Battery pack thermal management control method and system

Abstract

The present invention relates to the field of battery liquid cooling technology, and discloses a battery pack thermal management control method and system. The method comprises: establishing a mathematical model based on the initial parameters of the liquid cooling plate flow channel; obtaining the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel; calculating the heat transfer power between the coolant in each branch flow channel and the battery based on the heat transfer coefficient; calculating the average heat transfer power of all branch flow channels based on the heat transfer power; adjusting the parameters of the liquid cooling plate flow channel based on the deviation between the heat transfer power and the average heat transfer power, so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform; the system comprises: a modeling module, a heat transfer coefficient calculation module, a heat transfer power calculation module, and a thermal management control module. The present invention can effectively evaluate the heat transfer uniformity deviation during the liquid cooling plate design process, thereby improving the working efficiency of the liquid cooling plate thermal management control.

Description

Technical Field

[0001] The present invention relates to the field of battery liquid cooling technology, and in particular to a battery pack thermal management control method and system. Background Art

[0002] Liquid cooling technology, which uses flowing liquid to transfer heat, is currently the predominant thermal management design approach in the power battery field. Improper liquid cooling plate flow path design not only results in large pressure drops in the circulation system, leading to energy loss, but also leads to large temperature differences between individual cells at different locations in the battery pack, which in turn affects battery life and even the overall performance of the battery system. Therefore, a rational design of the liquid cooling plate flow path in power batteries is essential.

[0003] However, in the current design process of the liquid cooling plate of the power battery, especially for the design of multi-branch flow channels, the traditional fluid simulation can only realize the evaluation of the pressure drop index under the required flow rate, and cannot realize the effective evaluation of the heat exchange uniformity of each branch flow channel. To address this problem, the existing technology has adopted a method of adjusting the shape and size of each branch flow channel to make the flow rate of each branch flow channel uniform, so as to achieve thermal management by making the heat exchange efficiency of each branch flow channel equal. However, the heat exchange efficiency of each branch flow channel of the liquid cooling plate is jointly affected by relevant factors such as the heat exchange area of ​​the liquid cooling plate, the flow rate of the coolant, the viscosity, the cross-sectional shape of the flow channel, and the temperature difference at the position. Therefore, using the flow deviation alone as an indicator to measure the heat exchange uniformity without considering the actual thermal management working conditions and its flow channel distribution and other influencing factors will inevitably lead to uneven heat exchange of each branch flow channel, resulting in excessive temperature deviation between each battery at each position of the battery pack, which ultimately affects the overall performance of the battery system. Summary of the Invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a battery pack thermal management control method and system, which can comprehensively consider influencing factors such as flow deviation, actual thermal management conditions and flow channel distribution, to achieve effective evaluation of heat exchange uniformity deviation during the liquid cooling plate design process, and improve the work efficiency of liquid cooling plate thermal management control.

[0005] To solve the above technical problems, the present invention provides a battery pack thermal management control method, comprising:

[0006] Establishing a mathematical model based on initial parameters of the liquid cooling plate flow channel, obtaining the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel;

[0007] Calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, and calculating the average heat exchange power of all branch flow channels based on the heat exchange power between the coolant in each branch flow channel and the battery;

[0008] The parameters of the liquid cooling plate flow channel are adjusted according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform.

[0009] In one embodiment of the present invention, when adjusting the parameters of the liquid cooling plate flow channel based on the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, the individual batteries under each branch flow channel are divided as follows:

[0010] Calculate the average heat exchange power of a single battery in each branch flow channel based on the heat exchange power between the coolant and the battery in each branch flow channel, and calculate the average heat exchange power of a single battery in all branch flow channels based on the average heat exchange power of a single battery in all branch flow channels;

[0011] Combined with the average heat exchange power of the single battery in each branch flow channel and the average heat exchange power of the single battery in all branch flow channels, the heat exchange power deviation of the single battery in each branch flow channel is calculated, and the parameters of the liquid cooling plate flow channel are adjusted according to the heat exchange power deviation of the single battery in each branch flow channel.

[0012] In one embodiment of the present invention, obtaining the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel includes:

[0013] Obtaining the cross-sectional area, cross-sectional perimeter, and length of each branch flow channel in the mathematical model, and obtaining the flow rate of each branch flow channel by obtaining the fluid solution of the mathematical model;

[0014] Calculate the Reynolds number and Prandtl number of each branch flow channel based on the dynamic viscosity, density, specific heat capacity and thermal conductivity of the coolant;

[0015] Determining the flow state of the coolant in each branch flow channel according to the Reynolds number, and calculating the Nusselt number of each branch flow channel under different flow states;

[0016] The heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel is calculated by combining the Nusselt number, the thermal conductivity and the equivalent diameter of the cross section of each branch flow channel. The equivalent diameter of the flow channel cross section is calculated based on the cross section circumference and cross section area of ​​the branch flow channel.

[0017] In one embodiment of the present invention, the circumference of the flow channel section is determined based on the bottom edge flow channel width, the fixed edge flow channel width, the fillet radius and angle of the upper edge of the flow channel, and the fillet radius of the lower edge of the flow channel, and the cross-sectional area of ​​the flow channel is determined based on the bottom edge flow channel width, the fixed edge flow channel width, the flow channel depth, the fillet radius and angle of the upper edge of the flow channel, and the angle correction coefficient.

[0018] In one embodiment of the present invention, judging the flow state of the coolant in each branch flow channel according to the Reynolds number and calculating the Nusselt number of each branch flow channel under different flow states includes:

[0019] When the flow state of the coolant in the branch flow channel is judged to be a laminar state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the different kinematic viscosities of the coolant in the branch flow channel; wherein the kinematic viscosity includes the kinematic viscosity at the qualitative temperature and the kinematic viscosity at the temperature close to the wall of the liquid cooling plate, and the qualitative temperature is the average value of the coolant temperature at the inlet position and the coolant temperature at the outlet position in the branch flow channel, wherein the kinematic viscosity at the qualitative temperature is determined based on the qualitative temperature under different working conditions.

[0020] In one embodiment of the present invention, judging the flow state of the coolant in each branch flow channel according to the Reynolds number and calculating the Nusselt number of each branch flow channel under different flow states further includes:

[0021] When the coolant flow state in the branch flow channel is determined to be a transitional flow state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the Prandtl value at the temperature of the wall surface close to the liquid cooling plate in the branch flow channel.

