A phase change liquid cooling device for improving battery module consistency

Abstract

The present invention discloses a phase change liquid cooling device for improving the consistency of battery modules, including a porous battery rack, a temperature sensor, a flow guide assembly, an electromagnetic one-way valve, an immersion liquid cooling battery compartment and a pressure sensor. The present invention uses flow boiling technology to greatly improve the heat transfer performance of phase change liquid cooling, achieving a grouping efficiency of more than 90%. The present invention adopts gradient spacing to improve the temperature difference between groups caused by natural convection and heat accumulation effects in the design process of traditional battery modules, and reduces the maximum temperature difference of the battery module to below 2°C, with extremely high temperature consistency. The present invention can overcome the temperature difference of battery cells caused by the boundary layer effect and flow field structure of the working fluid during the immersion cooling design process through the introduction of porous battery racks and flow guide assemblies, thereby further improving temperature consistency.

Description

Technical Field

[0001] The invention relates to the field of battery temperature control, and in particular to a phase change liquid cooling device for improving the consistency of a battery module. Background Art

[0002] With the development of economy, the number of cars has increased rapidly, which has brought about energy shortage and environmental pollution. In order to alleviate this situation, it is of great significance to vigorously develop new energy vehicles. Pure electric vehicles have gradually become the first choice for purchasing new energy vehicles due to their advantages such as low pollution, high energy utilization efficiency, low noise and strong comfort.

[0003] As the power source of pure electric vehicles, the safety and life of lithium-ion battery packs have become important factors restricting the development of the industry. In terms of safety, a large number of vehicle spontaneous combustion incidents are caused by battery problems. This is because the overall temperature of the battery rises during operation, especially when charging and discharging at a high rate, a large amount of heat will be generated. If the heat is not discharged in time, it will cause thermal runaway, violent combustion or even explosion. Therefore, the battery thermal management system of electric vehicles has become an indispensable and important component.

[0004] Existing battery thermal management methods include air cooling, liquid cooling, and phase change material cooling, but facing the future high-power batteries, immersion flow boiling is one of the most promising thermal management technologies. Numerous studies have shown that compared with existing thermal management methods, the thermal conductivity of flow boiling is dozens of times that of traditional thermal management methods, and the temperature rise can be controlled below 5°C at a charge and discharge rate of 5C, which is much lower than the 20°C of air cooling.

[0005] In terms of service life, the energy density of electric vehicle power battery packs has shown an exponential growth trend in recent years, which has also led to a further increase in the number of internal power batteries. During the charging and discharging process of the power battery pack, due to the battery layout, boundary convection and heat accumulation effects, the discharge temperature of the power battery will inevitably be inconsistent, which will in turn cause differences in the charging and discharging internal resistance, voltage and capacity of the power battery. The increasing number of cells in the power battery pack will inevitably lead to the "barrel effect", that is, the cell with the lowest capacity limits the overall energy storage capacity of the battery module. The uneven local temperature during the discharge process of the battery pack will further cause some battery cells to be overcharged and over-discharged, and the end of the life of some batteries will cause a butterfly effect, which will in turn affect the service life of the battery pack connected in series.

[0006] Therefore, for future high-energy-density battery packs, developing a cooling device that efficiently controls temperature and improves the consistency of battery modules is crucial to increasing service life and ensuring safe use. Summary of the invention

[0007] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a phase change liquid cooling device that improves the consistency of battery modules.

[0008] The technical solution of the present invention to solve the technical problem is to provide a phase change liquid cooling device for improving the consistency of battery modules, characterized in that the liquid cooling device includes a porous battery rack, a temperature sensor, a flow guide component, an electromagnetic one-way valve, an immersion liquid cooling battery compartment and a pressure sensor;

[0009] The bottom of the immersion liquid-cooled battery compartment is provided with a plurality of battery slots, each of which contains a power battery; along the arrangement direction of the battery slots, from the side wall to the center of the immersion liquid-cooled battery compartment, the spacing between two adjacent battery slots increases gradually, the spacing between the inner side of the side wall of the immersion liquid-cooled battery compartment and the two outermost battery slots is the smallest, and the spacing between the two battery slots at the center is the largest;

