Self-circulation immersed battery cooling system coupled with direct cooling pipe and operation method of self-circulation immersed battery cooling system

Abstract

The invention discloses a self-circulation immersed battery cooling system coupled with a direct cooling pipe and an operation method, and belongs to the technical field of battery thermal management. The system comprises a battery immersion module and a distributed direct cooling pipe module. Each distributed direct cooling pipe module comprises an upper group of pipelines and a lower group of pipelines which are spatially separated, the upper group of pipelines are positioned above the battery modules and are arranged in a staggered snake-shaped manner, and the lower group of pipelines are positioned in gaps of the battery modules and are arranged in a parallel snake-shaped manner. Refrigerant in the direct cooling pipe exchanges heat with the immersion liquid through phase change, a temperature gradient is formed in the battery pack through upper and lower pipeline layout, and the immersion liquid is driven to generate natural convection. The operation method is based on segmented control of the highest temperature of the battery, and the refrigerant is controlled to circulate only in the lower group of pipelines, only in the upper group of pipelines or simultaneously in the upper and lower pipelines according to the temperature interval, so that three natural convection modes of microcirculation, heat sink driving and self-circulation are respectively formed. The device does not need an external power source, realizes efficient and uniform heat dissipation of the battery, and has the advantages of compact structure and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of battery thermal management technology, specifically relating to a self-circulating immersion battery cooling system with coupled direct cooling pipes and its operation method. Background Technology

[0002] With the rapid development of large-scale energy storage technology, the energy density and power density of battery packs are constantly increasing, and the resulting thermal management problems are becoming increasingly serious. Large-capacity battery packs generate a lot of heat during high-rate charging and discharging. If timely and uniform heat dissipation cannot be achieved, it will easily lead to excessively high local temperatures or excessive overall temperature differences in the battery pack, which will seriously affect its electrochemical performance, cycle life and safety of use, and may even cause extreme safety accidents such as thermal runaway.

[0003] Among existing battery thermal management technologies, liquid cooling has become one of the mainstream methods due to its high-efficiency heat exchange capability. Among them, immersion cooling technology, as a cutting-edge approach, achieves full contact between the cooling medium and the cell surface by directly immersing the battery cell in the cooling medium. This results in significant advantages such as large heat exchange area and good temperature uniformity, and is considered to have great potential in addressing the thermal management challenges of high-energy-density batteries.

[0004] However, immersion cooling technology still faces key bottlenecks in practical applications. For immersion cooling structures using forced convection, although their heat dissipation efficiency is high, the need for pumps, pipes, and interfaces introduces a high risk of seal failure and immersion liquid leakage, severely impacting system reliability and lifespan. On the other hand, while fully enclosed static immersion cooling effectively avoids leakage, the lack of external driving force and an effective heat exchange circulation mechanism makes it difficult to continuously remove heat during prolonged, multi-cycle high-load charging and discharging, leading to heat accumulation and failing to meet the thermal management requirements of actual operation. Therefore, resolving the contradiction between leakage and continuous heat dissipation during long-term operation while maintaining the excellent temperature uniformity of immersion cooling has become a core issue that urgently needs to be addressed for this technology to achieve large-scale engineering applications.

[0005] To address the aforementioned issues, current methods for large-capacity battery thermal management often employ multi-mode coupling, such as "phase change material + liquid cooling," "heat pipe + immersion cooling," and "microchannel + immersion cooling," to achieve optimal matching of time, space, and function in battery thermal management. In addition, researchers have explored coupling direct cooling plates with immersion cooling to improve overall battery thermal management efficiency. For example, patent CN120300361A discloses an innovative battery thermal management solution that couples immersion cooling with direct cooling pipes. Its core lies in eliminating the external circulation loop of the immersion liquid, instead directly embedding and immersing the direct cooling pipes within the battery module's immersion liquid. This allows for direct heat exchange with the cooling medium, supplemented by a built-in micro-pump that activates under high-temperature, high-rate conditions to enhance fluid flow. This significantly simplifies the system structure, reduces cycle energy consumption, and fundamentally eliminates the leakage risk of traditional immersion cooling, while also providing excellent heat dissipation and temperature uniformity. However, this highly integrated design also presents challenges in terms of maintainability, and the long-term reliability of the system depends heavily on the durability of key components such as the built-in micro-pump. The complexity of the manufacturing process and the initial cost are also factors that need to be considered in practical applications.

