Thermal management system for power battery of new energy automobile

Abstract

A new energy automobile power battery thermal management system disclosed by the present invention comprises a battery pack module and a battery pack thermal management system, the battery pack module is composed of a battery module, the battery module comprises a lithium battery and a heat exchange module, and the battery pack thermal management system comprises a heat exchange mechanism simulation module and an experiment verification module. The battery pack heat management system constructs a heat management strategy through mutual verification of the heat exchange mechanism simulation module and the experimental verification module. The heat exchange structure of the power battery is formed by the heat exchange combination of the cooling liquid and the phase change material and the rubber heating belt, and the optimal parameters and the optimal heat exchange strategy of the heat dissipation structure are given through the heat exchange mechanism simulation module and the experimental verification module in the battery pack heat management system; and efficient heat dissipation and heating can be performed on the power battery.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy electric vehicles, and in particular to a thermal management system for a power battery of a new energy electric vehicle. Background Art

[0002] As the power source of new energy vehicles, the performance of power batteries is not only related to the length of the continuous driving mileage of the whole vehicle, but also to the safety and reliability of the product. The performance, life and safety of power batteries are greatly affected by the operating temperature. Excessive temperature will cause the active substances of the power battery to decay continuously, the energy density to decrease, and the aging to accelerate, shortening the service life. In extreme cases, it may even cause thermal runaway, resulting in fire or explosion; too low temperature will cause the diffusion rate of particles inside the power battery to decrease, resulting in increased internal resistance and decreased power. When charging at extremely low temperatures, a lithium plating layer will appear on the surface of the anode, causing the battery capacity to be lost; at the same time, if the temperature difference between batteries is too large, the battery with a higher temperature will accelerate aging, produce local degradation, and reduce the overall performance of the battery pack. Therefore, it is necessary to develop a thermal management system for power batteries for new energy vehicles. Summary of the invention

[0003] In view of the above problems, the present invention provides a new energy vehicle power battery thermal management system, which mainly solves the technical problems existing in the above background technology.

[0004] To achieve the above object, the technical solution of the embodiment of the present invention is implemented as follows:

[0005] A new energy vehicle power battery thermal management system includes a battery pack module and a battery pack thermal management system. The battery pack module is composed of a battery module, and the battery module includes a lithium battery and a heat exchange module. The heat exchange module includes a phase change material, a radiator, a water cooling jacket, a cooling channel and a rubber heating belt. The radiator is an aluminum honeycomb hollow design. The lithium battery is embedded in the radiator. Phase change material is filled between the lithium battery and the radiator. The cooling channel is arranged on the outside of the radiator. Coolant is passed through the cooling channel. The water cooling jacket is arranged between the cooling channels on the outside of the radiator. The rubber heating belt is arranged on the outside of the water cooling jacket. The battery pack thermal management system includes a heat exchange mechanism simulation module and an experimental verification module. The battery pack thermal management system constructs a thermal management strategy by mutually verifying the heat exchange mechanism simulation module and the experimental verification module.

[0006] Furthermore, the heat exchange mechanism simulation module performs numerical calculations and simulations on the heat exchange mechanism in the battery pack module, including the following steps: Step 1: Determine the relevant parameters of the temperature of the lithium battery module and the thermal physical properties of the phase change material; Step 2: Determine the working status of the lithium battery, coolant, and rubber heating belt during the heat exchange process; Step 3: Perform energy analysis of the lithium battery, phase change material, and coolant, determine the control equation of the battery pack thermal management system through the laws of thermophysics, and establish a numerical model of the battery pack thermal management system through the control equations and boundary conditions; Step 4: Perform numerical simulation of the computational fluid dynamics of the heat exchange model of the battery pack module.

