Vehicle battery pack and its thermal management module coupling modeling and co-simulation method

Abstract

The application relates to the technical field of vehicle battery packs, and discloses a vehicle battery pack and a coupling modeling and joint simulation method of a thermal management module of the vehicle battery pack. A battery pack three-dimensional model is converted into a battery pack quasi-three-dimensional model through discretization processing, the quasi-three-dimensional model is applied to one-dimensional simulation calculation of the battery pack, the rationality of a heat preservation layer design of the battery pack is judged, and design optimization is realized; one-dimensional modeling of a battery thermal management integrated system is realized by adding a unified model of a coupling peripheral thermal management system of the battery pack with a qualified heat preservation layer; one-dimensional modeling of a thermal management system at a vehicle level is realized by combining the integrated system with related systems of the vehicle, and simulation calculation of the battery thermal management integrated system under different working conditions is completed. The application mainly solves the problems that one-dimensional modeling and calculation of battery thermal management are difficult to describe the battery temperature field distribution in detail, battery thermal management simulation calculation usually ignores the influence of other thermal management systems, and battery thermal management technology is applied under multiple working conditions.

Description

Technical Field

[0001] This invention relates to the field of automotive battery pack technology, and in particular to a coupled modeling and co-simulation method for automotive battery packs and their thermal management modules. Background Technology

[0002] Pure electric vehicles are primarily powered by lithium-ion battery packs. In these packs, the lithium-ion cells are arranged in a regular, close-packed manner. The heat generated by the electrochemical reactions and their side reactions during charging and discharging easily accumulates within the pack. If operating in high-temperature, poorly insulated, or insufficiently heat-exchange environments, the temperature of the cells within the pack will continuously rise. This thermal coupling can cause overheating of a single cell within the pack, potentially leading to thermal runaway, fire, explosion, or other uncontrollable risks. Similarly, the difficulty of cold-starting electric vehicles in low-temperature environments and the poor uniformity of cell temperature distribution also restrict the widespread application of lithium-ion batteries in electric vehicles. Therefore, it is evident that implementing an effective power battery thermal management system is crucial for promoting the large-scale application of lithium-ion batteries in electric vehicles.

[0003] Currently, commonly used battery thermal management systems employ passive air cooling, which directly utilizes vehicle speed and ambient air for heat exchange. When passive air cooling is insufficient, most electric vehicles utilize liquid cooling. In low-temperature environments, heat pumps / PTCs are used to heat the coolant for battery insulation / heating. Components involved include: internal insulation structures within the battery pack, a battery pack thermal management module to remove heat from the cells, and a front compartment cooling module. Operating conditions include: cold / hot immersion in low / high temperature environments, steady-state / transient driving or charging conditions, etc.

[0004] The thermal flow simulation model of the battery thermal management system is usually a one-dimensional model, a three-dimensional model, or a one-dimensional / three-dimensional coupled model. The following problems often exist in modeling methods or calculation processes: One-dimensional models of vehicle thermal management for battery packs typically assume a fixed convective heat transfer coefficient, neglecting the influence of changes in the internal and external flow fields of the vehicle on the temperature distribution of the battery pack. The difference between natural and forced convection heat transfer coefficients is significant: the natural convection heat transfer coefficient for air is 5–25 W / (m²-K), while the forced convection heat transfer coefficient is 20–300 W / (m²-K). In one-dimensional modeling of the vehicle thermal management system, the battery pack is usually treated using the lumped parameter method, treating the entire battery pack as a thermal mass unit. While simplifying the heat transfer process of the battery pack helps reduce computational costs, it ignores the temperature distribution of components such as the cells inside the battery pack, significantly reducing simulation accuracy. Furthermore, since three-dimensional modeling is mostly battery pack-level simulation with fixed boundary conditions, it is difficult to combine actual vehicle driving conditions with the simulation of the vehicle thermal management system for calculation. Additionally, three-dimensional simulation involves mesh generation and boundary setting, greatly increasing the computational burden and complexity of the simulation. Summary of the Invention

[0005] This invention provides a coupled modeling and co-simulation method for automotive battery packs and their thermal management modules, which solves the problems that one-dimensional modeling and calculation of battery thermal management is difficult to describe in detail about the battery temperature field distribution; battery thermal management simulation calculations usually ignore the influence of other thermal management systems and the multi-condition application of battery thermal management technology.

[0006] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0007] A coupled modeling and co-simulation method for automotive battery packs and their thermal management modules includes the following steps:

[0008] Step S100: The 3D model of the battery pack is transformed into a pseudo-3D model of the battery pack through discretization processing;

[0009] Step S200: Based on the pseudo-3D model of the battery pack, perform high / low temperature environment hot immersion / cold immersion simulation to calculate the temperature change and temperature distribution of the cells inside the battery pack, and determine whether the heat preservation index is met. If the heat preservation index is not met, perform DOE optimization on the battery pack.

[0010] Step S300: After meeting the thermal insulation requirements, perform one-dimensional modeling of the battery pack thermal management module based on the battery electro-thermal coupling model;

[0011] Step S400: Simulate 3D modeling of the front compartment heat dissipation module and perform optimization matching;

[0012] Step S500: Build a one-dimensional battery thermal management integrated system model based on the battery pack thermal management module model and the front compartment heat dissipation module model;

[0013] Step S600: Perform multi-condition simulation of the battery thermal management integrated system in conjunction with the whole vehicle.

[0014] Through the above technical solution, the pseudo-3D model of the battery pack facilitates simulation calculations in one-dimensional software, thereby obtaining the temperature changes and distribution of the cells within the battery pack. Based on this, it can be determined whether the battery pack insulation design meets the insulation standards. The insulation design of the battery pack that does not meet the insulation standards is optimized using DOE (Design of Engineering) to make it meet the insulation standards after optimization. After the battery pack model that meets the insulation standards is transformed into a pseudo-3D model, it is combined with the environmental model, cooling circuit model, heating circuit model, and cell heating model to establish a battery pack thermal management module. The battery pack thermal management module describes the battery heating and heat transfer, as well as the working process of the thermal management system. The front compartment heat dissipation module is usually used to provide external airflow data for the heat exchange process and improve the system's heat dissipation performance based on optimization matching. Based on the above model, the surrounding thermal management system is coupled to complete the construction of a one-dimensional model of the battery thermal management integrated system. Then, the vehicle thermal management system is modeled in conjunction with the relevant vehicle systems, and multi-condition simulations are performed to take into account the temperature distribution of components such as cells inside the battery pack. At the same time, due to the setting of the pseudo-3D model, it is not necessary to perform battery pack-level simulations with fixed boundary conditions, making it easier to combine the actual driving conditions of the vehicle with the simulation of the vehicle thermal management system for coupled calculations.