[0010] A porous battery rack is provided at each battery slot; the porous battery rack is fixed on the bottom of the immersed liquid-cooled battery compartment; the porous battery rack is in close contact with the respective power batteries and supports the power batteries; the two ends of a plurality of flow guide components are respectively fixed between two adjacent porous battery racks or between the inner side of the side wall of the immersed liquid-cooled battery compartment and the two outermost porous battery racks, and are used to guide the flow of low-boiling-point working fluids; a temperature sensor is provided on each power battery, and is used to measure the temperature of each power battery; the immersed liquid-cooled battery compartment has a working fluid inlet and a working fluid outlet; an electromagnetic one-way valve and a pressure sensor are provided at the working fluid outlet, and the pressure sensor is used to measure the internal pressure of the immersed liquid-cooled battery compartment and to regulate the internal pressure of the immersed liquid-cooled battery compartment by opening and closing the electromagnetic one-way valve;

[0011] The guide assembly consists of three guide plates; the three guide plates are arranged in a vertical direction, and the two side walls of the three guide plates are respectively fixed between two adjacent porous battery racks or between the inner side of the side wall of the immersion liquid-cooled battery compartment and the two outermost porous battery racks; the setting of the three guide plates obeys a logarithmic distribution or a Fibonacci spiral distribution.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The present invention uses flow boiling technology to greatly improve the heat transfer performance of phase change liquid cooling. Compared with the traditional temperature control method, the present invention can meet the temperature control requirements of high charge and discharge rates on the track. And it can use less working fluid to control the temperature of electric vehicles under all working conditions, thereby achieving a group efficiency of more than 90%.

[0014] (2) The present invention adopts gradient spacing to improve the temperature difference between groups caused by natural convection and heat accumulation effect in the design process of traditional battery modules. Theoretical analysis and experiments have proved that the introduction of gradient spacing can regulate the boiling state between each power battery, so that the heat removed by flow boiling and the heat removed by heat conduction combined with flow boiling are equivalent, which significantly reduces the temperature difference between groups and reduces the maximum temperature difference of the battery module to below 2°C, with extremely high temperature consistency. In addition, the gradient spacing designed by the present invention is suitable for any connection mode of power batteries in series, parallel or series-parallel hybrid.

[0015] (3) The present invention can overcome the temperature difference of battery cells caused by the boundary layer effect and flow field structure of the working fluid during the immersion cooling design process by introducing a porous battery rack and a flow guide component. Theoretical analysis and experiments have shown that the flow guide component with logarithmic curve and Fibonacci spiral distribution can improve the flow field distribution of immersion liquid cooling, and cooperate with the porous battery rack to reduce the contact thermal resistance while increasing enough nucleation sites, thereby achieving enhanced boiling heat transfer of low-boiling-point working fluids and further improving temperature consistency.

[0016] (4) The overall design of the immersed liquid-cooled battery compartment of the present invention enables the various components in the compartment to be in close contact and support each other, thereby enhancing the structural rigidity and stability and reducing the contact thermal resistance.

[0017] (5) The electromagnetic one-way valve and the pressure sensor work together to reasonably adjust the pressure distribution in the bin, use the pressure difference in the phase change process to achieve self-driving of the working fluid, and reduce the energy consumption caused by pump intervention.

[0018] (6) The liquid cooling method of the present invention can realize the autonomous circulation of low-boiling-point working fluid in the system through the pressure difference generated by the gas-liquid phase change of the low-boiling-point working fluid under low-speed and low-power discharge conditions, without the need for a circulation pump to provide power. Under high-speed and high-power discharge conditions, the circulation pump can be used to provide auxiliary power to achieve energy-saving effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the overall structure of an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the overall structure of another embodiment of the present invention is shown in front;

[0021] Figure 3 A three-dimensional diagram of an immersion liquid-cooled battery compartment of the present invention;

[0022] Figure 4 It is an installation diagram of the power battery, the porous battery rack and the flow guide assembly of the present invention;

[0023] Figure 5 This is a flow chart of the phase change liquid cooling method for the power battery of the present invention;

[0024] Figure 6 is a structural block diagram of the thermal management system of the present invention;

[0025] Figure 7 This is a curve diagram showing the maximum temperature difference of 12 power batteries with different gradient spacings versus test time in Example 1 of the present invention;

[0026] Figure 8 The temperature distribution curves of 12 power batteries with different gradient spacings in Example 1 of the present invention when the test time is 40s and 116s;

[0027] Fig. 9 This is a curve diagram showing the average temperature rise of 12 power batteries at different grouping efficiencies versus test time in Example 1 of the present invention;

[0028] Fig.10 This is a graph showing the maximum temperature difference of 12 power batteries at different grouping efficiencies versus test time in Example 1 of the present invention.