[0007] Furthermore, the control equation in step 3 includes:

[0008] Battery energy conservation equation:

[0009] Battery heat per unit volume:

[0010] Enthalpy change of phase change material:

[0011] Coolant continuity equation:

[0012] Coolant momentum equation:

[0013] Coolant energy conservation equation:

[0014] Where t is time, λ x , y , z Respectively represent the heat transfer coefficients of the lithium battery in the x, y, and z directions, ρ, V, C p , T, Q, λ represent the density, volume, specific heat capacity, temperature, heat generation rate, and heat transfer coefficient of the lithium battery, respectively. OC Respectively represent the charging and discharging current, resistance, and open circuit voltage of the lithium battery; Represents the entropy coefficient of the chemical reaction in the battery; C p , PCM , k PCM , α, and L represent the specific heat capacity, density, heat transfer coefficient, liquid component, and latent heat of phase change of the phase change material, respectively; T0, T m 、T l Respectively represent the initial temperature, melting point temperature and complete melting temperature of the phase change material; ρ ω ,υ ω , C pω , μ ω 、T ω , kω They represent the density, flow rate, specific heat, dynamic viscosity, temperature and thermal conductivity of water respectively. Represents the gradient symbol.

[0015] Furthermore, the numerical simulation in step 4 includes: gridding the battery pack module model; establishing a transient energy conservation equation; setting the lithium battery as a heat source term; setting the coolant as a fluid; setting boundary conditions; setting an algorithm; and performing calculations.

[0016] Furthermore, the experimental verification module conducts a battery pack thermal management system experiment on the battery pack module to formulate a thermal management strategy, including the following steps: Step S1: design and build an experimental system, and divide the system experiment into two parts: a cooling experiment and a heating experiment; Step S2: determine the temperature control index; Step S3: design and verify the thermal management strategy.

[0017] Furthermore, the experimental system includes: a computer, a control unit, a switch controller, a water pump, a water tank, a flow meter, a constant temperature device, a multi-channel temperature meter, a refrigerator, and a power supply.

[0018] Furthermore, the thermal management strategy in step S3 includes a heating strategy, and the heating strategy is determined through the heating experiment. In the heating experiment, the ambient temperature is increased from -15°C to 10°C, and the maximum temperature difference during the process is less than 5°C. The heating time is controlled, and the effects of different strategies on the heating behavior of the lithium battery at -15°C are analyzed. The effects of different heating methods on the lithium battery are analyzed by increasing the ambient temperature to determine the optimal heating strategy.

[0019] Furthermore, the thermal management strategy in step S3 includes a cooling strategy, and the cooling strategy is determined through the cooling experiment. In the cooling experiment, the ambient temperature is set to 40°C, the number of cooling channels is 3 to 5, and the coolant flow mode is divided into downstream and convection according to the number of cooling channel layers. The optimal method of the cooling strategy is determined by the influence of the radiator size, the thickness of the phase change material, the number of cooling channels and the coolant flow combination mode on the heat dissipation behavior of the lithium battery under different coolant inlet flow rates.

[0020] Furthermore, the heat exchange mechanism of the battery pack module and the influence on the cooling performance of the battery pack thermal management system under different conditions are studied through experimental verification modules to verify the effectiveness of the thermal management strategy.

[0021] Furthermore, the cooling channels are designed in different levels and are evenly distributed in the height direction of the outside of the radiator. The battery modules that constitute the battery pack module are connected to each other through the cooling channels on the outside of the radiator. The cooling channels between the battery modules that constitute the battery pack module are interconnected. The cooling channels on the outside of the radiator of the first row and the last row are respectively provided with a coolant inlet and a coolant outlet.