[0006] Meanwhile, patent CN119695336A proposes a "sidewall cooling + static full immersion" energy storage thermal management solution. This solution combines a side-cooling plate with integrated complex flow channels, placed close to the heat-generating area of ​​the battery module, with static insulating immersion fluid within the casing, creating a system that combines efficient heat exchange with ultimate safety. Its advantages lie in achieving precise and efficient heat dissipation from the battery's heat-generating center using the side-cooling plate, while the fully immersed insulating fluid ensures excellent temperature uniformity, fundamentally eliminating the risk of thermal runaway and fire spread. The static design of the system also improves reliability and simplifies maintenance. However, this solution also faces significant challenges: the integrated side-cooling plate's internal flow channels are complex and costly to manufacture, and once internal blockage or leakage occurs, it is almost impossible to repair, requiring complete replacement; furthermore, direct contact with the battery side can lead to uneven cooling, affecting performance and lifespan, necessitating precise battery thermal management strategies. Both of these solutions suffer from complex system structures, high maintenance costs, and complex processes, making them unsuitable for long-term charging and discharging of large battery modules. Summary of the Invention

[0007] To address the above problems, this invention provides a self-circulating immersion battery cooling system with coupled direct cooling pipes, used to achieve heat transfer between the direct cooling pipes and the battery immersion fluid. By rationally arranging the direct cooling pipes and controlling their internal fluid flow rate, efficient natural convection of the immersion fluid is promoted within the battery pack, thereby improving overall heat dissipation performance. This system has the advantages of compact structure, high integration, low energy consumption, and high cooling efficiency. Its technical solution is as follows:

[0008] A self-circulating immersion battery cooling system with coupled direct cooling pipes, characterized in that it comprises:

[0009] A battery immersion module includes a module housing, a battery module disposed within the module housing, and an insulating immersion liquid filled within the module housing and completely immersing the battery module; the insulating immersion liquid is transformer oil, mineral oil, or synthetic ester, with a thermal conductivity of not less than 0.1 W / m·K and a viscosity of not more than 50 cSt.

[0010] A distributed direct cooling pipe module includes two sets of serpentine direct cooling pipes disposed inside the module housing and immersed in the immersion liquid; refrigerant flows inside the direct cooling pipes, and the refrigerant exchanges heat with the immersion liquid through a gas-liquid phase change.

[0011] The two sets of serpentine direct cooling pipes are arranged separately in space, including an upper set of pipes and a lower set of pipes: the upper set of pipes is arranged in the area above the battery module, and the lower set of pipes is interspersed in the gap area between the battery modules.

[0012] The spatial distribution of the upper and lower sets of pipes is configured to create a temperature gradient inside the battery immersion module, thereby promoting the overall natural convection of the insulating immersion liquid.

[0013] By controlling the flow and cut-off of refrigerant in the upper and lower pipelines, three different immersion liquid circulation modes can be formed inside the battery immersion module.

[0014] Preferably, the upper group of pipes includes two serpentine direct cooling pipes arranged in an alternating manner, and the lower group of pipes includes two serpentine direct cooling pipes arranged in a parallel manner.

[0015] Preferably, the diameter of the direct cooling pipe in the upper group of pipes is larger than the diameter of the direct cooling pipe in the lower group of pipes; the larger diameter of the upper group of pipes enhances the top cooling capacity; the smaller diameter of the lower group of pipes accommodates the battery gap space and optimizes flow.