[0029] In the figure, there are power battery 101, porous battery rack 102, temperature sensor 103, flow guide assembly 104, electromagnetic one-way valve 105, battery slot 106, immersed liquid-cooled battery compartment 107, pole ear 108, pole ear connecting piece 109, working fluid inlet 110, working fluid outlet 111, circulating pump 112, liquid storage tank 113, one-way valve 114, pressure sensor 115, and condenser 116. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the claims of the present invention.

[0031] The present invention provides a phase change liquid cooling device (hereinafter referred to as liquid cooling device) for improving the consistency of battery modules, characterized in that the liquid cooling device includes a porous battery rack 102, a temperature sensor 103, a flow guide component 104, an electromagnetic one-way valve 105, an immersion liquid cooling battery compartment 107 and a pressure sensor 115;

[0032] The bottom of the immersed liquid-cooled battery compartment 107 is provided with a plurality of (preferably, at least three) battery slots 106, and the battery slots 106 are used to place the power battery 101, and one power battery 101 is placed in each battery slot 106; the battery slot 106 is the main temperature-averaging component for improving the heat accumulation of the battery module and the natural convection temperature difference of the shell; along the arrangement direction of the battery slots 106, from the side wall to the center position of the immersed liquid-cooled battery compartment 107, the spacing between two adjacent battery slots 106 increases gradually, the spacing between the inner side of the side wall of the immersed liquid-cooled battery compartment 107 and the two outermost battery slots 106 (i.e., the first battery slot 106 or the last battery slot 106) is the smallest, and the spacing between the two battery slots 106 at the center position is the largest;

[0033] A porous battery rack 102 is provided at each battery slot 106; the porous battery rack 102 is fixed on the bottom of the immersion liquid-cooled battery compartment 107, and the inner wall is flush with the slot wall of the battery slot 106; each porous battery rack 102 is equipped with a power battery 101, and is in close contact with and supports the respective power battery 101; the two ends of a plurality of flow guide components 104 are respectively fixed between two adjacent porous battery racks 102 or on the inner side of the side wall of the immersion liquid-cooled battery compartment 107 and the outermost two porous battery racks 102 (i.e., the first porous battery rack 102 or the last porous battery rack 102), which is used to guide the flow of low-boiling-point working fluid; each power battery 101 is provided with a temperature sensor 103, which is used to measure the temperature of each power battery 101; the immersed liquid-cooled battery compartment 107 has a working fluid inlet 110 and a working fluid outlet 111; an electromagnetic one-way valve 105 and a pressure sensor 115 are provided at the working fluid outlet 111, and the pressure sensor 115 is used to measure the internal pressure of the immersed liquid-cooled battery compartment 107 and regulate the internal pressure of the immersed liquid-cooled battery compartment 107 by opening and closing the electromagnetic one-way valve 105.

[0034] Preferably, with the center position as the axis of symmetry, the spacing between the battery slots 106 at the same position on the left and right sides is equal.

[0035] Preferably, the spacing is calculated by the formula f(x)=kx+b, where f(x) is the spacing value of the xth spacing, k is the gradient, k is 6%~45%, b=(length of the immersion liquid-cooled battery compartment 107 along the arrangement direction of the battery slot 106 - the number of power batteries 101 * the thickness of the power battery 101) / 2, so as to gradually increase from the minimum spacing to the maximum spacing with a gradient of 6%~45%, and the spacing is distributed in an arithmetic progression. In this embodiment, the minimum spacing is 1~6mm, which can meet the temperature control requirements of high-load discharge.

