Battery cell cooling device based on low-density microstructure layer

Abstract

The invention relates to the technical field of battery thermal management, and provides a cell cooling device based on a low-density microstructure layer, the cell cooling device comprises a low-density microstructure heat sink, the low-density microstructure heat sink comprises a manifold layer and a microstructure layer, the manifold layer is used for flow distribution, and the microstructure layer is used for flow distribution. The microstructure layer is a low-density microstructure formed by a flow channel processed on the surface of a single battery cell and is used for directly cooling the battery cell under low heat flux. According to the battery cell cooling device of the low-density microstructure layer, the weight of the cooling device is reduced by adopting a low-density microstructure, more efficient heat conduction can be realized by directly attaching the cooling device to the surface of the battery cell, heat loss possibly caused by indirect cooling is avoided, and the cooling efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal management, and in particular to a battery core cooling device based on a low-density microstructure layer. Background Art

[0002] With the rapid development of electric vehicles and energy storage systems, improving battery performance and extending battery life have become key technical challenges. Batteries generate a lot of heat during the charging and discharging process. If the heat cannot be dissipated in a timely and effective manner, the battery temperature will rise, which will in turn affect the battery's performance, safety and service life. Therefore, battery thermal management technology is particularly important.

[0003] At present, the main cooling technologies used in the field of battery thermal management include air cooling, liquid cooling, and phase change material cooling. Among them, liquid cooling technology has attracted widespread attention due to its efficient and stable heat dissipation performance. However, the existing liquid cooling technology still has some problems and limitations. In the prior art, most of the mini / microstructure cooling technologies for battery thermal management are indirect cooling. For example, a Chinese patent with publication number CN108574073A discloses a high energy density liquid-cooled battery module, which realizes heat exchange and temperature control of the battery assembly by winding a close-fitting heat exchange tube between the battery assemblies. This design improves the heat dissipation efficiency of the battery to a certain extent, ensures that the battery operates within a suitable temperature range, and thus improves the safety and service life of the battery. However, this technology still has some limitations, including:

[0004] (1) Insufficient adaptability to battery expansion

[0005] The battery will expand to a certain extent during the charging and discharging process, but the cooling system in the prior art is mostly made of rigid materials, which is difficult to flexibly cope with the battery expansion. This may lead to poor contact between the cooling system and the battery, affecting the heat dissipation effect, and even squeezing the battery, causing safety hazards.

[0006] (2) System weight and cost issues

[0007] The liquid cooling system in the prior art usually contains complex cooling pipes, pumps, radiators and other components, which makes the overall weight of the system heavier and is not conducive to the lightweight design of the battery pack. At the same time, the complex structure and materials also increase the production cost of the system, limiting its competitiveness in large-scale commercial applications.

[0008] (3) Balance between heat dissipation efficiency and temperature uniformity

[0009] In battery thermal management, improving heat dissipation efficiency while maintaining uniform battery surface temperature is an important challenge. Existing cooling systems often find it difficult to meet these two requirements at the same time, resulting in local overheating or overcooling of the battery during charging and discharging, affecting battery performance and safety.

[0010] (4) Limitations of indirect cooling

[0011] As shown in patent CN108574073A, its cooling method is indirect cooling, that is, the cooling medium does not directly contact the surface of the battery cell, but exchanges heat with the battery assembly through a heat exchange tube. Although this method can control the battery temperature to a certain extent, the heat dissipation efficiency is relatively low, and it is difficult to achieve uniform cooling of the battery cell surface.

[0012] Although the existing battery thermal management cooling technology has improved the heat dissipation efficiency and safety of the battery to a certain extent, it still has problems such as poor adaptability to battery expansion, heavy system, high cost, difficulty in balancing heat dissipation efficiency and temperature uniformity, and limitations of indirect cooling methods. Therefore, it is particularly important to develop a more efficient, lightweight, low-cost thermal management technology that can directly cool the battery cell. Summary of the invention

[0013] In view of this, the present invention discloses a battery cell cooling device based on a low-density microstructure layer, which aims to solve the problems of low cooling efficiency, high cost and difficulty in adapting to battery expansion in existing battery cooling technology under low heat flux density. By introducing a low-density microstructure heat sink, cooling is performed directly on the surface of the battery cell, which reduces weight and improves cooling efficiency, avoids heat loss caused by indirect cooling, and combines with a flexible manifold layer to achieve self-adaptation to battery expansion, reducing safety hazards.