[0022] In one embodiment of the present invention, the heat exchange power between the coolant in each branch flow channel and the battery is calculated based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, including:

[0023] The heat transfer coefficient between the coolant in each branch flow channel and the battery is calculated based on the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel and the additional heat transfer coefficient on the heat transfer path.

[0024] The heat exchange power between the coolant in each branch flow channel and the battery is calculated based on the heat transfer coefficient between the coolant in each branch flow channel and the battery, the heat exchange area between the coolant in each branch flow channel and the coolant, and the temperature difference between the coolant in each branch flow channel and the battery.

[0025] In one embodiment of the present invention, when calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, the heat exchange power of each branch flow channel is compensated based on the temperature difference between the coolant and the battery in each branch flow channel under different working conditions and the temperature difference between one of the branch flow channels and the inlet position.

[0026] In one embodiment of the present invention, when calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, determining whether the inlet area of ​​each branch flow channel has an entry boundary layer effect includes:

[0027] Determine whether the ratio of the branch flow channel length to the equivalent diameter of the flow channel section is greater than a preset threshold. If not,

[0028] The inlet effect correction coefficient is set and combined with the flow channel length and equivalent diameter of each branch flow channel, the heat transfer coefficient between the coolant in each branch flow channel and the flow channel inner wall in the inlet stage is corrected. The heat transfer coefficient between the coolant in each branch flow channel and the flow channel inner wall in the fully developed stage is calculated normally.

[0029] The heat exchange power between the coolant in each branch flow channel and the battery in the inlet stage is calculated based on the corrected heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in the inlet stage, and the heat exchange power between the coolant in each branch flow channel and the battery in the fully developed stage is calculated based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in the fully developed stage;

[0030] The heat exchange power between the coolant in each branch flow channel and the battery at this time is obtained by combining the heat exchange power between the coolant in each branch flow channel and the battery at the inlet stage and the heat exchange power between the coolant in each branch flow channel and the battery at the fully developed stage.

[0031] In one embodiment of the present invention, when calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, it also includes determining whether there is a non-through flow channel:

[0032] If there is a non-straight flow channel, a corner effect correction coefficient is set. The heat exchange coefficient between the coolant and the inner wall of the flow channel in each branch of the non-straight flow channel is corrected in combination with the equivalent diameter of the flow channel section at the bend flow channel position and the curvature radius at the corner position.

[0033] In one embodiment of the present invention, adjusting the parameters of the liquid cooling plate flow channel according to the heat exchange power deviation obtained by the individual battery in each branch flow channel so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform includes:

[0034] The maximum value τ_max of the heat exchange power deviations obtained by a single battery in all branch flow channels is selected to determine whether the maximum heat exchange power deviation τ_max satisfies a preset threshold. If so, the heat exchange of each branch flow channel is considered balanced and meets the design requirements. If not, the heat exchange power deviation between each branch flow channel and the battery in the current liquid cooling plate design is considered too large. The flow channel shape or size of the liquid cooling plate is adjusted and optimized until the maximum heat exchange power deviation τ_max is less than or equal to the preset threshold.

[0035] The present invention also provides a battery pack thermal management control system, comprising:

[0036] A modeling module is used to establish a mathematical model based on the initial parameters of the liquid cooling plate flow channel;

[0037] a heat transfer coefficient calculation module, configured to obtain the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel;

[0038] a heat exchange power calculation module, configured to calculate the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, and calculate the average heat exchange power of all branch flow channels based on the heat exchange power between the coolant in each branch flow channel and the battery;

[0039] The thermal management control module is used to adjust the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so that the temperature difference between each position in each branch flow channel of the liquid cooling plate and the battery is uniform.

[0040] The above technical solution of the present invention has the following advantages over the prior art:

[0041] This invention designs multi-branch liquid cooling plates. Based on the principles of fluid mechanics and heat transfer, it comprehensively considers the characteristic dimensions and shapes of the cooling plate's channels, the flow rates of each branch channel, and actual thermal management conditions. This allows for effective assessment of heat transfer uniformity deviations during the cooling plate design process. This approach bypasses the sole criterion of flow rate as the sole basis for evaluating heat transfer uniformity, effectively avoiding the need for multiple cooling plate redesigns and optimizations after battery thermal simulations due to large temperature differences between individual cells at different locations, thereby improving the efficiency of cooling plate thermal management control. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0043] Figure 1 It is a flow chart of the method of the present invention.

[0044] Figure 2 This is a specific process step diagram of Example 5 of the present invention.

[0045] Figure 3 It is a schematic diagram of the mathematical model of the liquid cooling plate flow channel in the present invention.

[0046] Figure 4 It is a flow path schematic diagram of the coolant flowing through the main path and the branch paths in the present invention.

[0047] Explanation of the reference numerals in the accompanying drawings in the specification: 1. Upper cold plate; 2. Non-flow channel area; 3. No-slip fluid area; 4. Flow channel area; 5. Lower cold plate; 6. Fillet radius of the upper edge of the flow channel; 7. Fillet radius of the lower edge of the flow channel; 8. Liquid inlet; 9. Liquid outlet; 10. First liquid separation port; 11. Second liquid separation port. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0049] Example 1

[0050] Reference Figure 1 As shown, this embodiment discloses a battery pack thermal management control method, which is applicable to contacting batteries in the battery pack through a liquid cooling plate, that is, achieving thermal management through heat exchange between the liquid cooling plate and the batteries, including the following steps:

[0051] S1: Establishing a mathematical model of the liquid cooling plate flow channel: setting initial parameters of the liquid cooling plate flow channel according to the liquid cooling plate manufacturing process requirements, and establishing a mathematical model of the liquid cooling plate flow channel based on the initial parameters of the liquid cooling plate flow channel.

[0052] S2: Obtaining the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel.

[0053] S2-1: Obtain the cross-sectional area A, cross-sectional perimeter L and flow length l of each branch flow channel in the mathematical model, obtain the fluid solution of the mathematical model and obtain the flow rate V (unit: m) of each branch flow channel. 3 / s).

[0054] S2-2: Calculate the Reynolds number Re of each branch flow channel based on the dynamic viscosity μ and density ρ of the coolant i =u*D / ν, where i is the branch number, i=1, 2...N, and N is the total number of branches.

[0055] Specifically, S2-2-1: calculate the coolant flow rate u (unit: m / s), which is calculated from the branch flow rate V / t, where t is time.