[0036] Preferably, the number of battery slots 106 is n, and the number of guide components 104 is n+1; when n is an odd number, the two battery slots 106 at the center position are the n-1 / 2th battery slot and the n+1 / 2th battery slot, or the n+1 / 2th battery slot and the n+3 / 2th battery slot; when n is an even number, the two battery slots 106 at the center position are the n / 2th battery slot and the n+2 / 2th battery slot.

[0037] Preferably, the porous battery rack 102 serves as the main component and main nucleation site for fixing the power battery 101, and has a strong pre-tightening force; it has a porous structure, which increases the nucleation sites for boiling and enhances boiling heat exchange; it is made of foam metal with high thermal conductivity, has high structural strength and a PPI (pore density) higher than 2000; and the wall thickness is less than 0.5 mm.

[0038] Preferably, the guide assembly 104 is a main component for improving the temperature difference of the power battery 101, and is composed of three guide plates; the three guide plates are arranged in the vertical direction, and the two side walls of the three guide plates are respectively fixed between two adjacent porous battery racks 102 or between the inner side of the side wall of the immersion liquid-cooled battery compartment 107 and the two outermost porous battery racks 102; the arrangement of the three guide plates obeys logarithmic distribution or Fibonacci spiral distribution;

[0039] When the arrangement of the three guide plates obeys logarithmic distribution, a logarithmic curve with a base a is drawn with the vertical wall of the immersed liquid-cooled battery compartment 107 with the working fluid inlet 110 as the x-axis and the upper surface of the bottom of the immersed liquid-cooled battery compartment 107 as the y-axis. The coordinate points corresponding to the three points x=1 / 3a, 2 / 3a and a are taken on the logarithmic curve respectively. Then, one guide plate is installed according to the line segment formed by the coordinate point corresponding to x=1 / 3a and the midpoint of the vertical side of the porous battery rack 102, one guide plate is installed according to the line segment formed by the coordinate point corresponding to x=2 / 3a and the diagonal point of the side of the porous battery rack 102, and one guide plate is installed according to the line segment formed by the coordinate point corresponding to x=a and the midpoint of the top edge of the side of the porous battery rack 102;

[0040] When the arrangement of the three guide plates obeys the Fibonacci spiral distribution, a Fibonacci spiral is drawn with the vertical wall of the immersed liquid-cooled battery compartment 107 with the working fluid inlet 110 as the x-axis and the upper surface of the bottom of the immersed liquid-cooled battery compartment 107 as the y-axis. The coordinate points corresponding to the three points x=F3.5, F3 and F2.5 are taken on the Fibonacci spiral respectively, and then a guide plate is installed according to the line segment formed by the coordinate point corresponding to x=F3.5 and the midpoint of the vertical edge of the side of the porous battery rack 102, a guide plate is installed according to the line segment formed by the coordinate point corresponding to x=F3 and the diagonal point of the side of the porous battery rack 102, and a guide plate is installed according to the line segment formed by the coordinate point corresponding to x=F2.5 and the midpoint of the top edge of the side of the porous battery rack 102.

[0041] Preferably, the working medium outlet 111 is a tapered outlet, so that the flow field around each power battery 101 in the immersion liquid-cooled battery compartment 107 tends to be consistent.

[0042] Preferably, the main body of the immersion liquid-cooled battery compartment 107 is made of aluminum alloy, and is divided into a top cover and a compartment body. During assembly and maintenance, the top cover is opened, and the power battery 101 is inserted into the porous battery rack 102 with pre-tightening force, and the two are in close contact; after assembly and maintenance, the top cover and the compartment body are fixed by a corrosion-resistant fluororubber sealing ring and bolts.

[0043] Preferably, the wall of the battery slot 106 is coated with an insulating coating to achieve insulation of the contact surface between the power battery 101 and the immersed liquid-cooled battery compartment 107 .

[0044] Preferably, the low boiling point working fluid is an insulating, highly stable, flash-free working fluid, preferably R141b (monofluorodichloroethane).

[0045] Preferably, the tabs 108 and tab connecting pieces 109 of the power battery 101 face the working medium inlet 110 of the immersed liquid-cooled battery compartment 107. Such an arrangement is conducive to cooling the tabs 108 with higher heat generation and various components connected to the tabs, and is conducive to reducing the temperature difference inside the single battery.

