Two-phase immersed battery thermal management system capable of adjusting boiling point based on variable pressure

Abstract

The invention relates to the field of battery thermal management, in particular to a two-phase immersed battery thermal management system based on variable-pressure boiling point adjustment, which comprises a battery module unit, a low-pressure buffer tank, an air pump, a gas pipeline, a valve group and a controller, the gas in the battery box body is transferred into the low-pressure buffer tank in the depressurization mode so as to reduce the boiling point of the two-phase cooling medium, and the gas in the low-pressure buffer tank is transferred into the battery box body in the pressurization mode so as to increase the boiling point of the two-phase cooling medium. According to the invention, the air pump and the low-pressure buffer tank are utilized, the switching of a fluid control network is adopted, the gas phase space in the battery box body is actively inflated or deflated, and the absolute pressure in the battery box body is intelligently adjusted; efficient heat dissipation is realized in a voltage reduction mode; and rapid heating or heat preservation is realized in a pressurization mode.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management, and more specifically to a two-phase immersion battery thermal management system based on variable pressure regulating boiling point. Background Technology

[0002] The two-phase immersion cooling technology for power batteries involves directly immersing the battery in an insulating fluorinated liquid. It utilizes the latent heat of the liquid during phase change (boiling) to remove heat, resulting in extremely high heat exchange efficiency and temperature uniformity. However, this cooling technology has the following technical problems.

[0003] To cope with high-temperature operating conditions, the medium needs to have a low boiling point (e.g., 35°C) so that it can boil and dissipate heat as soon as possible; however, during normal cruising or standing, an excessively low boiling point will cause the medium to continue to evaporate, increasing the difficulty of internal pressure control and making it difficult to use the medium for heat preservation.

[0004] During cold starts in winter, the battery heats up very slowly due to the high specific heat capacity and low boiling point of the medium, often requiring an additional high-power heater, which consumes precious electrical energy. Summary of the Invention

[0005] The purpose of this invention is to provide a two-phase immersion battery thermal management system based on variable pressure to regulate boiling point. It aims to actively and flexibly adjust the boiling point of the cooling medium without increasing the complexity of the internal structure of the battery pack, thus taking into account both high-temperature heat dissipation and low-temperature heat preservation requirements.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: A two-phase immersion battery thermal management system based on variable pressure regulating boiling point includes: A battery module unit includes at least one sealed battery housing, the battery housing contains a battery module and a two-phase cooling medium, the battery module is immersed in the liquid phase of the two-phase cooling medium, and a condensation component is provided on the top of the battery housing; The central voltage regulating unit includes a low-pressure buffer tank and an air pump that are set separately from the battery housing. The interior of the low-pressure buffer tank is configured to maintain a negative pressure environment. A fluid control network, including gas pipelines and valve groups installed on the gas pipelines, for connecting the battery box, the low-pressure buffer tank and the air pump; The controller is electrically connected to the air pump and the valve group; The controller is configured to transfer gas from the battery housing to the low-pressure buffer tank in depressurization mode to lower the boiling point of the two-phase cooling medium, and to transfer gas from the low-pressure buffer tank to the battery housing in pressurization mode to raise the boiling point of the two-phase cooling medium, by controlling the fluid control network and the air pump.

[0007] Furthermore, the fluid control network includes a gas-liquid separator, a first gas valve, a second gas valve, a third gas valve, a fourth gas valve, a fifth gas valve, and a sixth gas valve; The air inlet of the gas-liquid separator is connected to the low-pressure buffer tank through the first air valve, and to the battery box through the second air valve; The outlet of the gas-liquid separator is connected to the inlet of the air pump through the third air valve; One end of the fourth, fifth, and sixth air valves is connected to the air outlet of the air pump, the other end of the fourth air valve is connected to the low-pressure buffer tank, the other end of the fifth air valve is connected to the battery box, and the other end of the sixth air valve is connected to the external atmospheric environment.