[0014] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0015] A battery cell cooling device based on a low-density microstructure layer comprises a low-density microstructure heat sink, wherein the low-density microstructure heat sink comprises a manifold layer and a microstructure layer, wherein the manifold layer is made of flexible material between battery cells, is used for flow distribution and can adapt to battery cell expansion, and the microstructure layer is a flow channel formed by grooves machined on the surface of a single battery cell, and is used for direct cooling of the battery cell.

[0016] Furthermore, the microstructure layer is a low-density microstructure layer formed by embossing, spraying, printing or directly making a groove pattern on the battery cell.

[0017] Furthermore, the microstructure layer is arranged on the two sides of the battery cell with the largest surface area.

[0018] Furthermore, the microstructure layer between two adjacent battery cells forms a low-density microstructure heat sink including at least one of the following methods:

[0019] A. Both layers are MMC heat sinks;

[0020] B. Both layers are MMPF heat sinks;

[0021] C. One layer is an MMC heat sink and the other layer is an MMPF heat sink.

[0022] Furthermore, the microstructure layers of two adjacent battery cells share a manifold system.

[0023] Furthermore, the manifold system includes an inlet manifold and an outlet manifold, and the coolant liquid is evenly distributed from the inlet manifold to the upper and lower microstructure layers, and converges from the outlet manifold after the microstructure layers complete heat exchange.

[0024] Furthermore, one or more battery cells use an inlet chamber flow channel to disperse the flow in, and one or more battery cells use an outlet chamber flow channel to gather the flow out.

[0025] Furthermore, in the MMC heat sink, the coolant liquid enters from the inlet chamber flow channel of the inlet manifold, flows into the parallel first flow channels along the inlet manifold flow channel, flows from each branch of the parallel first flow channels through the outlet manifold flow channel to the outlet chamber flow channel and then flows out.

[0026] Further, the first flow channel is arranged orthogonally to the inlet manifold and the outlet manifold of the manifold system.

[0027] Furthermore, in the MMPF heat sink, the coolant liquid enters from the inlet chamber flow channel of the inlet manifold, then vertically hits the bottom surface of the MPF, and evenly crosses and crisscrosses into the four second flow channels formed between the MPFs. The coolant liquid flows from each branch of the second flow channel through the outlet manifold flow channel to the outlet chamber flow channel and then flows out.

[0028] Compared with the prior art, the battery core cooling device of the low-density microstructure layer described in the present invention has the following advantages:

[0029] (1) The battery cell cooling device with a low-density microstructure layer described in the present invention reduces the weight of the cooling device by adopting a low-density microstructure, and enables it to be directly attached to the surface of the battery cell. It is a new combination of a printed circuit board type heat exchanger and battery immersion liquid cooling, which achieves more efficient heat conduction, avoids heat loss that may be caused by indirect cooling, and improves cooling efficiency.

[0030] (2) In the battery cell cooling device with a low-density microstructure layer described in the present invention, the manifold layer is made of flexible material and can adapt to the expansion of the battery, thereby avoiding the safety hazard caused by battery expansion. When the battery cell expands, the preload force and sealing can be enhanced to ensure that the immersion liquid does not leak. At the same time, the flexible manifold layer also makes the cooling device easier to install and maintain.

[0031] (3) The cell cooling device with a low-density microstructure layer described in the present invention can be completed by inexpensive processes such as embossing, spraying, printing, or directly making groove patterns on the surface of the cell. This manufacturing process not only simplifies the production process and reduces production costs, but also maintains the integrity of the cell surface. This ultra-thin design can not only reduce the weight and cost of the device itself, but also greatly reduce the amount of immersion liquid used while ensuring uniform flow, thereby reducing the cost and weight of the immersion liquid.

