Immersed liquid cooling battery cooling device and energy storage battery pack

Abstract

The invention provides an immersed liquid-cooled battery cooling device and an energy storage battery pack, and belongs to the field of battery liquid cooling, the top of a shell is provided with an exhaust port, and the exhaust port exhausts air above the liquid level of the shell; the cooling pipe is arranged in the shell and located at the top of the battery, and the cooling pipe is immersed below the liquid level of the heat-conducting medium; the air delivery pipe is arranged in the shell and located at the bottom of the battery, and air holes are distributed in the air delivery pipe; clean air is stored in the air storage tank; the bubble generating device is communicated between the air storage tank and the air conveying pipe and conveys high-pressure air flow to the heat conduction medium from bottom to top through the air holes. High-pressure gas is sprayed from the bottom of the battery from bottom to top through the gas conveying pipe, bubble flow is formed in gaps of the battery, immersion cooling liquid in a flow channel can be greatly disturbed, and then a thermal boundary layer formed on the surface of a battery pack due to low-speed flowing of the immersion cooling liquid is damaged; and the convective heat transfer coefficient of the immersion liquid on the surface of the battery pack can be greatly improved, and the cooling capacity of the immersion liquid on the battery side is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery liquid cooling, and particularly to an immersion liquid-cooled battery cooling device and an energy storage battery pack. Background Art

[0002] In recent years, with the rapid development of electrochemical energy storage technology, immersion liquid-cooled energy storage systems have gradually become the mainstream design solution for large-capacity battery packs due to their high heat dissipation capacity and intrinsic safety. For example, Tesla Patent US20210083221A1 forms a thermal cycle of upward and downward convection of the immersion liquid through the density difference of the immersion liquid caused by battery heating. Specifically, when the immersion liquid is heated and its temperature rises, its density becomes smaller. Therefore, the high-temperature immersion liquid rises and contacts the liquid cooling plate arranged at the top of the immersion liquid. After heat exchange between the high-temperature immersion liquid and the liquid cooling plate, the temperature drops, and then it descends back to the bottom again.

[0003] Currently, the cooling effect of relying on the natural convection cooling of the immersion coolant to cool the battery is limited. The reason is that in the cooling method relying on natural convection, when the immersion liquid flows through the battery surface, due to the slow flow rate, a relatively thick thermal boundary layer will be formed on the battery surface, and the thermal boundary layer will hinder the heat transfer effect of natural convection. Summary of the Invention

[0004] In view of this, the present invention provides an immersion liquid-cooled battery cooling device and an energy storage battery pack to solve the problem of poor cooling effect of currently relying on the natural convection cooling of the immersion coolant to cool the battery.

[0005] The technical solution of the present invention is realized as follows: The present invention provides an immersion liquid-cooled battery cooling device, including a housing, a cooling pipe, a gas transmission pipe, a bubble generating device and a gas storage tank; a plurality of batteries are arranged in the housing, the housing is filled with a heat-conducting medium and submerges the batteries, an exhaust port is arranged at the top of the housing, and the exhaust port discharges the air above the liquid level of the housing; the cooling pipe is arranged in the housing and located at the top of the batteries, and the cooling pipe is submerged under the liquid level of the heat-conducting medium; the gas transmission pipe is arranged in the housing and located at the bottom of the batteries, and air holes are arranged on the gas transmission pipe; clean air is stored in the gas storage tank; the bubble generating device is connected between the gas storage tank and the gas transmission pipe, and the bubble generating device conveys high-pressure air flow to the heat-conducting medium from bottom to top through the air holes.

[0006] Based on the above technical solution, preferably, it further includes a gas-liquid separation device; a return port is opened at a position on the side wall of the housing close to the liquid level of the heat-conducting medium; the gas-liquid separation device is connected between the gas storage tank and the exhaust port, and the gas-liquid separation device is also connected to the return port. The gas-liquid separation device collects the air discharged from the exhaust port, performs gas-liquid separation on the air, and then conveys the liquid phase back into the housing through the return port and conveys the gas phase to the gas storage tank.

[0007] Further preferably, there is a gap between the dry batteries, and several air holes arranged on each air delivery pipe are in a column, or several air holes corresponding to each other in position on each air delivery pipe are in a column, and each column of air holes is arranged opposite to the gap.

