Phase change gravity heat pipe type upper cover, battery pack and working medium filling amount estimation method

Abstract

The invention discloses a phase-change gravity heat pipe type upper cover, a battery pack and a working medium filling amount estimation method, and belongs to the field of batteries. The phase-change gravity heat pipe type upper cover comprises an upper cover main body and a phase-change gravity heat pipe type lower cover, the position of the heat exchanger in the vertical direction is higher than that of the evaporation chamber; the plurality of gas conveying pipes are connected with the evaporation chamber and the heat exchanger; the liquid return pipes are connected with the evaporation chamber and the heat exchanger; the evaporation chamber, the heat exchanger, the gas conveying pipe and the liquid backflow pipe are communicated and form a circulation loop filled with a phase change working medium, and the phase change gravity assisted heat pipe is formed. The phase-change gravity heat pipe type upper cover does not need to be driven by an external pump, and has the characteristics of environmental protection, energy conservation and high energy efficiency ratio. The battery pack comprises the phase change gravity heat pipe type upper cover and has better heat dissipation performance. According to the working medium filling amount estimation method, the mass of the phase change working medium needing to be filled in the phase change gravity heat pipe type upper cover can be calculated, and the method can be applied to pipeline numerical value design of the phase change gravity heat pipe type upper cover.

Description

[0001] This application is a divisional application of the invention application with application date of December 25, 2024, application number 202411919210.0, and name “A Energy Storage Container”. Technical Field

[0002] The present application relates to the field of batteries, and in particular to a phase change gravity heat pipe type upper cover, a battery pack and a method for estimating the filling amount of a working fluid. Background Art

[0003] In current energy storage products, energy storage cells, as one of the core energy storage units, often generate a lot of heat during operation, causing the temperature to rise. This high temperature state of the energy storage cell will not only affect its performance, but may also shorten its service life and even cause safety hazards. Therefore, it is necessary to use a cooling system to control the temperature of the energy storage cell to ensure the stable operation of the energy storage cell.

[0004] At present, the cooling systems used for energy storage cells are mainly divided into air cooling system and liquid cooling system. These two cooling systems have their own characteristics, but both have limitations.

[0005] The air cooling system uses a fan to draw hot air out of the battery pack and uses air convection to remove the heat generated by the battery cells to achieve cooling. The advantages of this method are simple structure and low cost. However, due to the poor thermal conductivity of air, the temperature uniformity between the battery cells is not high, that is, the temperature distribution of the battery cells is not uniform. In a high temperature environment, this uneven temperature distribution may cause local overheating of the battery cells, affecting their performance and life.

[0006] The liquid cooling system installs a liquid cooling plate at the bottom of the battery pack and uses the coolant to circulate inside the liquid cooling plate to remove the heat generated by the battery cells. This method has the advantages of high heat dissipation efficiency and precise temperature control. However, the coolant delivery pipeline is prone to bursting when the ambient temperature is extreme, which not only affects the heat dissipation effect, but also may cause damage to the battery pack. In addition, scale is easily accumulated inside the liquid cooling plate, which not only affects the heat conduction efficiency, but also may clog the pipeline. In addition, there is often condensation on the outside of the liquid cooling plate, which may penetrate into electrical components and cause a short circuit.

[0007] In addition, the energy efficiency ratio of both air cooling and liquid cooling systems is not high, which is also an important factor limiting the performance improvement of the cooling system. Summary of the invention

[0008] In view of this, the purpose of the present application is to provide a phase change gravity heat pipe type upper cover, a battery pack having the same, and a corresponding working fluid filling amount estimation method to solve at least one of the above technical problems.

[0009] In the first aspect, the present application provides a phase-change gravity heat pipe upper cover, which is filled with a phase-change working fluid, including: an upper cover body, in which an evaporation chamber is provided for approaching or contacting a battery module; a heat exchanger, which is used to exchange heat with the external environment, and the heat exchanger is located higher than the evaporation chamber in the vertical direction; a plurality of gas delivery pipes, connecting the evaporation chamber and the heat exchanger, and used to guide the phase-change working fluid vaporized into a gaseous state in the evaporation chamber to the heat exchanger; and a plurality of liquid reflux pipes, connecting the evaporation chamber and the heat exchanger, and used to guide the phase-change working fluid condensed into a liquid state in the heat exchanger to the evaporation chamber; wherein the evaporation chamber, the heat exchanger, the plurality of gas delivery pipes, and the plurality of liquid reflux pipes are connected to form a circulation loop filled with a phase-change working fluid, constituting a phase-change gravity heat pipe.

[0010] In combination with the first aspect, in some optional embodiments, it also includes: a first valve, arranged on the circulation loop, used for evacuating the inside of the circulation loop; a second valve, arranged on the circulation loop, used for inputting phase change working fluid into the circulation loop.

