluid inlet and outlet channels, the fluid inlet and outlet can be better matched with the channel;

[0058] (3) A boundary-based penalty format is used to match the flow and heat transfer behaviors of the fluid inlet and outlet with those in the channel.

[0059] 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

[0060] Figure 1 It is a schematic flow chart of a method for collaboratively optimizing the flow channel and inlet and outlet of a water-cooled flow plate of a power battery provided by the present invention;

[0061] Figure 2 It is a schematic diagram of the design domain and heat flow load of the structural initial design of the power battery water-cooling flow plate according to an embodiment of the present invention;

[0062] Figure 3 yes Figure 2 Schematic diagram of the final flow channel topology configuration of the power battery water-cooling flow plate. DETAILED DESCRIPTION

[0063] 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.

[0064] 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.

[0065] 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:

[0066] Step 1. Initialize, using the attached Figure 2 The flow channel and fluid inlet and outlet of the rectangular cold plate are shown. The design domain Ω is high H = 500mm, wide L = 1000mm, and the other dimensions are L1 = 50mm, L2 = 100mm, L3 = 100mm, H1 = 50mm, H2 = 100mm, and H3 = 50mm. The left shadow area Γ1 and the right shadow area Γ2 represent the structural boundaries where the fluid inlet and outlet may exist, respectively. The black rectangular area is the volume heat source q = 2×10 7 W / m 3 ; The default fluid material is water, and its physical property is 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 by default, 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). 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; 400×200 four-node finite elements are used to discretize the design domain, and each finite element is assigned a relative density variable The subscript i is the element number of the finite element; for element i, and Indicates that the unit is fluid and solid respectively; in this topology optimization model, the relative density variable of the structure With the design variable x i (i=1,2,…,N e ) is established through density filtering and projection function.

[0067] Step 2. Establish the Darcy linear seepage model. The finite element discretization form of the Darcy linear seepage model can be expressed as:

[0068]

[0069] Where P represents the pressure field of the structure, κ p represents the permeability matrix of the structure, κ pγ is the pressure field penalty matrix, f pγin and f pγout are the pressure penalty vectors acting on the inlet and outlet boundaries of the structure respectively; the unit form of the above matrix and vector can be expressed as:

[0070]

[0071] Where κ is the permeability of the material, μ is the dynamic viscosity of the material, N t is the unit shape function matrix, is the shape function gradient matrix, are the permeability matrix in unit form, the pressure field penalty matrix, and the pressure penalty vector of the inlet and outlet respectively; γ is a maximum value, which can restore the pressure of the fluid inlet and outlet to the specified inlet pressure p in and outlet pressure p out Γ1 and Γ2 represent the inlet boundary and outlet boundary, respectively. In addition, the continuous interpolation format related to the design is used in the optimization process to obtain the fluid inlet and outlet matching the flow channel layout. Based on the obtained pressure field, the velocity field of the structure can be obtained:

[0072]

[0073] Step 3. Establish a convection heat dissipation model. The finite element form of the convection heat dissipation model can be expressed as:

[0074]

[0075] Where T represents the temperature field of the structure, k t represents the heat conduction matrix of the structure, c(p) is the convection matrix of the structure, and k tγ is the temperature field penalty matrix, f tγ is the temperature penalty vector acting on the structure inlet boundary, f q is a uniformly distributed volume heat source; the unit form of the above matrix and vector is expressed as:

[0076]

[0077] Among them, γ is a maximum value, k,ρ,c p are the thermal conductivity, density and specific heat capacity of the material, q is the volume heat source, T A is the ambient temperature, c(p) e , are the heat conduction matrix, heat convection matrix, temperature field penalty matrix, temperature penalty vector, heat flow load vector in unit form, respectively. e is the unit flow rate, and the upwind format stability term It is expressed as:

[0078]

[0079] in h e Indicates the unit size.