[0008] Further preferably, the temperature difference between the battery surface and the heat conduction medium is adjusted by adjusting the width of the gap.

[0009] Further preferably, the calculation formula for the width of the gap is

[0010] S = CL×(gβ△TL 3 / αv) 0.25 ,

[0011] where C is an empirical constant, L is the height of the battery, g is the acceleration of gravity, β is the thermal expansion coefficient of the heat conduction medium, △T is the temperature difference between the battery surface and the heat conduction medium, α is the thermal diffusivity of the heat conduction medium, and v is the viscosity of the immersion coolant.

[0012] Further preferably, the width of the gap is not greater than 10 cm.

[0013] Further preferably, the air delivery pipe includes a branch pipe and a main pipe. A number of branch pipes are correspondingly arranged in each gap, and a number of air holes are arranged on the branch pipes; the main pipe is simultaneously connected to one end of a number of branch pipes, one end of the main pipe passes through the housing and extends to the external environment, and the outer end of the main pipe is connected to the gas storage tank through a bubble generating device.

[0014] On the basis of the above technical solutions, preferably, the aperture of the air hole is 1 - 2 cm, and the distance between adjacent air holes is 3 - 5 cm.

[0015] On the basis of the above technical solutions, preferably, it further includes a liquid storage tank and a delivery pump; the liquid storage tank is connected to the output end and the input end of the cooling pipe, and cooling water is stored in the liquid storage tank; the delivery pump is connected between the liquid storage tank and the input end of the cooling pipe, and the delivery pump pumps cooling water to the heat exchange pipe.

[0016] On the other hand, the present invention also provides an energy storage battery pack, which adopts the above-mentioned immersion liquid cooling battery cooling device.

[0017] The immersion liquid cooling battery cooling device and the energy storage battery pack of the present invention have the following beneficial effects compared with the prior art:

[0018] (1) In the present invention, high-pressure gas is ejected from the bottom of the battery upward through the air delivery pipe, and a bubble flow is formed in the battery gap, which will cause a large disturbance to the immersion coolant in the flow channel, thereby destroying the thermal boundary layer formed by the slow flow of the immersion coolant on the surface of the battery pack, and can greatly improve the convective heat transfer coefficient of the immersion liquid on the surface of the battery pack, and improve the heat dissipation ability of the immersion coolant on the battery side.

[0019] (2) According to the resistance of the high-viscosity oily fluid flow, the present invention adjusts the optimal gap distance of the battery, so that the thermal boundary layer formed by the low-speed flow of the immersion coolant on the surface of the battery pack can be effectively destroyed by the high-pressure air flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 is a perspective view of the immersion battery liquid cooling device of the present invention;

[0022] Figure 2 is a side sectional structure schematic diagram of the immersion battery liquid cooling device of the present invention;

[0023] Figure 3 is a top view of the infusion tube of the present invention.

[0024] In the figure: 1, housing; 11, return port; 12, exhaust port; 2, battery; 201, gap; 3, cooling pipe; 4, gas transmission pipe; 41, branch pipe; 42, main pipe; 401, air hole; 5, bubble generating device; 6, gas storage tank; 7, gas-liquid separation device; 8, liquid storage tank; 9, delivery pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] As Figure 1 shown, in combination with Figure 2 , an immersion liquid-cooled battery cooling device of the present invention includes a housing 1, a cooling pipe 3, a gas transmission pipe 4, a bubble generating device 5 and a gas storage tank 6.

[0027] Among them, a plurality of batteries 2 are arranged in the housing 1, the housing 1 is filled with a heat-conducting medium and immerses the batteries 2, and the heat-conducting medium is a hydrocarbon oil-based insulating liquid or a fluorohydrocarbon oil-based insulating liquid. Since the heat-conducting medium is a hydrocarbon oil-based insulating liquid or a fluorohydrocarbon oil-based insulating liquid, an exhaust port 12 is provided at the top of the housing 1, and the exhaust port 12 discharges the air above the liquid level of the housing 1.