[0011] Based on the above optional implementation manner, both the first valve and the second valve may be arranged on the heat exchanger, and the first valve may be located higher than the second valve in the vertical direction.

[0012] In combination with the first aspect, in some optional embodiments, a receiving cavity is further provided in the upper cover body, the receiving cavity is arranged below the evaporation chamber and separated from the evaporation chamber, and the receiving cavity is used to receive the battery module.

[0013] In combination with the first aspect, in some optional embodiments, a pipeline chamber is further provided in the upper cover body, the pipeline chamber is arranged above the evaporation chamber and separated from the evaporation chamber, and a plurality of gas delivery pipes and a plurality of liquid reflux pipes are arranged in the pipeline chamber.

[0014] In combination with the first aspect, in some optional embodiments, multiple gas delivery pipes are distributed along the width direction of the upper cover body, each gas delivery pipe includes a connected gas delivery main pipe and multiple gas delivery branch pipes, the gas delivery main pipe extends along the length direction of the upper cover body, one end of the gas delivery main pipe is bent on the inner side or the outer side of the heat exchanger and then guided to the top of the heat exchanger, and the multiple gas delivery branch pipes are distributed along the extension direction of the gas delivery main pipe and are connected to the top of the evaporation chamber.

[0015] In combination with the first aspect, in some optional embodiments, a plurality of liquid return pipes are distributed along the width direction of the upper cover body, each liquid return pipe includes a connected liquid return main pipe and a plurality of liquid return branch pipes, the liquid return main pipe is U-shaped and is extended along the length direction of the upper cover body, two ports of the liquid return main pipe are connected to the bottom of the heat exchanger, and the plurality of liquid return branch pipes are distributed along the extension direction of the liquid return main pipe and are connected to the top of the evaporation chamber.

[0016] Based on the above technical scheme, the phase change gravity heat pipe upper cover provided by the present application absorbs heat and vaporizes through the liquid phase change working fluid in the evaporation chamber of the upper cover body, and the gaseous phase change working fluid enters the heat exchanger through multiple gas delivery pipes for heat exchange. The phase change working fluid that releases heat and becomes liquid again returns to the evaporation chamber through multiple liquid reflux pipes under the action of gravity, forming a cycle. The entire process does not require an external pump to drive and consumes no energy, and is environmentally friendly, energy-saving, and has the characteristics of high energy efficiency.

[0017] In a second aspect, the present application provides a battery pack, comprising a phase change gravity heat pipe type upper cover, a liquid cooling base plate, and a plurality of battery modules in any one of the embodiments of the first aspect above, wherein the upper cover body of the phase change gravity heat pipe type upper cover and the liquid cooling base plate constitute a battery box accommodating a plurality of battery modules, and the evaporation chamber of the upper cover body covers the upper surfaces of the plurality of battery modules.

[0018] In combination with the second aspect, in some optional embodiments, a thermally conductive insulating sheet is further included, which is used to contact the outer wall of the evaporation chamber and the battery module to transfer the heat generated by the battery module to the phase change medium in the evaporation chamber.

[0019] Based on the above technical solution, the battery pack provided by this application adopts a combination of a phase-change gravity heat pipe upper cover and a liquid cooling base plate, which has better heat dissipation performance. The phase-change gravity heat pipe upper cover can fully cover the upper surface of the battery module, especially the position prone to uneven heat dissipation - the battery cells at the ends of the length direction of the battery pack, which can achieve the effect of fast and uniform heat dissipation, and the whole process does not require external pump drive, achieving a high energy efficiency ratio.

[0020] In a third aspect, the present application provides a method for estimating the amount of phase change fluid filled in a phase change gravity heat pipe type upper cover for an energy storage battery pack in any one of the embodiments of the first aspect above, comprising: estimating the heat generated by the battery, calculating the difference between the heat and the heat generated by the battery at the maximum operating temperature, and obtaining the heat that needs to be absorbed by the phase change fluid; estimating the heat absorbed by the phase change fluid during the phase change process; and calculating the mass of the phase change fluid that needs to be filled in the phase change gravity heat pipe type upper cover based on the heat that needs to be absorbed by the phase change fluid and the heat absorbed by the phase change fluid during the phase change process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic structural diagram of a phase change gravity heat pipe type upper cover provided in an embodiment of the present application.

[0023] Figure 2 A perspective schematic diagram of a phase change gravity heat pipe type upper cover provided in an embodiment of the present application.

[0024] Figure 3 A schematic cross-sectional view of a phase change gravity heat pipe type upper cover at the upper cover body provided in an embodiment of the present application.

[0025] Figure 4 A schematic cross-sectional view of a phase change gravity heat pipe type upper cover at a heat exchanger provided in an embodiment of the present application.

[0026] Figure 5 A schematic diagram of the structure of a battery pack provided in an embodiment of the present application.

[0027] Figure 6 A schematic diagram of the structure of a battery pack provided in an embodiment of the present application when viewed from an upward perspective.

