Liquid-cooled battery pack, design method and device thereof, storage medium and product

Abstract

The invention discloses a liquid-cooled battery pack and a design method, equipment, a storage medium and a product thereof, the liquid-cooled battery pack comprises a box body and a plurality of battery cell groups, the plurality of battery cell groups are arranged at intervals along a first direction, each battery cell group is formed by stacking a plurality of battery cell monomers along a second direction, and the second direction is perpendicular to the first direction; the wall surface which is parallel to the first direction and the second direction and is close to the tabs of the battery cell group is used as the top surface of the box body, and the surface opposite to the top surface is used as the bottom surface of the box body; a bottom plate is arranged on the bottom surface of the box body, and a first cooling liquid flow channel is arranged in the bottom plate corresponding to the two adjacent battery cell groups; a vertical plate is arranged in a gap between two adjacent battery cell groups, a second cooling liquid flow channel is arranged in the vertical plate, and the second cooling liquid flow channel is communicated with the corresponding first cooling liquid flow channel. According to the invention, the problem of heat accumulation in areas among the battery cell groups is effectively inhibited, and the heat dissipation effect and the temperature uniformity of the battery pack are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of energy storage batteries, and in particular relates to a liquid-cooled battery pack and a design method, equipment, storage medium and product thereof. Background Art

[0002] With the development and promotion of new energy technologies, energy storage technology, as an important support for the new energy industry, has also developed rapidly. Among them, electrochemical energy storage represented by lithium-ion batteries has become the most mainstream energy storage technology route with its advantages of low cost, high life, high energy density and strong environmental adaptability. However, the polarization heat, resistance heat, and even decomposition heat generated during the charging and discharging process of lithium-ion batteries will have a very obvious direct impact on battery performance and life.

[0003] With the development trend of energy storage batteries becoming larger and higher in charge and discharge rate, the requirements for energy storage system cooling technology are becoming more and more stringent. The traditional air cooling technology route is increasingly unable to meet the cooling needs under the current trend. Therefore, liquid cooling technology with better heat exchange capacity is gradually being applied and developed in the field of energy storage batteries.

[0004] The liquid cooling technology of energy storage system is mainly divided into: non-contact liquid cooling and contact liquid cooling. Contact liquid cooling is mainly immersion liquid cooling, that is, immersing the battery pack in the coolant for heat exchange. The advantages of contact liquid cooling are: large contact area of ​​​​the heat dissipation surface, high heat exchange efficiency, good temperature uniformity, and can effectively achieve thermal management of energy storage batteries under high heat power conditions and extreme environmental conditions. However, contact liquid cooling also has defects such as high cost, heavy equipment, and the need for large-scale packaging and modification of internal components of the energy storage system. Therefore, in response to the thermal management needs of the current development stage of electrochemical energy storage, the use of non-contact liquid cooling plate heat dissipation structure has become the mainstream of the technical route. At present, the industry mainly adopts the heat dissipation structure design of battery pack bottom plate heat dissipation + serpentine coolant flow channel. However, in the face of more extreme charging and discharging conditions and environmental conditions, this design has become increasingly difficult to meet higher thermal management requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a liquid-cooled battery pack and its design method, equipment, storage medium and product to solve the problems of low heat exchange capacity and poor temperature uniformity of the traditional bottom liquid cooling plate + serpentine flow channel heat dissipation structure.

[0006] The present invention solves the above technical problems through the following technical solutions: a liquid-cooled battery pack, comprising a box body and a plurality of battery cell groups arranged in the box body, the plurality of battery cell groups are arranged at intervals along a first direction, each of the battery cell groups is formed by stacking a plurality of battery cell monomers along a second direction, and the second direction is perpendicular to the first direction; the wall surface parallel to the first direction and the second direction and close to the pole ear of the battery cell group is the top surface of the box body, and the opposite surface of the top surface is the bottom surface of the box body; a bottom plate is provided on the bottom surface of the box body, and a first cooling liquid flow channel is provided in the bottom plate corresponding to two adjacent battery cell groups;

[0007] A vertical plate is provided in the gap between two adjacent battery cell groups and the vertical plate contacts the side wall surface between the two adjacent battery cell groups. A second coolant flow channel is provided in the vertical plate and is communicated with the corresponding first coolant flow channel.

[0008] Furthermore, the first coolant flow channel is a serpentine flow channel having a first outlet and a second outlet.

[0009] Further, the second coolant flow channel includes a first sub-channel and a second sub-channel in parallel, the first sub-channel has a first inlet and a third outlet, the second sub-channel has a second inlet and a fourth outlet, the first inlet and the second inlet are both located at the center of the top surface of the vertical plate, the third outlet and the fourth outlet are both located at the center of the bottom surface of the vertical plate and are connected to the first coolant flow channel.

[0010] Furthermore, the first sub-channel and the second sub-channel are both serpentine channels, and the cross-sectional widths of the first sub-channel and the second sub-channel are equal.

[0011] Further, a cross-sectional width of the first coolant flow channel is greater than twice a cross-sectional width of the first sub-flow channel or the second sub-flow channel.

[0012] Furthermore, the cross-sectional shapes of the first coolant flow channel and the second coolant flow channel are both rounded rectangles, and the radius of curvature of the rounded corners is half the length of the wide side of the rectangle.

[0013] Furthermore, a gap between an outer surface of the first coolant flow channel and an outer surface of the bottom plate, and a gap between an outer surface of the second coolant flow channel and an outer surface of the vertical plate are both less than or equal to 2 mm.

[0014] Furthermore, the bottom plate and the vertical plate are both in contact with corresponding surfaces of the battery cell group.