[0015] Optionally, the battery pack model includes: a battery pack housing, battery modules, insulation layer, water-cooling plate, and other internal accessories;

[0016] The heat exchange between the battery module and the external environment includes the following heat dissipation pathways:

[0017] Battery module - insulation layer - housing - external environment, this path mainly involves heat dissipation through solid contact conduction;

[0018] The path from battery module to internal air to housing to external environment involves convective heat transfer between the internal and external air. Due to the weak airflow and low thermal conductivity of the internal air, the heat transfer effect of the internal air is relatively small. The convective heat transfer of the external air has a greater impact on the heat transfer. Therefore, we should focus on the impact of vehicle speed / wind speed on the heat transfer between the battery pack and the external environment.

[0019] The battery module-water cooling plate-coolant path involves heat conduction between the module and the water cooling plate, and heat convection between the water cooling plate and the coolant. The cell temperature is mainly affected by the convective heat transfer of the coolant.

[0020] Using the above technical solution, when establishing the 3D model of the battery pack, all heat dissipation pathways are first constructed to represent a clear structure for subsequent calculations.

[0021] Optionally, the pseudo-3D model of the battery pack is derived from the discretization of the 3D model of the battery pack. The pseudo-3D model uses thermal mass units to replace each solid component in the 3D model. The parameters of the thermal mass unit include: solid material properties, solid mass, initial temperature, heat generation, distance on the heat transfer path, and effective heat transfer surface area. Each mass unit will conduct or convect heat with adjacent mass units or fluids. The heat transfer between adjacent thermal units is calculated using classical heat transfer formulas, as shown below:

[0022] Q=ΔT×R

[0023] Where: Q is the heat transfer of the solid, ΔT is the temperature difference between the solid's center of mass and the boundary, and R is the thermal resistance, where the formula for calculating the thermal resistance is:

[0024] R = L × k × A

[0025] In the formula: L is the heat transfer distance between the center of mass and the boundary, A is the heat transfer area between the center of mass and the boundary, and k is the thermal conductivity of the solid.

[0026] Simulating the external environment requires determining the external ambient temperature and the convective heat transfer coefficient between the external environment and the battery pack. This couples the ambient temperature model with the corresponding thermal mass units of the battery pack components in contact with the external environment, enabling heat convection between the external environment and the battery pack. The convective heat transfer coefficient can be an empirical value when the influence of the external environment is minimized.

[0027] Through the above technical solution, the quasi-3D model of the battery pack can represent the three-dimensional structure of the battery pack and determine the heat transfer contact in the three-dimensional space of the battery pack in a one-dimensional modeling form. In the one-dimensional simulation application, it can speed up the simulation calculation and achieve the observation of temperature field distribution and change that is comparable to the three-dimensional simulation calculation results.

[0028] Optionally, the steps for simulating the temperature changes and distribution of cells within the battery pack under high / low temperature environment hot / cold immersion include:

[0029] Initialize different ambient temperatures and battery pack temperatures to determine the simulation temperature conditions;

[0030] Set the convective heat transfer coefficient in a natural convection environment;

[0031] Set the simulation time;

[0032] Simulation calculations yielded the temperature field distribution and temperature changes of the battery pack.

[0033] The simulation does not consider the effect of coolant flow on thermal insulation performance; it does not consider cell discharge, nor does it consider cell heat generation.

[0034] By using the above technical solution, and excluding the influence of the coolant and the battery cell itself, simulation is performed according to the above steps to obtain the temperature field distribution and temperature change of the battery pack. This allows us to determine whether the insulation layer design meets the requirements and to optimize the design in a timely manner.

[0035] Optionally, the DOE optimization process includes the following steps:

[0036] Determine the design factors, number of levels, and response variables;

[0037] The fitted response surface is obtained by fitting the data.

[0038] Determine the sensitivity and correlation of the response variables to the design factors, and assess the degree of influence of each design factor;

[0039] The solution is obtained by using a globally optimized genetic algorithm.

[0040] Obtain the optimized design factors, and determine the optimal value of the design factors by comparing and analyzing the response variables before and after optimization.

[0041] By using the above technical solutions, the design factors are optimized to improve thermal insulation performance and achieve the thermal insulation target. This method effectively reduces the number of simulations, ensures that the thermal insulation design is scientific and accurate, and improves efficiency.

[0042] Optionally, the battery pack thermal management module model includes: a battery pack thermal mass model, an external environment model, a cell heating model, a battery cooling circuit model, and a battery heating circuit model;

[0043] The cell heating model is actually an electro-thermal coupling model, which can simulate the battery voltage characteristics and battery temperature characteristics.

[0044] The main components modeled in the battery cooling circuit model are: water-cooled plate, chiller, connecting pipes, and water pump. The water-cooled plate includes both the thermal mass model and the pipe model. The wall temperature of the pipe model is determined by the temperature of the thermal mass unit model.

[0045] The main components modeled in the battery heating circuit model are: PTC water pump, PTC heater, and Chiller. The Chiller has the same geometric structure as the Chiller in the cooling circuit mentioned above.

[0046] Optionally, the electrothermal coupling model is built using an equivalent circuit model and a heat generation rate formula. During battery operation, the equivalent circuit model can be used to calculate the open-circuit voltage, terminal voltage, and current. Substituting these values ​​into the heat generation rate formula yields the battery heat generation rate. Combined with ambient heat dissipation, the battery temperature response is simulated, and the obtained temperature value is fed back to the equivalent circuit model to achieve electrothermal coupling.

