Pump-free self-driven immersed battery thermal management system and control method

Abstract

The invention belongs to the technical field of lithium ion battery thermal management, and particularly discloses a pump-free self-driven immersed battery thermal management system and a control method, which realize high-speed jet flow of a cooling liquid and rapid reduction of the surface temperature of a battery through the height difference between a condensation cavity and a battery cavity by a jet flow impact technology. A thermal boundary layer is broken through the cavitation effect, the heat transfer coefficient is remarkably increased, and the transient heat dissipation requirement of high-rate charging and discharging is met. The condensation cavity cooperates with the intelligent control module to ensure uniform temperature distribution of the battery pack. Based on real-time regulation and control of sensor feedback, system response time is shortened, and temperature lag is avoided. The separation design of the battery cavity and the condensation cavity simplifies the traditional same-cavity structure, reduces the circulation resistance of the working medium, and guarantees the long-term stable operation of the system. Phase change heat absorption, intelligent control, potential energy driving and ultrasonic enhancement are fused, the energy efficiency limitation that traditional liquid cooling depends on external pump work is broken through, system power consumption is reduced, module temperature difference is effectively controlled, and thermal runaway response time is shortened.

Description

Technical Field

[0001] This application belongs to the technical field of lithium-ion battery thermal management, and particularly relates to a pump-free self-driven immersion battery thermal management system and a control method thereof. Background Art

[0002] With the rapid development of new energy vehicles and large-scale energy storage systems, lithium-ion batteries have become the core energy storage carriers due to their high energy density, long cycle life and other characteristics. Lithium-ion batteries will generate significant Joule heat and reaction heat under high-rate charge and discharge conditions, and their instantaneous heat flux density is extremely high. If the thermal management fails, a temperature gradient will be formed inside the battery, the overall temperature will be too high, which will induce the aggravation of internal resistance polarization, the acceleration of capacity decay, and the reduction of life. In extreme cases, it will even trigger a chain exothermic reaction, leading to the risk of thermal runaway. Therefore, constructing an efficient thermal management system is the core technical bottleneck to ensure the safety of the battery and extend its service life.

[0003] In the prior art, although the two-phase immersion cooling technology realizes heat dissipation by immersing the battery module in a low-boiling-point dielectric fluid and utilizing the latent heat of phase change, its technical architecture still has significant defects. Traditional systems rely on natural convection of the coolant and rely on mechanical pumps for condensate reflux, lacking active circulation enhancement measures, and it is difficult to match the transient heat dissipation requirements under high-rate working conditions. At the same time, most existing systems adopt the same cavity structure for the condensation cavity and the cooling chamber, and the condensed liquid cannot quickly cool the battery, and the cooling capacity needs to be further improved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects in the prior art that the lithium-ion battery cooling system relies on natural convection of the coolant and relies on mechanical pumps for condensate reflux, and the same cavity structure of the condensation cavity and the cooling chamber results in poor heat dissipation performance, so as to provide a pump-free self-driven immersion battery thermal management system and a control method thereof.

[0005] The present invention discloses a pump-free self-driven immersion battery thermal management system, including a steam circulation pipeline, a battery cavity, a control module, an ultrasonic transducer, a temperature sensor, a condensation cavity, a jet pipeline, a solenoid valve, a coolant, a lithium battery pack, and a liquid level sensor; the battery cavity is used to accommodate the lithium battery pack; the condensation cavity is used to cool the coolant; the steam circulation pipeline connects the battery cavity and the condensation cavity; the jet pipeline connects the battery cavity and the condensation cavity; a solenoid valve is arranged on the jet pipeline; the temperature sensor is used to detect the temperature of the lithium battery pack; the liquid level sensor is used to detect the liquid level in the condensation cavity; the ultrasonic transducer is fixed outside the battery cavity; the control module is respectively connected to the ultrasonic transducer, the temperature sensor, the solenoid valve and the liquid level sensor in signal, and is used to obtain the data of the temperature sensor and the liquid level sensor and control the solenoid valve and the ultrasonic transducer.

[0006] Further, it further includes a gas collecting bag, which is connected to the condensation cavity and is used to balance the pressure in the condensation cavity.