[0032] (4) The battery cell cooling device with a low-density microstructure layer described in the present invention forms an ultra-thin battery cell cooling device based on a low-density structure layer suitable for all battery cells through the flow distribution of the manifold layer and the enhanced heat transfer effect of the microstructure layer. The coolant can evenly and efficiently exchange heat with the surface of the battery cell, ensuring that the battery cell can maintain an appropriate temperature range at different charge and discharge rates, thereby extending the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention. In the accompanying drawings:

[0034] Figure 1 It is a schematic diagram of the principle of direct cooling using a microstructure heat sink provided on the battery according to an embodiment of the present invention;

[0035] Figure 2 for Figure 1 A schematic diagram of the partially enlarged structure of the middle Q section;

[0036] Figure 3 A schematic diagram of the structure of the battery cooling system according to an embodiment of the present invention;

[0037] Figure 4 Schematic diagrams of three structures of the microstructure heat sink according to the embodiments of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of the MMC cooling structure unit according to an embodiment of the present invention;

[0039] Figure 6 This is a schematic diagram of the structure of the MMPF cooling structure unit according to an embodiment of the present invention;

[0040] Figure 7This is a schematic structural diagram of the minimum repeating unit in the MMC cooling structure unit according to an embodiment of the present invention;

[0041] Figure 8 This is a schematic structural diagram of the minimum repeating unit in the MMPF cooling structure unit according to an embodiment of the present invention;

[0042] Fig. 9 This is a schematic diagram of the flow path structure of the MMC cooling structure unit according to an embodiment of the present invention;

[0043] Fig.10 This is a schematic diagram of the flow path structure of the MMPF cooling structure unit according to an embodiment of the present invention;

[0044] Fig.11 Schematic diagram of the hydrodynamic and thermal performance evaluation of the MMC heat sink and the MMPF heat sink according to the embodiment of the present invention;

[0045] Description of reference numerals:

[0046] 100- low-density microstructure heat sink; 200- battery cell; 1- inflow manifold; 11- inlet chamber flow channel; 12- inlet manifold flow channel; 2- outflow manifold; 21- outlet chamber flow channel; 22- outlet manifold flow channel; 3- microstructure layer; 31- microchannel layer; 311- first flow channel; 32- microneedle fin layer; 321- second flow channel; 4- manifold layer. DETAILED DESCRIPTION

[0047] In order to make the purpose and effect of the technical means of the present invention easy to understand, the embodiments of the present invention are described in detail below with reference to specific drawings.

[0048] It should be noted that all the terms used in the present invention for directional and positional indications, such as "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between the components in a certain state (as shown in the accompanying drawings), and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes, and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features.

[0049] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0051] In the field of battery thermal management, mini / microstructure cooling technology is considered to be a method that can effectively remove high heat flux from batteries and maintain temperature uniformity due to its high surface-to-volume ratio. However, the existing mini / microstructure heat sink design mainly continues the microstructure design concept of electronic chips, and there are many problems when it is directly applied to battery cooling. First of all, as a low heat flux heat source, the high integration and high temperature uniformity requirements of batteries require the cooling system to have higher comprehensive design requirements, and the existing designs often arrange high-density microstructures for high heat flux density, which not only increases the weight, but also is not conducive to the structural support and safety protection of the battery. Secondly, the battery will expand during the charging and discharging process, and the existing mini / microstructure heat sinks are mostly made of metal materials, which are difficult to flexibly respond to such changes, which may cause the battery to be squeezed and cause safety hazards. In addition, the high-density microstructure is complex to process and costly, which is not conducive to the economy and practicality of the battery thermal management system.

[0052] Based on the above technical status, Figures 1 to 10As shown, the present application discloses a battery core cooling device with a low-density microstructure layer, including a low-density microstructure heat sink 100, wherein the low-density microstructure heat sink 100 includes a manifold layer 4 and a microstructure layer 3, wherein the manifold layer 4 is processed from the original flexible material between the battery cells and is used for flow distribution, and the microstructure layer 3 is a low-density microstructure formed by a flow channel processed on the surface of a single battery cell, which is used for direct cooling of the battery cell and enhancing heat transfer. The battery core cooling device with a low-density microstructure layer disclosed in the present application is that a low-density microstructure heat sink 100 composed of a manifold layer 4 and a microstructure layer 3 is arranged on the surface of the battery cell, wherein the manifold layer 4 is responsible for the flow distribution of the coolant, ensuring that the coolant can flow evenly into each microstructure unit, and the microstructure layer 3 is a flow channel processed on the surface of a single battery cell, and these channels serve as the main place for heat exchange, and through direct contact with the coolant, the heat generated by the battery cell is quickly absorbed and transferred, so that the low-density microstructure heat sink 100 can directly cool the battery cell. The low-density microstructure heat sink 100 is applied to battery cell cooling, and its structural size can be increased to a few hundred microns to a millimeter level, thereby forming a low-density heat sink cooling and heat dissipation for the battery cell.