[0047] The circuit model uses a second-order RC equivalent circuit, and the battery polarization voltages U1, U2 and terminal voltage U can be expressed as follows:

[0048]

[0049]

[0050] U = U OCV -IR0-U1-U2

[0051] The heat generation rate takes into account the thermal characteristics of the battery during operation, considering four types of heat generation: ohmic heat, polarization heat, reaction heat, and side reaction heat. The formula for the heat generation rate is:

[0052]

[0053] By adopting the above technical solutions, the battery pack thermal management module model can describe in detail the battery heating and heat transfer, as well as the working process of the thermal management system.

[0054] After modeling, the continuity equation, momentum equation and energy equation are solved through iterative calculations under different steady-state conditions. Finally, the flow rate, pressure, temperature, current, voltage and heat exchange results of the power battery pack thermal management module are obtained and confirmed to be within a reasonable range.

[0055] Optionally, the front cabin heat dissipation module model realizes heat exchange between the air side and the liquid side based on the relationship between the inlet and outlet side temperature, pressure, flow rate, and heat exchange power determined by experiments or three-dimensional simulation, combined with the geometry and material properties of the radiator / condenser.

[0056] The front cabin heat dissipation module model adopts a pseudo-3D modeling approach: the parameter settings for the radiator and condenser include geometric position, geometric structure, selection, material properties, refrigerant type, coolant type, inlet and outlet conditions (temperature, pressure) on the wind side and coolant side, heat transfer characteristics, and flow resistance characteristics (i.e., experimental data on temperature, pressure, flow rate, and heat exchange power on the wind side and coolant side inlet and outlet sides); the spatial position of the flow field and the fluid material type are determined by the windward flow field space, and spatial interfaces are set to achieve the purpose of simulating the three-dimensional flow field of the front cabin; the three-dimensional model of the front cabin is discretized to generate a pseudo-3D model, and based on this, fluid inlet and outlet, drag coefficient, fan, etc. are added to build a complete front cabin heat dissipation module model;

[0057] The airflow on the radiator / condenser surface is determined by the vehicle speed and fan speed. The fan model needs to have its geometry, state parameters, fan type, and wind resistance characteristics determined through experiments or 3D simulation. The air-side inlet and outlet need to have their inlet conditions (pressure, temperature) and vehicle speed determined.

[0058] The formula for calculating the heat transfer Q of a radiator / condenser is as follows:

[0059] Q = hA(T0 - T1)

[0060] In the formula: h is the heat transfer coefficient, with units of W / (m²). 2 ·K); A is the heat transfer area, in m² 2 T0 and T1 are the temperatures of the coolant and the pipe wall, respectively, in K.

[0061] The heat transfer coefficient h can be calculated using the following formula:

[0062] Nusselt coefficient:

[0063]

[0064] Reynolds number:

[0065]

[0066] Prandtl number:

[0067]

[0068] Fluid velocity:

[0069]

[0070] In the above formula: k represents the thermal conductivity of the fluid at rest; μ is the fluid viscosity; C p ρ is the specific heat capacity; L is the geometric length; For mass flow rate; A f ρ is the cross-sectional area of ​​the fluid; h is the heat transfer coefficient; ρ is the fluid density.

[0071] Without considering the influence of the air intake grille, engine compartment and other components on the flow inside the compartment, the drag coefficient is used to calibrate the front compartment heat dissipation module model under steady-state conditions based on the experimental or three-dimensional simulation results.

[0072] Optionally, the front compartment heat dissipation module is being simulated in 3D and optimized using DOE, including:

[0073] Improve system heat dissipation performance by performing DOE design on condensers / radiators under steady-state operating conditions;

[0074] Design factors include: structural dimensions or location parameters of the heat sink / condenser and fan;

[0075] The response variables are coolant outlet temperature and heat dissipation power.

[0076] Optionally, a one-dimensional battery thermal management integrated system model generally includes the following modules: battery pack thermal management module, front compartment heat dissipation module, air conditioning circuit model, control unit, etc.

[0077] The front cabin heat dissipation module model provides external airflow data for each heat exchange process. The air conditioning system is connected to the thermal management system through the refrigerant flowing through the Chiller. Under heating conditions, both the air conditioning system and the battery pack thermal management system are heated by the heating circuit to complete the refrigerant heating.

[0078] The battery pack thermal management module model is as described in step S300.

[0079] The front cabin heat dissipation module model is as described in step S400.

[0080] The air conditioning circuit model includes the following components: compressor, evaporator, expansion valve, and chiller. Modeling requires defining the compressor efficiency map, refrigerant type, evaporator structural dimensions and heat exchange and flow resistance characteristics, and the flow characteristics of the expansion valve at different opening degrees.

[0081] The control loop model is built including but not limited to Matlab-Simulink. The controlled objects mainly include: fans, water pumps, compressors, PTC heaters, expansion valves, etc. The control targets are mainly cell temperature distribution, coolant outlet temperature and pressure, outlet wind speed and pressure, etc.

[0082] The model completes the transfer of matter, energy, and information through pipeline connections and information exchange, thus constructing a complete one-dimensional battery thermal management integrated system model.

[0083] After completing the modeling and calibration of the one-dimensional battery thermal management integrated system, the above model can be used for simulation calculations of a few steady-state / transient operating conditions.

[0084] Optionally, to increase the system's versatility and enable applications under more operating conditions, the above system can be combined with the vehicle driving module, motor circuit, passenger compartment module, control module, etc., to complete the modeling of the thermal management system at the vehicle level. Different driving conditions can be set in the vehicle driving module to realize the multi-condition application of the battery thermal management integrated system.

[0085] Simulations can be conducted under different environmental conditions according to different needs, such as steady-state conditions with constant vehicle speed, constant ambient temperature, and gradient, cyclic conditions, and multiple ambient temperatures and gradients.

[0086] The multiple operating conditions can include: high-power charging / discharging, low-temperature environment, high-temperature environment, and common driving conditions (such as NEDC cycle conditions). It can perform steady-state simulation calculations under constant operating conditions as well as transient calculations under varying operating conditions.

[0087] Preferably, the heat transfer coefficient between the bottom of the battery pack housing and the air under driving conditions can be determined by the formula in step S400. The flow velocity in the formula can be considered as the vehicle speed, thereby simulating forced convection heat transfer under transient conditions.