[0022] The beneficial effects of the present invention are:

[0023] This application provides a thermal management system for power batteries of new energy vehicles, and proposes a honeycomb battery pack radiator structure with multi-layer cooling channels, which dissipates heat from the power battery through coolant and phase change materials. The heat exchange process between the power battery, phase change material and coolant is studied through the heat exchange mechanism simulation module and the experimental verification module, and the control effect of the battery temperature under different parameter combinations is analyzed. The low-temperature heating and high-temperature cooling of the power battery are achieved through the formulated thermal management strategy, ensuring that the battery peak temperature and the maximum temperature difference are within a reasonable range. Through the constructed heating strategy, the battery module can be heated safely and quickly, so that the battery can also work in a low-temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a battery pack module in a thermal management system for a new energy vehicle power battery provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of a portion of the structure of a heat exchange module of a battery module in a thermal management system for a power battery of a new energy vehicle provided in an embodiment of the present application;

[0026] Figure 3 A flow chart constructed for the thermal management strategy in the thermal management system of the power battery of a new energy vehicle provided in the embodiments of the present application;

[0027] Figure 4 This is a schematic diagram of the test system in the experimental verification module of the new energy vehicle power battery thermal management system provided in the embodiment of the present application.

[0028] Description of Figure Numbers:

[0029] 1. Battery pack module; 2. Battery module; 3. Lithium battery; 4. Phase change material; 5. Radiator; 6. Water cooling jacket; 7. Cooling channel; 8. Rubber heating belt; 9. Coolant inlet; 10. Coolant outlet; 11. Computer; 12. Control unit; 13. Switch controller; 14. Water pump; 15. Water tank; 16. Flow meter; 17. Constant temperature device; 18. Multi-channel temperature meter; 19. Refrigerator; 20. Power supply. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, the expression "some embodiments" is related to a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0031] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0032] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and the scope of the present invention will be fully conveyed to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms of "one", "one" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "compose" and / or "include" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0033] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "inside", "outside", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0034] In order to fully understand the present invention, a detailed structure will be proposed in the following description to illustrate the technical solution proposed by the present invention. The optional embodiments of the present invention are described in detail as follows, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0035] Please refer to the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 , Attachment Figure 4 The present application provides a new energy vehicle power battery thermal management system, including a battery pack module 1 and a battery pack thermal management system, wherein the battery pack module 1 is composed of a battery module 2, wherein the battery module 2 includes a lithium battery 3 and a heat exchange module, wherein the heat exchange module includes a phase change material 4, a radiator 5, a water cooling jacket 6, a cooling channel 7 and a rubber heating belt 8, wherein the radiator 5 is an aluminum honeycomb hollow design, wherein the lithium battery 3 is embedded in the radiator 5, and the lithium battery 3 and the radiator 5 are filled with a phase change material 4, wherein the cooling channel 7 is arranged on the outside of the radiator 5, wherein a coolant is passed through the cooling channel 7, wherein the water cooling jacket 6 is arranged between the cooling channels 7 on the outside of the radiator 5, and wherein the rubber heating belt 8 is arranged on the outside of the water cooling jacket 6, wherein the battery pack thermal management system includes a heat exchange mechanism simulation module and an experimental verification module, wherein the battery pack thermal management system constructs a thermal management strategy by mutually verifying the heat exchange mechanism simulation module and the experimental verification module.

[0036] Exemplarily, the battery pack module can be composed of two rows and three columns of battery modules. When in use, the lithium battery 3 will generate a large amount of heat, which is absorbed by the phase change material 4 filled between the radiator 5 and the lithium battery 3. The battery heat absorbed by the phase change material 4 is transferred to the water cooling jacket 6 through the aluminum radiator 5, and the battery heat is then transferred to the coolant in the cooling channel 7 through the radiator 5 and the water cooling jacket 6, achieving the effect of cooling the phase change material 4 and the lithium battery 3. When the temperature of the lithium battery 3 is low, the rubber heating belt 8 starts to heat up, and the heat is transferred to the phase change material 4 through the water cooling jacket 6 and the radiator 5, and then transferred to the lithium battery 3 by the phase change material 4, realizing battery heating in a low temperature environment.