[0028] Figure 7 A schematic diagram of an exploded view of a battery pack provided in an embodiment of the present application.

[0029] Figure numerals: 1000, battery pack; 100, phase change gravity heat pipe upper cover; 10, upper cover body; 11, evaporation chamber; 12, accommodating chamber; 13, pipeline chamber; 20, heat exchanger; 21, heat exchanger shell; 22, fin; 30, gas delivery pipe; 31, gas delivery main pipe; 32, gas delivery branch pipe; 40, liquid reflux pipe; 41, liquid reflux main pipe; 42, liquid reflux branch pipe; 50, first valve; 60, second valve; 70, thermally conductive insulating sheet; 200, liquid cooling base plate; 300, battery module; 400, electrical component. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the description of the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0031] In the description of this application, unless otherwise clearly specified and limited, the terms "connection", "setting", "installation", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be that two elements are internally connected. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] The terms "upper", "lower", "left", "right", "front", "back", "center", "top", "bottom", "inside", "outside", "vertical", "horizontal", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship commonly placed when the product of the application is used. They are only for the convenience of description and simplified description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0033] The terms “first”, “second”, “third”, etc. are merely used to distinguish elements of similar nature, and do not indicate or imply relative importance or a particular order, unless expressly specified and limited otherwise.

[0034] The terms "comprises," "includes," "has," or any other variation thereof, are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0035] The term "plurality" means more than two (including two).

[0036] The term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0037] The terms "one embodiment", "as an example", "in one implementation", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example may be included in at least one embodiment or example of the present application. Schematic representations of such terms do not necessarily refer to the same embodiment, nor are they independent or alternative embodiments that are mutually exclusive with other embodiments. In the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined in a suitable manner.

[0038] Figure 1 This is a schematic structural diagram of a phase change gravity heat pipe type upper cover 100 provided in an embodiment of the present application. Figure 2 A perspective schematic diagram of a phase change gravity heat pipe type upper cover 100 provided in an embodiment of the present application.

[0039] See also Figure 1 and Figure 2 The embodiment of the present application provides a phase change gravity heat pipe upper cover 100, including an upper cover body 10, a heat exchanger 20, a plurality of gas delivery pipes 30, a plurality of liquid reflux pipes 40, a phase change working medium, a first valve 50, and a second valve 60.

[0040] Among them, the upper cover body 10 is provided with an evaporation chamber 11 and a receiving chamber 12 arranged in the up-down direction and separated from each other. The evaporation chamber 11 is for the internal phase change working fluid to absorb the heat of the battery module and vaporize, and the receiving chamber 12 is used to accommodate the battery module. A heat exchanger 20 is arranged on the outside of the upper cover body 10, and the position of the heat exchanger 20 in the vertical direction is higher than the evaporation chamber 11. The evaporation chamber 11 and the heat exchanger 20 are connected through a plurality of gas delivery pipes 30 and a plurality of liquid reflux pipes 40 to form a circulation loop, and the interior of the circulation loop is filled with phase change working fluid, thereby forming a phase change gravity heat pipe. The first valve 50 and the second valve 60 are both arranged on the circulation loop, and the first valve 50 is used when the interior of the circulation loop is evacuated, and the second valve 60 is used when the phase change working fluid is input into the circulation loop. The following is a detailed description of each part.

[0041] The evaporation chamber 11 of the upper cover body 10 is the core area where the phase change medium absorbs the heat of the battery module and vaporizes. It needs to be arranged close to or in contact with the battery module to ensure that the heat of the battery module can be effectively transferred to the phase change medium in the evaporation chamber 11. The evaporation chamber 11 also needs to be arranged at a lower position in the circulation loop to facilitate the natural reflux of the liquid phase change medium. The side wall of the accommodating cavity 12 may be provided with a through hole for arranging an integrated panel and / or an inspection cover for electrical components.

[0042] For example, Figure 2 As shown, the cross-sections of the evaporation chamber 11 and the accommodating chamber 12 are both rectangular and of the same size, and the height of the evaporation chamber 11 is significantly smaller than the height of the accommodating chamber 12. This design allows the evaporation chamber 11 to fully and evenly cover the upper surface of each battery module in the energy storage battery pack, so that the phase change medium in the evaporation chamber 11 can more quickly absorb the heat generated by the battery module and vaporize, achieving the effect of rapid and uniform heat dissipation, and the gaseous phase change medium can more easily enter the gas delivery pipe 30, improving the heat conduction efficiency. This design can also make the size of the upper cover body 10 more compact in the height direction.