[0053] The battery cell cooling device with a low-density microstructure layer disclosed in the present application, the heat sink 100 with a low-density microstructure design not only reduces the weight of the cooling device, but also enables the device to be directly attached to the surface of the battery cell to achieve more efficient heat conduction and avoid heat loss that may be caused by indirect cooling. Through the flow distribution of the manifold layer 4 and the enhanced heat transfer effect of the microstructure layer, the entire cooling device can achieve effective cooling of the battery cell while maintaining the uniformity of the surface temperature of the battery cell.

[0054] As a preferred example of the present application, the microstructure layer 3 is a low-density microstructure layer formed by embossing, spraying, printing or directly making a groove pattern on the battery cell 200, and the groove depth is less than 30 microns. In the example of the present application, the microstructure layer 3 is a low-density microstructure layer, which is formed by adopting cheap processes such as embossing, spraying, printing or directly making a groove pattern on the surface of the battery cell, so as to realize the innovation and optimization of the battery cell cooling device, which not only simplifies the manufacturing process, reduces the production cost, but also improves the cooling efficiency and uniformity. After the coolant is evenly distributed through the manifold layer 4, it flows into these tiny channels and directly exchanges heat with the heat generated by the battery cell. Since the low-density microstructure layer is closely attached to the surface of the battery cell, it ensures that the heat can be quickly and effectively conducted to the coolant, avoiding the problem of battery cell overheating caused by heat accumulation. At the same time, the groove depth is designed to be tens of microns, which not only ensures sufficient heat exchange area, but also avoids damage to the surface structure of the battery cell, and prolongs the service life of the battery cell.

[0055] As a preferred example of the present application, the microstructure layer is arranged on the two sides with the largest surface area. In the example of the present application, the low-density microstructure heat sink 100 includes a manifold microchannel (manifold microchannel MMC) or a manifold micro-pin-fin (manifold micro-pin-fin MMPF), and the two sides with the largest area of ​​the battery cell are set as MMC heat sinks or MMPF heat sinks to achieve direct cooling of the battery cell. From the perspective of the first law of thermodynamics, manifold microchannels (manifold microchannel MMC) and manifold micro-pin-fin (manifold micro-pin-fin MMPF) can solve the temperature non-uniformity and local hot spot problems that may be caused by the design of low-density microstructure heat sinks. MMC and MMPF multi-layer shunts, uniform flow, more uniform temperature, and increased heat dissipation area, increased convective heat transfer between the coolant and the wall, increased fluid disturbance, broke the thermal boundary layer, reduced temperature gradient, and lowered temperature. The present invention adopts MMC and MMPF structures as the basic design of battery thermal management.

[0056] On this basis, there are three embodiments of the low-density microstructure heat sink 100 formed between two adjacent battery cells 200:

[0057] A. Both layers are MMC heat sinks. Figure 4 a) indicates;

[0058] B. Both layers are MMPF heat sinks. Figure 4 b) indicates;

[0059] C. One layer is MMC heat sink, and the other layer is MMPF heat sink. Figure 4 In c), the upper layer is the MMPF heat sink, and the lower layer is the MMC heat sink (it can be reversed);

[0060] Through the above settings, the microstructure layer is directly set on the two sides of the battery cell with the largest surface area, which greatly increases the cooling area and improves the heat dissipation efficiency. Combined with the use of various combination structures of MMC and MMPF heat sinks, multi-layer diversion makes the coolant flow more uniform and the temperature distribution more balanced, effectively avoiding local hot spots and significantly improving the cooling effect of the battery cell.