[0056] S2-2-2: Calculate the equivalent diameter D (in meters) of the flow channel cross section, calculated from the cross-sectional area A and the perimeter L of the flow channel cross section, i.e., D = 4*A / L. This embodiment takes into account the forming characteristics of the liquid-cooled flow channel and, based on the flow and convective heat transfer theory of viscous fluids in a closed flow channel cavity, posits that when the viscous fluid flows through the descending region at the contact edge of the upper and lower cold plates 1 and 5, its flow velocity decreases dramatically. Near the non-flow channel region 2, the fluid approaches stagnation and enters a no-slip state, namely, the no-slip fluid region 3 and the flow channel region 4. As the fluid in the no-slip fluid region 3 and the flow channel region 4 approaches stagnation, its convective heat transfer efficiency approaches zero, and the heat transfer mode can be equivalent to a single heat conduction state. Therefore, to evaluate the convective heat transfer efficiency between the liquid-cooled flow channel and the inner wall of the cold plate, corrections are required when calculating the characteristic parameters of the fluid. On the one hand, it can be consistent with the morphology of the subsequent thermal simulation geometric model (when processing the geometric model during thermal simulation, the upper edge fillet and the edge of the upper cold plate 1 will be removed to ensure the quality of the fluid domain mesh); on the other hand, it is more consistent with the actual heat exchange state, that is, the convection effect of the no-slip fluid area 3 and the flow channel area 4 is low, and the main mode is heat conduction. Its structure is as follows Figure 3 shown. Figure 3 Where d represents the channel depth, L1 represents the bottom channel width, and L2 represents the top channel width. The following method is used to calculate and correct the channel cross-sectional perimeter and cross-sectional area to improve their accuracy.

[0057] The circumference of the flow channel section is determined according to the bottom flow channel width, the fixed edge flow channel width, the fillet radius and angle of the upper edge of the flow channel, and the fillet radius of the lower edge of the flow channel. The calculation method is:

[0058] L=L1+π*R2+R1*[π / 2-θ+2θ*sinθ-2cosθ]+L2,

[0059] Wherein, L is the circumference of the flow channel section, L1 is the bottom flow channel width, R1 is the fillet radius of the upper edge of the flow channel 6, R2 is the fillet radius of the lower edge of the flow channel 7, θ is the angle between the upper edge radian and the upper cold plate 1, in radians; L2 is the top flow channel width.

[0060] The cross-sectional area of ​​the flow channel is determined according to the bottom flow channel width, the fixed edge flow channel width, the flow channel depth, the fillet radius and angle of the upper edge of the flow channel, and the angle correction coefficient. The calculation method is:

[0061] A=L1*d+[g*θ*R1*sin(g*θ)+d]*[(L2-L1) / 2-g*θ*R1*cos(g*θ)]+1 / 2*θ 2 *R1 2 *[g 2*sin(2g*θ)-sin(2θ)];

[0062] Where A is the channel cross-sectional area, d is the channel depth, and g is the angle correction coefficient, which is adjusted according to the process radius and stamping depth and is set between 1.2 and 2. The channel cross-sectional area A here refers to the Z-direction cross-sectional area of ​​the channel.

[0063] S2-2-3: Calculate the kinematic viscosity ν (unit: m) of the coolant at a certain temperature. 2 / s), which can be obtained from the dynamic viscosity μ (unit: Pa.s) and density ρ (unit: kg / m 3 ) is calculated, that is, ν = μ / ρ. Since the battery operating temperature range is between -30℃ and 60℃, the viscosity of the coolant will vary with different thermal management conditions. Therefore, in order to consider the extreme conditions, in this embodiment, when evaluating and calculating the heat exchange efficiency under the heating condition of a low temperature environment, the viscosity parameter at -30℃, that is, μ max =43.98mPa.s. When evaluating the thermal management efficiency under cooling conditions in a high-temperature environment, the viscosity parameter at 50°C, i.e. μ min =1.78mPa.s. By determining the dynamic viscosity under different working conditions, the accuracy and adaptability of the coolant kinematic viscosity ν are further improved.

[0064] S2-3: Calculate the Prandtl number of each branch flow channel based on the coolant's kinematic viscosity, density, specific heat capacity, and thermal conductivity: Pri = ν / a. Here, a is the coolant's thermal diffusivity, i.e., a = λ / ρ*c, where λ is the thermal conductivity (in W / mK), c is the specific heat capacity (in J / kg.°C), and ρ is the density.

[0065] S2-4: Determine the flow state of the coolant in each branch flow channel according to the Reynolds number, and calculate the Nusselt number of each branch flow channel under different flow states.

[0066] When the coolant flow state in the branch flow channel is judged to be a laminar flow state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the different kinematic viscosities of the coolant in the branch flow channel; wherein, the kinematic viscosity includes the kinematic viscosity at the qualitative temperature and the kinematic viscosity at the temperature close to the liquid cooling plate wall surface, and the kinematic viscosity at the qualitative temperature is determined based on the qualitative temperature under different working conditions; the qualitative temperature is the average value of the coolant temperature at the inlet position and the coolant temperature at the outlet position in the branch flow channel. When the coolant flow state in the branch flow channel is judged to be a transition flow state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the Prandtl value at the temperature close to the liquid cooling plate wall surface in the branch flow channel. Limited by the power of the water pump of the vehicle circulation system and the flow channel shape of the battery box water cooling plate, the current flow state of the coolant in the flow channel is all in the laminar flow or transition flow state. Correspondingly, the Reynolds number Re iThe value is usually less than or equal to 10 4 , specifically:

[0067] S2-4-1: Determine the Reynolds number Re i The size of Re i ≤2300, execute S2-4-2; if 2300<Re i ≤10 4 , execute S2-4-3.

[0068] S2-4-2: At this time, the flow state of the coolant inside the flow channel is laminar flow. The Nusselt number Nu of the branch flow channel in the laminar flow stage is calculated using the correlation equation 1. f for:

[0069] Nu f =1.86*(Re f *Pr f *D / l) 1 / 3*(μ f / μ w ) 0.14 ,

[0070] Among them, Re f is the Reynolds number of the coolant at the qualitative temperature in the branch flow channel, Pr f is the Prandtl number of the coolant at the qualitative temperature in the branch flow channel, D is the equivalent diameter of the flow channel section, l is the flow channel length of the branch flow channel, μ f is the kinematic viscosity of the coolant at the qualitative temperature in the branch flow channel, μ w It is the kinematic viscosity of the coolant in the branch channel at the temperature close to the liquid cold plate wall.