[0043] The upper cover body 10 may also be provided with a pipeline chamber 13 for arranging a plurality of gas delivery pipes 30 and a plurality of liquid return pipes 40. In one embodiment, Figure 2As shown, the pipeline chamber 13 is arranged above the evaporation chamber 11 and separated from the evaporation chamber 11, and a plurality of gas delivery pipes 30 and a plurality of liquid return pipes 40 are fixedly arranged in the pipeline chamber 13. By centrally arranging a plurality of gas delivery pipes 30 and a plurality of liquid return pipes 40 in the pipeline chamber 13, not only can the space occupation be reduced, but also the necessary protection can be provided for the gas delivery pipes 30 and the liquid return pipes 40 to prevent them from being affected by external impact, vibration or corrosion, and at the same time, it helps to ensure the stability of the flow of the phase change working medium.

[0044] Figure 3 It is a schematic cross-sectional view of a phase change gravity heat pipe type upper cover 100 at the upper cover body 10 provided in an embodiment of the present application.

[0045] The gas delivery pipe 30 is used to guide the phase change medium vaporized into gaseous state in the evaporation chamber 11 to the heat exchanger 20. In one embodiment, Figure 2 and Figure 3 As shown, a plurality of gas delivery pipes 30 are evenly spaced and distributed in the pipeline chamber 13 along the width direction of the upper cover body 10 , and each gas delivery pipe 30 includes a gas delivery main pipe 31 and a plurality of gas delivery branch pipes 32 .

[0046] The gas delivery main pipe 31 extends along the length direction of the upper cover body 10, one end of the gas delivery main pipe 31 passes through the outside of the upper cover body 10 and is connected to the heat exchanger 20, and multiple gas delivery branch pipes 32 are evenly distributed along the extension direction of the gas delivery main pipe 31. Each gas delivery branch pipe 32 is arranged in the vertical direction, and its two ends are respectively connected to the bottom of the gas delivery main pipe 31 and the top of the evaporation chamber 11.

[0047] The structure of the gas delivery pipe 30 itself and the overall arrangement structure of the multiple gas delivery pipes 30 can ensure that the gaseous phase change medium in the evaporation chamber 11 is uniformly and quickly delivered to the heat exchanger 20, avoiding local overheating or overcooling, and improving the heat transfer efficiency. The gas delivery branch pipe 32 arranged in the vertical direction also reduces the fluctuation and resistance of the gas when it rises, and improves the stability and reliability of gas delivery.

[0048] Furthermore, in order to prevent liquid phase-change medium from entering the gas delivery pipe 30 and to prevent gaseous phase-change medium from entering the liquid reflux pipe 40 , one end of the gas delivery main pipe 31 may be bent inside or outside the heat exchanger 20 and then directed to the top of the heat exchanger 20 . Figure 2 and Figure 3 As shown, one end of the gas delivery main pipe 31 is bent on the inner side of the heat exchanger 20 and then guided to the top of the heat exchanger 20. Compared with being set on the outer side of the heat exchanger 20, this structure can reduce the risk of leakage and make the appearance of the heat exchanger 20 more concise.

[0049] The liquid return pipe 40 is used to guide the phase change medium condensed into liquid in the heat exchanger 20 to the evaporation chamber 11. In one embodiment, Figure 2 and Figure 3 As shown, a plurality of liquid reflux pipes 40 are distributed in the pipeline chamber 13 along the width direction of the upper cover body 10 at equal intervals, and each liquid reflux pipe 40 includes a liquid reflux main pipe 41 and a plurality of liquid reflux branch pipes 42 .

[0050] The liquid return main pipe 41 is U-shaped, which is placed flat inside the upper cover body 10 and extends along the length direction of the upper cover body 10. Both ports of the liquid return main pipe 41 pass through the outer side of the upper cover body 10 and are connected to the heat exchanger 20. A plurality of liquid return branch pipes 42 are evenly spaced along the extension direction of the liquid return main pipe 41. Each liquid return branch pipe 42 is arranged in the vertical direction, and both ends of each liquid return branch pipe 42 are connected to the bottom of the liquid return main pipe 41 and the top of the evaporation chamber 11, respectively. Among them, the position of the liquid return main pipe 41 in the vertical direction is lower than the gas delivery main pipe 31, and both ports are connected to the bottom of the side of the heat exchanger 20. This structure allows the liquid return pipe 40 to be filled with the refluxed liquid phase change medium, and prevents the gaseous phase change medium from entering the liquid return pipe 40.

[0051] The structure of the liquid return pipe 40 itself and the overall arrangement of the plurality of liquid return pipes 40 can allow the liquid phase-change medium in the heat exchanger 20 to flow back to the evaporation chamber 11 evenly and quickly from the bottom, and can allow the phase-change medium to evenly cover the entire evaporation chamber 11, avoiding retention and accumulation, and improving the efficiency and stability of liquid reflux. The U-shaped liquid return pipe 41 not only increases the number of ports for the return of the liquid phase-change medium at the bottom of the heat exchanger 20, but also can reduce the fluctuation and impact of the liquid to a certain extent, and improve the reliability and safety of liquid reflux.