[0061] As a preferred example of this application, Figure 5 for Figure 3 The schematic diagram of the cooling structure in the yellow dotted box is the schematic diagram of the structure of the MMC heat sink. Figure 7 for Figure 5The structural diagram in the yellow dotted box is the minimum repeating unit of the MMC heat sink. In the MMC heat sink, the coolant liquid enters from the inlet cavity flow channel 11 of the inlet manifold 1, flows into the parallel first flow channel 311 along the inlet manifold flow channel 12, and flows from each branch of the parallel first flow channel 311 through the outlet manifold flow channel 22 to the outlet cavity flow channel 21 and then flows out. Fig. 9 As shown, Fig. 9 for Figure 5 The flow path of the cooling structure, the microstructure layer 3 is a microchannel layer 31, and the ultra-thin battery cell cooling device based on the MMC heat sink works in the following way: the coolant fluid enters from the inlet manifold 1, flows evenly into the parallel microchannels along the manifold, and the parallel microchannels are orthogonal to the manifold system to ensure that the coolant is evenly distributed in the microchannels. In the microchannels, the coolant exchanges heat with the surface of the battery cell and absorbs the heat generated by the battery cell. Subsequently, the coolant flows out from the outflow manifold 2 after converging from each branch of the parallel microchannels. During the whole process, the manifold layer 4 formed by the manifold system provides flow distribution for the coolant, while the microchannel layer 31 directly acts on the surface of the battery cell for efficient heat exchange, thereby realizing direct cooling of the battery cell. In the example of the present application, the MMC heat sink has a three-dimensional topological structure, and in the microstructure layer, the MMC heat sink has a two-dimensional flow (Y and Z). By adopting the microstructure layer of MMC, the structure is simpler and easier to process and realize.

[0062] As a preferred example of this application, Figure 6 for Figure 3 The schematic diagram of the cooling structure in the yellow dashed box is the schematic diagram of the structure of the MMPF heat sink. Figure 8 for Figure 6 The structural diagram in the yellow dotted box is the minimum repeating unit of the MMPF heat sink. In the MMPF heat sink, the coolant liquid enters from the inlet cavity flow channel 11 of the inlet manifold 1, and then vertically hits the bottom surface of the micro-pin fin (MPF), and evenly crosses and crisscrosses into the four second flow channels 321 formed between the MPFs. The coolant liquid flows from each branch of the second flow channel 321 through the outlet manifold flow channel 22 to the outlet cavity flow channel 21 and then flows out. Fig.10 As shown, Fig.10 for Figure 6The flow path of the cooling structure, the microstructure layer 3 is a micro-needle fin layer 32, and the ultra-thin battery cell cooling device based on the MMPF heat sink works in the following way: the micro-needle fin (MPF) can have a variety of shapes, such as square, round, etc. The coolant first flows into the parallel inlet manifold 1, and then hits the bottom surface of the MPF vertically, and evenly crosses and crisscrosses into the four second flow channels formed between the MPFs. In the second flow channel 321, the coolant absorbs the heat generated by the battery cell from the bottom and wall of the MPF. After completing the heat exchange, the coolant of each branch converges in the outlet manifold and finally flows out from the outlet. This design ensures the uniform distribution of the coolant on the surface of the battery cell, effectively improves the heat exchange efficiency, and realizes efficient cooling of the battery cell.

[0063] In the example of the present application, the MMPF heat sink also has a three-dimensional topological structure, which increases the heat dissipation area, makes the coolant more fully in contact with the wall of the battery cell, and improves the convective heat transfer efficiency. At the same time, the coolant forms a three-dimensional flow when flowing through the MPF, which increases the fluid disturbance, breaks the thermal boundary layer, further reduces the temperature gradient, reduces the maximum temperature of the battery cell surface, and reduces the surface temperature difference, ensuring the uniformity of the battery cell temperature.