[0080] Step 4. Based on SIMP interpolation, the permeability κ, thermal conductivity k, density ρ, specific heat c of the unit are calculated. p The following interpolation format is established with the import and export boundary penalty term γ:

[0081]

[0082] where κ s , k s , ρ s , c s , γ s , κ f , k f , ρ f , c f , γ f are the permeability, thermal conductivity, density, specific heat and penalty parameter of solid and fluid respectively (subscripts s and f represent solid and fluid respectively), p k =p γ =3, p k =p ρ =p f =1;

[0083] Based on the above interpolation format, the topology optimization model used to realize the coordinated design of water cooling channel and fluid inlet and outlet can be expressed as:

[0084] find: x

[0085] min:φ

[0086] sth j ≤0,j=1,2,…,M

[0087]

[0088] 0≤x i ≤1,i=1,2,…,N e

[0089] Where x is the design variable field, N e represents the number of design variables, M represents the number of constraints, and the objective function φ is to minimize the target heat source area Ω * The average temperature is calculated by the following formula:

[0090]

[0091] in and N1 represent the area and total number of nodes of the region, respectively, and L1 is the indicator vector;

[0092] The fluid volume constraint h1 is calculated by the following formula:

[0093]

[0094] Where V f represents the upper limit of fluid volume fraction;

[0095] The fluid inlet volume constraint h2 and outlet volume constraint h3 are calculated by the following two formulas:

[0096]

[0097] Where V in and V out Respectively represent the upper limit of the inlet and outlet volume fractions, N in and N out They represent the number of cells at the inlet boundary Γ1 and the outlet boundary Γ2 respectively;

[0098] The adjoint method is used to calculate the sensitivity of the objective function and constraint function with respect to the design variables.

[0099] Step 5. Use the moving asymptote algorithm to update the design variables and determine whether it converges; if not, go to step 2; if converged, output the optimization results.

[0100] The above implementation method is used to carry out collaborative design of the design structure to obtain the flow channel and fluid inlet and outlet design. Figure 3 As shown, white represents pores and black represents fluid. Under the above working conditions, the average temperature of the structure is 309.18K, indicating that the cooling performance of the optimized design is good.

[0101] The present invention adopts a linear Darcy seepage model to approximately describe the flow behavior of the fluid in the flow channel, so as to replace the cumbersome, time-consuming and highly nonlinear fluid model; a boundary-based penalty format is used in the optimization model to force the fluid inlet and outlet to match the fluid flow and heat transfer behavior in the flow channel, which can not only improve the design efficiency and the robustness of the optimization, but also make full use of the coupling effect between the flow channel and the fluid inlet and outlet layout.

[0102] 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 method for collaboratively optimizing the flow channel and inlet and outlet of a water-cooled flow plate of a power battery, characterized in that: The method comprises the following steps: Step 1: Determine the load and boundary conditions according to the design requirements; define the design domain and non-design domain of the structure to be designed, discretize the structure to be designed into multiple macro units; assign an initial relative density value to each macro unit; Step 2: Establish the Darcy linear seepage model and solve the velocity field of the structure to be designed. The finite element discretization form of Darcy linear seepage model is expressed as: Where x is the design variable field, P represents the pressure field of the structure Ω, and κ p represents the permeability matrix of the structure, κ pγ is the pressure field penalty matrix, f pγin and f pγout are the pressure penalty vectors acting on the inlet and outlet boundaries of the structure respectively; Step 3: Establish a convection heat dissipation model to solve the temperature field of the structure to be designed. The finite element form of the convection heat dissipation model is expressed as: Among them, x is the design variable field, T represents the temperature field of the structure, k t represents the heat conduction matrix of the structure, c(p) is the convection matrix of the structure, and k tγ is the temperature field penalty matrix, f tγ is the temperature penalty vector acting on the structure inlet boundary, f q is a uniformly distributed volume heat source; Step 4: Establish an interpolation format based on the SIMP method. On the basis of the above interpolation format, establish a topology optimization model for realizing the coordinated design of the water cooling channel and the fluid inlet and outlet; Step 5: Use the moving asymptote algorithm to optimize and update the design variables and determine whether it converges; if not, go to step 2; if converged, output the optimization results.