[0046] Preferably, the electromagnetic one-way valve 105 is installed at the working fluid outlet 111 through a fluororubber sealing ring and a self-clamping collar.

[0047] The present invention also provides an immersion flow boiling thermal management system (hereinafter referred to as thermal management system) of the device, characterized in that the thermal management system includes a circulation pump 112, a liquid storage tank 113, a one-way valve 114, a controller and a condenser 116;

[0048] The liquid storage tank 113 stores a liquid low-boiling-point working medium; the working medium inlet 110 of the immersed liquid-cooled battery compartment 107 is connected to the outlet of the liquid storage tank 113 through a pipeline, and a one-way valve 114 is provided on the pipeline; the one-way valve 114 ensures that the low-boiling-point working medium can only flow from the liquid storage tank 113 to the immersed liquid-cooled battery compartment 107, but cannot flow from the immersed liquid-cooled battery compartment 107 to the liquid storage tank 113; the working medium outlet 111 of the immersed liquid-cooled battery compartment 107 is connected to the inlet of the condenser 116 through a pipeline; the function of the condenser 116 is to condense the vaporized low-boiling-point working medium vapor into a liquid state; the outlet of the condenser 116 is connected to the inlet of the liquid storage tank 113 through a pipeline; a circulating pump 112 is provided in the entire circulation pipeline as a power source for the flow of the low-boiling-point working medium (in this embodiment, the outlet of the condenser 116 is connected to the inlet of the liquid storage tank 113 through a pipeline, and a circulating pump 112 is provided on the pipeline);

[0049] The controller is communicatively connected with the circulation pump 112 , the temperature sensor 103 , the electromagnetic one-way valve 105 and the pressure sensor 115 , respectively.

[0050] The present invention also provides a phase change liquid cooling method for a power battery based on the thermal management system (hereinafter referred to as the method), characterized in that the method is specifically as follows:

[0051] The battery module is started. When the controller detects that the temperatures measured by all temperature sensors 103 are less than 40°C, the low-boiling-point working medium enters the self-driving mode. In the self-driving mode, the controller controls the circulation pump 112 and the electromagnetic one-way valve 105 to be closed, and the immersed liquid-cooled battery compartment 107 is in a closed state. The low-boiling-point working medium in the immersed liquid-cooled battery compartment 107 absorbs heat rapidly and undergoes a gas-liquid phase change under the action of the porous battery rack 102. The continuous increase in the gas phase causes the internal pressure of the immersed liquid-cooled battery compartment 107 to continue to increase. Until the controller detects that the pressure measured by the pressure sensor 115 reaches the pressure difference required to overcome the resistance along the way, the controller controls the electromagnetic one-way valve 105 to open, and the low-boiling-point working medium in a gas-liquid two-phase coexistence state. Driven by the pressure difference, it flows out from the working medium outlet 111, flows through the condenser 116 and changes into the liquid phase. The liquid low-boiling-point working medium flows through the liquid storage tank 113 and pushes the liquid low-boiling-point working medium in the liquid storage tank 113 to flow, passes through the one-way valve 114, and enters the immersed liquid-cooled battery compartment 107 from the working medium inlet 110. Then, under the action of the battery slot 106 with a gradient spacing, the flow is redistributed, and then guided by the guide component 104 until the power battery 101 is immersed in the low-boiling-point working medium. Under the action of the porous battery rack 102 to enhance the boiling heat exchange, the heat generated by the power battery 101 is taken away. When the internal pressure of the immersed liquid-cooled battery compartment 107 is in a stable state, the controller controls the electromagnetic one-way valve 105 to close, completing a cooling cycle.