[0071] In this embodiment, the design experience of the battery pack liquid cooling system is combined to calculate the characteristic value Pr of the design flow channel. f The value range of (μ f / μ w ) ranges from 0.005 to 9.7. In addition, the above equation needs to be explained in that, considering the actual working conditions of the battery pack thermal management and the significant change of the coolant dynamic viscosity with temperature, the coolant qualitative temperature T f The calculation is as follows:

[0072] T f =(T f '+T f ") / 2,

[0073] Among them, T f ' is the coolant temperature at the inlet of the branch channel, T f " is the coolant temperature at the outlet of the branch flow channel;

[0074] It is further emphasized that, due to the large difference in coolant temperature in the branch flow channel under thermal management conditions, it is necessary to perform calculations based on the thermal management conditions. For example, under cooling conditions, the coolant temperature difference in the branch flow channel is relatively small, so T f '=T inlet , T f =q*T inlet +b, where T inlet is the battery pack inlet temperature, q represents the correction coefficient of the battery pack inlet temperature, and the value of q is greater than or equal to 1; if under heating conditions, due to the relatively large temperature difference at the branch flow channel inlet, the following formula needs to be used for correction: T f =b1*T inlet n +b2T inlet n-1 +…+b3, that is, T f " is a high-order polynomial function of the inlet water temperature. b, b1, b2, and b3 are all constant coefficients obtained by fitting the actual data.

[0075] S2-4-3: At this time, the flow state of the coolant in the flow channel is the transition flow state. The Nusselt number of the branch flow channel in the transition flow stage is calculated using the second correlation equation:

[0076] Nu f =0.012*(Re f 0.87 -280)*Pr f 0.4 *[1+(D / l) 2 / 3 ]*(Pr f / Pr w ) 0.11 ,

[0077] Among them, Pr w is the Prandtl number of the fluid at the temperature close to the liquid cooling plate wall surface. That is, the Prandtl number at this time is calculated based on the dynamic viscosity at the temperature close to the liquid cooling plate wall surface to improve the calculation accuracy.

[0078] S2-5: Calculate the heat transfer coefficient between the coolant and the inner wall of each branch channel by combining the Nusselt number, the thermal conductivity λ and the equivalent diameter D of each branch channel cross section. The equivalent diameter of the channel cross section is calculated based on the cross section perimeter and cross section area of ​​the branch channel. According to the characteristic number equation: Nusselt number Nu=h*D / λ, where h is the heat transfer coefficient (unit: w / m 2 .k), the heat transfer coefficient between the coolant in each branch channel and the inner wall of the channel can be obtained as h=Nu*λ / D.

[0079] S3: Calculating the heat exchange power P between the coolant in each branch flow channel and the battery based on the heat exchange coefficient h between the coolant in each branch flow channel and the inner wall of the flow channel.

[0080] S3-1: Calculate the heat transfer coefficient between the coolant in each branch flow channel and the battery based on the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel and the additional heat transfer coefficient on the heat transfer path:

[0081] k i =1 / (1 / h i +δ1 / λ1+…+δ i / λ i +…+δ n / λ n ),

[0082] Among them, k i is the heat transfer coefficient between the coolant in the i-th branch channel and the battery (unit: w / m 2 .k), h i is the heat transfer coefficient between the coolant and the inner wall of the i-th branch channel, λ i / δ i is the additional heat transfer coefficient on the heat transfer path, δ i is the thickness of the thermal conductive material of each solid component in the heat transfer path from the battery to the coolant medium, λi is the thermal conductivity of each solid component in the heat transfer path from the battery to the coolant medium, and is only related to the material type of each component itself, such as the insulating film, thermal adhesive, aluminum plate and other parts wrapped around the battery. n is the number of solid components. Since the heat transfer path between the branches of the liquid cooling plate and the battery is the same, the main factor affecting the heat transfer coefficient is the heat transfer coefficient h i ;

[0083] S3-2: Based on Newton's cooling theorem and Fourier's heat transfer equation, the heat exchange power between the coolant and the battery in each branch flow channel is calculated as:

[0084] P i =k i *A i *△T i ,

[0085] Among them, P i is the heat exchange power between the coolant and the battery in the i-th branch flow channel, △T i is the temperature difference between the coolant and the battery in the i-th branch flow channel (unit: °C), A i is the heat exchange area between the i-th branch flow channel and the coolant (unit: m 2 ). Heat exchange area A i Calculated from the flow channel section perimeter L and the flow channel length l, that is, A i =L*l. It should be noted that the heat exchange area A here isi Unlike the cross-sectional area A of the flow channel, the heat exchange area refers to the area of ​​the entire inner wall along the entire length of the flow channel. Therefore, the calculation method is the perimeter of the flow channel cross section * the flow channel length. For example, in a thermal management design, the battery is placed above the water-cooled plate. From a structural perspective, the battery is indeed only in contact with the upper surface of the flow channel. However, because the flow channel is a closed cavity, heat exchange also occurs between the remaining surfaces and the coolant, and is transferred to the battery through the water-cooled plate area in the non-flow channel area 2. In addition, if the thermal management design adopts a vertical water-cooled plate solution, that is, the large surface of the battery is cooled, all surfaces of the flow channel will also be in contact with the battery, so the perimeter is multiplied by the length, thereby improving the accuracy of the heat exchange area calculation.

[0086] When the coolant flows through the main channel and each branch channel, due to the heat exchange along the path, the inlet positions of each branch channel are different, so the inlet temperature of the coolant in each branch channel has deviations, such as Figure 4 As shown, Figure 4 The arrow direction represents the flow direction of the coolant. The coolant flows into the main channel through the liquid inlet 8, is divided into various branch channels through the first liquid separation port 10 and the second liquid separation port 11, and finally flows out through the liquid outlet 9 after merging.