[0052] In order to make the overall arrangement of the plurality of gas delivery pipes 30 and the plurality of liquid return pipes 40 more compact, as shown in FIG. Figure 2 and Figure 3 As shown, a plurality of gas delivery pipes 30 are arranged corresponding to a plurality of liquid return pipes 40 , and each gas delivery pipe 30 is arranged in the gap between two mutually parallel sections of the corresponding liquid return main pipe 41 . This arrangement structure significantly improves space utilization.

[0053] Figure 4 A schematic cross-sectional view of a phase change gravity heat pipe upper cover 100 at a heat exchanger 20 provided in an embodiment of the present application.

[0054] The heat exchanger 20 is used to convert the gaseous phase-change medium into a liquid state by exchanging heat with the external environment. Figure 2 and Figure 4As shown, the heat exchanger 20 includes a heat exchanger housing 21 and a plurality of fins 22 disposed in the heat exchanger housing 21 .

[0055] The length of the heat exchanger shell 21 is the same as the width of the upper cover body 10, so that the overall structure of the phase change gravity heat pipe upper cover 100 is compact and reduces space occupancy. At the same time, this design also facilitates the connection of the heat exchanger shell 21 with multiple gas delivery pipes 30 and multiple liquid return pipes 40, thereby improving integration. The bottom of the heat exchanger shell 21 is vertically higher than the evaporation chamber 11, so that the liquid phase change medium naturally flows to the bottom of the heat exchanger shell 21 under the action of gravity, and flows back to the evaporation chamber 11 through the liquid return pipe 40. This natural circulation method does not require additional power equipment, reducing energy consumption and operating costs.

[0056] A plurality of fins 22 are evenly spaced in the length direction of the heat exchanger housing 21. Each fin 22 is approximately rectangular and arranged in the vertical direction. A gap is left between the edge of the fin 22 and the inner wall of the heat exchanger housing 21, so that the spaces between the plurality of fins 22 are interconnected. The fins 22 of this shape and layout increase the heat exchange area, which helps to evenly distribute and quickly transfer heat, so that the heat of the phase change medium can be transferred to the external environment more quickly, thereby accelerating the transformation process of the phase change medium from gas to liquid, and improving the heat transfer efficiency.

[0057] The first valve 50 is used to evacuate the inside of the circulation loop, and the second valve 60 is used to input the phase change medium into the circulation loop. Before the phase change medium is filled into the circulation loop through the second valve 60, the inside of the circulation loop needs to be evacuated in advance through the first valve 50 and an external vacuum pump.

[0058] In one embodiment, if Figure 1 and Figure 2 As shown, the first valve 50 and the second valve 60 are both arranged on an end face of the heat exchanger housing 21 in the longitudinal direction. The first valve 50 is located higher in the vertical direction than the second valve 60. During the vacuuming process, since the first valve 50 is located at a higher position, the air inside the circulation loop can be more easily pumped out, thereby speeding up the vacuuming process. When the vacuuming is completed, when the phase change medium is filled through the second valve 60, since the second valve 60 is located at a lower position, it can be ensured that the phase change medium is filled from a lower position, further reducing the presence of residual air inside the circulation loop.

[0059] The phase change medium can be Freon or other existing refrigerants. The height of the filled phase change medium must be above the two ports of the liquid return pipe 41, that is, the evaporation chamber 11 and the plurality of liquid return pipes 40 must be filled, so as to ensure the efficient and stable operation of the phase change gravity heat pipe.

[0060] The various components in the phase change gravity heat pipe type upper cover 100 can be connected into one, which can reduce the number of connection points, reduce the risk of leakage and failure, and improve stability and reliability. At the same time, the compact structure can reduce the impact of external factors such as vibration and impact, and enhance durability.

[0061] The working principle of the phase change gravity heat pipe upper cover 100 is as follows: after the evaporation chamber 11 of the upper cover body 10 receives the heat of each battery module transmitted by the heat conductive insulation sheet 70, the liquid phase change medium inside absorbs heat and evaporates and boils, and quickly changes from liquid to gas. Since the volume of the gas phase change medium is larger than that of the liquid phase change medium, the pressure in the evaporation chamber 11 increases, causing the gas phase change medium to rise and enter the gas delivery pipe 30, and enter the heat exchanger 20 through the gas delivery pipe 30. In the heat exchanger 20, the gas phase change medium releases heat through a large number of fins 22 through heat exchange with the external environment, and then changes back to liquid, and flows to the bottom of the heat exchanger 20. Since the heat exchanger 20 is higher than the evaporation chamber 11 in the vertical direction, and the liquid return pipe 40 is connected to the bottom of the heat exchanger 20, the liquid phase change medium flows back to the evaporation chamber 11 through the liquid return pipe 40 under the action of gravity, and continues to participate in phase change heat dissipation to form a cycle.