[0008] Furthermore, the bottom of the gas-liquid separator is provided with a drain port, which is connected back to the battery housing through a thin tube with a one-way valve, so as to return the separated liquid phase medium to the battery housing.

[0009] Furthermore, the outer wall of the gas pipeline between the battery box and the gas-liquid separator is wrapped with an insulation layer and an electric heating tape, which is electrically connected to the controller.

[0010] Furthermore, the first air valve, the second air valve, the third air valve, the fourth air valve, the fifth air valve, and the sixth air valve are all two-position two-way solenoid valves; The air pump is a corrosion-resistant vacuum pump or an oil-free vortex pump.

[0011] Furthermore, a temperature sensor and a first pressure sensor are installed inside the battery housing; A second pressure sensor is installed inside the low-pressure buffer tank; The temperature sensor, the first pressure sensor, and the second pressure sensor are all connected to the controller signal.

[0012] Furthermore, the condensation assembly is disposed close to the inner side of the top cover of the battery housing; The condensation assembly is a flat-plate pulsating heat pipe or a liquid cooling plate.

[0013] Furthermore, a first safety pressure relief valve is provided on the battery housing; The low-pressure buffer tank is equipped with a second safety relief valve.

[0014] Furthermore, the gas phase space of the battery housing is filled with a non-condensable inert gas, the volume fraction of which is 30% to 50%, and the non-condensable inert gas is dry nitrogen.

[0015] Furthermore, the battery housing has a flattened structure and is configured to be mounted in the chassis area of ​​the electric vehicle; The low-pressure buffer tank is configured to be installed in the trunk area or under the seat area of ​​the electric vehicle.

[0016] Compared with the prior art, this application has the following advantages: This invention utilizes an air pump and a low-pressure buffer tank, and through switching of a fluid control network, actively fills or evacuates the gas phase space inside the battery box, intelligently regulating the absolute pressure inside the battery box. In depressurization mode, the gas inside the battery box is transferred to the low-pressure buffer tank to create a low-pressure environment, forcing the boiling point of the cooling medium to decrease, allowing it to boil violently at a lower temperature, thus achieving efficient heat dissipation. In pressurization mode, the gas in the low-pressure buffer tank is reversed and forced into the battery box to create a high-pressure environment, raising the boiling point of the cooling medium, suppressing boiling, and using the sensible heat of the medium and the air cushion effect to lock in heat, achieving rapid heating or heat preservation. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0018] Figure 1 This refers to the system initialization or vacuum storage mode in this embodiment of the invention; Figure 2 This is an active buck mode for overcharging or high-temperature response in an embodiment of the present invention; Figure 3 This is an active boosting mode for low-temperature or cold-start response in an embodiment of the present invention; The labels in the diagram represent the following: 1-Battery housing; 2-Battery module; 3-Condensation assembly; 4-Low-pressure buffer tank; 5-Air pump; 6-Gas-liquid separator; 61-One-way valve; 71-First air valve; 72-Second air valve; 73-Third air valve; 74-Fourth air valve; 75-Fifth air valve; 76-Sixth air valve. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments 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.

[0020] refer to Figure 1 , Figure 2 , Figure 3 This invention provides a two-phase immersion battery thermal management system based on variable pressure regulating boiling point. The system mainly consists of a battery module unit, a central voltage regulating unit, and a fluid control network connecting the two, which is uniformly coordinated and controlled by a controller.