[0007] Further, it further includes safety valves, which include a first safety valve and a second safety valve; the first safety valve is connected to the battery cavity, and the second safety valve is connected to the condensation cavity, and is used to relieve the pressure of the connected cavity and recover the coolant.

[0008] Further, the coolant is one of fluorine-containing compounds and fluorocarbon compounds.

[0009] Further, it further includes a condensation channel, which is connected to the condensation cavity and is used to condense the coolant; the condensation channel is one of a straight tube type, a coil tube type, and a serpentine tube type; the condensation method of the condensation channel is one of a water-cooled type, an air-cooled type, and an evaporative-cooled type.

[0010] Further, the liquid level sensor is one of a capacitive type, an infrared type, and a float type; the temperature sensor is a thermocouple.

[0011] A control method for a pump-free self-driven immersion battery thermal management system, the structure of the immersion battery thermal management system is as described above. Compare the detected value of the liquid level sensor with a set threshold, and at the same time compare the detected value of the temperature sensor with a set threshold. If the current liquid level reaches the set threshold, the control module is made to execute the jet mode and open the solenoid valve to generate a jet; if the current temperature or the maximum temperature difference in the lithium battery pack reaches the set threshold, the control module is made to execute the ultrasonic mode and control the ultrasonic transducer to reduce the temperature of the lithium battery pack.

[0012] Further, when the liquid level reaches the set threshold, the relay is turned on and the solenoid valve is opened for a period of time; when the temperature reaches the set threshold, the relay is turned on and the ultrasonic transducer is opened; if the temperature is lower than the set threshold, the ultrasonic transducer is closed.

[0013] Further, in the jet mode: when the liquid level in the condensation cavity is greater than or equal to a first set threshold, the liquid level sensor transmits a signal to the control module to open the solenoid valve to generate a jet; in the early stage of heat generation of the lithium battery pack, the jet continues until the liquid level in the condensation cavity drops to a second set threshold, and the second set threshold is less than the first set threshold; in the later stage of heat generation of the lithium battery pack, the jet continues for a preset time and then closes.

[0014] Further, in the ultrasonic mode: when the maximum temperature of the lithium battery pack reaches a first set threshold, the temperature sensor transmits an output signal to the control module to turn on the ultrasonic transducer; when the temperature of the lithium battery pack is less than a second set threshold, where the second set threshold is less than the first set threshold, the ultrasonic transducer is turned off; or when the maximum temperature difference of the lithium battery pack reaches a third set threshold, the temperature sensor transmits an output signal to the control module to turn on the ultrasonic transducer; when the maximum temperature difference of the lithium battery pack is less than a fourth set threshold, where the fourth set threshold is less than the third set threshold, the ultrasonic transducer is turned off.

[0015] Beneficial effects: An immersion-type battery thermal management system and control method without a pump and self-driven disclosed by the present invention utilize gravitational potential energy and phase change for self-driven circulation, reduce system power consumption, and improve energy efficiency. Through jet impingement technology, a height difference between the condensation cavity and the battery cavity is used to achieve high-speed jet of the coolant, rapidly reducing the battery surface temperature. The cavitation effect is utilized to break the thermal boundary layer, significantly enhancing the heat transfer coefficient and meeting the transient heat dissipation requirements for high-rate charge and discharge. The condensation cavity and the intelligent control module cooperate to ensure uniform temperature distribution of the battery pack. Based on real-time regulation feedback from the sensor, the system response time is shortened, avoiding temperature lag. The separate design of the battery cavity and the condensation cavity simplifies the traditional same-cavity structure, reduces the resistance of the working fluid circulation, and the closed-loop circulation of the coolant and the design of the gas collection bag ensure the long-term stable operation of the system. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic structural diagram of the system of the present invention; Figure 2 It is a schematic structural diagram of the system device of the present invention; Figure 3 It is a schematic structural diagram of the battery cavity of the present invention; Figure 4 It is a schematic structural diagram of the condensation cavity of the present invention; Figure 5 It is a schematic block diagram of the regulation module structure of the present invention; Figure 6 It is a comparison diagram of the test effects of the present invention.