[0087] Under cooling conditions, the coolant temperature will gradually increase, while under heating conditions, the coolant temperature will gradually increase and the temperature difference between the front and back will be large. If it is necessary to keep the battery temperature values ​​at each cooling or heating position consistent, when calculating the theoretical value of the heat exchange power between the coolant and the battery in each branch flow channel, it is necessary to consider the temperature difference △T between the battery and the coolant in each branch flow channel due to the water temperature difference at the inlet of different branch flow channels. i The heat transfer coefficient k of the rear end of the branch channel is affected by the water temperature. i If compensation is needed, the temperature difference between one of the branch flow channels and the inlet position △T can be used. inlet-1 The temperature difference of each branch flow channel is corrected based on the temperature difference between the first branch flow channel and the inlet position to achieve the calculation compensation of the heat exchange power of each branch flow channel. Therefore, when calculating the heat exchange power between the coolant and the battery in each branch flow channel, based on the temperature difference between the coolant and the battery in each branch flow channel under different working conditions, the heat exchange power of each branch flow channel can be compensated based on the temperature difference between the first branch flow channel and the inlet position to improve the accuracy of the heat exchange power calculation. Specifically, considering the heat exchange of the coolant along the flow path, the calculation method of the temperature difference between the coolant and the battery is:

[0088] Under cooling conditions, △T i =△T*ζ*S i *△T inlet-1 / S1;

[0089] Under heating conditions, △T i =-△T*△T inlet-1 *{[ln(S1 / S i)] i +[ln(S1 / S i )] i-1 +…+[ln(S1 / S i )] 1 -1};

[0090] Among them, △T i is the temperature difference between the coolant in the i-th branch flow channel and the battery, △T is the required temperature difference for thermal management design, which is 3-7°C in this embodiment; ζ is the temperature difference compensation coefficient, which is 0.05≤ζ≤0.28 in this embodiment; S i is the length of the path from the i-th branch flow channel to the inlet, S1 is the length of the path from the first branch flow channel to the inlet; △T inlet-1 is the assumed temperature difference between the total inlet of the branch flow channel and the first branch flow channel, △T inlet-1 It is the reference value and can be eliminated during calculation.

[0091] Combining the above formulas and explanation conditions, the heat exchange power between the coolant and the battery in each branch flow channel can be calculated according to the actual flow channel design, and the theoretical heat exchange power of different branch flow channels can be obtained, that is, the heat exchange power between the coolant and the battery in the i-th branch flow channel is P i =k i *A i *△T i When the heat exchange between the coolant and the battery is the same, in order to ensure the consistency of the temperature difference between the batteries, the temperature difference between the two can be considered to be i The same, so in summary, the main factor affecting the battery temperature difference is the heat transfer coefficient h i and heat exchange area A i .

[0092] S4: Calculate the average heat exchange power of all branch flow channels according to the heat exchange power between the coolant in each branch flow channel and the battery: P_avg = (P1 + ... + P i +…+P N ) / N, where P i is the heat exchange power between the coolant and the battery in the i-th branch flow channel, and N is the total number of branch flow channels in the entire flow channel;

[0093] S5: Adjusting the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform.

[0094] In one embodiment, the heat exchange power deviation of each branch flow channel, ξ=|P i-P_avg| / P_avg, or calculate several deviations to adjust the parameters of the liquid cooling plate flow channel.

[0095] In other embodiments, since the number of batteries corresponding to each branch flow channel may be different, in order to improve the accuracy of the heat exchange power deviation, the heat exchange deviation is determined based on the number of batteries corresponding to each branch flow channel, so as to more accurately determine the deviation source and improve the optimization efficiency. When calculating the deviation, the individual batteries under each branch flow channel are divided, including:

[0096] S5-1: Calculate the average heat exchange power P of a single battery in each branch flow channel based on the heat exchange power between the coolant and the battery in each branch flow channel ij =P i / n i , where P ij is the average heat transfer power of a single battery in the i-th branch flow channel, P i is the heat exchange power between the coolant and the battery in the i-th branch flow channel, n i The total number of batteries cooled or heated by the i-th branch flow channel.

[0097] S5-2: Based on the average heat transfer power P of a single battery in all branch flow channels ij Calculate the average heat transfer power of all branch flow channels and individual cells P_avg'=(P 1j +P 2j +…+P Nj ) / N.

[0098] In the design of each branch flow channel, due to the need to avoid the structure of the connection between the liquid cooling plate and the battery pack, and at the same time, due to factors such as the different distances between each branch flow channel and the inlet and outlet positions of the liquid cooling plate and the different battery arrangements, the cross-sectional size, shape, length, etc. of each branch flow channel will not be exactly the same. These factors will affect the deviation of the heat exchange power between each branch flow channel and the battery. Under the condition of a certain battery heat generation, if the heat exchange deviation is too large, it will lead to a large temperature difference between each battery. Therefore, there will be a difference in heat exchange power. The factors affecting the heat exchange power are the heat exchange area, the heat exchange coefficient and the temperature difference between each component. Therefore, the focus of the present invention is to evaluate and control the heat exchange power deviation between the coolant and the battery in each branch flow channel, and then evaluate the consistency of heat exchange between each branch flow channel and its battery. Through the consistency evaluation, the liquid cooling plate flow channel parameters are controlled and adjusted to ensure the temperature uniformity between each branch flow channel and its corresponding battery, thereby achieving efficient and precise control of battery pack thermal management.

[0099] S5-3: Based on the average heat exchange power of the single battery in each branch flow channel and the average heat exchange power P_avg' of the single battery in all branch flow channels, the heat exchange power deviation obtained by the single battery in each branch flow channel is calculated as:

[0100] τi'=|P ij -P_avg'| / P_avg',

[0101] Wherein, τi' is the heat transfer power deviation of a single battery in the i-th branch flow channel.

[0102] S5-4: Adjust the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform.

[0103] The maximum value among the deviations is selected to determine whether the maximum heat transfer power deviation satisfies a preset threshold. If so, the heat transfer across each branch flow channel is considered balanced, meeting design requirements. If not, the current liquid cold plate design assumes excessive heat transfer power deviations between each branch flow channel and the battery, leading to large inter-battery temperature differences under subsequent battery thermal management conditions. Further adjustments and optimizations to the flow channel shape or dimensions (including channel length, channel circumference, and number of channels) are necessary until the maximum heat transfer power deviation is less than or equal to the preset threshold to ensure heat transfer uniformity. The deviation here can be the heat transfer power deviation ξ for each branch flow channel or the heat transfer power deviation τi' for a single battery within each branch flow channel.

[0104] For example, when calculating the heat exchange power deviation of a single battery in each direct current flow channel, the maximum value τ_max in the deviation is selected to determine whether the maximum heat exchange power deviation τ_max satisfies a preset threshold, i.e., τ_max ≤ η, where η is a preset heat exchange uniformity coefficient, which in this embodiment is 0.05 to 0.2. If so, it is considered that the heat exchange of each branch flow channel is balanced and meets the design requirements. If not, i.e., τ_max > η, it is considered that the heat exchange power deviation between each branch flow channel and the battery in the current liquid cooling plate design is too large and needs to be adjusted.