[0016] Preferably, the battery module includes multiple rows of battery cells, and the direct cooling pipe in the lower group pipeline passes through the gaps on both sides of the battery module and passes through the central area of ​​the battery module.

[0017] Preferably, the battery immersion module further includes end plates disposed at both ends of the battery cell array, a support plate disposed at the bottom of the battery cell array, and a heat insulation pad disposed between the parallel-arranged battery cells.

[0018] Preferably, it further includes a direct cooling unit, which is connected to the distributed direct cooling pipe module through an inlet pipe and an outlet pipe to form a closed refrigerant circulation loop; the direct cooling unit includes a compressor, a condenser, and a throttling valve; the inlet pipe is connected to the inlet manifold of the direct cooling pipe, and the outlet pipe is connected to the outlet manifold of the direct cooling pipe; after the refrigerant evaporates and absorbs heat in the direct cooling pipe, it returns to the direct cooling unit for condensation and recirculation.

[0019] The present invention also discloses a control method for the above-mentioned battery immersion cooling system, characterized by comprising the following steps:

[0020] Monitor the highest temperature of the battery pack;

[0021] Based on the preset temperature range where the highest temperature is located, the operating mode of the direct cooling unit and the flow state of the refrigerant in the upper and / or lower piping are controlled.

[0022] Preferably, the step of controlling the operating mode of the direct-cooling unit based on the highest temperature includes:

[0023] When the maximum temperature is lower than the first set temperature T1, the direct cooling unit is controlled not to operate;

[0024] When the highest temperature is between the first set temperature T1 and the second set temperature T2, the direct cooling unit is partially operated so that the refrigerant only flows in the lower group of pipes, forming a micro-circulation immersion liquid natural convection mode.

[0025] When the highest temperature is between the second set temperature T2 and the third set temperature T3, the direct cooling unit is partially operated to allow the refrigerant to flow only in the upper pipeline, forming a heat sink-driven immersion liquid natural convection mode.

[0026] When the highest temperature is higher than the third set temperature T3, the direct cooling unit is controlled to operate at full load, so that the refrigerant flows simultaneously in the upper and lower pipelines, forming a self-circulating immersion liquid natural convection mode.

[0027] Where T1 < T2 < T3.

[0028] Preferably, the first set temperature T1, the second set temperature T2, and the third set temperature T3 can be configured independently according to the battery characteristics or the operating environment.

[0029] Preferably, the direct cooling unit includes a compressor, a condenser, and a throttling valve, and the refrigerant exchanges heat with the immersion liquid in the direct cooling pipe through a gas-liquid phase change.

[0030] Beneficial effects

[0031] First, the present invention adopts a fully enclosed static immersion cooling scheme, which fundamentally reduces the risk of immersion liquid leakage, while avoiding complex mechanical transmission structures, reducing potential mechanical failure points, improving the long-term operational reliability of the system, and ensuring high system safety and reliable structure.

[0032] Secondly, by adopting a direct cooling system, this invention can be directly connected to a direct cooling unit, eliminating the need for a separate heat exchange circuit and heat exchanger in traditional liquid cooling systems. This not only simplifies the system architecture but also reduces heat loss in intermediate heat exchange links, thereby significantly improving the overall energy efficiency of the system. The system has high integration and excellent energy efficiency.

[0033] Third, the distributed serpentine direct cooling pipe design adopted in this invention effectively extends the flow path and heat exchange time of the refrigerant in the battery pack and provides a larger effective heat exchange area, thereby achieving more sufficient heat exchange with the immersion liquid and significantly improving the cooling efficiency.

[0034] Fourth, the present invention, through the distributed layout of direct cooling pipes in the upper and lower regions of the battery pack, can precisely adjust the temperature of the immersion liquid in each region, and actively guide and enhance the natural convection of the immersion liquid by utilizing the temperature difference, effectively improving the temperature uniformity within the battery pack and avoiding local overheating.