[0015] Based on the same concept, the present invention also provides a design method for a liquid-cooled battery pack, comprising:

[0016] Step S1: constructing a simplified model of the liquid-cooled battery pack as described above;

[0017] Step S2: performing finite element meshing on the simplified model of the liquid-cooled battery pack to obtain a finite element analysis model;

[0018] Step S3: Initializing the finite element analysis model, and then performing temperature distribution simulation calculation to obtain the temperature field distribution on the surface of the battery cell;

[0019] Step S4: judging whether the maximum temperature, average temperature and maximum temperature difference meet the thermal management design requirements according to the surface temperature field distribution of the battery core, and if so, obtaining the sizes of the first coolant flow channel and the second coolant flow channel;

[0020] If not, the sizes of the first coolant flow channel and the second coolant flow channel are adjusted, and the process goes to step S1.

[0021] Based on the same concept, the present invention also provides an electronic device, including a memory, a processor, and a computer program / instructions stored in the memory, wherein the processor executes the computer program / instructions to implement the design method of the liquid-cooled battery pack as described above.

[0022] Based on the same concept, the present invention also provides a computer-readable storage medium having a computer program / instruction stored thereon, which, when executed by a processor, implements the design method of the liquid-cooled battery pack as described above.

[0023] Based on the same concept, the present invention also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the design method of the liquid-cooled battery pack as described above.

[0024] Beneficial Effects

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] The present invention adds a vertical plate and a coolant flow channel (i.e., a second coolant flow channel) located in the vertical plate between two battery cell groups. The coolant flow channel in the vertical plate is connected to the coolant flow channel (i.e., the first coolant flow channel) in the bottom plate. When the coolant is pumped in from the coolant flow channel inlet (i.e., the first inlet and the second inlet) in the vertical plate, the coolant flows between the two battery cell groups to dissipate heat from the inner wall surface of the battery cell group. The coolant flows from the coolant flow channel in the vertical plate to the coolant flow channel in the bottom plate to dissipate heat from the bottom surface of the battery cell group. The T-shaped liquid cooling plate formed by the vertical plate and the bottom plate effectively suppresses the problem of heat accumulation in the area between the battery cell groups, thereby improving the heat dissipation effect and temperature uniformity of the battery pack.

[0027] The present invention only requires the introduction of vertical plates (including internal coolant flow channel structures) into the cooling and heat dissipation structure of existing products, with minor modifications and low design costs. It can greatly improve the thermal management performance of the battery pack, and effectively improve the charging and discharging performance and life of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 is a schematic diagram of a simplified model of the internal structure of a liquid-cooled battery pack in an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of a simplified model of a T-shaped liquid cooling plate structure in an embodiment of the present invention;

[0031] Figure 3 is a schematic diagram of an embodiment of the present invention in which only a first coolant flow channel is provided and the first coolant flow channel is of a single-inlet and single-outlet type;

[0032] Figure 4 is a schematic diagram of an embodiment of the present invention in which only a first coolant flow channel is provided and the first coolant flow channel is of a single-inlet and double-outlet type;

[0033] Figure 5 is a schematic diagram of an embodiment of the present invention in which only a second coolant flow channel is provided and the second coolant flow channel is of a single-inlet and single-outlet type;

[0034] Figure 6 : is a simulation result diagram of an embodiment of the present invention in which only the first coolant flow channel is provided and the first coolant flow channel is of a single-inlet and single-outlet type; wherein the numbers in the color code represent the temperature;

[0035] Figure 7 : is a simulation result diagram of an embodiment of the present invention in which only the first coolant flow channel is provided and the first coolant flow channel is of a single-inlet and double-outlet type; wherein the numbers in the color code represent the temperature;

[0036] Figure 8 It is a simulation result diagram in which only the second coolant flow channel is provided in the embodiment of the present invention and the second coolant flow channel is of single-inlet and single-outlet type; wherein the numbers in the color code represent the temperature.

[0037] Explanation of the reference numerals: 1-box body, 2-cell (square lithium iron phosphate battery), 21-ear, 22-busbar, 3-bottom plate, 31-first coolant channel, 311-first outlet, 312-second outlet, 4-vertical plate, 41-first sub-channel, 42-second sub-channel, 43-inlet consisting of the first inlet and the second inlet. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0040] Example 1

[0041] like Figure 1 and Figure 2 As shown, a liquid-cooled battery pack provided by an embodiment of the present invention includes a box body 1 and a plurality of battery cell groups arranged in the box body 1, the plurality of battery cell groups are arranged at intervals along a first direction, each battery cell group is formed by stacking a plurality of battery cell monomers 2 along a second direction, and the second direction is perpendicular to the first direction; the wall surface parallel to the first direction and the second direction and close to the pole ear 21 of the battery cell group is the top surface of the box body 1, and the opposite surface of the top surface is the bottom surface of the box body 1; a bottom plate 3 is provided on the bottom surface of the box body 1, and a first coolant flow channel 31 is provided in the bottom plate 3 corresponding to two adjacent battery cell groups; a vertical plate 4 is provided in the gap between two adjacent battery cell groups and the vertical plate 4 is in contact with the side wall surface between the two adjacent battery cell groups, a second coolant flow channel is provided in the vertical plate 4, and the second coolant flow channel between the two adjacent battery cell groups is connected with the first coolant flow channel 31 at the bottom of the two adjacent battery cell groups, and the vertical plate 4 and the bottom plate 3 constitute a T-shaped liquid cooling plate.

[0042] In view of the characteristics of the two battery cell groups having high heat transfer coefficients in the height and width directions and the phenomenon of heat accumulation easily occurring in the middle area of ​​the two battery cell groups, the present invention provides a vertical plate 4 in the gap area between the two battery cell groups on the basis of a bottom plate 3 provided on the bottom surface of the box body 1. When the coolant flows through the vertical plate 4, the middle area of ​​the two battery cell groups is dissipated, which effectively suppresses the phenomenon of heat accumulation easily occurring in the middle area of ​​the two battery cell groups, improves the heat dissipation effect of the battery pack, improves the temperature uniformity, and obtains good PACK-level temperature uniformity; at the same time, the coolant flows into the bottom plate 3 under the action of gravity, and dissipates the heat on the bottom surface of the battery cell group when flowing through the bottom plate 3, further improving the heat dissipation effect and temperature uniformity, and the gravity can effectively reduce the pressure drop of the coolant.