[0064] As a preferred example of the present application, the microstructure layers of two adjacent cells 200 share a set of manifold systems to form a manifold layer 4. The two microstructure layers share a set of manifold systems, and the manifold system has a staggered fluid reciprocating device for supplying and recovering coolant to the lower microchannel, that is, an inlet manifold 1 and an outlet manifold 2. The coolant fluid flows through the inlet manifold 1, which includes an inlet cavity flow channel 11 and an inlet manifold flow channel 12, and is evenly divided to the upper and lower microstructure layers. The microstructure layer can be a combination of two layers of MMC heat sinks, two layers of MMPF heat sinks, or one layer of MMC heat sinks and the other layer of MMPF heat sinks. In the MMC heat sink, the coolant flows evenly into the parallel microchannels along the manifold to complete the heat exchange; in the MMPF heat sink, the coolant vertically hits the bottom surface of the micro-needle fins, crosses into the flow channel in a cross shape to complete the heat exchange, and after the heat exchange is completed in the microstructure layer, it converges from the outflow manifold 2 including the outlet cavity flow channel 21 and the outlet manifold flow channel 22 to form an effective cooling cycle. In the example of the present application, one or more battery cells use an inlet flow channel 11 for dispersed inflow and an outlet flow channel 21 for convergent outflow.

[0065] In the example of the present application, the manifold layer 4 is formed of a flexible material for adapting to the expansion of the battery cell 200. In the example of the present application, the manifold layer 4 is made of a flexible material (such as silicone rubber, nitrile rubber, etc.). When the battery cells are actually processed into groups, silicone rubber, nitrile rubber and other materials will be used for the connection between the battery cells. These materials not only have good buffering properties, but also can be adaptively adjusted according to the expansion of the battery cells during the charging and discharging process. The manifold layer of this device is directly processed from the flexible material between the battery cells, which can ensure that the cooling device always maintains close contact with the surface of the battery cell, thereby improving the heat conduction efficiency.

[0066] The battery cell cooling device with a low-density microstructure layer disclosed in the present application introduces a low-density microstructure layer and combines it with a flexible manifold layer 4. The low-density microstructure layer in the device includes two forms: manifold microchannels (MMC) and manifold microneedle fins (MMPF). They are directly arranged on the surface of the battery cell, thereby achieving efficient and direct cooling of the battery cell. The heat generated by the battery cell is taken away by the flow of coolant. The design of the flexible manifold layer 4 enables the cooling device to adapt to the expansion of the battery cell, thereby avoiding the separation of the cooling device from the battery cell surface due to the expansion of the battery cell, thereby ensuring a continuous cooling effect.

[0067] As a specific example of this application, two heat sinks have a coolant mass flow rate of 3.575×10 -4 kg / s, heat dissipation for 15Ah lithium iron phosphate battery 5C (2145W / m 2 ) was simulated and analyzed, and the hydrodynamic and thermal performance of the fluid domains of the two heat sinks were evaluated. The evaluation results are as follows Fig.11 As shown, the left side is the MMC cooling structure unit, the right side is the MMPF cooling structure unit, a) is the streamline diagram of the cooling structure unit fluid domain, b) is the pressure cloud diagram of the cooling structure unit fluid domain, c) is the temperature cloud diagram of the cooling structure unit fluid domain, d) is the entropy generation diagram generated by heat transfer in the cooling structure unit fluid domain:

[0068] The irreversible phenomena existing in the fluid flow and heat transfer process cause the system to generate entropy. This process is accompanied by a decrease in thermal mass, which is due to thermal dissipation and viscous dissipation. There are three situations in the heat sink that will generate entropy: heat transfer between areas and elements with limited temperature differences within the system, friction in the fluid flow, and heat transfer to the outside of the system. The entropy generation generated by the last item is very small, because the heat dissipated to the environment through the wall surface is usually negligible. Therefore, the total entropy generation rate per unit volume of the system is It can be expressed as follows:

[0069]

[0070] in is the entropy generation rate per unit volume related to heat transfer:

[0071]

[0072] and Express the entropy production rate per unit volume due to friction caused by fluid viscosity:

[0073]

[0074] Dissipation function:

[0075]

[0076] From the above formula, we can see that the entropy generated by heat transfer is proportional to the thermal conductivity of the material, while the entropy generated by friction in the cooling medium is related to the fluid viscosity, proportional to the square of the velocity derivative, and inversely proportional to the temperature. Sum the above entropy production rate over the volume of the entire system to obtain and The total entropy generation rate of the system is thus obtained

[0077] The dimensionless Bejan number based on the second law of thermodynamics is often used to estimate the share of each irreversible heat in entropy generation for analysis. It represents the ratio of the entropy generated by heat transfer in the system to the total entropy generation, which is obtained by the following formula:

[0078]

[0079] The Bejan number is a parameter used to compare various types of heat exchanger configurations. Witte and Shamsundar proposed a straightforward criterion for evaluating the performance of any heat exchanger, and the efficiency formula named after them is as follows:

[0080]

[0081] in T amb are the thermal power of the equipment and the ambient temperature respectively. From the second law of thermodynamics, the Witte-Shamsundar efficiency is an overall standard for evaluating the efficiency of a heat exchanger.