[0028] The cooling pipe 3 is arranged inside the housing 1 and on top of the battery 2, and the cooling pipe 3 is immersed below the liquid level of the heat-conducting medium. A coolant flows through the cooling pipe 3, and water cooling or oil cooling can be adopted. The cooling pipe 3 adopts a coil structure.

[0029] The gas transmission pipe 4 is arranged inside the housing 1 and at the bottom of the battery 2, and air holes 401 are arranged on the gas transmission pipe 4.

[0030] The air storage tank 6 stores clean air. Specifically, inert gases such as nitrogen can be adopted.

[0031] The bubble generating device 5 is connected between the air storage tank 6 and the gas transmission pipe 4, and the bubble generating device 5 conveys high-pressure air flow to the heat-conducting medium from bottom to top through the air holes 401. The bubble generating device 5 can adopt a compressor, and a check valve is arranged at the outlet of the compressor to prevent the heat-conducting medium inside the housing 1 from flowing into the compressor. In addition, a check valve needs to be arranged between the bubble generating device 5 and the gas transmission pipe 4 to prevent the heat-conducting medium from flowing back into the bubble generating device 5 through the gas transmission pipe 4.

[0032] When the above technical solution is adopted, after the high-pressure gas is generated by the bubble generating device 5, it passes through the gas transmission pipe 4 and is ejected into the gap 201 of the battery 2 from the air holes 401 from bottom to top to form a high-pressure bubble flow channel; after the high-pressure gas flows into the flow channel of the gap 201 of the battery 2, it will cause a large disturbance to the heat-conducting medium fluid in the flow channel, thereby destroying the thermal boundary layer formed on the surface of the battery 2 due to the low-speed flow state of the heat-conducting medium caused by objective factors such as its oiliness and viscosity, and then greatly improving the convective heat transfer coefficient of the heat-conducting medium on the surface of the battery 2, enhancing the heat dissipation ability of the heat dissipation mechanism on the side of the battery 2, and meeting the large heat dissipation requirements of the battery 2 during high-rate charge and discharge.

[0033] In Figure 2 In a preferred embodiment shown, since the high-pressure gas will carry part of the heat-conducting medium and flow out from the exhaust port 12, the gas flowing out cannot directly enter the air storage tank 6, and gas-liquid separation needs to be carried out on it. Therefore, this embodiment further includes a gas-liquid separation device 7.

[0034] Wherein, a return port 11 is opened at a position on the side wall of the housing 1 close to the liquid level of the heat-conducting medium.

[0035] The gas-liquid separation device 7 is connected between the gas storage tank 6 and the exhaust port 12. The gas-liquid separation device 7 can adopt a commercially available gas-liquid separator. The gas-liquid separation device 7 is also connected to the return port 11. The gas-liquid separation device 7 collects the air discharged from the exhaust port 12. After the gas-liquid separation device 7 separates the air into gas and liquid phases, the liquid phase is transported back into the housing 1 through the return port 11, and the gas phase is transported to the gas storage tank 6. The gas discharged from the exhaust port 12 first enters the gas-liquid separation device 7 for gas-liquid separation. The separated gas phase flows through the filter and into the gas storage tank 6, and the separated liquid phase returns to the interior of the housing 1 again.

[0036] In Figure 2 a preferred embodiment shown, there is a gap 201 between several batteries 2. The several air holes 401 arranged on each gas pipeline 4 are in a column, or the several air holes 401 at corresponding positions on each gas pipeline 4 are in a column. Each column of air holes 401 is arranged opposite to the gap 201, so that the high-pressure gas will not be blocked when spraying out of the air holes 401 and the spraying flow rate thereof will not be reduced.

[0037] In Figure 2 a preferred embodiment shown, the temperature difference between the surface of the battery 2 and the heat-conducting medium is adjusted by adjusting the width of the gap 201. In fluid mechanics, the Rayleigh number (Ra) of a fluid is a dimensionless number related to buoyancy-driven convection (also known as free convection or natural convection); when the Rayleigh number of a certain fluid is lower than the critical value, the main form of heat transfer is heat conduction; when the Rayleigh number exceeds the critical value, the main form of heat transfer is convection; and the Rayleigh number is proportional to the cross-sectional area of the fluid. Therefore, when the length and width of the housing 1 are determined, the denser the batteries 2 arranged in the housing 1, the smaller the cross-sectional area of the fluid, and the looser the batteries 2 arranged, the larger the cross-sectional area of the fluid. Furthermore, the Rayleigh number of the heat-conducting medium fluid can be changed by adjusting the width of the gap 201, that is, the temperature difference between the surface of the battery 2 and the heat-conducting medium is adjusted.