[0105] Example 2

[0106] A battery pack thermal management control method disclosed in this embodiment, when calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in Example 1, determines whether the inlet area of ​​each branch flow channel enters the boundary layer effect, specifically:

[0107] S3-3: Based on the thermal conductivity of the liquid cooling plate flow channel size and flow restrictions, the current liquid cooling flow state of the liquid cooling plate internal flow channel is mostly in a laminar state. However, even in the laminar stage, the fluid heat exchange and flow in the closed tube flow channel also have an inlet boundary layer effect, that is, when the fluid flows through the channel at a certain speed, the boundary layer thickness at this time is 0. After entering the flow channel, the influence of the wall viscous stress will gradually transfer to the inside of the flow fluid, and the boundary layer will gradually thicken. In the laminar boundary layer, the motion trajectories of the fluid particles are close to being parallel to each other, showing an orderly sliding layer by layer. The existence of the laminar boundary layer will affect the heat transfer coefficient between the fluid and the cold plate. The heat transfer coefficient is the highest near the inlet end of the branch flow channel, and then gradually decreases with the existence of the inlet boundary layer until it enters the transition flow stage. In this way, if the fluid state of the branch flow channel is regarded as having the same heat transfer efficiency, it will be different from the actual fluid convection heat transfer. Therefore, when calculating the heat transfer efficiency of each branch flow channel, it is necessary to consider the inlet boundary layer effect and make corrections to the calculation. Including:

[0108] S3-3-1: The calculation of the heat transfer coefficient is divided into the inlet stage and the fully developed stage. When the ratio of the flow channel length of the branch flow channel to the equivalent diameter of the flow channel section is greater than the preset threshold value of 60, that is, l / D>60, the inlet section and the entire flow channel have little effect on the heat transfer coefficient and can be ignored. The heat transfer coefficient is calculated normally. When l / D≤60, that is, the flow channel of the branch flow channel is short, the inlet effect must be considered and the heat transfer coefficient is corrected using the correction coefficient. At this time, the heat transfer coefficient h between the coolant in each branch flow channel and the inner wall of the flow channel at the inlet stage is i 'for:

[0109] h i '=h i *[1+(D / l) ξ ],

[0110] Where ξ is the inlet effect correction factor (ξ = 0.7 in this embodiment); l is the length of the branch flow channel; and D is the equivalent diameter of the flow channel cross section. By correcting the heat transfer coefficient, the heat transfer coefficient is corrected, thereby improving the accuracy of heat transfer power calculations.

[0111] S3-3-2: Calculate the heat transfer power between the coolant and the battery in each branch flow channel at the inlet stage:

[0112] P i '=k i '*A i '*△T i ',

[0113] Among them, P i ' is the heat exchange power between the coolant and the battery in the i-th branch flow channel at the inlet stage, k i' is the heat transfer coefficient between the coolant and the battery in the i-th branch flow channel at the inlet stage, k i '=1 / (1 / h i '+δ1 / λ1+…+δ i / λ i +…+δ n / λ n );A i ' is the heat exchange area between the i-th branch flow channel and the coolant at the inlet stage, A i '=D*l'=D*ε*l, ε is the heat exchange area coefficient, ε is 0.001~0.01; △T i ' is the qualitative temperature difference between the coolant and the battery in the i-th branch flow channel at the inlet stage;

[0114] The heat transfer power between the coolant and the battery in each branch flow channel at the fully developed stage is calculated as:

[0115] P i =k i "*A i "*△T i ",

[0116] Among them, P i " is the heat exchange power between the coolant and the battery in the i-th branch flow channel at the fully developed stage, k i " is the heat transfer coefficient between the coolant and the battery in the i-th branch flow channel at the fully developed stage, k i =1 /

[0117] (1 / h i +δ1 / λ1+…+δ i / λ i +…+δ n / λ n );A i " is the heat exchange area between the i-th branch flow channel and the coolant in the fully developed stage, A i =D*(1-ε)*l; △T i " is the qualitative temperature difference between the coolant and the battery in the i-th branch flow channel at the fully developed stage.

[0118] S3-3-3: In this embodiment, the heat exchange power between the coolant in each branch flow channel and the battery at the inlet stage and the heat exchange power between the coolant in each branch flow channel and the battery at the fully developed stage are added together to obtain the heat exchange power between the coolant in each branch flow channel and the battery at this time:

[0119] P i =P i '+P i ",

[0120] Among them, Pi is the heat exchange power between the coolant and the battery in the i-th branch flow channel when the inlet effect is considered.

[0121] In this embodiment, in the above formula, under the same thermal management conditions, considering that the flow path length of the inlet stage accounts for a small proportion of the total length of the branch flow path, the average temperature difference deviation between the two stages is small, so it can be considered that △T i '=△T i ".

[0122] In this embodiment, the heat transfer coefficient and the temperature difference between the coolant and the battery can be corrected simultaneously, rather than determining the heat exchange power by a single value. This makes the heat exchange power closer to reality, improves the optimization efficiency of the liquid cooling plate design, and thus improves the overall thermal management control efficiency.

[0123] Example 3

[0124] A battery pack thermal management control method disclosed in this embodiment determines whether there is a non-through flow channel when calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in Example 1.

[0125] In actual flow channel design, the actual arrangement of batteries inside the battery pack and the system pressure drop indicators need to be taken into consideration. Generally, there are different numbers of bends in each branch flow channel. When the fluid flows through the bends, due to the centrifugal force of the fluid particles, a secondary circulation phenomenon is generated along the cross section, which will increase convective heat transfer. Therefore, when calculating the heat transfer coefficient between the coolant and the inner wall of each branch flow channel, if there are multiple bends, the accuracy of the heat transfer coefficient calculation will be affected. In this embodiment, the influence of the flow channel bend position and its number on convective heat transfer is considered, specifically:

[0126] If there is a non-straight flow channel, the heat transfer coefficient of the non-straight flow channel is corrected. The corrected heat transfer coefficient h between the coolant in each branch flow channel and the inner wall of the flow channel is i "for:

[0127] h i ”=h i *{[1+ψ*(D / R) 3 ]} p ,

[0128] Among them, h i is the heat transfer coefficient between the coolant in the i-th branch flow channel and the inner wall of the flow channel, ψ is the correction coefficient for the bend effect, and in this embodiment, ψ = 10.3; p is the number of bends in the branch flow channel, D is the equivalent diameter of the flow channel cross section at the bend flow channel position, and R is the curvature radius at the corner position.