[0018] Description of the reference numerals: 1, steam flow pipeline; 2, battery cavity; 3, control module; 4, ultrasonic transducer; 5, temperature sensor; 6, condensation cavity; 8, jet pipeline; 9, solenoid valve; 11, safety valve; 7, condensation cavity spacer; 10, solenoid valve spacer; 201, coolant; 202, lithium battery pack; 203, battery fixing bracket; 601, condensation channel; 602, liquid level sensor; 603, gas collecting bag. Detailed implementation manners

[0019] To make the above objects, features, and advantages of the present application more apparent and understandable, the following describes the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0020] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0021] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0022] In the present application, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0023] Refer toFigures 1 to 4 As shown, in a specific embodiment provided by the present application, a pump-free self-driven immersion battery thermal management system mainly includes a steam circulation pipeline 1, a battery cavity 2, a control module 3, an ultrasonic transducer 4, a temperature sensor 5, a condensation cavity 6, a jet pipeline 8, a solenoid valve 9, a safety valve 11, a condensation channel 601, a liquid level sensor 602, and a gas collection bag 603.

[0024] Among them, the battery cavity 2 is the main component of this system. A certain amount of coolant 201 is contained in the battery cavity 2, which is mainly used to place the lithium battery pack 202, so as to completely immerse the lithium battery pack 202 through the coolant 201 and achieve immersion liquid cooling for the lithium battery pack 202. Moreover, the boiling point of the coolant is relatively low, and it can relatively easily form coolant steam through the way of absorbing heat or form liquid coolant through the way of releasing heat. The gas collection bag 603 is arranged in the top area of the condensation cavity 6, and is mainly used to adjust the air pressure in the condensation cavity 6 to be the same as the atmospheric pressure, so that the air pressure in the condensation cavity 6 is always lower than the air pressure in the battery cavity 2 during the discharging process, so that the coolant steam can enter the condensation cavity 6 from the battery cavity 2 through the steam circulation pipeline 1.

[0025] The condensation channel 601 is arranged in the upper side area of the condensation cavity 6, and is mainly used for the circulation of the condensation medium, so that the condensation medium flows through the inside of the condensation cavity 6. Since the coolant steam flows into the upper side area inside the condensation cavity 6 from the battery cavity 2 through the steam circulation pipeline 1 due to the pressure difference, the coolant steam will contact the condensation channel 601 during the flowing process, and then be condensed by the condensation medium. After phase change to form liquid coolant, the liquid level of the coolant inside the condensation cavity 6 rises. When enough liquid level potential energy is accumulated, the solenoid valve 9 is opened, and the coolant 201 forms a jet through the jet pipeline 8 and shoots into the battery cavity 2 to realize the recycling of the coolant 201.

[0026] The liquid level sensor 602 is mainly used to detect the liquid level in the condensation cavity 6, that is, the height of the coolant 201 in the condensation cavity 6. The temperature sensor 5 is mainly used to detect the maximum temperature and temperature difference of the lithium battery pack 202, and its change is mainly generated by the heat dissipation of the lithium battery pack 202. The regulation module is mainly used to execute the preset temperature regulation action or liquid level regulation action.

[0027] The control module 3 is signal-connected to the temperature sensor 5 and the liquid level sensor 602, and is mainly used to calculate the current maximum temperature and the maximum temperature difference deviation of the lithium battery pack 202 according to the difference between the detection value of the temperature sensor 5 and the preset threshold. At the same time, according to whether the detection value of the liquid level sensor 602 reaches the set height, different regulation methods are selected for execution. Specifically, if the detection value of the liquid level sensor reaches the set height, the liquid level parameter is regulated. At this time, the control module 3 controls the regulation module to execute the preset liquid level adjustment action. If the current temperature deviation ratio exceeds the set threshold, the temperature parameter is regulated. At this time, the control module 3 controls the regulation module to execute the preset temperature adjustment action.