[0062] Figure 5 A schematic diagram of the structure of a battery pack 1000 provided in an embodiment of the present application is shown in FIG. Figure 6 This is a schematic diagram of the structure of a battery pack 1000 provided in an embodiment of the present application when viewed from above. Figure 7 A schematic diagram of an exploded view of a battery pack 1000 provided in an embodiment of the present application.

[0063] See also Figures 5 to 7 The embodiment of the present application also provides a battery pack 1000, including a phase change gravity heat pipe upper cover 100, a liquid cooling base plate 200, a battery module 300, a thermally conductive insulating sheet 400, and an electrical component 500.

[0064] The upper cover body 10 of the phase change gravity heat pipe upper cover 100 and the liquid cooling bottom plate 200 together form a battery box, in which a battery module 300, a heat conductive insulating sheet 400, and an electrical component 500 are arranged. The upper cover body 10 and the liquid cooling bottom plate 200 are both provided with mounting holes (not shown in the figure) for inserting fasteners to connect with each other.

[0065] The heat-conducting insulating sheet 400 is disposed on the surface of the evaporation chamber 11 in the accommodating cavity 12 and is in direct contact with the upper surface of the energy storage cell of the battery module 300 and the aluminum bar. The heat-conducting insulating sheet 400 is used to transfer the heat generated by the battery module 300 to the phase change medium in the evaporation chamber 11. The heat-conducting insulating sheet 400 can be fixed on the surface of the evaporation chamber 11 in the accommodating cavity 12 by bonding.

[0066] When the battery pack 1000 is working, the phase change gravity heat pipe type upper cover 100 and the liquid cooling base plate 200 dissipate heat for the battery module 300. For example, in spring and autumn weather (ambient temperature is about 20°C), only the phase change gravity heat pipe type upper cover 100 can be operated to dissipate heat. The phase change gravity heat pipe type upper cover 100 can achieve no power consumption and efficient heat dissipation. At the same time, the temperature of the refluxed phase change working fluid is not very low, and the condensation caused is also less than that of the liquid cooling base plate 200.

[0067] When the temperature is low in winter, only the liquid cooling base plate 200 can be operated to dissipate heat. It is worth noting that before charging and discharging the battery cells, the battery cells need to be preheated to reach a suitable operating temperature range. Since the temperature is low in winter, the battery cell temperature is low, and the heat generated is relatively small, the phase change working medium in the phase change gravity heat pipe type upper cover 100 is more in liquid state, rather than frequently undergoing gas-liquid phase change. At this time, the phase change gravity heat pipe type upper cover 100 is more in standby state.

[0068] When the temperature is high in summer, due to the high initial temperature, the phase change medium in the phase change gravity heat pipe type upper cover 100 may have been in a state close to or exceeding its phase change temperature, and the heat absorption threshold becomes smaller. The phase change gravity heat pipe type upper cover 100 alone cannot effectively dissipate heat. At this time, the liquid cooling base plate 200 needs to work to dissipate heat for the battery module 300.

[0069] In summary, the battery pack 1000 provided in the embodiment of the present application adopts a combination of a phase change gravity heat pipe type upper cover 100 and a liquid cooling base plate 200, and has better heat dissipation performance. The phase change gravity heat pipe type upper cover 100 fully covers the upper surface of the battery module 300, especially the position prone to uneven heat dissipation - the battery cells at the ends of the length direction of the battery pack 1000, which can achieve the effect of fast and uniform heat dissipation, and the whole process does not require external pump drive, achieving a high energy efficiency ratio.

[0070] The embodiment of the present application also provides a method for estimating the filling amount of a phase-change working fluid in a phase-change gravity heat pipe type upper cover for an energy storage battery pack, comprising: S1. Estimate the heat generated by the batteries in the energy storage battery pack.

[0071] The total heat Q generated by the battery in the energy storage battery pack is divided into four parts, namely the reaction heat Q r , Joule heat Q j , polarization heat Q p and side reaction heat Q s , so the total heat Q can be determined according to formula (1) as: (1) According to the principles of thermodynamics, the heat generated by the chemical reaction of the battery is the reaction heat Q r, can be obtained from the change in Gibbs free energy, see formula (2) (2) Among them, △G is the change in Gibbs free energy, in kJ / mol; △H is the enthalpy change, in kJ / mol; T is the temperature of the battery during charging and discharging; △S is the entropy change, in kJ / (mol·K).

[0072] The relationship between the change in Gibbs free energy △G and the change in entropy △S is shown in formula (3): (3) in, It represents the rate of change of Gibbs free energy △G with the temperature T during battery charging and discharging.

[0073] During the battery charging and discharging process, the change in Gibbs free energy △G is equal to the electrical energy, see formula (4): (4) Where n is the number of moles of transferred electrons; F is the Faraday constant, which is 96484.5 C / mol; and E is the electromotive force.