[0035] Fifth, this invention proposes a segmented thermal management operation strategy based on battery temperature, which can intelligently adjust the operating status and cooling power of the direct cooling unit according to the actual heat load. Under the premise of ensuring stable battery temperature, it can minimize system operating energy consumption and achieve a balance between high efficiency and low power consumption. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the external structure of the battery immersion cooling system with distributed serpentine direct cooling pipes described in this invention.

[0038] Figure 2 for Figure 1 The diagram shows the internal structure of the battery immersion cooling system.

[0039] Figure 3 This is a schematic diagram of the internal battery module of the battery immersion cooling system.

[0040] Figure 4This is a schematic diagram of the arrangement of the two serpentine direct cooling pipes at the top of this system.

[0041] Figure 5 This is a schematic diagram of the arrangement of the two serpentine direct cooling pipes at the bottom of this system.

[0042] Figure 6 This is a schematic diagram of the cross-sectional structure of a battery immersion cooling system along a certain direction.

[0043] Figure 7 This is a schematic diagram of a heat sink-driven natural convection mode for a battery immersion cooling system.

[0044] Figure 8 This is a schematic diagram of a micro-circulation immersion liquid natural convection mode for a battery immersion cooling system.

[0045] Figure 9 This is a schematic diagram of a self-circulating immersion liquid natural convection mode for a battery immersion cooling system.

[0046] Figure 10 This is a schematic diagram of the operating strategy of the direct-cooling unit under a certain operating condition of this system.

[0047] In the figure: 1. Distributed serpentine direct cooling pipe battery immersion cooling system; 10. Battery pack shell; 11. Immersion liquid; 12. Battery module; 201-204. Serpentine direct cooling pipe; 100. Battery end plate; 101. Battery cell; 102. Electrode connector; 103. Support plate; 104. Heat insulation pad. Detailed Implementation

[0048] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described examples are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] like Figures 1 to 5 As shown, this embodiment provides a battery immersion cooling system 1. The system mainly includes a battery pack housing 10, a battery module 12 disposed inside the housing, an immersion liquid 11 filled inside the housing for immersing the battery module 12, and distributed direct cooling pipe modules (201, 202, 203, 204).

[0050] The battery module 12 is housed inside the battery pack housing 10 and is completely submerged in the immersion fluid 11. The immersion fluid 11 must have excellent insulation, good thermal conductivity, and low viscosity to ensure the electrical safety of the battery and promote heat transfer, such as transformer oil.

[0051] Specifically, such as Figure 3 and Figure 6 As shown, the battery module 12 includes multiple battery cells 101, battery end plates 100, electrode connectors 102, support plates 103, and heat insulation pads 104. All components together constitute a stable and thermally efficient cell integration unit.

[0052] The plurality of battery cells 101 are arranged in an array. In a preferred embodiment, the battery cells 101 are configured in four columns, each column containing thirteen battery cells, which are connected in series to form the required voltage platform.

[0053] The battery end plates 100 are disposed at both ends of the battery module 12 along the length direction, respectively applying clamping force to the array of battery cells 101 from the outside, forming a stable mechanical constraint together with the support plate 103 to prevent each battery cell from shifting under vibration or impact.

[0054] The electrode connector 102 is connected across the electrode terminals of adjacent battery cells 101 to achieve electrical connection between the battery cells. The connector 102 is preferably a metal plate with good conductivity, such as a copper busbar or an aluminum busbar, and is fixed to the electrode terminals by means of laser welding or bolt connection.

[0055] The support plate 103 is disposed at the bottom of the array of battery cells 101 and extends along the width direction of the battery module. Its primary function is to provide a solid bottom support and critical structural rigidity for the entire battery module 12, ensuring the relative positional stability between the battery cells 101. Simultaneously, the structural design of the support plate 103 creates a continuous fluid channel between the bottom of the battery cells 101 and the bottom plate of the battery pack casing 10. This design ensures that the immersion liquid 11 can circulate sufficiently in the bottom region of the battery cells 101, thereby providing a direct and effective liquid cooling path for the bottom of the battery, comprehensively improving the temperature uniformity and thermal management efficiency of the battery module 12 during operation.