[0021] The battery module unit includes at least one sealed battery housing 1, which preferably has a flat structure suitable for installation in the chassis area of ​​an electric vehicle. A first safety pressure relief valve is provided on the battery housing 1 for passive physical pressure relief when the internal pressure rises abnormally. The battery housing 1 contains a battery module 2 and a two-phase cooling medium (e.g., fluorinated liquid), with the battery module 2 completely immersed in the liquid phase of the two-phase cooling medium. A condensing assembly 3 is provided above the battery housing 1 in the height direction, closely attached to the inner side of the housing top cover. The condensing assembly 3 is preferably a flat plate-type pulsating heat pipe (PHP) or a liquid cooling plate for condensing and recirculating the vapor in the gas phase space. In order to accurately monitor the thermodynamic state within the system, a temperature sensor and a first pressure sensor are also provided inside the battery housing 1 for real-time monitoring of the battery temperature and the internal pressure, respectively, and are connected to the controller signal.

[0022] To achieve active pressure regulation, the gas phase space of the battery housing 1 is pre-filled with a non-condensable inert gas, such as dry nitrogen, with a volume fraction of 30% to 50%. Since the molecular weight of the selected two-phase cooling medium (such as fluorinated liquid) is much larger than that of the filled inert gas, a natural density stratification will form in the gas phase space under the action of gravity. The less dense inert gas mainly accumulates at the top of the housing and near the exhaust port, while the denser medium vapor is located below the inert gas layer.

[0023] The central pressure regulating unit includes a low-pressure buffer tank 4 and an air pump 5, which are set independently of the battery box 1. The low-pressure buffer tank 4 can be arranged in non-chassis areas such as the trunk of the vehicle or the gap under the seat. A second safety pressure relief valve and a second pressure sensor are installed on the tank. The tank is configured to preset or maintain a negative pressure environment below atmospheric pressure. The air pump 5 is preferably a corrosion-resistant vacuum pump or an oil-free vortex pump, which can realize bidirectional gas transfer through the switching of pipelines and valves.

[0024] The fluid control network is used to connect the battery box 1, the low-pressure buffer tank 4 and the air pump 5. The specific connection structure is as follows: The system is equipped with a gas-liquid separator 6, which is connected in series before the air inlet of the air pump 5; the air inlet of the gas-liquid separator 6 is connected to the low-pressure buffer tank 4 through the first air valve 71 and to the battery box 1 through the second air valve 72.

[0025] The outlet of the gas-liquid separator 6 is connected to the inlet of the air pump 5 through the third air valve 73; the outlet of the air pump 5 is connected to one end of the fourth air valve 74, the fifth air valve 75 and the sixth air valve 76, and the other three ports of the fourth air valve 74, the fifth air valve 75 and the sixth air valve 76 are respectively connected to the low-pressure buffer tank 4, the battery box 1 and the external atmospheric environment.

[0026] The first air valve 71, the second air valve 72, the third air valve 73, the fourth air valve 74, the fifth air valve 75, and the sixth air valve 76 are all two-position two-way solenoid valves.

[0027] To ensure the reliability of the system, the outer wall of the gas pipeline connecting the battery housing 1 and the central pressure regulating unit is wrapped with an insulation layer and an electric heating tape. The controller is configured to activate the electric heating tape when performing the evacuation operation to maintain the pipe wall temperature above the dew point temperature of the medium (e.g., above 50°C) to prevent the high-temperature medium vapor from condensing during transmission. At the same time, the gas-liquid separator 6 is used to intercept trace amounts of mist entrained in the airflow, which protects the air pump 5. The bottom of the gas-liquid separator 6 is equipped with a drain port, which is connected back to the battery housing 1 through a thin tube with a one-way valve 61. The separated liquid medium is returned to the battery housing 1 by the system pressure difference or gravity, realizing closed-loop management of the medium.

[0028] This system coordinates the status of air pump 5 and various air valves through a controller to achieve switching between multiple working modes.