[0038] In Figure 2 a preferred embodiment shown, the calculation formula for the width of the gap 201 is

[0039] S = CL×(gβ△TL 3 / αv) 0.25 , (1)

[0040] where C is an empirical constant, usually determined by experiments, L is the height of the battery 2, g is the acceleration due to gravity, β is the thermal expansion coefficient of the heat-conducting medium, △T is the temperature difference between the surface of the battery 2 and the heat-conducting medium, α is the thermal diffusivity of the heat-conducting medium, and v is the viscosity of the immersion coolant.

[0041] The derivation process of the above calculation formula (1) is as follows:

[0042] First, assume: 1) The fluid is laminar: In natural convection, the Reynolds number is relatively low, and the flow is usually assumed to be laminar; 2) The thermal boundary layers do not overlap: The thermal boundary layers of adjacent fins should just touch but not overlap to balance the heat dissipation area and the flow resistance; 3) Thermal driving is dominant: Buoyancy (caused by temperature difference) is the main driving force for fluid flow;

[0043] Then, based on the above assumptions, the estimation of the thermal boundary layer thickness can be carried out. In natural convection on a vertical flat plate, the typical expression for the thermal boundary layer thickness δ is,

[0044] δ = L×Ra 0.25 , (2)

[0045] The boundary layer thickness decreases as the Rayleigh number increases because stronger buoyancy will accelerate the fluid flow and compress the boundary layer.

[0046] Again, the derivation of the optimal width of the gap 201 is carried out. Since the non - overlapping of the boundary layers is used as an assumption condition, the optimal spacing S should satisfy that the boundary layers of adjacent fins just touch, that is,

[0047] S = 2δ, (3)

[0048] Substitute Equation (2) into Equation (3) to obtain the following equation,

[0049] S = 2L×Ra 0.25 , (4)

[0050] Finally, by introducing an experimental correction coefficient, it is found through experiments and numerical simulations that the actual optimal spacing needs to correct the proportionality coefficient and drive the Rayleigh number calculation formula,

[0051] Ra = gβΔTL 3 / αv, (5)

[0052] Finally, Equation (1) is obtained, where the value of C is 2.714; therefore, the greater the temperature difference, the thinner the boundary layer, and denser fins are required. High - viscosity fluids have large flow resistance, and a larger spacing is required to avoid flow blockage.

[0053] In Figure 2 a preferred embodiment shown, the width of the gap 201 is not greater than 10 cm.

[0054] In Figure 3 a preferred embodiment shown, the gas pipeline 4 includes branch pipes 41 and a main pipe 42. A number of branch pipes 41 are arranged in each gap 201 in one - to - one correspondence. A number of air holes 401 are arranged on the branch pipes 41; one end of the main pipe 42 is connected to one end of a number of branch pipes 41 at the same time. One end of the main pipe 42 passes through the housing 1 and extends to the external environment. The outer end of the main pipe 42 is connected to the gas storage tank 6 through a bubble generating device 5.

[0055] InFigure 3 In a preferred embodiment shown, the pore diameter of the air holes 401 is 1 - 2 cm, and the distance between adjacent air holes 401 is 3 - 5 cm. The size and distance of the air holes 401 will have a certain impact on the damage effect of high-pressure gas on the thermal boundary.

[0056] In Figure 2 In a preferred embodiment shown, it further includes a liquid storage tank 8 and a delivery pump 9.

[0057] Among them, the liquid storage tank 8 is connected to the output end and the input end of the cooling pipe 3, and the liquid storage tank 8 stores cooling water or cooling oil.

[0058] The delivery pump 9 is connected between the liquid storage tank 8 and the input end of the cooling pipe 3, and the delivery pump 9 pumps cooling water to the heat exchange pipe. The delivery pump 7 is a water pump or an oil pump.

[0059] As Figure 1 shown, combined with Figure 2 , an energy storage battery pack adopts the above-mentioned immersion liquid cooling battery cooling device.