[0043] In a specific embodiment of the present invention, the first coolant flow channel 31 is a serpentine flow channel having a first outlet 311 and a second outlet 312; the second coolant flow channel includes a first sub-flow channel 41 and a second sub-flow channel 42 in parallel, the first sub-flow channel 41 has a first inlet and a third outlet, the second sub-flow channel 42 has a second inlet and a fourth outlet, the first inlet and the second inlet are both located at the center of the top surface of the vertical plate 4, the third outlet and the fourth outlet are both located at the center of the bottom surface of the vertical plate 4 and are connected to the first coolant flow channel 31. The first sub-flow channel 41 and the second sub-flow channel 42 are both serpentine flow channels, and the cross-sectional widths of the first sub-flow channel 41 and the second sub-flow channel 42 are equal. That is, the first coolant flow channel 31 is a serpentine flow channel with a middle inlet and outlets at both ends, and the second coolant flow channel is a parallel serpentine flow channel with a single inlet (the first inlet and the second inlet are combined into one inlet 43) and double outlets. The first sub-flow channel 41 and the second sub-flow channel 42 are mirror-symmetrical in space.

[0044] When the coolant is pumped in from the first inlet and the second inlet of the second coolant flow channel, it flows through the inner wall surfaces of the two battery cell groups along the parallel serpentine flow channel, realizing non-contact heat exchange of the inner wall surfaces of the battery cell groups; under the action of gravity, it then flows into the middle of the first coolant flow channel 31 from the third outlet and the fourth outlet, respectively, flows to both sides along the first coolant flow channel 31, and flows out from the first outlet 311 and the second outlet 312 on both sides, realizing non-contact heat exchange of the bottom surface of the battery cell group. The present invention relies on natural convection heat dissipation to realize non-contact heat exchange from top (vertical plate 4) to bottom (bottom plate 3); considering the problem of heat accumulation in the middle area of ​​the battery cell group, the inlet and outlet of the second coolant flow channel are both located at the top and bottom centers of the vertical plate 4.

[0045] In a specific embodiment of the present invention, the cross-sectional width of the first coolant channel 31 is greater than twice the cross-sectional width of the first sub-channel 41 or the second sub-channel 42. On the one hand, it can match the dual outlets of the second coolant channel, and on the other hand, it can reduce the cooling liquid drop, save power loss, and increase the coolant flow rate.

[0046] In a specific embodiment of the present invention, the cross-sectional shape of the first coolant flow channel 31 and the second coolant flow channel (i.e., the cross-sectional shape of the first sub-flow channel 41 or the second sub-flow channel 42) are both rounded rectangles, and the radius of curvature of the rounded corners is half the length of the wide side of the rectangle. The cross-sectional widths of the first coolant flow channel 31 and the second coolant flow channel both refer to the length of the wide side of the rectangle. The cross-sectional shape of the first coolant flow channel 31 and the second coolant flow channel is a rounded rectangle (i.e., left semicircle + rectangle + right semicircle), which increases the heat exchange area of ​​the flow channel, improves the heat exchange efficiency, reduces the flow resistance of the coolant, reduces power loss, and is easy to process.

[0047] In a specific embodiment of the present invention, the bottom plate 3 is fitted with the bottom surface of the battery cell group to achieve effective heat dissipation of the bottom surface of the battery cell group; the vertical plate 4 is fitted with the inner wall surfaces of the two battery cell groups to achieve effective heat dissipation of the inner wall surfaces of the battery cell groups.

[0048] In a specific embodiment of the present invention, taking into account the process difficulty, cost and heat transfer efficiency, the gap between the outer surface of the first coolant flow channel 31 and the outer surface of the bottom plate 3, and the gap between the outer surface of the second coolant flow channel and the outer surface of the vertical plate 4 are both less than or equal to 2 mm, preferably 1 to 2 mm. This avoids the gap between the outer surface of the first coolant flow channel 31 and the outer surface of the bottom plate 3 or the gap between the outer surface of the second coolant flow channel and the outer surface of the vertical plate 4 being too large, resulting in reduced heat exchange efficiency; and the gap being too small, resulting in insufficient structural strength and processing accuracy.

[0049] The thickness of the vertical plate 4 is adapted to the gap between the battery cell groups. For example, when the gap between the two battery cell groups is 12 mm, the thickness of the vertical plate 4 is 12 mm, the rounded corner diameter of the rounded rectangle of the first sub-channel 41 or the second sub-channel 42 is 8 mm, the length of the wide side of the rectangle is 4 mm, and the gap between the outer surface of the first sub-channel 41 or the second sub-channel 42 and the outer surface of the vertical plate 4 is 2 mm; the channel gap of the first sub-channel 41 or the second sub-channel 42 is 27 mm.

[0050] Considering that the heat transfer path at the bottom of the battery cell is long and the heat exchange is low (see Table 4), the thickness of the bottom plate 3 is slightly smaller than that of the vertical plate 4, and the cross-sectional width of the first coolant flow channel 31 is greater than twice the cross-sectional width of the first sub-flow channel 41 or the second sub-flow channel 42 to reduce the coolant flow resistance. In this embodiment, the thickness of the bottom plate 3 is 8mm, the width of the first coolant flow channel 31 is 36mm (i.e., the radius of the left semicircle + the wide side of the rectangle + the radius of the right semicircle), the gap between the outer surface of the first coolant flow channel 31 and the outer surface of the bottom plate 3 is 2mm, and the serpentine gap of the first coolant flow channel 31 is 42mm.