[0088] In summary, the present invention has at least one of the following beneficial technical effects:

[0089] 1. The battery pack pseudo-3D model of the present invention can easily realize the optimized design of the insulation layer in one-dimensional software, avoiding the problems of repeated settings and high calculation costs in three-dimensional simulation;

[0090] 2. This invention discretizes the three-dimensional model of the battery pack into a pseudo-three-dimensional model and couples it with the surrounding thermal management system to build a one-dimensional battery thermal management integrated system. The combination with the vehicle-related systems can realize the simulation calculation of the thermal management system at the vehicle level. This not only considers the influence of the flow field and the surrounding system on battery thermal management, but also describes in detail the temperature distribution of the cells in the battery pack. At the same time, the multi-condition application of the integrated system effectively improves the simulation calculation speed.

[0091] 3. This invention can be applied to battery thermal management simulation calculations under multiple operating conditions simultaneously. Compared with 3D software, which requires continuous input of fixed boundary conditions, it can greatly improve calculation efficiency and simulation level.

[0092] 4. This invention considers the influence of vehicle speed / wind speed on the environment and battery pack convective heat transfer under driving conditions. That is, the setting of the convective heat transfer coefficient during forced convection no longer depends on empirical values, but is related to wind speed and temperature.

[0093] 5. This invention considers the optimized design of the insulation layer and the front compartment heat dissipation module to ensure the insulation performance of the battery pack and the heat dissipation performance of the front compartment. Attached Figure Description

[0094] Figure 1 This is a flowchart of a method for coupled modeling and co-simulation of a vehicle battery pack and its thermal management module according to one embodiment of the present invention.

[0095] Figure 2 This is a flowchart of a one-dimensional modeling process for a battery thermal management system according to one embodiment of the present invention.

[0096] Figure 3 This is a schematic diagram of a simulated three-dimensional model of a battery pack according to one embodiment of the present invention.

[0097] Figure 4 This is a DOE flowchart of one embodiment of the present invention.

[0098] Figure 5 This is a schematic diagram of an electrothermal-fluid coupling model according to one embodiment of the present invention.

[0099] Figure 6 This is a schematic diagram of a one-dimensional model of a battery thermal management integrated system according to one embodiment of the present invention.

[0100] Figure 7 This is a schematic diagram of a vehicle thermal management system model according to one embodiment of the present invention. Detailed Implementation

[0101] The following is in conjunction with the appendix Figure 1-7 The present invention will be described in further detail below.

[0102] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0103] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0104] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0105] Reference Figure 1 and Figure 2 As shown, a coupled modeling and co-simulation method for automotive battery packs and their thermal management modules includes the following steps:

[0106] Step S100: The 3D model of the battery pack is transformed into a pseudo-3D model of the battery pack through discretization processing;

[0107] Step S200: Based on the pseudo-3D model of the battery pack, perform high / low temperature environment hot immersion / cold immersion simulation to calculate the temperature change and temperature distribution of the cells inside the battery pack, and determine whether the heat preservation index is met. If the heat preservation index is not met, perform DOE optimization on the battery pack.

[0108] Step S300: After meeting the thermal insulation requirements, perform one-dimensional modeling of the battery pack thermal management module based on the battery electro-thermal coupling model;

[0109] Step S400: Simulate 3D modeling of the front compartment heat dissipation module and perform optimization matching;

[0110] Step S500: Build a one-dimensional battery thermal management integrated system model based on the battery pack thermal management module model and the front compartment heat dissipation module model;

[0111] Step S600: Perform multi-condition simulation of the battery thermal management integrated system in conjunction with the whole vehicle.

[0112] In step S100, the 3D model of the battery pack is transformed into a pseudo-3D model of the battery pack through discretization.

[0113] The battery pack model mainly includes: battery pack housing, battery modules, insulation layer, water-cooled plate, and other internal accessories.

[0114] The main heat exchange pathways between the battery module and the external environment are as follows: Battery module - insulation layer - housing - external environment, this path mainly involves heat dissipation through solid contact conduction; Battery module - air inside the pack - housing - external environment, this path involves convective heat exchange between the air inside and outside the pack. Due to the weak airflow and low thermal conductivity of the air inside the pack, the heat transfer effect of the air inside the pack is relatively small, while the convective heat transfer of the outside air has a greater impact on heat transfer. That is, the impact of vehicle speed / wind speed on the heat exchange between the battery pack and the external environment should be considered; Battery module - water-cooled plate - coolant: heat conduction between the module and the water-cooled plate, and heat convection between the water-cooled plate and the coolant. The cell temperature is mainly affected by the convective heat transfer of the coolant.

[0115] The 3D model of the battery pack was discretized into a quasi-3D model using GEM3D software, such as... Figure 3 As shown, the pseudo-3D model uses thermal mass elements to replace the various solid components in the 3D space. The parameters of the thermal mass element include: solid material properties, solid mass, initial temperature, heat generation, distance along the heat transfer path, and effective heat transfer surface area. The heat transfer area (including the area of ​​convection and conduction), boundary conditions, and heat transfer distance of each mass element are automatically processed by the software, which can effectively simulate the heat transfer process in 3D space. For cell heat transfer, the thermal conductivity of the cell needs to be set to 3.2 W / (m·K), 15 W / (m·K), and 15 W / (m·K). The solid region of the liquid cooling plate is modeled using thermal mass elements, and the heat transfer distance and heat transfer area need to be set manually: the heat transfer area is the sum of the areas of the six channels, and the heat transfer distance is set to half the wall thickness of the water cooling plate. Considering the heat conduction between the solid components of the water cooling plate, corresponding heat conduction ports between the water cooling plates need to be set, and the software is set to simulate convection heat transfer between pipes and fluids in a Chilton-Colburn similar manner.

[0116] The air inside the pack is also modeled using thermal mass elements, with the material properties set to air. After discretization by GEM3D, it automatically establishes a conduction and heat transfer relationship with the internal components of the battery pack. The connection is made via ConnectionConn, and the thermal boundary, effective thermal conduction area, and heat transfer distance are automatically determined by the software.