2. The method for collaboratively optimizing the flow channel and inlet and outlet of the water-cooling flow plate of a power battery as claimed in claim 1, characterized in that: The unit form of the matrix and vector in step 2 is expressed as: Where κ is the permeability of the material, μ is the dynamic viscosity of the material, N t is the unit shape function matrix, is the shape function gradient matrix, are the permeability matrix in unit form, the pressure field penalty matrix, and the pressure penalty vector of the inlet and outlet respectively; γ is a maximum value, which can restore the pressure of the fluid inlet and outlet to the specified inlet pressure p in and outlet pressure p out ; Γ1 and Γ2 represent the inlet boundary and outlet boundary, respectively; In addition, the design-related continuous interpolation format is used in the optimization process to obtain the fluid inlet and outlet matching the flow channel layout; Based on the obtained pressure field, the flow velocity field of the structure can be obtained:

3. The method for collaboratively optimizing the flow channel and inlet and outlet of the water-cooling flow plate of a power battery as claimed in claim 2, characterized in that: The unit form of the matrix and vector in step 3 is expressed as: Among them, γ is a maximum value, k,ρ,c p are the thermal conductivity, density and specific heat capacity of the material, q is the volume heat source, T A is the ambient temperature, are the heat conduction matrix, heat convection matrix, temperature field penalty matrix, temperature penalty vector, heat flow load vector in unit form, respectively. e is the unit flow rate, and the upwind format stability term It is expressed as: in h e Indicates the unit size.

4. The method for collaboratively optimizing the flow channel and inlet and outlet of the water-cooling flow plate of a power battery as claimed in claim 3, characterized in that: The step 4 is specifically as follows: based on SIMP interpolation, the permeability κ, thermal conductivity k, density ρ, specific heat c of the unit are respectively calculated. p The following interpolation format is established with the import and export boundary penalty term γ: Among them, κ s , k s , ρ s , c s , γ s , κ f , k f , ρ f , c f , γ f are the permeability, thermal conductivity, density, specific heat and penalty parameter of solid and fluid respectively. The subscripts s and f represent solid and fluid respectively. κ =p γ =3, p k =p ρ =p f =1; Based on the above interpolation format, the topology optimization model used to realize the coordinated design of water cooling channel and fluid inlet and outlet can be expressed as: Where N e represents the number of design variables, M represents the number of constraints, and the objective function φ is to minimize the target heat source area Ω * The average temperature is calculated by the following formula: in and N1 represent the area and total number of nodes of the region, respectively, and L1 is the indicator vector; The fluid volume constraint h1 is calculated by the following formula: Where V f represents the upper limit of fluid volume fraction; The fluid inlet volume constraint h2 and outlet volume constraint h3 are calculated by the following two formulas: Where V in and V out Respectively represent the upper limit of the inlet and outlet volume fractions, N in and N out They represent the number of cells at the inlet boundary Γ1 and the outlet boundary Γ2 respectively; The adjoint method is used to calculate the sensitivity of the objective function and constraint function with respect to the design variables.

5. The method for collaboratively optimizing the flow channel and inlet and outlet of the water-cooling flow plate of a power battery as claimed in claim 4, characterized in that: 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, fluid volume constraint value h1, pressure drop constraint value h2, and minimum characteristic size constraint value h3 in a given area are calculated.

6. A water-cooled flow plate for a power battery, characterized in that: The power battery water-cooling flow plate is designed by the flow channel and inlet and outlet coordinated optimization method of the power battery water-cooling flow plate according to any one of claims 1 to 5.

7. A power battery, characterized in that: The power battery includes the power battery water-cooling flow plate as claimed in claim 6.

8. A power battery module, characterized in that: Comprising a plurality of power batteries as claimed in claim 7.

9. A power battery pack, characterized in that: Comprising a plurality of power battery modules as claimed in claim 8.

10. A device using a power battery, characterized in that: Comprising the power battery as claimed in claim 7, wherein the power battery is used to provide electrical energy.

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