[0037] The heat exchange mechanism simulation module performs calculation and simulation on the heat exchange mechanism values ​​in the battery pack module 1, including the following steps: Step 1: Determine the relevant parameters of the temperature of the lithium battery 3 module 2 and the thermophysical properties of the phase change material 4; Step 2: Determine the working status of the lithium battery 3, coolant, and rubber heating belt 8 during the heat exchange process; Step 3: Perform energy analysis of the lithium battery 3, phase change material 4, and cooling liquid, determine the control equation of the battery pack thermal management system through the laws of thermophysics, and establish the numerical model of the battery pack thermal management system through the control equation and boundary conditions; Step 4: Perform numerical simulation of the computational fluid dynamics of the heat exchange model of the battery pack module 1.

[0038] For example, in step 1, the phase change point of the phase change material 4 is 45°C, while the maximum temperature of the lithium battery 3 is maintained at about 50°C. During the cooling process, the specific heat of the phase change material 4 will change with the increase of temperature. This simulation uses the average specific heat value between the working temperature of 40°C and 50°C. During the heating process, the phase change material 4 does not undergo phase change, and the specific heat takes a constant value.

[0039] In step 2, during the cooling process of the lithium battery 3, the lithium battery 3 is used as a heat source, water is used as a cooling medium, the flow of the coolant is regarded as laminar flow, and a laminar flow model is adopted. During the heating process of the lithium battery 3, the rubber heating belt 8 is simplified as a surface heat source to preheat the lithium battery 3.

[0040] In step 3, the control equation of the heat exchange system between the cooling liquid and the phase change material 4 is determined according to the Fourier law, the law of conservation of energy, the continuity equation and other thermophysical laws. Among them, the battery mainly follows the law of conservation of energy during the charging and discharging process, that is, the change in the internal energy of the battery is equal to its heat generation minus the heat dissipation; the change in the enthalpy value of the phase change material 4 is related to its temperature field, heat transfer coefficient, phase change rate and other parameters; and the heat exchange process of the cooling liquid follows the continuity equation, momentum equation and energy conservation equation. A numerical model of the heat exchange system is established based on the control equation and boundary conditions.

[0041] The control equation in step 3 includes:

[0042] Battery energy conservation equation:

[0043] Battery heat per unit volume:

[0044] Enthalpy change of phase change material:

[0045] Coolant continuity equation:

[0046] Coolant momentum equation:

[0047] Coolant energy conservation equation:

[0048] Where t is time, λ x , y , z Respectively represent the heat transfer coefficients of the lithium battery in the x, y, and z directions, ρ, V, C p , T, Q, λ represent the density, volume, specific heat capacity, temperature, heat generation rate, and heat transfer coefficient of the lithium battery, respectively. OC Respectively represent the charging and discharging current, resistance, and open circuit voltage of the lithium battery; Represents the entropy coefficient of the chemical reaction in the battery; Cp , PCM , k PCM , α, and L represent the specific heat capacity, density, heat transfer coefficient, liquid content, and latent heat of phase change of phase change materials, respectively; T0, T m 、T l Respectively represent the initial temperature, melting point temperature and complete melting temperature of the phase change material; ρ ω ,υ ω , C pω , μ ω 、T ω , k ω They represent the density, flow rate, specific heat, dynamic viscosity, temperature and thermal conductivity of water respectively. Represents the gradient symbol.

[0049] The numerical simulation in step 4 includes: meshing the battery pack module model; establishing a transient energy conservation equation; setting the lithium battery as a heat source term and the coolant as a fluid; setting boundary conditions; setting an algorithm; and performing calculations.

[0050] The experimental verification module conducts a battery pack thermal management system experiment on the battery pack module to formulate a thermal management strategy, including the following steps: Step S1: designing and building an experimental system, dividing the system experiment into two parts: a cooling experiment and a heating experiment; Step S2: determining the temperature control index; Step S3: designing and verifying the thermal management strategy.

[0051] Exemplarily, the experimental verification module is used to study the heat exchange mechanism of the battery module 1 and the impact on the cooling performance of the battery thermal management system under different conditions, and verify the effect of the thermal management strategy.