[0056] The heat insulation pad 104 is disposed between the parallel-arranged battery cells 101 to delay the spread of heat between adjacent batteries in extreme situations such as thermal runaway, thereby improving the thermal safety of the battery module. At the same time, under normal battery operation, the heat insulation pad 104 also plays a certain role in structural buffering and positioning.

[0057] The direct cooling pipes 201, 202, 203, and 204 are disposed inside the battery pack housing 10 and are completely submerged in the immersion liquid 11. In terms of arrangement, the direct cooling pipes 201, 203, and 204 enter from one side of the battery pack housing 10 and exit from the opposite side; while the direct cooling pipe 202 enters and exits from the same side of the battery pack housing 10, but its serpentine path still covers the area above the battery module, and it is staggered with the direct cooling pipe 201 to ensure uniform heat exchange. All the through-wall interfaces between the direct cooling pipes and the battery pack housing 10 are tightly sealed to ensure the overall airtightness of the battery pack housing 10 and effectively prevent leakage of the immersion liquid 11.

[0058] Under normal operating conditions, the coolant flowing within the direct cooling pipe modules 201-204 undergoes efficient heat exchange with the immersion liquid 11 through a gas-liquid phase change, thereby continuously removing the heat generated during the operation of the battery module 12. The refrigerant can be Freon, hydrocarbon, or other phase change refrigerants suitable for direct cooling systems.

[0059] Specifically, such as Figure 6 As shown, the direct cooling pipe module is spatially divided into upper and lower parts. The direct cooling pipes 201 and 202, located above the battery module 12, are designed with a larger diameter than the direct cooling pipes 203 and 204 located below. In this embodiment, the upper direct cooling pipes 201 and 202 constitute the main heat dissipation source and natural convection drive unit of the system; the lower direct cooling pipes 203 and 204 serve as auxiliary heat dissipation sources and convection enhancement units, jointly participating in system thermal management.

[0060] Furthermore, such as Figure 4 and Figure 6 As shown, the direct cooling pipes 201 and 202 are arranged in a spatially staggered serpentine pattern above the battery module 12, covering most of the area above the battery module. When the direct cooling unit is running, this set of pipes can efficiently and evenly absorb the heat of the immersion liquid in the upper area, which not only improves the cooling temperature uniformity of the top of the battery module, but also establishes a directional flow channel for the immersion liquid, effectively guiding and enhancing its natural convection.

[0061] like Figure 5 and Figure 6 As shown, the direct cooling pipes 203 and 204 are arranged parallel to each other in the vertical direction. They both enter from the same side of the battery module 12, pass through the gaps between the battery cells and through the central area of ​​the battery module, and finally exit from the other side of the battery module 12. This arrangement can provide auxiliary cooling for the immersion liquid in the middle and core areas of the battery module, further optimize the temperature field distribution, and enhance the overall natural convection effect.

[0062] like Figures 7-9As shown, based on the specific arrangement of the direct cooling pipes, a differentiated temperature distribution can be formed inside the battery module, thereby constituting different immersion liquid natural convection modes.

[0063] Specifically, such as Figure 7 As shown, when refrigerant flows through the direct cooling pipes 203 and 204, the immersion liquid in the first, third, and fifth cooling channels located on both sides and in the center of the battery module has a lower temperature than that in the second and fourth channels due to its direct or proximity to the cooling pipes. This temperature difference leads to uneven fluid density distribution: the low-temperature immersion liquid flows downward along the first, third, and fifth channels under the action of gravity, converges at the bottom of the module, and flows laterally into the second and fourth channels; the immersion liquid with lower density in the corresponding area rises under the drive of buoyancy and flows from the top of the module to both sides, forming a micro-circulation immersion liquid natural convection mode.