[0052] When the controller detects that the highest value of the temperature measured by all temperature sensors 103 is greater than 40°C, the low-boiling-point working medium enters the forced convection mode; in the forced convection mode, the controller controls the circulation pump 112 and the electromagnetic one-way valve 105 to be opened. Driven by the circulation pump 112, the low-boiling-point working medium flows out of the liquid storage tank 113, passes through the one-way valve 114, and enters the immersion liquid-cooled battery compartment 107 from the working medium inlet 110; then, the flow is redistributed under the action of the battery slot 106 with a gradient spacing. After being matched, it is guided by the guide component 104 until the power battery 101 is immersed in the low-boiling-point working fluid. The heat generated by the power battery 101 is taken away by the porous battery rack 102 under the action of enhanced boiling heat exchange, and then flows out from the working fluid outlet 111 to complete a cooling cycle; in the forced convection mode, when the controller monitors that the temperatures measured by all temperature sensors 103 have dropped to 20-30°C, the controller controls the circulation pump 112 and the electromagnetic one-way valve 105 to be closed, and the low-boiling-point working fluid enters the self-driving mode.

[0053] Example 1

[0054] like Figure 1 As shown, in this embodiment, n=12 power batteries 101 are used, and the tabs 108 and tab connectors 109 of the power batteries 101 face upward (i.e., located at the top); the length of the immersion liquid-cooled battery compartment 107 is 400mm, and the thickness of the power battery 101 is 27mm; in this embodiment, the gradients of k=0%, 6%, 45%, 81%, and 110% are used to gradually increase the spacing, for example, the minimum spacing corresponding to the 6% gradient is f(1)=0.06*1+5.62=5.68mm. In this embodiment, the low-boiling-point working fluid uses R141b, the saturation temperature at normal pressure is 32.1°C, the inlet working fluid is in a supercooled state, and the flow rate is 0.01m / s. The flow rate used in the present invention is a relatively suitable flow rate for battery thermal flow temperature control.

[0055] Depend on Figure 7 It can be seen that under different gradient spacing conditions, the temperature difference of each battery first increases, then decreases, and then gradually tends to be stable, and the corresponding flow state gradually transitions from supercooled convection to flow boiling.

[0056] Depend on Figure 8 It can be seen that the temperature distribution of the batteries between the groups in the convection and boiling ranges without using the gradient spacing shows that the temperature of the middle battery is higher than that of the two sides. However, as the spacing gradient gradually increases, the temperature distribution of both the convection area and the boiling area gradually tends to be consistent and then changes to a state where the temperature is low in the middle and high on both sides. Therefore, the spacing gradient of k in the range of 6% to 45% described in the present invention can make the battery module have better temperature consistency.

[0057] This embodiment tests the change of the heat transfer characteristics of the battery module over time at grouping efficiencies of 73%, 80%, 84%, 98% and 95%, respectively. The grouping efficiency calculation formula is the volume of the immersed liquid-cooled battery compartment 107 divided by the volume of the power battery 101.

[0058] Depend on Fig. 9 It can be seen that as the group efficiency gradually increases, the temperature rise of the internal batteries remains basically consistent as the liquid cooling device transitions from supercooling convection to boiling state.

[0059] Depend on Fig.10 It can be seen that with the improvement of grouping efficiency, the working fluid is more likely to reach a boiling state, and the maximum temperature difference between groups is maintained within 0.8 K. Therefore, the gradient spacing and grouping efficiency of the liquid cooling device of the present invention can effectively improve the consistency of the battery module.

[0060] The above characteristics are tested based on the discharge data of high-performance electric racing tracks. Its temperature control performance and battery consistency can meet the needs of home electric vehicles.

[0061] Example 2

[0062] like Figure 2 As shown, in this embodiment, the pole ear 108 and the pole ear connecting piece 109 of the power battery 101 are directly opposite to the working medium inlet 110 of the immersion liquid-cooled battery compartment 107. Such an arrangement is conducive to cooling the pole ear 108 with higher heat generation and various components connected to the pole ear, and is conducive to reducing the temperature difference inside the single battery.