[0074] Reaction heat Q r Substituting the difference between the corresponding enthalpy change △H and the Gibbs free energy change △G into formulas (3) and (4), we can obtain formula (5): (5) Joule heat Q j is the heat generated by the internal resistance of the battery, polarization heat Q p It can be regarded as the heat generated by polarization internal resistance, and the side reaction heat Q s The heat is small and can be ignored. Therefore, the Joule heat Q j and polarization heat Q p The total heat is calculated as follows: (6) Where I is the battery charging and discharging current, R j is the internal resistance of the battery, R p is the polarization internal resistance, and t is the charging and discharging time.

[0075] Substituting formulas (5) and (6) into formula (1), we can obtain the total heat Q generated by the battery, as shown in formula (7): (7) Continuing with step S1, the difference between the estimated heat generated by the battery and the heat generated by the battery at the maximum operating temperature is calculated to obtain the heat that needs to be absorbed by the phase change working fluid.

[0076] Since the total heat generated by the battery will be absorbed by the battery itself, the macroscopic manifestation is the rise in battery temperature, and the battery has a stable and normal operating temperature range. Therefore, for the phase change gravity heat pipe cover used for heat dissipation of the energy storage battery pack, the phase change working fluid inside it needs to absorb the part of the heat that exceeds the maximum operating temperature when the battery is working. Taking lithium iron phosphate battery as an example, its operating temperature range is 25℃~35℃, and the phase change working fluid needs to absorb the heat generated when the lithium iron phosphate battery exceeds 35℃ when working. Therefore, the heat that the phase change working fluid needs to absorb is Q g The calculation of is shown in formula (8): (8) Among them, Q T is the heat generated by the battery at the maximum operating temperature, c is the average specific heat capacity of the battery, m is the total weight of the battery, and T0 is the initial temperature of the battery when it is not charged or discharged.

[0077] Continuing with step S1, estimating the heat absorbed by the phase-change working fluid during the phase-change process.

[0078] The heat absorbed by the phase change medium during the phase change process can be divided into heat transferred by heat conduction and heat transferred by latent heat. Ignoring the heat loss in the heat conduction between the battery cell and the phase change medium, the heat absorbed by the phase change medium is Q g The calculation of is shown in formula (9): (9) Among them, Q0 is the heat absorbed by the phase change working fluid and transferred by heat conduction, Q H is the heat absorbed by the phase change medium and transferred by latent heat, T0 is the initial temperature, T B is the boiling point of the phase change medium, is the specific heat capacity of the phase change medium, is the mass of the phase change medium, △H vap It is the latent heat of vaporization of the phase change fluid.

[0079] Since the phase change gravity heat pipe cover is in a dynamic equilibrium process during normal operation, the latent heat of vaporization of the phase change medium △H vap It can be calculated by the integrated form of the Clausius-Clapeyron equation. The integrated form of the Clausius-Clapeyron equation is shown in formula (10). The calculated latent heat of vaporization of the phase change working fluid △H vap See formula (11): (10) (11) Among them, P B The phase change medium is B P0 is the pressure of the phase change fluid at T0, and R is the ideal gas constant.

[0080] S2. According to the heat required to be absorbed by the phase change working fluid calculated in step S1 and the estimated heat absorbed by the phase change working fluid during the phase change process, the mass of the phase change working fluid that needs to be filled in the phase change gravity heat pipe type upper cover is calculated to be used in the numerical design of the pipeline of the phase change gravity heat pipe type upper cover.

[0081] The specific process is as follows: Combining formulas (8), (9) and (11), we get the heat transfer performance formula (12) of the phase change gravity heat pipe upper cover: (12) Then, the mass of the phase change fluid to be filled is calculated , see formula (13): (13) The mass of the phase change fluid to be filled is obtained according to formula (13): , which can be used in the numerical design of pipelines for phase change gravity heat pipe upper cover.

[0082] Taking the numerical design of the liquid return pipe 40 in the phase change gravity heat pipe upper cover 100 as an example, Figure 2 It can be seen that the number of liquid return pipes 40 in the phase change gravity heat pipe upper cover 100 is 9, and the number of liquid return branches 42 of each liquid return pipe 40 is 15. If the liquid phase change medium in the heat exchanger 20 is to flow evenly into the evaporation chamber 11, the flow rate and the opening diameter of a single liquid return pipe 40 need to be calculated to ensure that the phase change medium flows out of the outlets of all liquid return branches 42 during normal operation, thereby achieving a uniform heat dissipation effect.

[0083] Therefore, the volume V of each liquid return pipe 40 is U The formula (14) must be satisfied: (14) Among them, V E is the total volume of the phase-changing medium in the heat exchanger 20, is the density of the phase change fluid.

[0084] The mass flow rate Q inside each liquid return pipe 40 is as follows: (15) Wherein, L is the length of the liquid return main pipe 41, the length of the liquid return branch pipe 42 can be ignored, and v is the flow rate of the phase change medium, which can be obtained by the Bernoulli equation.