[0052] The experimental system includes: a computer 11, a control unit 12, a switch controller 13, a water pump 14, a water tank 15, a flow meter 16, a constant temperature device 17, a multi-channel temperature meter 18, a refrigerator 19, and a power supply 20.

[0053] In step S1, the battery pack thermal management system experiment is divided into two parts: cooling experiment and heating experiment. In the cooling experiment part, water is used as a coolant and stored in a water tank. The water pump 14 is driven by a power supply to input the coolant into the cooling channel 7 on the battery module 2 to cool the lithium battery. The coolant flow is measured by a flowmeter 16. In the heating experiment part, a pulse width modulation heating strategy is adopted. The computer 11 sends a heating instruction to the control unit 12, and the control unit 12 sends a control signal to the switch controller 13 to operate the heating belt to heat the lithium battery in a low temperature environment. The initial temperature of the environment in the experiment is set by adjusting the temperature of the refrigerator 19, and the multi-channel thermometer is used to collect the real-time temperature of the battery pack thermal management system and input it into the computer 11 for data analysis.

[0054] In step S2, the cooling and heating of the cylindrical lithium battery 3 are studied under the ambient temperature of 40°C and -15°C respectively. The three parameters of the peak temperature of the lithium battery 3, the maximum temperature difference of the battery, and the phase change rate of the phase change material 4 are used as indicators to judge the heat dissipation performance. The peak temperature and the maximum temperature difference should be within 50°C and 5°C respectively, and the phase change rate of the phase change material 4 should be controlled at about 50%.

[0055] In step S3, the thermal management strategy includes a heating strategy and a cooling strategy, and the heating strategy and the cooling strategy are determined by heating experiments and cooling experiments. In the heating experiment, the influence of different heating methods on the single battery is analyzed by increasing the ambient temperature, and the optimal parameter combination of the heating strategy is determined. The specific method is: increase the ambient temperature from -15°C to 10°C, the maximum temperature difference during the process should be less than 5°C, control the heating time, and the heating time should be as short as possible. Analyze the influence of different strategies on the heating behavior of the lithium battery 3 at -15°C to determine the best heating strategy. In the cooling experiment, the best method of the cooling strategy is determined by the influence of the size of the radiator 5, the thickness of the phase change material 4, the number of cooling channels 7 and the combination of coolant flow on the thermal behavior of the lithium battery at different coolant inlet 9 flow rates. The specific method is: in the cooling experiment, the ambient temperature is set to 40°C, and the influence of the size of the radiator 5, the thickness of the phase change material 4, the number of cooling channels 7 and the combination of coolant flow on the heat exchange behavior of the lithium battery 3 at different coolant inlet 9 flow rates is studied. The number of cooling channel levels is 3 to 5, and the flow mode of the coolant is divided into different arrangements and combinations such as co-current and convection according to the number of cooling channel layers.

[0056] Exemplarily, in the heating experiment, the battery pack module is first placed in a refrigerator, and the refrigerator temperature is set to -15°C to simulate the ambient temperature. A pulse signal is sent to the control unit through a computer to operate the rubber heating belt to heat the lithium battery. During the heating process, the temperature of the lithium battery is detected by a multi-channel thermometer, and the maximum temperature difference of the lithium battery should be less than 5°C. In the previous pulse signal heating test, the next heating experiment is carried out by adjusting the width of the pulse signal. The real-time temperature data of the lithium battery is used to analyze the effects of different pulse modulation strategies on the heating behavior of the lithium battery 3 at -15°C to determine the best heating strategy.