[0063] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A phase change liquid cooling device for improving the consistency of battery modules, characterized in that: The liquid cooling device comprises a porous battery rack (102), a temperature sensor (103), a flow guide component (104), an electromagnetic one-way valve (105), an immersion liquid cooling battery compartment (107) and a pressure sensor (115); A plurality of battery slots (106) are provided at the bottom of the immersed liquid-cooled battery compartment (107), and a power battery (101) is placed in each battery slot (106); along the arrangement direction of the battery slots (106), from the side wall to the center of the immersed liquid-cooled battery compartment (107), the spacing gradient between two adjacent battery slots (106) increases, the spacing between the inner side of the side wall of the immersed liquid-cooled battery compartment (107) and the two outermost battery slots (106) is the smallest, and the spacing between the two battery slots (106) at the center is the largest; the spacing is calculated by the formula f(x)=kx+b, wherein f(x) is the spacing value of the xth spacing, k is the gradient, k is 6%~45%, and b=(length of the immersed liquid-cooled battery compartment-number of power batteries*thickness of the power batteries) / 2; A porous battery rack (102) is provided at each battery slot (106); the porous battery rack (102) is fixed on the bottom of the immersed liquid-cooled battery compartment (107); the porous battery rack (102) is in close contact with the respective power battery (101) and supports the power battery (101); two ends of a plurality of flow guide components (104) are respectively fixed between two adjacent porous battery racks (102) or between the inner side of the side wall of the immersed liquid-cooled battery compartment (107) and the outermost two porous battery racks (102), and are used to guide the flow of the low-boiling-point working medium. each power battery (101) is provided with a temperature sensor (103) for measuring the temperature of each power battery (101); the immersed liquid-cooled battery compartment (107) has a working fluid inlet (110) and a working fluid outlet (111); an electromagnetic one-way valve (105) and a pressure sensor (115) are provided at the working fluid outlet (111); the pressure sensor (115) is used to measure the internal pressure of the immersed liquid-cooled battery compartment (107) and to regulate the internal pressure of the immersed liquid-cooled battery compartment (107) by opening and closing the electromagnetic one-way valve (105); The flow guide assembly (104) is composed of three flow guide plates; the three flow guide plates are arranged in a vertical direction, and the two side walls of the three flow guide plates are respectively fixed between two adjacent porous battery racks (102) or between the inner side of the side wall of the immersion liquid cooling battery compartment (107) and the two outermost porous battery racks (102); the arrangement of the three flow guide plates obeys a logarithmic distribution or a Fibonacci spiral distribution.

2. The phase change liquid cooling device for improving the consistency of battery modules according to claim 1, characterized in that: With the center position as the axis of symmetry, the spacing between the battery slots (106) at the same position on the left and right sides is equal.

3. The phase change liquid cooling device for improving the consistency of battery modules according to claim 1, characterized in that: When the number of battery slots (106) is n, the number of flow guide components (104) is n+1; when n is an odd number, the two battery slots (106) at the center are the n-1 / 2th battery slot and the n+1 / 2th battery slot, or the n+1 / 2th battery slot and the n+3 / 2th battery slot; when n is an even number, the two battery slots (106) at the center are the n / 2th battery slot and the n+2 / 2th battery slot.

4. The phase change liquid cooling device for improving the consistency of battery modules according to claim 1, characterized in that: The porous battery frame (102) is made of foam metal with high thermal conductivity and a PPI higher than 2000; the wall thickness of the porous battery frame (102) is less than 0.5 mm; and the wall of the battery slot (106) is coated with an insulating coating.

5. The phase change liquid cooling device for improving the consistency of battery modules according to claim 1, characterized in that: When the arrangement of the three guide plates obeys a logarithmic distribution, a logarithmic curve with a base a is drawn with the vertical wall of the immersed liquid-cooled battery compartment (107) having the working fluid inlet (110) as the x-axis and the upper surface of the bottom surface of the immersed liquid-cooled battery compartment (107) as the y-axis. Coordinate points corresponding to the three points x=1 / 3a, 2 / 3a and a are taken on the logarithmic curve respectively. Then, one guide plate is installed along the line segment formed by the coordinate point corresponding to x=1 / 3a and the midpoint of the vertical edge of the side of the porous battery rack (102), one guide plate is installed along the line segment formed by the coordinate point corresponding to x=2 / 3a and the diagonal point of the side of the porous battery rack (102), and one guide plate is installed along the line segment formed by the coordinate point corresponding to x=a and the midpoint of the top edge of the side of the porous battery rack (102).

6. The phase change liquid cooling device for improving the consistency of battery modules according to claim 1, characterized in that: The working fluid outlet (111) is a tapered outlet, so that the flow field around each power battery (101) in the submerged liquid-cooled battery compartment (107) tends to be consistent.