[0117] Each mass element will have heat conduction or convection with adjacent mass elements or fluids. Heat transfer between adjacent heat elements is calculated using classical heat transfer formulas, as shown below:

[0118] Q=ΔT×R

[0119] Where: Q is the heat transfer of the solid, ΔT is the temperature difference between the solid's center of mass and the boundary, and R is the thermal resistance, where the formula for calculating the thermal resistance is:

[0120] R = L × k × A

[0121] In the formula: L is the heat transfer distance between the center of mass and the boundary, A is the heat transfer area between the center of mass and the boundary, and k is the thermal conductivity of the solid.

[0122] The external environment is modeled using the temperature module to determine the external ambient temperature. The external environment and the battery pack housing undergo convective heat transfer, which is connected using Convection Conn, where the convective heat transfer coefficient is set.

[0123] Because the temperature setting is not high, the influence of thermal radiation is not considered in the entire modeling process. The convective heat transfer coefficient can be an empirical value when the influence of the external environment is weakened.

[0124] S200, based on a pseudo-3D model of the battery pack, performs high / low temperature environment hot / cold immersion simulation calculations to determine the temperature changes and distribution of the cells inside the battery pack, and determines whether the insulation index is met. If the insulation index is not met, the battery pack is optimized using DOE.

[0125] The simulation process does not consider the impact of coolant flow on thermal insulation performance, cell discharge, or cell heat generation. Based on the pseudo-3D model of the battery pack from step S100, the simulation is performed as follows: Cold immersion: The initial ambient temperature is set to -30℃ in the temperature settings, and the initial temperature of the entire battery pack is 25℃. The natural convection heat transfer coefficient is set to 6W / (m^2-K) in the Convection Conn settings, and the simulation time is set to 12h. The temperature field changes and distribution of the battery pack are obtained: After 12 hours of cold immersion, the lowest cell temperature appears in the four corners of the module, with a minimum temperature of -10.8℃, and the maximum temperature difference between cells does not exceed 2℃. Hot immersion: The initial ambient temperature is set to 55℃, and the initial temperature of the battery pack is 25℃. The natural convection heat transfer coefficient is set to 6W / (m^2-K) in the Convection Conn settings, and the simulation time is set to 6h. The temperature field changes and distribution of the battery pack are obtained: After 6 hours of hot immersion, the highest temperature is 37℃, and the temperature difference between cells does not exceed 2℃.

[0126] Based on the proposed insulation performance indicators—a temperature drop rate not exceeding 3℃ / h—the insulation layer design is deemed satisfactory and applicable to various working conditions. However, if the temperature field distribution and temperature changes do not meet the standards, the insulation layer needs to be redesigned. This requires DOE (Design of Experiments) experiments to be conducted on influencing parameters such as the battery pack insulation layer thickness and casing thickness. Figure 4 As shown.

[0127] DOE technology is a cutting-edge technology that integrates mathematical statistics, computational modeling, and optimization analysis, and is widely used in actual product manufacturing and design. It first identifies the design factors that affect the battery insulation temperature, analyzes the degree of influence of the design factors on the target variable, screens out the factors that are more sensitive to the battery insulation temperature, and improves the insulation performance by optimizing the factor to achieve the insulation target. This method effectively reduces the number of simulations, ensures that the insulation design is scientific and accurate, and improves efficiency.

[0128] By using Design of Elements (DOE) to jointly optimize multiple parameters, optimal results across multiple objectives can be achieved. Based on experience, designable factors affecting insulation performance are determined, such as insulation layer thickness, enclosure thickness, and cold plate thickness, with the cell temperature as the response. The DOE method is selected, typically a fully factorial design approach, to determine the range and number of levels of the design factors, and to determine n experimental schemes. DOE experiments yield the cell temperature response variable value. Regression analysis of the experimental data results can determine the sensitivity and correlation of the response variable to the design factors, thereby determining the degree of influence of each factor, and discarding factors with low influence when necessary.

[0129] The response model obtained through data fitting can be a multinomial model, a neural network (MLP) model, an inverse distance (IDW) model, a Kriging model, etc. The software automatically confirms the goodness of fit and residual mean square error of each model to measure the model fitting quality. If the fitting accuracy is poor, the number of experiments is increased and the experiment is redesigned to select an approximate model for the battery pack design factor and cell temperature.

[0130] The optimization problem is defined as the minimum temperature of the battery cell / the maximum temperature of the battery cell. A global optimization genetic algorithm (NSGA-Ⅲ by default) is selected to perform multi-objective and multi-parameter Pareto optimization to obtain the value corresponding to the Pareto front, thereby determining the optimal values ​​of insulation layer thickness, box thickness, and cold plate thickness. If the calculation results do not converge, the approximate model is redesigned until convergence.

[0131] The optimized design factors are reintroduced into the battery pack model settings to obtain the verification values ​​of the response variables. These values ​​are then compared and analyzed with the response variables before and after optimization to complete the updated battery pack design. Temperature field analysis continues.

[0132] Step S300: After meeting the thermal insulation requirements, perform one-dimensional modeling of the battery pack thermal management module based on the battery electro-thermal coupling model.

[0133] The battery pack thermal management module model includes the battery pack pseudo-3D model and external environment model mentioned in step S100. In addition, it should also include the cell heating model, battery cooling circuit model, and battery heating circuit model.

[0134] The cell heating model is actually an electrothermal coupling model, which can simulate both battery voltage characteristics and battery temperature characteristics.

[0135] The circuit model adopts a second-order RC equivalent circuit. The heat generated by the battery mainly includes ohmic heat, polarization heat, reaction heat, and side reaction heat. The heat generation rate model formula can comprehensively consider the above four types of heat to simulate the thermal characteristics of the battery during operation. An electrothermal coupling model is constructed by comprehensively utilizing the equivalent circuit model and the heat generation rate formula: During battery operation, the equivalent circuit model can be used to obtain the open-circuit voltage, terminal voltage, and current. Substituting these into the heat generation rate model yields the battery heat generation rate. Combined with ambient heat dissipation, the battery temperature response is simulated. The obtained temperature value is fed back to the equivalent circuit model to achieve electrothermal coupling. Figure 5 The coupling principle is shown.

[0136] The battery polarization voltages U1, U2 and terminal voltage U in the second-order RC equivalent circuit can be expressed as follows:

[0137]

[0138]

[0139] U = U OCV -IR0-U1-U2

[0140] The formula for the rate of heat generation is:

[0141]

[0142] The cell heating model is described by a second-order RC equivalent circuit model. Using the core template of GT-SUITE software, the series / parallel connection of voltage and current between cores is realized. The temperature data of the cell thermal mass unit is transmitted to the cell equivalent circuit module through the gain module, and the cell heating power data is transmitted to the cell template through gain.