[0057] In the cooling experiment, the battery pack module is first placed in a constant temperature device, and the temperature of the constant temperature device is set to 40℃ to simulate the ambient temperature. The thickness of the water cooling jacket is set to 1mm, the length and width of the cooling channel is 5mm×3.5mm, the length and width of the channel in the cooling channel is 3mm×1.5mm, and the number of cooling channels is set to 4. The flow mode of the coolant in the upper two cooling channels is downstream, and the flow mode of the coolant in the lower cooling channel is convection. Water is stored in the water tank as a coolant. The battery pack module starts working through computer control, and the water pump is driven by power to input water into the cooling channel on the battery pack module to cool the battery pack module. The peak temperature of the lithium battery is controlled to be 50℃. Experiments with different strategies are carried out by changing different radiator size parameters, the number of cooling channels, the flow mode of coolant, and the flow rate of coolant. The real-time temperature of the lithium battery is used to analyze the impact of different strategies on the heat dissipation behavior of the lithium battery to determine the best cooling strategy.

[0058] Through experiments, the heat transfer mechanism of lithium battery 3 under different phase change material 4 thickness, radiator 5 size, and cooling channel level is studied, and the influence of coolant flow rate and coolant flow combination on the cooling performance of battery thermal management system is studied to verify the effect of thermal management strategy.

[0059] The cooling channels 7 are designed in different levels and are evenly distributed in the height direction of the outside of the radiator 5. The levels of the cooling channels 7 are determined according to the heat exchange mechanism simulation module and the experimental verification module to obtain the best level for heat dissipation. The even distribution of the cooling channels 7 is beneficial to improving the efficiency of heat dissipation of the radiator 5 and the water cooling jacket 6. The battery modules 2 constituting the battery pack module 1 are interconnected through the cooling channels 7 on the outside of the radiator 5. The cooling channels 7 between the battery modules 2 constituting the battery pack module 1 are interconnected. The interconnection of the cooling channels 7 between the battery modules 2 ensures that the coolant can pass through all the battery modules 2 constituting the battery pack module 1. The cooling channels 7 on the outside of the radiator 5 of the first row and the last row are respectively provided with a coolant inlet 9 and a coolant outlet 10. The coolant enters the cooling channel 7 through the coolant inlet 9 on the first row, flows through the battery module 2 to dissipate heat for the battery, and finally flows out through the coolant outlet 10.

[0060] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A thermal management system for a power battery of a new energy vehicle, characterized in that: It includes a battery pack module and a battery pack thermal management system. The battery pack module is composed of a battery module. The battery module includes a lithium battery and a heat exchange module. The heat exchange module includes a phase change material, a radiator, a water cooling jacket, a cooling channel and a rubber heating belt. The radiator is an aluminum honeycomb hollow design. The lithium battery is embedded in the radiator. Phase change material is filled between the lithium battery and the radiator. The cooling channel is arranged on the outside of the radiator. Coolant is passed through the cooling channel. The water cooling jacket is arranged between the cooling channels on the outside of the radiator. The rubber heating belt is arranged on the outside of the water cooling jacket. The battery pack thermal management system includes a heat exchange mechanism simulation module and an experimental verification module. The battery pack thermal management system constructs a thermal management strategy by mutually verifying the heat exchange mechanism simulation module and the experimental verification module.

2. The new energy vehicle power battery thermal management system according to claim 1, characterized in that: The heat exchange mechanism simulation module calculates and simulates the heat exchange mechanism values ​​in the battery module. The method comprises the following steps: Step 1: determining the temperature of the lithium battery module and the relevant parameters of the thermophysical properties of the phase change material; Step 2: determining the working states of the lithium battery, the coolant and the rubber heating belt during the heat exchange process; Step 3: performing energy analysis of the lithium battery, the phase change material and the coolant, determining the control equation of the battery pack thermal management system through the laws of thermophysics, and establishing a numerical model of the battery pack thermal management system through the control equation and boundary conditions; Step 4: performing numerical simulation of the computational fluid dynamics of the heat exchange model of the battery pack module.