[0028] In this way, for a pump-free self-driven immersion battery thermal management system and control method provided in this embodiment, the liquid level parameter in the condensation cavity 6 is detected in real time by the liquid level sensor 602, and the temperature parameter of the lithium battery pack 202 is detected in real time by the temperature sensor 5. If the detection value of the liquid level sensor 602 reaches the set height, the solenoid valve 9 is opened for a period of time. Under the action of the liquid level potential energy, the coolant 201 forms a jet through the jet pipe 8 and shoots into the battery cavity 2. The liquid level of the coolant in the condensation cavity 6 drops. At the same time, the jet destroys the thermal boundary layer on the surface of the lithium battery pack 202, enhancing the heat dissipation effect of the coolant 202 on the lithium battery pack 202. If the current temperature deviation ratio exceeds the set threshold, the ultrasonic transducer 4 is turned on, and the heat dissipation effect of the lithium battery 202 group is enhanced through the cavitation effect, so as to achieve the effect of reducing the temperature and improving the temperature uniformity. At the same time, enhancing the heat dissipation is beneficial to the rise of the liquid level in the condensation cavity 6, thereby increasing the jet frequency and enhancing the heat dissipation effect. During the adjustment process, when the heat generation of the lithium battery pack 202 is small, the jet is mainly formed through the liquid level adjustment action to enhance the heat dissipation effect. When the heat generation of the lithium battery 202 is large, the temperature adjustment action and the liquid level adjustment action are carried out in parallel, thereby realizing the improvement of the heat dissipation effect of the lithium battery pack 202 and maintaining the normal state of the system.

[0029] The safety valve 11 connects the battery cavity 2 and the condensation cavity 6 to the gas recovery system, and is mainly used to prevent the internal air pressure of the cavity from exploding when the battery is thermally out of control, so that the coolant vapor enters the gas recovery system through the safety valve 11 to reduce the air pressure and recover the coolant. In this embodiment, the maximum temperature of the lithium battery pack 202 is mainly detected by the temperature sensor 5. When the temperature signal output by the temperature sensor 5 is higher than the safety warning value, the safety valve is opened and an alarm is given to improve the safety of the system.

[0030] In summary, a pump-free self-driven immersion battery thermal management system and control method provided in this embodiment can balance the coordinated control of temperature and liquid level during the operation of the system and maintain the normal state of the system.

[0031] In a specific embodiment of the battery cavity 2, considering that the lithium battery pack 202 includes multiple lithium batteries which are connected in parallel, in order to facilitate the installation of multiple lithium batteries in the battery cavity 1, in this embodiment, a plurality of battery fixing brackets 203 are provided in the battery cavity 2 to respectively install each lithium battery on the corresponding battery fixing bracket 203. Specifically, each battery fixing bracket 203 is installed in a horizontal posture in the battery cavity 2. Generally, 2 to 4 or more lithium batteries can be installed at the same time, and each battery fixing bracket 203 is arranged in an array in the horizontal direction. With such an arrangement, each lithium battery can be horizontally arranged in an array and respectively installed on each battery fixing bracket 203, so as to realize the horizontal array installation of each lithium battery in the battery cavity 2. Generally, two adjacent battery fixing brackets 203 can be connected to each other to facilitate the array arrangement and installation of lithium batteries in the horizontal space.

[0032] Among them, the system utilizes the latent heat of phase change of the coolant 201 to absorb heat, causing the coolant 201 to boil and vaporize on the surface of the lithium battery pack 202, so as to quickly take away the heat and ensure the heat dissipation efficiency. The coolant can specifically be a liquid with a relatively low boiling point such as a fluorinated compound or a fluorocarbon compound. In this embodiment, the selected model of the coolant 201 is SF33, and the boiling point is 33.4 0 °C. By utilizing its latent heat of phase change to absorb heat, it boils and vaporizes on the surface of the lithium battery pack 202, so as to quickly take away the heat and ensure the heat dissipation efficiency.

[0033] In a specific embodiment of the lithium battery pack 202, considering that the lithium battery pack 202 can be composed of lithium batteries of different models, such as 21700 and 4680 cylindrical lithium batteries, or can also be composed of square lithium batteries. In this embodiment, the lithium battery pack 202 is composed of 4680 lithium batteries, which is suitable for small-scale experiments and popularization and processing.

[0034] Considering that the battery fixing bracket 203 is usually rectangular, in order to facilitate the installation of lithium batteries, in this embodiment, the battery cavity 2 is also in a rectangular structure as a whole, that is, a rectangular box, so as to regularly install lithium batteries and avoid installation blind spots. Of course, the specific shape and structure of the battery cavity 2 are not fixed, and the rest such as a columnar or polygonal box can also be adopted.