[0085] The mass flow rate Q at the outlet of each liquid return branch 42 is outlet , see formula (16): (16) Wherein, S is the cross-sectional area at the outlet of the liquid return branch pipe 42 .

[0086] Since each liquid return pipe 40 is guaranteed to be filled with phase-change working fluid, formula (17) can be obtained: (17) According to the above formula, the length and inlet area of ​​the liquid reflux main pipe 41 and the outlet area of ​​the liquid reflux branch pipe 42 can be calculated.

[0087] The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the field can easily think of various changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A phase change gravity heat pipe upper cover, filled with a phase change working medium, characterized in that: include: An upper cover body, inside of which is provided an evaporation chamber for approaching or contacting the battery module; A heat exchanger, used for exchanging heat with the external environment, wherein the heat exchanger is located higher than the evaporation chamber in the vertical direction; A plurality of gas delivery pipes, connecting the evaporation chamber and the heat exchanger, and used for guiding the phase change working medium vaporized into a gaseous state in the evaporation chamber to the heat exchanger; as well as A plurality of liquid return pipes, connecting the evaporation chamber and the heat exchanger, and used for guiding the phase change working medium condensed into liquid in the heat exchanger to the evaporation chamber; The evaporation chamber, the heat exchanger, the plurality of gas delivery pipes, and the plurality of liquid reflux pipes are interconnected to form a circulation loop filled with the phase-change working medium, thereby constituting a phase-change gravity heat pipe.

2. The phase change gravity heat pipe type upper cover according to claim 1, characterized in that: Also includes: A first valve, disposed on the circulation loop, for use when evacuating the interior of the circulation loop; The second valve is arranged on the circulation loop and is used for inputting the phase-change working medium into the circulation loop.

3. The phase change gravity heat pipe type upper cover according to claim 2, characterized in that: The first valve and the second valve are both arranged on the heat exchanger, and the first valve is located higher than the second valve in the vertical direction.

4. The phase change gravity heat pipe type upper cover according to claim 1, characterized in that: A receiving cavity is also provided in the upper cover body. The receiving cavity is arranged below the evaporation chamber and is separated from the evaporation chamber. The receiving cavity is used to receive the battery module.

5. The phase change gravity heat pipe type upper cover according to claim 1, characterized in that: A pipeline chamber is also provided in the upper cover body. The pipeline chamber is arranged above the evaporation chamber and separated from the evaporation chamber. A plurality of the gas delivery pipes and a plurality of the liquid reflux pipes are arranged in the pipeline chamber.

6. The phase change gravity heat pipe type upper cover according to claim 1 or 5, characterized in that: The plurality of gas delivery pipes are distributed along the width direction of the upper cover body, and each of the gas delivery pipes includes a gas delivery main pipe and a plurality of gas delivery branch pipes connected to each other. The gas delivery main pipe extends along the length direction of the upper cover body, and one end of the gas delivery main pipe is bent at the inner side or the outer side of the heat exchanger and then directed to the top of the heat exchanger. The plurality of gas delivery branch pipes are distributed along the extension direction of the gas delivery main pipe and are connected to the top of the evaporation chamber.

7. The phase change gravity heat pipe type upper cover according to claim 1 or 5, characterized in that: The plurality of liquid return pipes are distributed along the width direction of the upper cover body, and each of the liquid return pipes comprises a liquid return main pipe and a plurality of liquid return branch pipes connected to each other. The liquid return pipe is U-shaped and extends along the length direction of the upper cover body. Both ports of the liquid return pipe are connected to the bottom of the heat exchanger. The plurality of liquid reflux branch pipes are distributed along the extension direction of the liquid reflux main pipe and are connected to the top of the evaporation chamber.

8. A battery pack, characterized in that: It comprises a phase change gravity heat pipe upper cover, a liquid cooling bottom plate, and a plurality of battery modules as described in any one of claims 1 to 7, The upper cover body of the phase change gravity heat pipe type upper cover and the liquid cooling bottom plate form a battery box that accommodates a plurality of the battery modules. The evaporation chamber of the upper cover body covers the upper surfaces of the plurality of battery modules.

9. The battery pack according to claim 8, characterized in that: It also includes a heat-conducting insulating sheet, which is used to contact the outer wall of the evaporation chamber and the battery module to transfer the heat generated by the battery module to the phase-change working medium in the evaporation chamber.

10. A method for estimating the amount of phase change medium in a phase change gravity heat pipe upper cover for an energy storage battery pack according to any one of claims 1 to 7, characterized in that: include: estimating the heat generated by the battery, calculating the difference between the heat generated by the battery at the maximum operating temperature, and obtaining the heat that needs to be absorbed by the phase change working fluid; estimating the amount of heat absorbed by the phase-change working fluid during the phase-change process; The mass of the phase-change working medium that needs to be filled in the phase-change gravity heat pipe upper cover is calculated based on the heat that the phase-change working medium needs to absorb and the heat that the phase-change working medium absorbs during the phase change process.

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