[0064] like Figure 8 As shown, when and only when the direct cooling pipes 201 and 202 are put into operation, the immersion liquid first exchanges heat with the battery module, the temperature rises and the density decreases, and the fluid moves upward driven by the buoyancy of the heat. After reaching the cold pipe area, the immersion liquid is cooled and the temperature drops and the density increases. Under the action of gravity, it flows back, forming a heat sink driven immersion liquid natural convection mode.

[0065] like Figure 9 As shown, when all the direct cooling pipes are circulated with refrigerant, the above-mentioned micro-circulation and heat sink drive modes work together to couple into a comprehensive and more efficient self-circulating natural convection cooling system.

[0066] In summary, by optimizing the spatial layout of the direct cooling pipeline, this invention creates a clear temperature gradient and directional flow path within the battery module, effectively stimulating and maintaining efficient natural convection of the immersion liquid. Thus, it achieves efficient and uniform heat dissipation of the battery without relying on an external pump to drive the immersion liquid.

[0067] Based on the establishment of the cooling medium circulation loop, the thermal management state of the battery module 12 is related to the operating mode of the direct cooling unit. For example... Figure 10 As shown, the graded temperature control operation strategy of the present invention is illustrated below with reference to a typical operating condition:

[0068] 1. When the maximum temperature of battery module 12 is below 30℃, the battery is in its optimal operating temperature range. At this time, the direct cooling unit is in a shutdown state, and no refrigerant flows in the direct cooling pipes 201-204. The heat generated by battery module 12 is completely dissipated by the immersion liquid 11 through natural convection.

[0069] 2. When the highest temperature of battery module 12 is between 30°C and 35°C, it indicates that the natural heat dissipation capacity of the immersion liquid 11 is insufficient to balance the heat generation power of the battery. At this time, the direct cooling unit partially starts, with refrigerant only introduced into the lower direct cooling pipes 203 and 204, forming a configuration as follows: Figure 7 This illustrates a micro-circulation natural convection mode. This mode can partially absorb the heat of the immersion liquid in the middle of the battery module and guide the immersion liquid on both sides and in the middle of the battery module to flow downwards, thereby effectively promoting the formation of overall natural convection of the immersion liquid 11.

[0070] 3. When the highest temperature of battery module 12 is between 35°C and 40°C, the direct cooling unit partially operates, but the refrigerant only flows in the upper direct cooling pipes 201 and 202, forming a configuration as follows: Figure 8 This illustrates a heat sink-driven natural convection mode for the immersion liquid. In this mode, the system primarily absorbs heat from the upper part of the immersion liquid 11, lowering its temperature and increasing its density. The low-temperature immersion liquid sinks under gravity, significantly accelerating the overall natural convection rate, thereby enhancing the heat exchange intensity between the immersion liquid and the battery module 12.

[0071] 4. When the maximum temperature of battery module 12 exceeds 40℃, the direct cooling unit enters full-load operation, and refrigerant is introduced into all direct cooling pipes 201 to 204, forming a self-circulating natural convection cooling system. This system simultaneously provides powerful cooling to the upper and middle parts of the immersion liquid 11, maximizing the natural convection circulation of the immersion liquid through significant temperature and density differences, thereby achieving rapid cooling of battery module 12.