[0129] Example 4

[0130] like Figure 2 As shown, the present embodiment discloses a battery pack thermal management control method that comprehensively considers the entry boundary layer effect existing in the flow channel inlet area in the second embodiment and the existence and number of non-straight-through flow channels in the third embodiment on the basis of the first embodiment.

[0131] Example 5

[0132] This embodiment discloses a battery pack thermal management control system, which includes a modeling module, a heat transfer coefficient calculation module, a heat transfer power calculation module and a thermal management control module.

[0133] A modeling module is used to establish a mathematical model based on the initial parameters of the liquid cooling plate flow channel;

[0134] a heat transfer coefficient calculation module, configured to obtain the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel;

[0135] a heat exchange power calculation module, configured to calculate the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, and calculate the average heat exchange power of all branch flow channels based on the heat exchange power between the coolant in each branch flow channel and the battery;

[0136] The thermal management control module is used to adjust the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so that the temperature difference between each position in each branch flow channel of the liquid cooling plate and the battery is uniform.

[0137] Example 6

[0138] This embodiment discloses a storage medium having a computer program stored thereon. When the computer program is executed by a processor, the battery pack thermal management control method of the first embodiment is implemented.

[0139] Example 7

[0140] This embodiment discloses a device including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the battery pack thermal management control method of the first embodiment is implemented.

[0141] This invention utilizes fluid mechanics and heat transfer theory, based on the design characteristics of power battery liquid cooling plates. Based on basic design parameters such as the flow rate, shape, size, and length of each branch flow channel of the liquid cooling plate, and with reference to the performance parameters of the cooling medium, the flow state of the cooling medium in the flow channel is calculated. Heat transfer correlation formulas are then used to obtain the average heat transfer power obtained by a single battery in each branch flow channel under different flow states. Furthermore, based on experimental test data of the liquid cooling plate, the heat transfer coefficient is used as the basis for evaluating the heat transfer uniformity of each branch flow channel of the liquid cooling plate. Compared with existing liquid cooling plate designs, this invention has the following advantages:

[0142] (1) Based on the design characteristics of the flow channel of the power battery liquid cooling plate and the theory of fluid mechanics, the Reynolds number of the fluid in a specific flow channel is calculated and optimized, which is closer to the actual flow channel characteristics and more consistent with the model processing of thermal simulation.

[0143] (2) When calculating the Nusselt number of each branch flow channel, the change in coolant viscosity under different thermal management conditions and its impact on the qualitative temperature of the fluid are considered, and the qualitative temperature of the fluid at the inlet and outlet positions of a single branch flow channel is calculated separately, which is more in line with the actual thermal management application scenario.

[0144] (3) The motion state of the fluid is judged according to the Reynolds number of the fluid in each branch flow channel, and the corresponding correlation equation is introduced to realize the solution and calculation of the Nusselt number under different flow states. Different calculation methods are more targeted and more accurate.

[0145] (4) Referring to the design characteristics of the liquid cooling plate, the flow channel of the branch flow channel is divided into the inlet stage and the fully developed stage. The influence of the inlet effect and the corner efficiency on the convective heat transfer is considered to achieve the optimization correction of the heat transfer coefficient of the branch flow channel.

[0146] (5) Considering the situation where the coolant flows through the main channel to each branch channel, the heat exchange along the path causes the coolant inlet temperature of each branch channel at different locations to deviate. To address this, under different thermal management conditions, the temperature difference of each branch channel is corrected by using the path distance between the branch channel inlet position and the main inlet end, thereby realizing the subsequent compensation calculation of the heat exchange power, which is closer to the actual thermal management channel design arrangement.

[0147] (6) When evaluating and comparing the heat transfer power deviation of each branch flow channel, considering the actual layout requirements in the battery pack, the number of cooling or heating batteries provided by each branch flow channel is not exactly the same. Therefore, the average heat transfer power obtained by a single battery in each branch flow channel is used as the heat transfer deviation evaluation standard, which is more in line with the actual engineering status.

[0148] In summary, the present invention can avoid the need to optimize the flow channel heat exchange uniformity after complex thermal condition simulation. In the process of battery system design, the step of evaluating the temperature difference control of the battery pack thermal management is advanced. At the beginning of the liquid cooling plate design, the flow channel structural parameters of the liquid cooling plate are optimized according to the heat exchange uniformity, which significantly improves the efficiency of thermal management control. While achieving uniform heat exchange in the liquid cooling plate flow channel, the design efficiency of the battery factor is greatly improved.

[0149] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0150] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0151] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0152] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0153] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A battery pack thermal management control method, characterized in that: include: Establishing a mathematical model based on initial parameters of the liquid cooling plate flow channel, obtaining the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel; Calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, and calculating the average heat exchange power of all branch flow channels based on the heat exchange power between the coolant in each branch flow channel and the battery; Adjusting the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels so that the temperature difference between each position in each branch flow channel of the liquid cooling plate and the battery is uniform; Based on the mathematical model, the Reynolds number and Prandtl number of each branch flow channel are obtained to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, including: Obtaining the cross-sectional area, cross-sectional perimeter, and length of each branch flow channel in the mathematical model, and obtaining the flow rate of each branch flow channel by obtaining the fluid solution of the mathematical model; Calculate the Reynolds number and Prandtl number of each branch flow channel based on the dynamic viscosity, density, specific heat capacity and thermal conductivity of the coolant; Determining the flow state of the coolant in each branch flow channel according to the Reynolds number, and calculating the Nusselt number of each branch flow channel under different flow states; The heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel is calculated by combining the Nusselt number, the thermal conductivity and the equivalent diameter of the cross section of each branch flow channel. The equivalent diameter of the flow channel cross section is calculated based on the cross section circumference and cross section area of ​​the branch flow channel.

2. The battery pack thermal management control method according to claim 1, characterized in that: When adjusting the parameters of the liquid cooling plate flow channel according to the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, the individual batteries under each branch flow channel are divided as follows: Calculate the average heat exchange power of a single battery in each branch flow channel based on the heat exchange power between the coolant and the battery in each branch flow channel, and calculate the average heat exchange power of a single battery in all branch flow channels based on the average heat exchange power of a single battery in all branch flow channels; Combined with the average heat exchange power of the single battery in each branch flow channel and the average heat exchange power of the single battery in all branch flow channels, the heat exchange power deviation of the single battery in each branch flow channel is calculated, and the parameters of the liquid cooling plate flow channel are adjusted according to the heat exchange power deviation of the single battery in each branch flow channel.