[0035] In a specific embodiment of the condensation channel 601, both ends of the condensation channel 601 penetrate through the two side walls of the condensation cavity 6 respectively, and the inlet of the condensation channel 601 is communicated with the condensation medium source. In this embodiment, the condensation channel 601 is a vertically arranged double-row pipe, and the arrangement form and the number of rows of the condensation channel 601 can be changed according to the actual heat generation situation, taking into account cost control and condensation effect.

[0036] In another specific embodiment of the condensation channel 601, the condensation channel 601 is a horizontally arranged copper pipe. AsFigure 2 As shown in the figure, taking the right - hand condensation chamber as an example - in this embodiment, in order to enhance the condensation heat transfer of the gaseous working medium, the inlet position of the condensation channel 601 is set on the right side of the condensation channel 601, and the flow direction of the condensation medium in the condensation channel 601 is from the inlet of the condensation channel 601 to the outlet of the condensation channel 601. Specifically, this setting method will make the flow direction of the condensation medium in the condensation channel 601 from right to left, while the steam flow direction in the working medium steam in the condensation cavity 6 is from left to right. Therefore, this setting method will make the flow direction of the condensation medium in the condensation channel 601 counter - flow to the working medium steam, thereby enhancing the condensation heat transfer of the gaseous working medium and improving the condensation efficiency.

[0037] In another specific embodiment regarding the condensation channel 601, in order to facilitate the timely discharge of the coolant from the condensation channel 601, the extending direction of the condensation channel 601 in the condensation cavity 6 forms a preset inclination angle with the horizontal direction. By this means, the condensed coolant can converge into droplets on the outer wall of the condensation channel 601 under the action of gravity and fall off, further reducing the heat transfer thermal resistance generated by the condensate film outside the tube. Among them, the preset inclination angle can be custom - set according to the actual situation. It can be set to ten degrees or twenty degrees, so that the condensation channel 601 can be installed with a slight downward inclination, or it can be set to ninety degrees, so that the condensation channel 601 is perpendicular to the bottom surface of the condensation cavity 6 for installation, thereby maximizing the efficiency of discharging the coolant from the condensation channel 601.

[0038] In a specific embodiment regarding the condensation cavity 6, the condensation cavity 6 adopts a smaller bottom area, so that only a small amount of coolant 201 is required in the condensation cavity 6 to obtain a large liquid - level potential energy, thereby obtaining a large jet frequency and saving the amount of external coolant 201. In addition, the air - collecting bag 603 is installed at the top of the condensation cavity 6, making the air pressure in the condensation cavity 6 equal to the external atmospheric pressure, which can reduce the strength requirements of the box material of the condensation cavity 6 and achieve the effect of cost savings.

[0039] In another specific embodiment regarding the condensation cavity 6, the system includes multiple condensation cavities 6, and the condensation cavities 6 are arranged circumferentially near the battery cavity 2. The adjacent jet pipes 8 in the battery cavity 2 are arranged at 60°, 75°, 90°, 180°, etc., so as to generate jets in multiple directions, thereby enhancing the heat - dissipation effect on the lithium - battery pack 202. In this embodiment, the condensation cavity 6 with a symmetric double - chamber structure is adopted, and the condensation cavity 6 is centrosymmetric about the center of the battery cavity, which is beneficial to the stability of the battery thermal state.

[0040] In a specific embodiment of the ultrasonic transducer 4, to enhance the cavitation effect of the coolant inside the battery cavity 2, ultrasonic transducers 4 of different types (frequency, power, etc.) and different placement positions (around, top, or bottom) can be set. In this embodiment, to maximize economic benefits, an ultrasonic transducer 4 with a frequency of 43 kHz and a power of 35 W is selected. In addition, to balance the heat dissipation effect and save energy costs, a fixed-power adjustable-frequency ultrasonic transducer 4 can be used to find the optimal frequency and then fix the frequency to find the minimum power. In this embodiment, the ultrasonic transducer 4 is placed at the rear of the battery cavity to generate a cavitation effect and enhance the heat dissipation effect of the lithium battery pack 202.