7. An immersed flow boiling thermal management system according to any one of claims 1 to 6, characterized in that: The thermal management system comprises a circulation pump (112), a liquid storage tank (113), a one-way valve (114), a controller and a condenser (116); A liquid low-boiling-point working medium is stored in the liquid storage tank (113); the working medium inlet (110) of the immersed liquid-cooled battery compartment (107) is connected to the outlet of the liquid storage tank (113) through a pipeline, and a one-way valve (114) is provided on the pipeline; the one-way valve (114) ensures that the low-boiling-point working medium can only flow from the liquid storage tank (113) to the immersed liquid-cooled battery compartment (107); the working medium outlet (111) of the immersed liquid-cooled battery compartment (107) is connected to the inlet of a condenser (116) through a pipeline; the function of the condenser (116) is to condense the vaporized low-boiling-point working medium vapor into a liquid state; the outlet of the condenser (116) is connected to the inlet of the liquid storage tank (113) through a pipeline; and a circulating pump (112) is provided in the entire circulating pipeline; The controller is communicatively connected to the circulation pump (112), the temperature sensor (103), the electromagnetic one-way valve (105) and the pressure sensor (115) respectively.

8. A phase change liquid cooling method for a power battery based on the thermal management system according to claim 7, characterized in that: The method is as follows: When the controller detects that the temperatures measured by all temperature sensors (103) are less than 40°C, the low-boiling-point working fluid enters the self-driving mode; in the self-driving mode, the controller controls the circulation pump (112) and the electromagnetic one-way valve (105) to be closed, and the immersed liquid-cooled battery compartment (107) is in a closed state; the low-boiling-point working fluid in the immersed liquid-cooled battery compartment (107) rapidly absorbs heat and undergoes a gas-liquid phase transition under the action of the porous battery rack (102), and the continuous increase of the gas phase causes the internal pressure of the immersed liquid-cooled battery compartment (107) to continuously increase, until the controller detects that the pressure measured by the pressure sensor (115) reaches the pressure difference required to overcome the resistance along the way, the controller controls the electromagnetic one-way valve (105) to open, and the low-boiling-point working fluid in the gas-liquid two-phase coexistence state is driven by the pressure difference. The liquid low-boiling-point working medium flows out from the working medium outlet (111) under the action of the fluid flow, flows through the condenser (116) and changes into a liquid phase, the liquid low-boiling-point working medium flows through the liquid storage tank (113) and pushes the liquid low-boiling-point working medium in the liquid storage tank (113) to flow, passes through the one-way valve (114) and enters the immersed liquid-cooled battery compartment (107) from the working medium inlet (110), and then, after the flow is redistributed under the action of the battery slot (106), it is guided through the flow guide component (104) until the power battery (101) is immersed in the low-boiling-point working medium, and the heat generated by the power battery (101) is taken away under the action of the enhanced boiling heat exchange of the porous battery rack (102), until the internal pressure of the immersed liquid-cooled battery compartment (107) is in a stable state, and the controller controls the electromagnetic one-way valve (105) to close, completing a cooling cycle; When the controller detects that the highest temperature measured by all temperature sensors (103) is greater than 40°C, the low-boiling-point working medium enters a forced convection mode. In the forced convection mode, the controller controls the circulation pump (112) and the electromagnetic one-way valve (105) to be opened. Driven by the circulation pump (112), the low-boiling-point working medium flows out of the liquid storage tank 113, passes through the one-way valve (114), and enters the immersed liquid-cooled battery compartment (107) from the working medium inlet (110). Then, the flow is redistributed under the action of the battery compartment (106), and then the low-boiling-point working medium flows into the submerged liquid-cooled battery compartment (107). The flow guide component (104) guides the flow until the power battery (101) is immersed in the low-boiling-point working medium, and the heat generated by the power battery (101) is taken away under the effect of enhanced boiling heat exchange by the porous battery rack (102), and then flows out from the working medium outlet (111), completing a cooling cycle; in the forced convection mode, when the controller detects that the temperatures measured by all temperature sensors (103) have dropped to 20-30° C., the controller controls the circulation pump (112) and the electromagnetic one-way valve (105) to be closed, and the low-boiling-point working medium enters the self-driving mode.

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