[0051] In order to verify the heat dissipation effect and temperature uniformity of the liquid-cooled battery pack of the present invention, a simulation test of the liquid-cooled battery pack of the present invention is carried out by taking a 1P18S battery pack with two rows of cells (i.e., comprising two cell groups, each cell group comprising nine cell monomers 2, and the positive and negative pole tabs 21 of the 18 cell monomers 2 are connected in series through a busbar 22) as an example. The battery pack adopts a 280Ah large-capacity lithium iron phosphate cell, with a height × width × thickness of 207 × 173 × 72mm. The specific simulation process is:

[0052] Step S1: construct a simplified geometric model of a liquid-cooled battery pack with different heat dissipation designs.

[0053] In this embodiment, the heat dissipation design includes only a first coolant flow channel and the first coolant flow channel is a single-inlet and single-outlet type (i.e., one inlet and one outlet, such as Figure 3 As shown), only the first coolant flow channel is provided and the first coolant flow channel is a single-inlet and double-outlet type (i.e., one inlet and two outlets, such as Figure 4 As shown), only a second coolant flow channel is provided and the second coolant flow channel is a single-inlet and single-outlet type (i.e., one inlet and one outlet, such as Figure 5 As shown), and the heat dissipation design of the present invention (as shown Figure 2 shown).

[0054] Step S2: Mesh the simplified geometric model of each liquid-cooled battery pack, encrypt the mesh at each inlet, outlet, tab and busbar, and obtain a finite element mesh model of each liquid-cooled battery pack.

[0055] In this embodiment, the tetrahedral meshing method is used for meshing, the maximum mesh size is about 40-50 mm, the minimum mesh size is about 0.4-0.5 mm, and the number of generated meshes is 5-10 million. The tabs and busbars are meshed with encryption, and the mesh size of the tabs and busbars is 2.5 mm. The first coolant flow channel and the second coolant flow channel are meshed with encryption, and the mesh size of the first coolant flow channel and the second coolant flow channel is 2 mm.

[0056] Step S3: Import the finite element mesh model of each liquid-cooled battery pack into the finite element analysis software Fluent to construct a thermal fluid-solid coupling heat transfer analysis model of each liquid-cooled battery pack. The specific construction process is as follows:

[0057] Step S3.1: Select the steady-state solver based on pressure boundary and set the gravity direction and value;

[0058] Step S3.2: Open the energy equation, and determine the viscosity model based on the inlet flow rate and the Reynolds number calculated from the coolant fluid characteristics, and determine that the coolant flow is a laminar flow model;

[0059] Step S3.3: Set material properties. Deionized water is selected as the coolant based on the software material library. Aluminum and copper are selected as the structure of the tabs, busbars and other components based on the software material library. The interior of the battery cell is regarded as a homogeneous entity. The equivalent density, specific heat capacity and anisotropic thermal conductivity are set based on the test parameters and equivalent calculations of the lithium iron phosphate battery cell used.

[0060] Step S3.4: assign material properties to each structure part, wherein the assignment of material properties of the cell monomer requires opening the source term, and based on the charge and discharge condition test, set its heating power (equivalent) to 6700W;

[0061] Step S3.5: Boundary conditions are set, the coolant is an incompressible fluid, and the inlet coolant temperature is set (according to the cooling demand and energy consumption, it is generally 10-20°C, and the present invention is set to a constant 13°C); the first outlet and the second outlet are both set as pressure outlets, and the contact surfaces of the calculation domains of different materials are set to natural convection heat transfer, and the convection heat transfer coefficient is 5W / m 2 K;

[0062] Step S3.6: Initialize and set the number of iterations to 200, perform finite element calculations, and obtain the calculated values ​​of key physical parameters of the battery pack cooling system, such as the flow velocity distribution, average flow velocity, and average flow rate of the coolant inlet section, and other flow field calculation parameters, and the thermal field calculation parameters such as the cell surface temperature, and obtain the pressure drop of the single battery pack liquid cooling system by calculating the difference between the average pressure of the coolant flow channel inlet section and the outlet section;

[0063] Step S3.7: Import the calculation results into the post-processing software to unify the inlet flow rate to 0.17m 3 / h, and retrieve the visualized numerical calculation results of the battery pack temperature field distribution, the coolant flow channel pressure field and the temperature field distribution, such as Figures 6 to 8 shown.

[0064] As the simulation results Figure 6 As shown, the maximum temperature of the single-inlet and single-outlet first coolant channel is 300.2K, the maximum temperature difference is 11.9K, and the temperature distribution is extremely uneven. Figure 7 As shown, the maximum temperature of the single-inlet and double-outlet first coolant channel is 300.5K, the maximum temperature difference is 10K, the horizontal temperature distribution is uniform, and the vertical temperature distribution is uneven; as shown in the simulation calculation results Figure 8 As shown, when only the second coolant flow channel is provided and the second coolant flow channel is of single-inlet and single-outlet type, the maximum temperature is 297.4K, the maximum temperature difference is 8.4K, the temperature distribution is mirror-symmetrical along the middle symmetry plane, and the temperature distribution in the vertical direction is relatively uniform.

[0065] From the design and simulation results of the above embodiment, it can be seen that at the same cooling medium (deionized water) inlet total flow rate (0.17m 3 / h) and coolant temperature (13°C), the single-inlet and double-outlet serpentine flow channel of the bottom plate can make the temperature distribution of the battery cell group in the horizontal direction more uniform, and the single-inlet and single-outlet parallel serpentine flow channel of the vertical plate can make the temperature distribution of the battery cell group mirror-symmetrical along the middle symmetry plane. Therefore, combined with the structural design of the coolant flow channel of the bottom plate and the vertical plate, the present invention proposes a cooling and heat dissipation structure of a T-shaped liquid cooling plate parallel serpentine flow channel.

[0066] The simulation calculation results of the present invention show that the maximum temperature of the battery pack under different coolant flow rates is reduced from 305.5K to 299.1K, and the temperature difference of the battery pack is reduced from 7.7K to 4.8K. The results show that as the coolant flow rate increases, the maximum temperature and temperature difference of the battery pack decrease accordingly; at the same time, it also verifies that the T-type liquid cold plate design can effectively meet the thermal management requirements of energy storage batteries.