[0143] In the thermal management system, the cell heat dissipation path is as described in step S100. The battery pack cooling circuit includes, but is not limited to, a water-cooled plate, a chiller, connecting pipes, and a water pump. The water-cooled plate includes both a thermomass model and a pipe model. The thermomass model needs to determine parameters such as the water-cooled plate's material properties, mass, temperature, and heat source power. The pipe model needs to define the cold liquid properties, pipe geometry, surface roughness, heat transfer characteristics, and flow resistance characteristics. The pipe model wall temperature is determined by the thermomass unit model temperature. The chiller parameter settings are similar to those of a heat exchanger, including chiller geometry parameters, liquid types on both sides, wall temperature, heat transfer characteristics, and flow resistance characteristics. The water pump model requires inputting a PumpMap, i.e., the pump's speed-flow rate-pressure head / pressure rise characteristics.

[0144] The main components modeled in the heating circuit model are: PTC water pump, PTC heater, and Chiller. The PTC water pump model is input with the PumpMap diagram. The PTC heater model requires setting parameters such as water jacket volume, PTC flow resistance curve, and heating power. The Chiller has the same geometric structure and MAP data as the Chiller in the cooling circuit.

[0145] The remaining pipelines in the system are modeled and connected according to the actual pipeline geometry.

[0146] Through iterative calculations under different steady-state conditions, the continuity equation, momentum equation, and energy equation are solved, and the flow rate, pressure, current, voltage, temperature, and heat exchange results of the power battery pack thermal management module are finally obtained and confirmed to be within a reasonable range.

[0147] Step S400: Simulate 3D modeling of the front compartment heat dissipation module and perform optimization matching.

[0148] The front compartment cooling module also employs a pseudo-3D modeling method: existing templates for the condenser and radiator are introduced into GT-COOL3D. Positional parameters are determined according to the overall vehicle layout to ensure consistency between the front compartment model and the overall vehicle 3D model. The configuration of the aforementioned components is selected, and their geometric parameters are determined. In this model, both the condenser and radiator utilize horizontally mounted tube-fin heat exchanger modules with aluminum structures. Air-side and coolant-side state parameters are set: coolant type, coolant temperature and pressure, initial wall temperature, air temperature and pressure, and heat transfer test data (i.e., inlet and outlet temperature, pressure, flow rate, and heat transfer power relationship), etc., to determine the windward flow field space. The front compartment 3D model is discretized and converted into a pseudo-3D model. Based on this, the following are added: fan, air-side and coolant-side inlets and outlets, air inlet drag coefficient, and wind pressure coefficient. The fan model requires determination of its geometry, state parameters, fan type, and drag characteristics determined through experiments or 3D simulation. The air-side inlet and outlet require determination of their inlet conditions (pressure, temperature) and vehicle speed.

[0149] The formula for calculating the heat transfer Q of a radiator / condenser is as follows:

[0150] Q = hA(T0 - T1)

[0151] In the formula: h is the heat transfer coefficient, with units of W / (m²). 2 ·K); A is the heat transfer area, in m² 2 T0 and T1 are the temperatures of the coolant and the pipe wall, respectively, in K; the heat transfer coefficient h is calculated by combining the Nusselt coefficient, Reynolds number, Prandtl number and fluid velocity.

[0152] In the pseudo-3D model of the front compartment, the influence of the air intake grille and other components in the engine compartment besides the radiator, intercooler, condenser, and fan on the airflow within the compartment is not considered. Therefore, the front compartment model needs to be calibrated. Calibration involves measuring the airflow distribution through the condenser and radiator at vehicle speeds of 10km / h, 20km / h, 40km / h, 80km / h, and 120km / h to ensure that the calculated airflow and its distribution in the front compartment model are consistent with the results of 3D simulation or experiments. The main calibration focuses on the drag coefficient and wind pressure coefficient of the front compartment air intake. First, the drag coefficient is calibrated, as it primarily affects the airflow at different fan speeds when the vehicle is stationary. Then, the wind pressure coefficient is calibrated based on the drag coefficient calibration, as it primarily affects the airflow into the front compartment when the vehicle is in motion.

[0153] The DOE design of the condenser / radiator under steady-state conditions is as follows: Figure 4 As shown, the design factors are: structural dimensions or positional parameters of the radiator / condenser and fan, etc.; the response variables are coolant outlet temperature, heat dissipation power, etc. Following the same optimization steps as step S200: determine the experimental factors, levels, and response variables, fit the response surface, perform correlation / sensitivity analysis, optimize using a genetic algorithm, determine the optimal value of the design factors, and achieve the optimized matching design of the front compartment heat dissipation module model.

[0154] Step S500: Build a one-dimensional battery thermal management integrated system model based on the battery pack thermal management module model and the front compartment heat dissipation module model;

[0155] A one-dimensional battery thermal management system simulation model typically includes the following modules: battery pack thermal management module model, front compartment heat dissipation module model, air conditioning circuit model, control unit, etc.

[0156] The working principle of the one-dimensional battery thermal management integrated system: During the cooling process, the refrigerant in the condenser undergoes thermal convection with the outside air. In the battery cooling circuit, the refrigerant passes through the expansion valve on the branch and through Chiller1 to exchange heat with the cooling water in the water-cooled plate, thereby reducing the battery temperature. In the air conditioning circuit, the refrigerant passes through the expansion valve on this branch and through the evaporator to exchange heat with the air, thereby reducing the temperature of the passenger compartment. During the heating process, the common heat source in the battery heating circuit and the air conditioning circuit is the PTC heater. The PTC heater heats the battery pack and passenger compartment through Chiller2 and the warm air core to achieve the temperature rise effect.

[0157] The modeling of the air conditioning circuit components includes: compressor, evaporator, expansion valve, etc. Modeling requires defining the compressor efficiency MAP, refrigerant type, evaporator structural dimensions and heat exchange and flow resistance characteristics, and the flow characteristics of the expansion valve at different opening degrees.