[0072] In summary, the temperature control operation strategy of this invention can adapt to the thermal management needs of battery modules under various operating conditions. Through the distributed layout of the direct cooling pipes 201 to 204 and the coordinated control of the internal refrigerant, the system can accurately achieve the temperature control target of the battery pack with lower operating power consumption and higher thermal management efficiency without the need for forced convection, ensuring that the battery module always operates within an efficient and safe temperature range.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A self-circulating immersion battery cooling system coupled to a direct cooling tube, characterized by, The battery immersion module comprises a module shell, a battery module arranged in the module shell, and an insulating immersion liquid filled in the module shell and completely immersing the battery module. The distributed direct cooling pipe module comprises two groups of serpentine direct cooling pipes arranged inside the module shell and immersed in the immersion liquid; the inside of the direct cooling pipes circulates refrigerant which exchanges heat with the immersion liquid through gas-liquid phase change. The direct cooling unit is connected with the distributed direct cooling pipe module through inlet and outlet pipelines to form a closed refrigerant circulation loop; the direct cooling unit comprises a compressor, a condenser and a throttle valve. The two groups of serpentine direct cooling pipes are arranged separately in space and comprise an upper group of pipes and a lower group of pipes; the upper group of pipes is arranged above the battery module, and the lower group of pipes is arranged in the gap region between the battery modules. The spatial distribution of the upper group of pipes and the lower group of pipes forms a temperature gradient in the battery immersion module to promote the overall natural convection of the insulating immersion liquid. By controlling the circulation and cutoff of the refrigerant in the upper group of pipes and the lower group of pipes, three different immersion liquid circulation modes can be formed in the battery immersion module. The upper group of pipes comprises two serpentine direct cooling pipes arranged in an interleaved manner, and the lower group of pipes comprises two serpentine direct cooling pipes arranged in a parallel manner.

2. The system of claim 1, wherein, The pipe diameter of the direct cooling pipes in the upper group of pipes is greater than that of the direct cooling pipes in the lower group of pipes.

3. The system of claim 1 or 2, wherein, The battery module comprises a plurality of battery monomers, and the direct cooling pipes in the lower group of pipes pass through the gap between the two sides of the battery module and pass through the central region of the battery module.

4. The system of claim 1, wherein, The battery immersion module further comprises end plates arranged at both ends of the array of battery monomers, a support plate arranged at the bottom of the array of battery monomers, and thermal insulation pads arranged between the parallelly arranged battery monomers.

5. The system of claim 1, wherein, The direct cooling unit is connected with the distributed direct cooling pipe module through pipelines to form a refrigerant circulation loop; the direct cooling unit comprises a compressor, a condenser and a throttle valve.

6. The system of claim 1, wherein, The method comprises the following steps:

7. A control method of self-circulating immersion battery cooling coupled with direct cooling tubes, the method being applied to the self-circulating immersion battery cooling system coupled with direct cooling tubes according to any one of claims 1 to 6, characterized in that, Monitoring the highest temperature of the battery pack; According to the preset temperature interval in which the highest temperature is located, the operation mode of the direct cooling unit and the circulation state of the refrigerant in the upper group of pipes and / or the lower group of pipes are controlled. The step of controlling the operation mode of the direct cooling unit according to the highest temperature comprises:

8. The method of claim 7, wherein, When the highest temperature is lower than a first set temperature T1, the direct cooling unit is controlled not to operate; When the highest temperature is between the first set temperature T1 and a second set temperature T2, the direct cooling unit is controlled to operate partially, so that the refrigerant only circulates in the lower group of pipes to form a microcirculation type immersion liquid natural convection mode; When the highest temperature is between the second set temperature T2 and a third set temperature T3, the direct cooling unit is controlled to operate partially, so that the refrigerant only circulates in the upper group of pipes to form a heat sink driven immersion liquid natural convection mode; When the highest temperature is higher than the third set temperature T3, the direct cooling unit is controlled to operate under full load, so that the refrigerant circulates in the upper group of pipes and the lower group of pipes to form a self-circulation type immersion liquid natural convection mode. ​ Wherein, T1 < T2 < T3.

9. The method of claim 8, wherein, The first set temperature T1, the second set temperature T2 and the third set temperature T3 can be independently configured according to the battery characteristics or the operation environment.

10. The method of claim 7, wherein, The direct cooling unit comprises a compressor, a condenser and a throttle valve, and the refrigerant exchanges heat with the immersion liquid through gas-liquid phase change in the direct cooling pipe.

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