[0082] The heat sink is divided into solid and fluid domains, and the entropy generation rates related to heat transfer and fluid friction in each region of the three embodiments are calculated, as shown in Table 1. Each value in the table is the value in the heat sink unit multiplied by the number of units to obtain the sum of the region over the entire cell surface. As can be seen from Table 1, entropy generation is mainly caused by thermal effects. In the initial configuration, the entropy generation rate caused by fluid friction is about eight orders of magnitude smaller than the total entropy generation rate caused by the temperature gradient, which results in a Bejan number of 1, which is the maximum value. Increasing the aspect ratio of the microstructure or the mass flow rate of the cooling medium can reduce this value, and reducing the Bejan number by a few percentage points may help reduce the total entropy generated in the system. Table 1 also contains the share of entropy generation in each region of the entire system. The entropy generation generated by heat transfer in the fluid is almost the total entropy generation of the system. Although the temperature is higher in the solid region, the temperature gradient is not significant, so the entropy generation generated does not exceed 1%.

[0083] Table 1 Entropy generation rate of each part of three low-density microstructure heat sinks

[0084]

[0085] According to the simulation results, the MMPF heat sink is significantly better than the MMC heat sink in terms of pressure drop and temperature control, as shown in the following:

[0086] (1) The overall pressure drop of the MMPF heat sink is lower, and the temperature distribution is more uniform. The overall temperature is also lower than that of the MMC heat sink. This is due to the larger heat dissipation area and stronger fluid disturbance of the MMPF heat sink. These designs increase the convective heat transfer efficiency between the coolant and the surface of the battery cell.

[0087] (2) In terms of fluid dynamics, the pressure distribution of the two heat sinks in the Z direction (perpendicular to the coolant flow direction) is relatively uniform, but there is an obvious pressure gradient in the X direction (coolant flow direction). The pressure drop mainly occurs at the inlet, and the pressure drop on the symmetry plane is the largest, which also has a significant impact on the fluid velocity. In terms of temperature field, there is an obvious low-temperature area at the inlet. Due to the boundary layer effect, the temperature gradient in the inlet area is the largest, and the heat transfer rate is also higher.

[0088] The maximum temperature of the heating surface of the MMC heat sink is 313.51K, and the maximum surface temperature difference is 0.04K, indicating that the surface temperature fluctuation of the battery cell is small and the thermal stress is low. The maximum temperature of the heating surface of the MMPF heat sink is 309.95K, and the maximum surface temperature difference is 0.06K. The overall temperature of the MMPF heat sink is lower than that of the MMC heat sink, and the thermal performance is better. This is because the MMPF has a large heat dissipation area, which increases the convective heat transfer between the coolant and the wall, and increases the fluid disturbance, which improves the convective heat transfer.

[0089] (3) The entropy generation associated with heat transfer is proportional to the temperature gradient and inversely proportional to the average temperature. Therefore, it should decrease with the increase of the average temperature. However, it will still increase after the increase of the temperature gradient exceeds the increase of the average temperature, and the maximum value area coincides with the highest pressure and temperature. The entropy generation associated with fluid friction increases with the increase of friction resistance. Since the mass flow rate and velocity of the coolant are relatively small, it is much smaller than the entropy generation generated by heat transfer. Therefore, the entropy generation associated with fluid friction is not given. It can also be seen from Table 1 that the MMPF heat sink has a smaller entropy generation and a larger Witte-Shamsundar efficiency than the MMC heat sink, which confirms the superiority of the MMPF heat sink from the perspective of the second law of thermodynamics.