[0158] The control loop model is built including but not limited to Matlab-Simulink. The controlled objects mainly include: fans, water pumps, compressors, PTC heaters, expansion valves, etc. The control targets are mainly cell temperature distribution, coolant outlet temperature and pressure, outlet wind speed and pressure, etc.

[0159] The model completes the transfer of matter, energy, and information through pipeline connections and information exchange, constructing a complete one-dimensional battery thermal management system model. The one-dimensional integrated system model in GT software is as follows: Figure 6 As shown, the battery thermal management circuit includes a battery pack thermal mass model, an external environment model, a cell heating model, and a battery cooling circuit model. The battery thermal management circuit and the heating circuit together constitute the battery pack thermal management module.

[0160] After modeling, simulation calculations were performed under high / low temperature and charge / discharge conditions to solve the continuity equation, momentum equation, and energy equation. The final results for flow rate, pressure, temperature, etc. of each loop were within a reasonable range.

[0161] Step S600: Perform multi-condition simulation of the battery thermal management integrated system in conjunction with the whole vehicle.

[0162] To increase the system's versatility and enable applications in more operating conditions, the aforementioned system can be combined with the vehicle's driving module, motor circuit, passenger compartment module, and related control modules to complete the modeling of the vehicle-level thermal management system, such as... Figure 7 As shown.

[0163] Motor circuit: mainly includes pipelines, electric water pump, water tank, liquid-side model of radiator, motor, charger, motor controller, DC / DC, etc. Each heat-generating element is connected in series through the water circuit, and heat dissipation and cooling are completed through low-temperature radiator.

[0164] The vehicle driving module mainly includes the vehicle driving model (simulated driving and braking), atmospheric environment, motor, motor control module, energy recovery control module, etc.

[0165] Crew compartment module: mainly includes crew compartment module, evaporator, piping, etc.

[0166] Multiple driving conditions are set in the vehicle driving module to realize the multi-condition application of the battery thermal management integrated system.

[0167] Simulations can be conducted under different environmental conditions depending on the specific needs, such as steady-state and cyclic operating conditions with constant vehicle speed, ambient temperature, and gradient, as well as environments with varying temperature changes and gradient changes.

[0168] The multiple operating conditions can include: high-power charging / discharging, low-temperature environment, high-temperature environment, and common driving conditions (such as NEDC cycle conditions). It can perform steady-state simulation calculations under constant operating conditions as well as transient calculations under varying operating conditions.

[0169] Under driving conditions, the heat transfer coefficient between the bottom of the battery pack housing and the air can be determined by the formula in step S400. The flow velocity in the formula can be considered as the vehicle speed, thereby simulating the forced convection heat transfer under transient conditions.

[0170] Simulation calculations solve the continuity equation, momentum equation, and energy equation, ultimately obtaining the coolant flow rate, pressure, and temperature of different components in the battery thermal management system under vehicle driving conditions; the heat transfer and outlet air temperature of the radiator and condenser; the heat exchange and outlet air temperature and refrigerant pressure of the condenser and evaporator in the air conditioning system; and the temperature distribution of thermal mass elements such as battery cells and cold plates.

[0171] The simulation calculation method described above can use a batch processing method when comparing and analyzing different schemes. That is, when the same simulation model is used for the same simulation operation, multiple parameters can be calculated at the same time, and the results of multiple schemes can be compared at the same time. This is more intuitive and convenient, and it is easier to determine the better scheme or combination of schemes.

[0172] Through the above scheme, the quasi-3D model of the battery pack of this invention can conveniently realize the optimized design of the insulation layer in one-dimensional software, avoiding the problems of repetitive settings and high computational costs in 3D simulation. This invention discretizes the 3D model of the battery pack into a quasi-3D model and couples it with a surrounding thermal management system to build a one-dimensional battery thermal management integrated system. Combined with relevant vehicle systems, this enables vehicle-level thermal management system simulation calculations. This not only considers the influence of the flow field and surrounding systems on battery thermal management but also describes the temperature distribution of the cells within the battery pack in detail. Simultaneously, the multi-condition application of the integrated system effectively improves the simulation calculation speed. This invention can be applied simultaneously to battery thermal management simulation calculations under various operating conditions. Compared to 3D software that requires continuous input of fixed boundary conditions, it can greatly improve computational efficiency and simulation level. This invention considers the influence of vehicle speed / wind speed on the convective heat transfer of the environment and battery pack under driving conditions. That is, the setting of the convective heat transfer coefficient during forced convection no longer depends on empirical values ​​but is related to wind speed and temperature. This invention considers the optimized design of the insulation layer and the front compartment module to ensure the thermal insulation performance of the battery pack and the heat dissipation performance of the front compartment.

Claims

1. A coupled modeling and co-simulation method for automotive battery packs and their thermal management modules, characterized in that, Includes the following steps: Step S100: The 3D model of the battery pack is transformed into a pseudo-3D model of the battery pack through discretization processing; The pseudo-3D model of the battery pack is derived from the discretization of the 3D model of the battery pack. The pseudo-3D model uses thermal mass elements to replace each solid component in the 3D model. The parameters of the thermal mass element include: solid material properties, solid mass, initial temperature, heat generation, distance on the heat transfer path, and effective heat transfer surface area. Each mass element will conduct or convect heat with adjacent mass elements or fluids. The heat transfer between adjacent thermal elements is calculated using the classical heat transfer formula, as shown below: Where: Q is the solid heat exchange capacity. Let R be the temperature difference between the solid's center of mass and the boundary, and R be the thermal resistance. The formula for calculating the thermal resistance is: Where: L is the heat transfer distance between the center of mass and the boundary, A is the heat transfer area between the center of mass and the boundary, and k is the thermal conductivity of the solid. Simulating the external environment requires determining the external ambient temperature and the convective heat transfer coefficient between the external environment and the battery pack, so that the ambient temperature model is coupled with the thermal mass unit corresponding to the battery pack components in contact with the external environment, thereby realizing thermal convection between the external environment and the battery pack. Step S200: Based on the pseudo-3D model of the battery pack, perform high / low temperature environment hot immersion / cold immersion simulation to calculate the temperature change and temperature distribution of the cells inside the battery pack, and determine whether the heat preservation index is met. If the heat preservation index is not met, perform DOE optimization on the battery pack. Step S300: After meeting the thermal insulation requirements, perform one-dimensional modeling of the battery pack thermal management module based on the battery electro-thermal coupling model; The electro-thermal coupling model is built using an equivalent circuit model and a heat generation rate formula. During battery operation, the equivalent circuit model can be used to calculate the open-circuit voltage, terminal voltage, and current. Substituting these values ​​into the heat generation rate formula yields the battery heat generation rate. Combined with ambient heat dissipation, the battery temperature response is simulated, and the obtained temperature value is fed back to the equivalent circuit model to achieve electro-thermal coupling. The circuit model uses a second-order RC equivalent circuit, and the battery polarization voltage is... The terminal voltage U can be expressed as follows: The heat generation rate takes into account the thermal characteristics of the battery during operation, considering four types of heat generation: ohmic heat, polarization heat, reaction heat, and side reaction heat. The formula for the heat generation rate is: ； Step S400: Simulate 3D modeling of the front compartment heat dissipation module and perform optimization matching; Step S500: Build a one-dimensional battery thermal management integrated system model based on the battery pack thermal management module model and the front compartment heat dissipation module model; Step S600: Perform multi-condition simulation of the battery thermal management integrated system in conjunction with the whole vehicle.