[0041] In a specific embodiment of the jet pipe 8, to enhance the effect of the jet on the thermal boundary layer of the lithium battery pack 202, different jetting methods can be adopted. In this embodiment, the extending direction of the jet pipe 8 in the battery cavity 2 forms a preset inclination angle with the horizontal direction. In this way, the jet can be vertically directed at the lithium battery pack 202, intensifying the destruction of its surface thermal boundary layer. Among them, the preset inclination angle can be custom-set according to the actual situation and can be set to ten degrees or twenty degrees, so that the jet pipe 8 can be slightly inclined for installation to better destroy the thermal boundary layer on its surface, thereby achieving the effect of enhancing the heat dissipation of the lithium battery pack 202.

[0042] In addition, under the condition of the same liquid level potential energy, the jet pipe 8 can select silicone hoses of different pipe diameters. If the pipe diameter of the jet pipe 8 increases, the jet area increases, but the jet velocity decreases; if the pipe diameter of the jet pipe 8 decreases, the jet velocity increases and the jet area decreases. The jet pipe 8 in this embodiment adopts a pipe diameter with an inner diameter of 4 mm and an outer diameter of 6 mm, which can obtain a relatively large jet velocity and a moderate jet area, thereby maximizing the destruction effect on the thermal boundary layer.

[0043] In a specific embodiment of the control module, to adjust the jet rate of the jet pipe 8, the control module includes a control module 3, a liquid level sensor 602, and a solenoid valve 9. The liquid level sensor 602 is arranged on the side wall of the condensation cavity 6 and is signal-connected to the control module 3, and is used to adjust the flow rate of the coolant in the jet pipe 8. Specifically, the opening and closing of the solenoid valve 9 are controlled by the output signal of the liquid level sensor received by the control module 3, so as to obtain the corresponding flow rate of the coolant in the jet pipe 8 by adjusting the liquid level height of the condensation cavity 6. Moreover, obtaining different jet velocities by controlling the liquid level height of the condensation cavity 6 without using a pump can not only improve the energy utilization efficiency but also save the amount of the internal coolant 202.

[0044] It should be noted that in order to achieve rapid adjustment of the liquid level without disturbing the properties of the internal coolant 202, the liquid level sensor 602 can adopt different types. In this embodiment, to achieve this goal, the liquid level sensor 602 used is a capacitive liquid level sensor, whose principle is based on the characteristic that different media have different dielectric constants. When the liquid level changes, the medium distribution between the sensor electrodes changes, resulting in a change in the overall dielectric constant. For example, in a coaxial cylinder type sensor, when the coolant liquid level rises, since the dielectric constant of the coolant is greater than that of air, its equivalent dielectric constant increases. According to the capacitance calculation formula, the capacitance value also increases accordingly. By detecting the change in the capacitance value, the change in the liquid level can be obtained. Moreover, the capacitive liquid level sensor is a non-contact liquid level sensor and will not cause pollution to the coolant and other effects.

[0045] In this embodiment, according to theoretical calculations, the average liquid level rising rate of the coolant 202 in the condensation chamber 6 is 0.0318 mm / s. In the experiment under the jet unit, the actual liquid level rising rate is slightly greater than this speed, so a relatively large jet frequency can be obtained.

[0046] In another specific embodiment of the regulation module, in order to adjust the maximum temperature and the maximum temperature difference of the lithium battery pack 202, the regulation module includes a control module 3, a temperature sensor 5, and an ultrasonic transducer 6. The ultrasonic transducer is arranged on the wall surface of the battery cavity 2, and the temperature sensor 5 is arranged on the lithium battery pack 202 and is signal-connected to the control module 3 for controlling the opening and closing of the ultrasonic transducer. Specifically, the opening and closing of the ultrasonic transducer are controlled by the output signal of the temperature sensor received by the control module 3. Moreover, by controlling the opening and closing of the ultrasonic transducer 6 through the temperature signal to generate the cavitation effect, not only can the maximum temperature of the lithium battery pack 202 be reduced, but also the temperature non-uniformity of the lithium battery pack 202 can be reduced. And the cavitation effect will accelerate the steam generation rate, so the liquid level rising speed of the coolant 202 in the condensation chamber 6 can be accelerated, thereby increasing the jet frequency and achieving a better heat dissipation effect.