[0067] In addition, from the calculation results of the temperature field distribution and the pressure field distribution of the first coolant flow channel and the second coolant flow channel, it can be seen that the temperature difference of the T-type liquid cold plate under different inlet flow rates is reduced from 11.5K to 3.4K, and the pressure drop is increased from 46.7Pa to 361.7Pa. This result shows that as the coolant inlet flow rate increases, the pressure drop of the first coolant flow channel and the second coolant flow channel increases, which will lead to an increase in energy consumption. In addition, the increase in the coolant inlet flow rate leads to a decrease in the heat exchange per unit mass of the coolant, which in turn leads to a decrease in the energy utilization of the T-type liquid cold plate and an increase in the heat dissipation energy consumption cost.

[0068] In order to clarify the setting process of simulation calculation, the setting of relevant physical quantities and the equivalent calculation process are supplemented:

[0069] (1) Battery cell parameter setting

[0070] The nominal voltage of the 280Ah large-capacity lithium iron phosphate battery in the embodiment of the present invention is 3.2V, the charge and discharge cut-off voltage is 2.7-3.6V, the mass of the battery cell is 5.5kg, and the density is about 2133.4kg / m 3 , the battery internal resistance is 0.25mΩ, and the charge and discharge conditions are 0.5C constant rate at 25±3℃. According to the relevant research on 280Ah lithium iron phosphate batteries of the same size (references: Song Laifeng; Mei Wenxin; Jia Zhuangzhuang; Wang Qingsong; Analysis of thermal runaway characteristics of 280Ah large lithium iron phosphate batteries under adiabatic conditions [J]; Energy Storage Science and Technology; Issue 08, 2022), the equivalent specific heat capacity of lithium iron phosphate batteries is about 1029.5J / kg·℃, and the anisotropic thermal conductivity is 2.11W / m·℃ in the thickness direction, 21.63W / m·℃ in the width direction and height direction. In order to establish the corresponding heat generation characteristic model and thermal conductivity characteristic model of the battery cell, it is necessary to clarify the heat generation power of the battery cell under different working conditions, and perform equivalent calculations on the specific heat capacity and thermal conductivity of the battery cell.

[0071] (2) Setting of equivalent heating power

[0072] The description of the heat generation process of the battery cell mainly adopts the battery heat generation rate model proposed by Bernardi et al. (Liu Feifei, Chen Yangyang, Hu Jiantai, et al. Study on temperature rise characteristics of double cold plate liquid-cooled lithium-ion battery [J]. Automobile Technology, 2022(12):8.), and the specific expression is:

[0073]

[0074] Where Q is the heat generation power per unit volume of the battery cell, V c is the cell volume, I is the charge and discharge current intensity, E0 is the open circuit voltage, E is the cell operating voltage (terminal voltage), T is the thermodynamic temperature, is the temperature influence coefficient. Studies have shown that the temperature influence coefficient of lithium-ion batteries is approximately 2.3×10 -4 V / K. It can be seen from the temperature state of the battery under normal charging and discharging that the temperature coefficient has little effect. Therefore, the heat generation model of the battery cell ignoring the temperature influence coefficient can be simplified to:

[0075]

[0076] Among them, R is the equivalent internal resistance of the battery cell.

[0077] The equivalent heat generation power of the lithium iron phosphate square battery used in the present invention during the 0.5C constant rate charge and discharge process (the complete charge and discharge time is 7200s, i.e. 2 hours) is shown in Table 1 below according to relevant research.

[0078] Table 1 Equivalent heating power under different working conditions

[0079]

[0080] The main materials of the internal structure of the square wound lithium iron phosphate battery include: copper foil, aluminum foil, lithium iron phosphate, graphite, diaphragm, electrolyte, aluminum shell and insulating film, and their specific heat capacity and mass ratio are shown in Table 2. It should be noted that the mass ratio data is given by the document "Thermal Properties and Heating Power Calculation of Square Wound Lithium Iron Phosphate Battery", and the accurate mass ratio data of each part of the 280Ah lithium iron phosphate battery used in the embodiment of the present invention can be obtained later by actual disassembly and weight measurement.

[0081] Table 2 Specific heat capacity and mass ratio of main materials of square wound lithium iron phosphate battery

[0082] serial number Material Name <![CDATA[Specific heat capacity c p (J / kg·K)]]> <![CDATA[Mass fraction m i (%)]]> 1 Copper Foil 390 8.75 2 Aluminum foil 900 4.01 3 Cathode material (lithium iron phosphate) 1269 33.50 4 Anode material (graphite) 712 18.11 5 Diaphragm (polymer) 890 2.86 6 Electrolyte (Lithium Hexafluorophosphate LiPF6) 2055 20.97 7 Aluminum shell 1000 11.52 8 Insulation film (aluminum-plastic composite material) 1978 0.28

[0083] If the other additives and structures are ignored, the equivalent specific heat capacity of the square wound lithium iron phosphate battery is c d The calculation formula is as follows:

[0084]

[0085] Among them, c i represents the specific heat capacity of the i-th layer material, m i % represents the mass weight of the material in the i-th layer.

[0086] The internal structure of a square wound lithium iron phosphate battery is as follows: the positive and negative electrodes are sandwiched with a diaphragm, and a variety of foil materials are wound and stacked to form a battery cell, with hundreds of layers. Therefore, in order to simplify the calculation process, the thickness of the foil of the same material is stacked. When simulating the heat generation of the battery, the main body of the battery cell needs to be equivalent to a homogeneous body, and its heat conduction process needs to be equivalent to a heat transfer process in three directions. Therefore, the heat conduction process inside the battery pack cell can be represented by anisotropic thermal conductivity. The thermal conductivity of the structural materials of each part of the square wound lithium iron phosphate battery is shown in Table 3.