[0060] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An immersion liquid-cooled battery cooling device, characterized in that: It includes a housing (1), a cooling pipe (3), a gas transmission pipe (4), a bubble generating device (5) and a gas storage tank (6); A number of batteries (2) are arranged in the housing (1). The housing (1) is filled with a heat-conducting medium and submerges the batteries (2). An exhaust port (12) is provided at the top of the housing (1), and the exhaust port (12) discharges the air above the liquid level of the housing (1); The cooling pipe (3) is arranged in the housing (1) and located above the batteries (2). The cooling pipe (3) is submerged under the liquid level of the heat-conducting medium; The gas transmission pipe (4) is arranged in the housing (1) and located at the bottom of the batteries (2). Air holes (401) are arranged on the gas transmission pipe (4); Clean air is stored in the gas storage tank (6); The bubble generating device (5) is connected between the gas storage tank (6) and the gas transmission pipe (4). The bubble generating device (5) conveys high-pressure air flow to the heat-conducting medium from bottom to top through the air holes (401).

2. The battery cooling device with immersion liquid cooling according to claim 1, wherein: It also includes a gas-liquid separation device (7); A return port (11) is opened at a position on the side wall of the housing (1) close to the liquid level of the heat-conducting medium; The gas-liquid separation device (7) is connected between the gas storage tank (6) and the exhaust port (12). The gas-liquid separation device (7) is also connected to the return port (11). The gas-liquid separation device (7) collects the air discharged from the exhaust port (12). After gas-liquid separation of the air, the liquid phase is conveyed back into the housing (1) through the return port (11) and the gas phase is conveyed to the gas storage tank (6).

3. The battery cooling device with immersion liquid cooling according to claim 2, characterized in that: A gap (201) is left between a number of the batteries (2). A number of air holes (401) arranged on each gas transmission pipe (4) form a column, or a number of air holes (401) at corresponding positions on each gas transmission pipe (4) form a column. Each column of the air holes (401) is arranged to align with the gap (201).

4. The battery cooling device with immersion liquid cooling according to claim 3, characterized in that: The temperature difference between the surface of the battery (2) and the heat-conducting medium is adjusted by adjusting the width of the gap (201).

5. The battery cooling device with immersion liquid cooling according to claim 4, characterized in that: The calculation formula for the width of the gap (201) is S = CL×(gβ△TL 3 / αv) 0.25 , where C is an empirical constant, L is the height of the battery (2), g is the acceleration of gravity, β is the thermal expansion coefficient of the heat-conducting medium, △T is the temperature difference between the surface of the battery (2) and the heat-conducting medium, α is the thermal diffusivity of the heat-conducting medium, and v is the viscosity of the immersed coolant.

6. The battery cooling device with immersion liquid cooling according to claim 4, characterized in that: The width of the gap (201) is not greater than 10 cm.

7. The battery cooling device with immersion liquid cooling according to claim 3, characterized in that: The gas transmission pipe (4) includes a branch pipe (41) and a main pipe (42), A number of the branch pipes (41) are arranged in each gap (201) in one-to-one correspondence. A number of air holes (401) are arranged on the branch pipe (41); The main pipe (42) is connected to one end of a number of the branch pipes (41) at the same time. One end of the main pipe (42) extends through the housing (1) to the external environment. The outer end of the main pipe (42) is connected to the gas storage tank (6) through the bubble generating device (5).

8. An immersion liquid-cooled battery cooling device according to claim 1, characterized in that: The aperture of the air hole (401) is 1 - 2 cm, and the distance between adjacent air holes (401) is 3 - 5 cm.

9. The battery cooling device with immersion liquid cooling according to claim 1, characterized in that: It also includes a liquid storage tank (8) and a delivery pump (9); The liquid storage tank (8) is communicated with the output end and the input end of the cooling pipe (3), and cooling water is stored in the liquid storage tank (8); The delivery pump (9) is connected between the liquid storage tank (8) and the input end of the cooling pipe (3), and the delivery pump (9) pumps cooling water to the heat exchange pipe.

10. An energy storage battery pack, characterized in that: An immersion liquid cooling battery cooling device according to any one of claims 1 to 9 is adopted.

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