3. The thermal management system for a new energy vehicle power battery according to claim 2, characterized in that: The control equation in step 3 includes: Battery energy conservation equation: Battery heat per unit volume: Enthalpy change of phase change material: Coolant continuity equation: Coolant momentum equation: Coolant energy conservation equation: Where t is time, λ x , y , z Respectively represent the heat transfer coefficients of the lithium battery in the x, y, and z directions, ρ, V, C p , T, Q, λ represent the density, volume, specific heat capacity, temperature, heat generation rate, and heat transfer coefficient of the lithium battery, respectively. OC Respectively represent the charging and discharging current, resistance, and open circuit voltage of the lithium battery; Represents the entropy coefficient of the chemical reaction in the battery; C p , PCM , k PCM , α, and L represent the specific heat capacity, density, heat transfer coefficient, liquid component, and latent heat of phase change of the phase change material, respectively; T0, T m , T l Respectively represent the initial temperature, melting point temperature and complete melting temperature of the phase change material; ρ ω ,υ ω , C pω , μ ω , T ω , k ω They represent the density, flow rate, specific heat, dynamic viscosity, temperature and thermal conductivity of water respectively. Represents the gradient symbol.

4. The new energy vehicle power battery thermal management system according to claim 2, characterized in that: The numerical simulation in step 4 includes: gridding the battery pack module model; establishing a transient energy conservation equation; setting the lithium battery as a heat source; setting the coolant as a fluid; setting boundary conditions; setting an algorithm; and performing calculations.

5. The new energy vehicle power battery thermal management system according to claim 1, characterized in that: The experimental verification module conducts a battery pack thermal management system experiment on the battery pack module to formulate a thermal management strategy, including the following steps: Step S1: designing and building an experimental system, dividing the system experiment into two parts: a cooling experiment and a heating experiment; Step S2: determining the temperature control index; Step S3: designing and verifying the thermal management strategy.

6. The new energy vehicle power battery thermal management system according to claim 5, characterized in that: The experimental system includes: a computer, a control unit, a switch controller, a water pump, a water tank, a flow meter, a constant temperature device, a multi-channel temperature meter, a refrigerator, and a power supply.

7. The new energy vehicle power battery thermal management system according to claim 6, characterized in that: The thermal management strategy in step S3 includes a heating strategy, and the heating strategy is determined through the heating experiment. In the heating experiment, the ambient temperature is increased from -15°C to 10°C, and the maximum temperature difference in the process is less than 5°C. The heating time is controlled, and the effects of different strategies on the heating behavior of the lithium battery at -15°C are analyzed. The effects of different heating methods on the lithium battery are analyzed by increasing the ambient temperature to determine the optimal heating strategy.

8. The new energy vehicle power battery thermal management system according to claim 7, characterized in that: The thermal management strategy in step S3 includes a cooling strategy, and the cooling strategy is determined through the cooling experiment. In the cooling experiment, the ambient temperature is set to 40°C, the number of cooling channels is 3 to 5, and the coolant flow mode is divided into downstream and convection according to the number of cooling channel layers. The optimal method of the cooling strategy is determined by the influence of the radiator size, the thickness of the phase change material, the number of cooling channels and the coolant flow combination mode on the heat dissipation behavior of the lithium battery under different coolant inlet flow rates.

9. The new energy vehicle power battery thermal management system according to claim 8, characterized in that: The experimental verification module is used to study the heat exchange mechanism of the battery pack module and the impact on the cooling performance of the battery pack thermal management system under different conditions, and verify the effectiveness of the thermal management strategy.

10. The new energy vehicle power battery thermal management system according to claim 1, characterized in that: The cooling channels are designed in different levels and are evenly distributed in the height direction of the outside of the radiator. The battery modules that constitute the battery pack module are connected to each other through the cooling channels on the outside of the radiator. The cooling channels between the battery modules that constitute the battery pack module are interconnected. The cooling channels on the battery modules in the first row and the last row are respectively provided with a coolant inlet and a coolant outlet.

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