[0087] Table 3 Thermal conductivity of main materials of square wound lithium iron phosphate battery

[0088]

[0089] Due to the winding structure inside the battery cell, based on the series-parallel thermal resistance theory in heat transfer, the battery pack can be regarded as series heat transfer in the two directions of the horizontal plane (i.e., the first direction and the second direction), and as parallel heat transfer in the vertical direction (i.e., the direction perpendicular to the first direction and the second direction). However, due to the complex internal structure, the equivalent thermal conductivity coefficients in each direction of different battery manufacturers and different battery models can be equivalently calculated by the series-parallel mixed thermal resistance. The calculation formulas for the equivalent thermal conductivity coefficients of series-parallel heat transfer are:

[0090]

[0091] Among them, λ i represents the thermal conductivity of the i-th layer material, d i % represents the thickness weight of the i-th layer of material. According to formulas (4) and (5), it can be seen that the equivalent thermal conductivity λ of parallel heat transfer is the weighted sum of the thermal conductivity of each layer of material, and the equivalent thermal conductivity of series heat transfer is the reciprocal of the weighted sum of the thermal conductivity of each layer of material. The thermal conductivity of the 280Ah large-capacity lithium iron phosphate battery in this embodiment is obtained as follows: 2.11, 21.63, 21.63W / m℃ respectively.

[0092] Since there are structural parts such as tabs and busbars on the top of the battery cell, it is not studied as a heat dissipation surface. Therefore, the heat transfer behavior and characteristics of the remaining five surfaces of the battery cell are studied to provide a basis for the subsequent design of the heat dissipation structure of the battery pack. Due to the square winding structure characteristics of the battery cell, the five surfaces are divided into three groups, of which the two surfaces in the x-axis direction (i.e., the second direction) are group A, the two surfaces in the y-axis direction are group B, and one surface in the z-axis direction is group C, corresponding to the heat transfer paths of the battery cell in the three directions. Specifically, for the x-axis direction, the heat generated by the battery cell in the working state is transmitted through the thermal conductivity λ in the width direction. x The heat is transferred outward through the surface of group A along the path; for the y-axis direction (i.e., the first direction), the heat generated by the battery cell in the working state is transferred through the thickness direction thermal conductivity λy The heat is transferred outward through the surface of group B along the path; for the z-axis direction (perpendicular to the first direction and the second direction), the heat generated by the battery cell in the working state is transferred through the height direction thermal conductivity λ z The heat is transferred outwards through the surface of group C.

[0093] (3) Calculation of heat transfer of battery cells

[0094] Based on the heat transfer characteristics of the above-mentioned square lithium iron phosphate battery, the thermal management design of the battery pack is carried out. The basic principle of design is: give priority to convection heat exchange (air cooling, immersion liquid cooling or phase change heat transfer) or heat conduction (non-contact liquid cooling) on ​​the surface with the strongest heat dissipation performance of the battery cell. Therefore, it is necessary to study and analyze the heat transfer characteristics of each group of surfaces. Since the battery cell is equivalently treated inside, assuming that the thermal conductivity h of each surface is the same, the heat transfer balance equations in the x, y, and z axis directions are:

[0095]

[0096] Where x, y, and z represent the width, thickness, and height directions, respectively. wx 、T wy 、T wz Respectively represent the wall temperature of the heat dissipation surface of group A, B, and C, T ∞ is the ambient temperature. Assuming the external environment is in a steady state (including but not limited to temperature, humidity, pressure, air flow, etc.), assuming the internal structure of the battery cell is uniform, the temperature distribution is linear, and ignoring structures other than the square battery cell, the thermal balance equation along the coordinate axis (taking the x-axis as an example) is as follows:

[0097]

[0098] Where T1 represents the starting point temperature of the heat transfer path, T2 represents the ending point temperature of the heat transfer path, and L x Indicates the distance between the starting point and the end point. The heat flux density q in the x-axis direction x for:

[0099]

[0100] Get the heat flux Φ in the x-axis direction x for:

[0101]

[0102] Among them, S A Represents the heat dissipation surface area of ​​group A on the x-axis heat transfer path.

[0103] It can be deduced from the above formula that when the temperature difference between the inside and the surface of the battery cell is 1K, the heat flow on the surface of each group of battery cells A, B, and C can be calculated. The calculation results are shown in Table 4 below.

[0104] Table 4 Surface heat dissipation characteristic parameters of each group of battery cells

[0105] Heat dissipation surface Heat transfer path distance L / mm <![CDATA[Thermal conductivity λ / Wm -1 ·K-1]]> <![CDATA[Radiating surface area S / m 2 > Heat flow Φ / W A 86.5 21.63 0.015 3.751 B 36 2.11 0.036 2.11 C 103.5 21.63 0.012 2.508

[0106] From the calculation results of the heat dissipation characteristic parameters of each group of battery cells in the above table, it can be seen that the heat dissipation performance of the heat dissipation surface of group A is the strongest, and there are two surfaces that can dissipate heat. In addition, the heat transfer performance of the bottom of the battery cell represented by the heat dissipation surface of group C is better, and due to the arrangement of the battery pack, the bottom of the battery cell is more convenient to design a liquid cooling plate, so the design of the heat dissipation liquid cooling plate at the bottom of the battery cell can be considered next. The heat transfer performance of the heat dissipation surface of group B is poor, so it is usually filled with insulating thermal conductive materials. In addition, due to the structure of the pole ears, busbars, etc., the top of the battery pack cannot be cooled by the liquid cooling plate, so it can be considered to force convection heat exchange through superimposed air cooling technology.