[0047] Please refer to Figure 5 , Figure 5 which is a functional module structure schematic diagram of a regulation module provided by this application. It can be seen that the regulation module in this embodiment specifically includes a first execution unit S1 and a second execution unit S2.

[0048] Among them: when the liquid level in the condensation chamber is higher than a certain value of the battery cavity, the first execution unit, that is, the jet unit, is executed to enter the jet mode.

[0049] Specifically, the initial liquid level of the coolant 202 in the condensation cavity 6 is higher than the liquid level of the coolant 202 in the battery cavity 2. As the coolant in the condensation cavity 6 gradually accumulates, when the liquid level in the condensation cavity 6 is greater than or equal to the set threshold HSP1, the liquid level sensor 602 transmits the output signal to the control module 3, causing the solenoid valve 9 to open and generate a jet flow. To ensure that the liquid level in the condensation cavity 6 is always higher than that in the battery cavity 2, in the early stage of heat generation of the lithium battery pack 202, since the condensation rate of the coolant 201 in the condensation cavity 6 is relatively slow, the jet flow continues until the liquid level in the condensation cavity 6 drops to the set threshold HSP2. In the later stage of heat generation of the lithium battery pack 202, since the condensation rate of the coolant 201 in the condensation cavity 6 is relatively fast, the jet flow is turned off after a certain period of time. The solenoid valve 9 in the closed state helps to reduce energy consumption; the jet flow generated by the solenoid valve 9 in the open state helps to disrupt the thermal boundary layer on the surface of the lithium battery pack 202 and thus enhance convective heat transfer.

[0050] Wherein: when the maximum temperature or maximum temperature difference of the lithium battery pack reaches a certain value, the second execution unit, i.e., the ultrasonic unit, is executed to enter the ultrasonic mode.

[0051] Specifically, as the lithium battery pack 202 continuously generates heat, when the maximum temperature of the lithium battery pack 202 reaches the set threshold TSP1, the temperature sensor 5 transmits the output signal to the control module 3, causing the ultrasonic transducer 4 to open. When the temperature of the lithium battery pack 202 is less than the set threshold TSP2, the ultrasonic transducer 4 is closed; or when the maximum temperature difference of the lithium battery pack 202 reaches the set threshold TSP3, the temperature sensor 5 transmits the output signal to the control module 3, causing the ultrasonic transducer 4 to open. When the maximum temperature difference of the lithium battery pack 202 is less than the set threshold TSP4, the ultrasonic transducer 4 is closed. The ultrasonic transducer 4 in the closed state helps to reduce energy consumption; the ultrasonic transducer 4 in the open state can enhance boiling heat transfer through the cavitation effect and thus effectively dissipate heat from the lithium battery pack 202.

[0052] Figure 6 The test effect diagram of an embodiment provided by the present application is as Figure 6 shown. It can be determined that the maximum temperature that the natural air-cooled lithium battery pack 202 can reach is 44.8 0 °C. In this embodiment, the maximum temperature that the lithium battery pack 202 can reach is 33.5 0 °C, showing a good thermal management effect.

[0053] In summary, the pump-free self-driven immersion battery thermal management system and control method provided by this embodiment can balance the coordinated control of temperature and liquid level during the operation of the system and maintain the normal state of the system.

[0054] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0055] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An immersion battery thermal management system without a pump and self-driven, characterized in that, It includes a steam circulation pipeline (1), a battery cavity (2), a control module (3), an ultrasonic transducer (4), a temperature sensor (5), a condensation cavity (6), a jet pipeline (8), a solenoid valve (9), a coolant (201), a lithium battery pack (202), and a liquid level sensor (602); The battery cavity (2) is used to accommodate the lithium battery pack (202); The condensation cavity (6) is used to cool the coolant (201); The steam circulation pipeline (1) connects the battery cavity (2) and the condensation cavity (6); The jet pipeline (8) connects the battery cavity (2) and the condensation cavity (6); a solenoid valve (9) is provided on the jet pipeline (8); The temperature sensor (5) is used to detect the temperature of the lithium battery pack (202); The liquid level sensor (602) is used to detect the liquid level in the condensation cavity (6); The ultrasonic transducer (4) is fixed outside the battery cavity (2); The control module (3) is respectively signal-connected to the ultrasonic transducer (4), the temperature sensor (5), the solenoid valve (9), and the liquid level sensor (602), and is used to obtain the data of the temperature sensor (5) and the liquid level sensor (602) and control the solenoid valve (9) and the ultrasonic transducer (4).