[0029] refer to Figure 1 In system initialization or vacuum reserve mode, the controller controls the first gas valve 71 and the third gas valve 73 to open, and the second gas valve 72 to close; at the same time, the controller controls the sixth gas valve 76 to open, and the fourth gas valve 74 and the fifth gas valve 75 to close, thereby connecting the outlet of the air pump 5 with the atmospheric environment; then the air pump 5 is started. At this time, the buffer tank, the first gas valve 71, the gas-liquid separator 6, the third gas valve 73, the air pump 5, the sixth gas valve 76, and the atmosphere are connected in sequence. The air pump 5 discharges the gas inside the buffer tank into the atmosphere, thereby establishing a vacuum in the buffer tank and reserving potential energy for subsequent operations.

[0030] refer to Figure 2In the active buck mode for overcharging or high-temperature response, when the temperature sensor detects that the battery has entered a high-rate charging state or the temperature exceeds a set threshold, the controller controls the second air valve 72 and the third air valve 73 to open, and the first air valve 71 to close; at the same time, the controller controls the fourth air valve 74 to open, and the fifth air valve 75 and the sixth air valve 76 to close, thereby connecting the outlet of the air pump 5 to the low-pressure buffer tank 4, and activating the pipeline electric heating; after the air pump 5 is started, the battery box 1, the second air valve 72, the gas-liquid separator 6, the third air valve 73, the air pump 5, and the first air valve 71 are connected. The four gas valves 74 and the buffer tank are connected in sequence. The gas pump 5 transfers the high-temperature and high-pressure gas (preferably nitrogen at the top) in the battery box 1 to the buffer tank. As the gas pressure in the battery box drops sharply, the boiling point of the medium decreases significantly (for example, to about 30°C). This causes the liquid medium on the battery surface, which was originally not boiling or only slightly boiling, to quickly change to a state of violent boiling. A large amount of heat is dissipated by the latent heat of phase change, and the generated steam rises to the condenser component 3 at the top and is condensed and refluxed. This effectively suppresses the temperature rise of the battery without relying on a complex internal flow channel structure.

[0031] refer to Figure 3 In the active pressurization mode for low temperature or cold start response, when the ambient temperature is detected to be too low, the controller controls the first air valve 71 and the third air valve 73 to open and the second air valve 72 to close; at the same time, the controller controls the fifth air valve 75 to open and the fourth air valve 74 and the sixth air valve 76 to close, thereby connecting the outlet of the air pump 5 to the battery box 1; after the air pump 5 is started, the buffer tank, the first air valve 71, the gas-liquid separator 6, the third air valve 73, the air pump 5, the fifth air valve 75, and the battery box 1 are connected in sequence, and the air pump 5 forces the gas stored in the buffer tank into the battery box 1; as the gas pressure inside the box increases, the boiling point of the medium increases (for example, to above 45°C), thereby suppressing the boiling of the medium, using the sensible heat of the medium and the air cushion effect to lock in the heat of the battery, and achieving rapid heating.

[0032] In steady-state cruise and self-maintenance modes, the controller periodically monitors the status of the gas-liquid separator 6. If there is liquid accumulation, the working fluid can be sent back to the battery box through the automatic return pipeline. In addition, if the battery box pressure only needs to fluctuate slightly, the controller can simply open the valve to balance the pressure by utilizing the natural pressure difference between the buffer tank and the battery box, without having to start the air pump 5.

[0033] This invention, while eliminating the complex internal flow guiding structure and grid structure, still maintains the ability to actively, significantly, and bidirectionally adjust the boiling point of the cooling medium. This not only reduces the manufacturing difficulty and cost of the battery box 1, but also cleverly utilizes the low-pressure physical characteristics to enhance heat transfer, thus solving the core technical bottleneck of the traditional two-phase immersion cooling system.

[0034] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered as falling within the scope of protection of the embodiments of the present invention.