[0107] (4) Example Analysis

[0108] Taking the parameters of the 280Ah square lithium iron phosphate battery used in this embodiment as an example, the continuous discharge current is 140A, the maximum discharge current is 280A, the internal resistance of the battery is 0.25mΩ, and the size of the battery is 207*173*72mm (height, width and thickness). Therefore, the maximum heat generation power of the battery is 7902W / m 3 The heat generation power of continuous charge and discharge is 1900W / m 3 The maximum heat generation power parameter of the battery cell can be used to perform thermal simulation analysis and design of the battery pack and energy storage system. In order to further explore the changes in the heat generation power of the battery cell during the charging and discharging process, a battery cell heat generation power change model can be generated based on the current control strategy of the battery cell charging and discharging, which can be used to refine the analysis of the heat generation of the battery pack and energy storage system under different working conditions and form a real-time heat dissipation control strategy.

[0109] By establishing an equivalent model of heat transfer and heat generation of the battery pack, the heat generation and heat transfer behavior of the square lithium iron phosphate battery under constant rate charge and discharge conditions was explored, and the heat dissipation capacity of each surface of the battery cell was evaluated and calculated, providing a theoretical basis for the subsequent thermal management design of the energy storage battery pack and energy storage system. In addition, by exploring the heat generation and heat transfer behavior of energy storage batteries from the battery cell level, a refined control technology route system from system-level thermal management to PACK-level thermal management can be effectively established, providing theoretical guidance for PACK-level control of systems such as EMS, and providing new ideas and methods for the structural design and technical route of high-efficiency battery thermal management systems. By establishing a heat generation and heat transfer model for square lithium iron phosphate batteries, the study of the above process found that:

[0110] The thermal conductivity of square lithium iron phosphate batteries in all directions is affected by four parameters: the anisotropic thermal conductivity of the battery cell, the length of the heat transfer path, the size of the heat dissipation surface, and the temperature difference between the heat dissipation surface and the environment. When designing the heat dissipation structure of the battery pack, in addition to considering the heat dissipation capacity of the above-mentioned heat dissipation surface, it is also necessary to consider the dense arrangement of the battery pack to ensure sufficient heat dissipation capacity while improving the energy density of the battery pack. Combining the above-mentioned equivalent theoretical model with finite element simulation calculations can effectively evaluate the rationality of the heat dissipation structure design of thermal management, effectively reduce the optimization design cost, and improve the design efficiency.

[0111] Based on the internal structure and heat generation mechanism of the square wound lithium iron phosphate battery cell, the present invention establishes an equivalent heat generation model of the battery cell monomer in all directions, laying a theoretical foundation for the temperature field distribution inside the battery cell group and battery pack; combining the thermal fluid-solid coupling heat transfer model and finite element simulation technology of non-contact heat dissipation, simulation calculation verification is carried out for the above theoretical analysis, and combined with the above analysis and calculation results, a T-type liquid cooling plate heat dissipation structure with parallel serpentine flow channels is proposed.

[0112] Example 2

[0113] A design method for a liquid-cooled battery pack provided by an embodiment of the present invention comprises the following steps:

[0114] Step S1: Construct a simplified model of the liquid-cooled battery pack as described in Example 1.

[0115] A simplified model of the liquid-cooled battery pack is constructed according to its three-dimensional structure. The simplified model includes a box body, a cell group in the box body, a tab, a busbar, and a first coolant flow channel and a second coolant flow channel.

[0116] Step S2: Perform finite element meshing on the simplified model of the liquid-cooled battery pack to obtain a finite element analysis model.

[0117] In this embodiment, the tetrahedral meshing method is used for meshing, the maximum mesh size is about 40-50 mm, the minimum mesh size is about 0.4-0.5 mm, and the number of generated meshes is 5-10 million. The tabs and busbars are meshed with encryption, and the mesh size of the tabs and busbars is 2.5 mm. The first coolant flow channel and the second coolant flow channel are meshed with encryption, and the mesh size of the first coolant flow channel and the second coolant flow channel is 2 mm.

[0118] Step S3: Initialize the finite element analysis model, and then perform temperature distribution simulation calculation to obtain the temperature field distribution on the cell surface.

[0119] During initialization, the solver uses the pressure-based steady-state solver, the viscosity model uses the k-Omega SST turbulence model, and the cell thermal physical parameters are: density is 2118kg / m 3, the specific heat capacity is 1029.5 J / kg·K, and the anisotropic thermal conductivity coefficients are 2.11, 21.63, and 21.63 W / m·K, respectively. The inlet temperature of the coolant is 13°C, and the flow rate of the first inlet and the second inlet combined is 0.17 m 3 / h.

[0120] Step S4: judging whether the maximum temperature, average temperature and maximum temperature difference meet the thermal management design requirements according to the temperature field distribution on the surface of the battery cell, and if so, obtaining the sizes of the first coolant flow channel and the second coolant flow channel;

[0121] If not, the sizes of the first coolant flow channel and the second coolant flow channel are adjusted, and the process goes to step S1.

[0122] Adjusting the dimensions of the first coolant flow channel and the second coolant flow channel includes the cross-sectional shape and size, the flow channel distribution gap, the distance from the flow channel wall to the corresponding bottom plate or the outer surface of the vertical plate, etc. These adjustments may change the geometric shape, so it is necessary to rebuild the simplified model. After adjusting the dimensions of the first coolant flow channel and the second coolant flow channel, it is necessary to modify the inlet boundary conditions (such as coolant flow rate) in step S3. For example, if the flow channel cross-sectional area is too small, the number of flow channel turns is too large, the flow channel cross-sectional shape is more complex, etc., the coolant flow damping will increase, the workload of the circulating pump will increase, and energy waste and cooling efficiency will be reduced.

[0123] Based on more accurate theories and simulation calculation methods, the present invention establishes a heat generation model of the battery cell group, effectively predicts the high-temperature accumulation area, and carries out targeted heat dissipation structure design and verification closed loop, retaining the simulation platform foundation for later upgrades, improvements and optimizations, and can achieve rapid iteration and upgrade of the cooling system design. In view of the problem of heat accumulation between battery cell groups, a vertical plate is designed, and coolant is injected through the first and second inlets of the vertical plate to preferentially cool the heat accumulation area, and then flow through the bottom of the battery cell group for cooling. This cooling path better takes into account the problem of temperature uniformity. Since the vertical plate has captured a large part of the heat of the battery cell, the cooling demand of the bottom plate is relatively low. In order to reduce the pressure of the coolant circulation pump and reduce the energy consumption of the cooling system, the cross-sectional size of the bottom plate coolant flow channel is designed to be larger to reduce the resistance along the way. The structure and process of the present invention are relatively simple, and the manufacturing cost is low.