[0090] (4) Due to the structural design of the inlet and outlet of the MMC and MMPF heat sinks, such as Figure 7 , Figure 8 As shown in the figure, (the blue box is the inlet, the red box is the outlet, and the geometric and operating parameters and material properties of the two heat sinks are given in Tables 2 and 3) the flow circulation disturbs the thermal boundary layer and reduces the temperature gradient. Therefore, the temperature gradient at the solid-liquid interface is large, the entropy generation on the wall is large, and the entropy generation downstream is reduced. More inlets and outlets in the MMPF heat sink shorten the flow length of the fluid in each flow channel, further reducing the temperature gradient, resulting in a lower temperature gradient and less entropy generation.

[0091] Table 2 Geometry and operating parameters of MMC and MMPF heat sinks

[0092]

[0093]

[0094] Table 3 Material properties

[0095]

[0096] The battery cell cooling device with a low-density microstructure layer disclosed in the present application achieves efficient and uniform cooling of the battery cell through innovative design and manufacturing processes, which not only improves the performance and service life of the battery, but also reduces production costs and maintenance difficulty, and has broad application prospects and market value.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery core cooling device based on a low-density microstructure layer, characterized in that: The invention comprises a low-density microstructure heat sink (100), wherein the low-density microstructure heat sink (100) comprises a manifold layer (4) and a microstructure layer (3), wherein the manifold layer (4) is made of flexible material between battery cells, is used for flow distribution and can adapt to the expansion of the battery cell (200), and the microstructure layer (3) is a flow channel formed by grooves processed on the surface of a single battery cell, and is used for direct cooling of the battery cell (200) under low heat flux density.

2. The battery core cooling device based on the low-density microstructure layer according to claim 1, characterized in that: The microstructure layer (3) is a low-density microstructure layer formed by embossing, spraying, printing or directly making a groove pattern on the battery core (200).

3. The battery core cooling device based on the low-density microstructure layer according to claim 1 or 2, characterized in that: The microstructure layer (3) is arranged on the two side surfaces of the battery core (200) with the largest surface areas.

4. The battery core cooling device based on the low-density microstructure layer according to claim 3 is characterized in that: The microstructure layer (3) between two adjacent battery cells (200) forms a low-density microstructure heat sink (100) including at least one of the following methods: A. Both layers are MMC heat sinks; B. Both layers are MMPF heat sinks; C. One layer is an MMC heat sink and the other layer is an MMPF heat sink.

5. The battery core cooling device based on the low-density microstructure layer according to claim 4, characterized in that: The microstructure layers (3) of two adjacent battery cells (200) share a set of manifold systems.

6. The battery core cooling device based on the low-density microstructure layer according to claim 5, characterized in that: The manifold system comprises an inlet manifold (1) and an outlet manifold (2). The coolant liquid is evenly distributed from the inlet manifold (1) to the upper and lower microstructure layers (3), and converges and flows out from the outlet manifold (2) after the heat exchange in the microstructure layer (3) is completed.

7. The battery core cooling device based on the low-density microstructure layer according to claim 4, characterized in that: One or more battery cells (200) use an inlet flow channel (11) to disperse the inflow, and use an outlet flow channel (21) to collect the outflow.

8. The battery core cooling device based on the low-density microstructure layer according to claim 6 or 7, characterized in that: In the MMC heat sink, the coolant liquid enters from the inlet chamber flow channel (11) of the inlet manifold (1), flows into the parallel first flow channel (311) along the inlet manifold flow channel (12), flows from each branch of the parallel first flow channel (311) through the outlet manifold flow channel (22) to the outlet chamber flow channel (21) to merge and then flows out.

9. The battery core cooling device based on the low-density microstructure layer according to claim 8, characterized in that: The first flow channel (311) is arranged orthogonally to the inflow manifold (1) and the outflow manifold (2) of the manifold system.

10. The battery core cooling device based on the low-density microstructure layer according to claim 6 or 7, characterized in that: In the MMPF heat sink, the coolant liquid enters from the inlet chamber flow channel (11) of the inlet manifold (1), then vertically hits the bottom surface of the MPF, and evenly crosses and crisscrosses into the four second flow channels (321) formed between the MPFs. The coolant liquid flows from each branch of the second flow channel (321) through the outlet manifold flow channel (22) to the outlet chamber flow channel (21) and then flows out after merging.

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