2. The self - driven pump - less immersion - type battery thermal management system according to claim 1, wherein, It further includes a gas collection bag (603), and the gas collection bag (603) is connected to the condensation cavity (6) and is used to balance the pressure in the condensation cavity (6).

3. The self - driven immersion battery thermal management system without a pump according to claim 1, characterized in that, It further includes a safety valve (11), and the safety valve (11) includes a first safety valve and a second safety valve; the first safety valve is connected to the battery cavity (2), and the second safety valve is connected to the condensation cavity (6), and is used to relieve pressure on the connected cavity and recover the coolant (201).

4. The self - driven immersion battery thermal management system without a pump according to claim 1, characterized in that, The coolant (201) is one of a fluorine-containing compound and a fluorocarbon compound.

5. The self-driven immersion battery thermal management system without a pump according to claim 1, wherein It further includes a condensation channel (601), and the condensation channel (601) is connected to the condensation cavity (6) and is used to condense the coolant (201); the condensation channel (601) is one of a straight tube type, a coil type, and a serpentine tube type; the condensation method of the condensation channel (601) is one of a water-cooled type, an air-cooled type, and an evaporative-cooled type.

6. The self-priming immersion battery thermal management system without a pump according to claim 1, characterized in that, The liquid level sensor (602) is one of a capacitive type, an infrared type, and a float type; the temperature sensor (5) is a thermocouple.

7. The control method of a pump-free self-driven immersion battery thermal management system according to claim 1, wherein the structure of the immersion battery thermal management system is as described in any one of claims 1 to 6, characterized in that, Compare the detected value of the liquid level sensor (602) with a set threshold, and at the same time compare the detected value of the temperature sensor (5) with a set threshold. If the current liquid level reaches the set threshold, the control module (3) is made to execute the jet mode and open the solenoid valve (9) to generate a jet; if the current temperature or the maximum temperature difference in the lithium battery pack (202) reaches the set threshold, the control module (3) is made to execute the ultrasonic mode and control the ultrasonic transducer (4) to lower the temperature of the lithium battery pack (202).

8. The control method of a pump-free self-driven immersion battery thermal management system according to claim 7, wherein When the liquid level reaches the set threshold, the relay is turned on to open the solenoid valve (9) for a period of time; when the temperature reaches the set threshold, the relay is turned on to activate the ultrasonic transducer (4); if the temperature is lower than the set threshold, the ultrasonic transducer (4) is turned off.

9. The control method of a pump - less self - driven immersion battery thermal management system according to claim 7, characterized in that, In the jet mode: when the liquid level in the condensation cavity (6) is greater than or equal to the first set threshold, the liquid level sensor (602) transmits an output signal to the control module (3) to open the solenoid valve (9) to generate a jet; in the early stage of heat generation of the lithium battery pack (202), the jet continues until the liquid level in the condensation cavity (6) drops to the second set threshold, and the second set threshold is less than the first set threshold; in the later stage of heat generation of the lithium battery pack (202), the jet is turned off after a preset time.

10. The control method of a pump-free self-driven immersion battery thermal management system according to claim 7, characterized in that In the ultrasonic mode: when the maximum temperature of the lithium battery pack (202) reaches the first set threshold, the temperature sensor (5) transmits an output signal to the control module (3) to activate the ultrasonic transducer (4), and when the temperature of the lithium battery pack (202) is lower than the second set threshold, and the second set threshold is less than the first set threshold, the ultrasonic transducer (4) is turned off; or when the maximum temperature difference of the lithium battery pack (202) reaches the third set threshold, the temperature sensor (5) transmits an output signal to the control module (3) to activate the ultrasonic transducer (4), and when the maximum temperature difference of the lithium battery pack (202) is less than the fourth set threshold, and the fourth set threshold is less than the third set threshold, the ultrasonic transducer (4) is turned off.

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