[0124] Example 3

[0125] An embodiment of the present invention also provides an electronic device, which includes: a memory, a processor, and a computer program / instructions stored in the memory, and the processor executes the computer program / instructions to implement the design method of the liquid-cooled battery pack in the embodiment of the present application.

[0126] Although not shown, the electronic device includes a processor, which can perform various appropriate operations and processes according to the program and / or data stored in the read-only memory (ROM) or the program and / or data loaded from the storage portion into the random access memory (RAM). The processor can be a multi-core processor, or it can include multiple processors. In some embodiments, the processor can include a general main processor and one or more special coprocessors, such as a central processing unit, a graphics processing unit (GPU), a neural network processor (NPU), a digital signal processor (DSP), etc. In RAM, various programs and data required for device operation are also stored. The processor, ROM and RAM are connected to each other via a bus. The input / output (I / O) interface is also connected to the bus.

[0127] The processor and memory are used together to execute the program / instructions stored in the memory. When the program / instructions are executed by the computer, the methods, steps or functions described in the above embodiments can be implemented.

[0128] Although not shown, an embodiment of the present invention further provides a computer-readable storage medium having a computer program / instruction stored thereon, which, when executed by a processor, implements the design method of the liquid-cooled battery pack in the embodiment of the present application.

[0129] Storage media in embodiments of the present invention include permanent and non-permanent, removable and non-removable items that can be implemented by any method or technology to store information. Examples of storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission medium that can be used to store information that can be accessed by a computing device.

[0130] Readable storage media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include temporary computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0131] Although not shown, an embodiment of the present invention further provides a computer program product, including: a computer program / instructions, which, when executed by a processor, implements the design method of the liquid-cooled battery pack in the embodiment of the present application.

[0132] What is disclosed above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, which should be covered within the protection scope of the present invention.

Claims

1. A liquid-cooled battery pack, comprising a box body and a plurality of battery cell groups arranged in the box body, wherein the plurality of battery cell groups are arranged at intervals along a first direction, each of the battery cell groups is formed by stacking a plurality of battery cell monomers along a second direction, and the second direction is perpendicular to the first direction; a wall surface parallel to the first direction and the second direction and close to the pole ear of the battery cell group is the top surface of the box body, and a surface opposite to the top surface is the bottom surface of the box body; a bottom plate is provided on the bottom surface of the box body, and a first cooling liquid flow channel is provided in the bottom plate corresponding to two adjacent battery cell groups; characterized in that: A vertical plate is provided in the gap between two adjacent battery cell groups and the vertical plate contacts the side wall surface between the two adjacent battery cell groups. A second coolant flow channel is provided in the vertical plate and is communicated with the corresponding first coolant flow channel.

2. The liquid-cooled battery pack according to claim 1, characterized in that: The first coolant flow channel is a serpentine flow channel having a first outlet and a second outlet.

3. The liquid-cooled battery pack according to claim 1, characterized in that: The second coolant flow channel comprises a first sub-flow channel and a second sub-flow channel connected in parallel, the first sub-flow channel has a first inlet and a third outlet, the second sub-flow channel has a second inlet and a fourth outlet, the first inlet and the second inlet are both located at the center of the top surface of the vertical plate, the third outlet and the fourth outlet are both located at the center of the bottom surface of the vertical plate and communicate with the first coolant flow channel; Preferably, the first sub-flow channel and the second sub-flow channel are both serpentine flow channels, and the cross-sectional widths of the first sub-flow channel and the second sub-flow channel are equal; Preferably, a cross-sectional width of the first coolant flow channel is greater than twice a cross-sectional width of the first sub-flow channel or the second sub-flow channel.

4. The liquid-cooled battery pack according to claim 1, characterized in that: The cross-sectional shapes of the first coolant flow channel and the second coolant flow channel are both rounded rectangles, and the radius of curvature of the rounded corners is half the length of the wide side of the rectangle.

5. The liquid-cooled battery pack according to claim 1, characterized in that: A gap between an outer surface of the first coolant flow channel and an outer surface of the bottom plate, and a gap between an outer surface of the second coolant flow channel and an outer surface of the vertical plate are both less than or equal to 2 mm.

6. The liquid-cooled battery pack according to any one of claims 1 to 5, characterized in that: The bottom plate and the vertical plate are both in contact with corresponding surfaces of the battery cell group.

7. A method for designing a liquid-cooled battery pack, characterized in that: The design method comprises: Step S1: constructing a simplified model of the liquid-cooled battery pack according to any one of claims 1 to 6; Step S2: performing finite element meshing on the simplified model of the liquid-cooled battery pack to obtain a finite element analysis model; Step S3: Initializing the finite element analysis model, and then performing temperature distribution simulation calculation to obtain the temperature field distribution on the surface of the battery cell; Step S4: judging whether the maximum temperature, average temperature and maximum temperature difference meet the thermal management design requirements according to the surface temperature field distribution of the battery core, and if so, obtaining the sizes of the first coolant flow channel and the second coolant flow channel; If not, the sizes of the first coolant flow channel and the second coolant flow channel are adjusted, and the process goes to step S1.

8. An electronic device comprising a memory, a processor, and a computer program / instruction stored in the memory, characterized in that: The processor executes the computer program / instructions to implement the design method of the liquid-cooled battery pack as claimed in claim 7.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the method for designing a liquid-cooled battery pack as described in claim 7 is implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method for designing a liquid-cooled battery pack as described in claim 7 is implemented.

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