Claims

1. A thermal management system for a two-phase immersion battery based on variable pressure-regulated boiling point, characterized in that, include: The battery module unit includes at least one sealed battery housing (1), the battery housing (1) contains a battery module (2) and a two-phase cooling medium, the battery module (2) is immersed in the liquid phase of the two-phase cooling medium, and a condensation component (3) is provided on the top of the battery housing (1). The central pressure regulating unit includes a low-pressure buffer tank (4) and an air pump (5) set independently of the battery housing (1). The interior of the low-pressure buffer tank (4) is configured to maintain a negative pressure environment. A fluid control network, including gas pipelines and valve groups installed on the gas pipelines, is used to connect the battery box (1), the low-pressure buffer tank (4) and the air pump (5). The controller is electrically connected to the air pump (5) and the valve group; The controller is configured to transfer gas in the battery housing (1) to the low-pressure buffer tank (4) in depressurization mode to lower the boiling point of the two-phase cooling medium by controlling the fluid control network and the air pump (5), and to transfer gas in the low-pressure buffer tank (4) to the battery housing (1) in pressurization mode to raise the boiling point of the two-phase cooling medium.

2. The two-phase immersion battery thermal management system as described in claim 1, characterized in that, The fluid control network includes a gas-liquid separator (6), a first gas valve (71), a second gas valve (72), a third gas valve (73), a fourth gas valve (74), a fifth gas valve (75), and a sixth gas valve (76). The air inlet of the gas-liquid separator (6) is connected to the low-pressure buffer tank (4) through the first air valve (71) and to the battery box (1) through the second air valve (72). The outlet of the gas-liquid separator (6) is connected to the inlet of the air pump (5) through the third air valve (73); One end of the fourth air valve (74), the fifth air valve (75) and the sixth air valve (76) are connected to the air outlet of the air pump (5), the other end of the fourth air valve (74) is connected to the low-pressure buffer tank (4), the other end of the fifth air valve (75) is connected to the battery box (1), and the other end of the sixth air valve (76) is connected to the external atmospheric environment.

3. The two-phase immersion battery thermal management system as described in claim 2, characterized in that, The bottom of the gas-liquid separator (6) is provided with a drain port, which is connected back to the battery box (1) through a thin tube with a one-way valve (61) to return the separated liquid phase medium to the battery box (1).

4. The two-phase immersion battery thermal management system as described in claim 2, characterized in that, The outer wall of the gas pipeline between the battery box (1) and the gas-liquid separator (6) is wrapped with a heat insulation layer and an electric heating tape, which is electrically connected to the controller.

5. The two-phase immersion battery thermal management system as described in claim 2, characterized in that, The first air valve (71), the second air valve (72), the third air valve (73), the fourth air valve (74), the fifth air valve (75), and the sixth air valve (76) are all two-position two-way solenoid valves; The air pump (5) is a corrosion-resistant vacuum pump or an oil-free vortex pump.

6. The two-phase immersion battery thermal management system as described in claim 1, characterized in that, The battery housing (1) is equipped with a temperature sensor and a first pressure sensor. The low-pressure buffer tank (4) is equipped with a second pressure sensor; The temperature sensor, the first pressure sensor, and the second pressure sensor are all connected to the controller signal.

7. The two-phase immersion battery thermal management system as described in claim 1, characterized in that, The condensation component (3) is disposed close to the inside of the top cover of the battery box (1); The condensation component (3) is a flat pulsating heat pipe or a liquid cooling plate.

8. The two-phase immersion battery thermal management system as described in claim 1, characterized in that, The battery box (1) is equipped with a first safety pressure relief valve; The low-pressure buffer tank (4) is equipped with a second safety relief valve.

9. The two-phase immersion battery thermal management system as described in claim 1, characterized in that, The gas phase space of the battery box (1) is filled with a non-condensable inert gas, the volume fraction of which is 30%~50%, and the non-condensable inert gas is dry nitrogen.

10. The two-phase immersion battery thermal management system as claimed in claim 1, characterized in that, The battery housing (1) has a flattened structure and is configured to be installed in the chassis area of ​​the electric vehicle; The low-pressure buffer tank (4) is configured to be installed in the trunk area or under the seat area of ​​the electric vehicle.

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