3. The battery pack thermal management control method according to claim 1, wherein: The circumference of the flow channel section is determined based on the bottom edge flow channel width, the fixed edge flow channel width, the fillet radius and angle of the upper edge of the flow channel, and the fillet radius of the lower edge of the flow channel. The cross-sectional area of ​​the flow channel is determined based on the bottom edge flow channel width, the fixed edge flow channel width, the flow channel depth, the fillet radius and angle of the upper edge of the flow channel, and the angle correction coefficient.

4. The battery pack thermal management control method according to claim 1, wherein: The flow state of the coolant in each branch flow channel is determined according to the Reynolds number, and the Nusselt number of each branch flow channel under different flow states is calculated, including: When the flow state of the coolant in the branch flow channel is judged to be a laminar state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the different kinematic viscosities of the coolant in the branch flow channel; wherein the kinematic viscosity includes the kinematic viscosity at the qualitative temperature and the kinematic viscosity at the temperature close to the wall of the liquid cooling plate, and the qualitative temperature is the average value of the coolant temperature at the inlet position and the coolant temperature at the outlet position in the branch flow channel, wherein the kinematic viscosity at the qualitative temperature is determined based on the qualitative temperature under different working conditions.

5. The battery pack thermal management control method according to claim 1, wherein: The method further comprises: determining the flow state of the coolant in each branch flow channel according to the Reynolds number, and calculating the Nusselt number of each branch flow channel under different flow states; When the coolant flow state in the branch flow channel is determined to be a transitional flow state according to the Reynolds number, the Nusselt number of the branch flow channel is determined based on the Prandtl value at the temperature of the wall surface close to the liquid cooling plate in the branch flow channel.

6. The battery pack thermal management control method according to claim 1, wherein: Calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, including: The heat transfer coefficient between the coolant in each branch flow channel and the battery is calculated based on the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel and the additional heat transfer coefficient on the heat transfer path. The heat exchange power between the coolant in each branch flow channel and the battery is calculated based on the heat transfer coefficient between the coolant in each branch flow channel and the battery, the heat exchange area between the coolant in each branch flow channel and the coolant, and the temperature difference between the coolant in each branch flow channel and the battery.

7. The battery pack thermal management control method according to claim 1, wherein: When calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, the heat exchange power of each branch flow channel is compensated based on the temperature difference between the coolant and the battery in each branch flow channel under different operating conditions, with the temperature difference between one of the branch flow channels and the inlet position as a reference.

8. The battery pack thermal management control method according to claim 1, characterized in that: When calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, determining whether there is an entry boundary layer effect in the inlet area of ​​each branch flow channel includes: Determine whether the ratio of the branch flow channel length to the equivalent diameter of the flow channel section is greater than a preset threshold. If not, The inlet effect correction coefficient is set and combined with the flow channel length and equivalent diameter of each branch flow channel, the heat transfer coefficient between the coolant in each branch flow channel and the flow channel inner wall in the inlet stage is corrected. The heat transfer coefficient between the coolant in each branch flow channel and the flow channel inner wall in the fully developed stage is calculated normally. The heat exchange power between the coolant in each branch flow channel and the battery in the inlet stage is calculated based on the corrected heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in the inlet stage, and the heat exchange power between the coolant in each branch flow channel and the battery in the fully developed stage is calculated based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel in the fully developed stage; The heat exchange power between the coolant in each branch flow channel and the battery at this time is obtained by combining the heat exchange power between the coolant in each branch flow channel and the battery at the inlet stage and the heat exchange power between the coolant in each branch flow channel and the battery at the fully developed stage.

9. The battery pack thermal management control method according to claim 1, characterized in that: When calculating the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, it also includes determining whether there is a non-through flow channel: If there is a non-straight flow channel, a corner effect correction coefficient is set. The heat exchange coefficient between the coolant and the inner wall of the flow channel in each branch of the non-straight flow channel is corrected in combination with the equivalent diameter of the flow channel section at the bend flow channel position and the curvature radius at the corner position.

10. The battery pack thermal management control method according to any one of claims 1 to 9, characterized in that: Adjusting the parameters of the liquid cooling plate flow channel according to the heat exchange power deviation obtained by the single battery in each branch flow channel so that the temperature difference between each position in each branch flow channel in the liquid cooling plate and the battery is uniform, including: The maximum value τ_max of the heat exchange power deviations obtained by a single battery in all branch flow channels is selected to determine whether the maximum heat exchange power deviation τ_max satisfies a preset threshold. If so, the heat exchange of each branch flow channel is considered balanced and meets the design requirements. If not, the heat exchange power deviation between each branch flow channel and the battery in the current liquid cooling plate design is considered too large. The flow channel shape or size of the liquid cooling plate is adjusted and optimized until the maximum heat exchange power deviation τ_max is less than or equal to the preset threshold.

11. A battery pack thermal management control system, characterized in that: include: A modeling module is used to establish a mathematical model based on the initial parameters of the liquid cooling plate flow channel; a heat transfer coefficient calculation module, configured to obtain the Reynolds number and Prandtl number of each branch flow channel based on the mathematical model to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel; a heat exchange power calculation module, configured to calculate the heat exchange power between the coolant in each branch flow channel and the battery based on the heat exchange coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, and calculate the average heat exchange power of all branch flow channels based on the heat exchange power between the coolant in each branch flow channel and the battery; a thermal management control module, configured to adjust the parameters of the liquid cooling plate flow channels based on the deviation between the heat exchange power between the coolant and the battery in each branch flow channel and the average heat exchange power of all branch flow channels, so as to achieve a uniform temperature difference between each position in each branch flow channel of the liquid cooling plate and the battery; Based on the mathematical model, the Reynolds number and Prandtl number of each branch flow channel are obtained to calculate the heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel, including: Obtaining the cross-sectional area, cross-sectional perimeter, and length of each branch flow channel in the mathematical model, and obtaining the flow rate of each branch flow channel by obtaining the fluid solution of the mathematical model; Calculate the Reynolds number and Prandtl number of each branch flow channel based on the dynamic viscosity, density, specific heat capacity and thermal conductivity of the coolant; Determining the flow state of the coolant in each branch flow channel according to the Reynolds number, and calculating the Nusselt number of each branch flow channel under different flow states; The heat transfer coefficient between the coolant in each branch flow channel and the inner wall of the flow channel is calculated by combining the Nusselt number, the thermal conductivity and the equivalent diameter of the cross section of each branch flow channel. The equivalent diameter of the flow channel cross section is calculated based on the cross section circumference and cross section area of ​​the branch flow channel.

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