2. The method according to claim 1, characterized in that, The battery pack model includes: battery pack housing, battery modules, insulation layer, water-cooling plate, and other internal accessories; The heat exchange between the battery module and the external environment includes the following heat dissipation pathways: Battery module - insulation layer - housing - external environment, this path involves heat dissipation through solid contact conduction; The path from battery module to internal air to housing to external environment involves convective heat transfer between internal and external air. Due to the weak airflow and low thermal conductivity of the internal air, the heat transfer effect of the internal air is small, while the convective heat transfer of the external air has a greater impact on heat transfer. Therefore, the focus should be on the impact of vehicle speed / wind speed on the heat transfer between the battery cell and the external environment. The battery module-water cooling plate-coolant path involves heat conduction between the module and the water cooling plate, and heat convection between the water cooling plate and the coolant. The cell temperature is affected by the convective heat transfer of the coolant.

3. The method according to claim 2, characterized in that, The steps for simulating and calculating the temperature changes and distribution of cells within the battery pack under high / low temperature environment hot / cold immersion include: Initialize different ambient temperatures and battery pack temperatures to determine the simulation temperature conditions; Set the convective heat transfer coefficient in a natural convection environment; Set the simulation time; Simulation calculation of battery pack temperature field changes; The simulation does not consider the effect of coolant flow on heat preservation; it does not consider cell discharge, nor does it consider cell heat generation.

4. The method according to claim 1, characterized in that, The DOE optimization process includes the following steps: Determine the design factors, number of levels, and response variables. The fitted response surface is obtained by fitting the data. Determine the sensitivity and correlation of the response variables to the design factors, and assess the degree of influence of each design factor; The solution is obtained by using a globally optimized genetic algorithm. Obtain the optimized design factors, and determine the optimal value of the design factors by comparing and analyzing the response variables before and after optimization.

5. The method according to claim 1, characterized in that, The battery pack thermal management module model includes: a battery pack thermal mass model, an external environment model, a cell heating model, a battery cooling circuit model, and a battery heating circuit model; The cell heating model is actually an electro-thermal coupling model, which can simulate the battery voltage characteristics and battery temperature characteristics. The battery cooling circuit model consists of the following components: water-cooled plate, chiller, connecting pipes, and water pump. The water-cooled plate includes both the thermal mass model and the pipe model. The wall temperature of the pipe model is determined by the temperature of the thermal mass unit model. The battery heating circuit model consists of the following components: PTC water pump, PTC heater, and Chiller. The Chiller has the same geometry as the Chiller in the cooling circuit described above.

6. The method according to claim 4, characterized in that, The front cabin heat dissipation module model realizes heat exchange between the air side and the liquid side based on the relationship between the inlet and outlet side temperature, pressure, flow rate, and heat exchange power determined by experiments or three-dimensional simulation, combined with the geometry and material properties of the radiator / condenser. The front cabin heat dissipation module model adopts a pseudo-3D modeling approach: the parameter settings for the radiator and condenser include geometric position, geometric structure, selection, material properties, refrigerant type, coolant type, inlet and outlet status on the wind side and coolant side, heat transfer characteristics, and flow resistance characteristics; the spatial position of the flow field and the fluid material type are determined by the windward flow field space, and spatial interfaces are set to achieve the purpose of simulating the three-dimensional flow field of the front cabin; the three-dimensional model of the front cabin is discretized to generate a pseudo-3D model, and based on this, fluid inlets and outlets, drag coefficients, and fans are added to build a complete front cabin heat dissipation module model; The formula for calculating the heat transfer Q of a radiator / condenser is as follows: In the formula: The heat transfer coefficient is expressed in units of... For heat transfer area, unit These are the temperatures of the coolant and the pipe wall, respectively, in units of... The heat transfer coefficient is among them. It is calculated by combining the Nusselt coefficient, Reynolds number, Prandtl number, and fluid velocity; Without considering the influence of the air intake grille, engine compartment and other components on the flow inside the compartment, the drag coefficient is used to calibrate the front compartment heat dissipation module model under steady-state conditions based on the experimental or three-dimensional simulation results.

7. The method according to claim 6, characterized in that, The engine compartment and front-end modules are undergoing 3D modeling and optimization matching, using DOE for optimization matching, including: Improve system heat dissipation performance by performing DOE design on condensers / radiators under steady-state operating conditions; Design factors include: structural dimensions or location parameters of the heat sink / condenser and fan; The response variables are coolant outlet temperature and heat dissipation power.

8. The method according to claim 1, characterized in that, The one-dimensional battery thermal management integrated system model includes the following modules: battery pack thermal management module, front compartment heat dissipation module, air conditioning circuit model, and control unit. To increase the applicable operating conditions, the vehicle driving module, motor thermal management circuit, passenger compartment circuit, and control module can be combined to complete the modeling of the thermal management system at the vehicle level. Different driving conditions can be set in the vehicle driving module to realize the multi-condition application of the battery thermal management integrated system.

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