Liquid cooling and phase change immersion cooling combined battery thermal management system and regulation and control method

Abstract

The invention relates to the technical field of battery thermal management, in particular to a liquid cooling and phase change immersion cooling combined battery thermal management system and a regulation and control method.The liquid cooling and phase change immersion cooling combined battery thermal management system comprises a heat conduction shell, a heat conduction upper cover and a composite phase change material filled in a battery gap, and two sets of refrigerating devices are arranged on the bottom face and the outer side of the periphery of the heat conduction shell; wherein one set of snakelike refrigeration pipes is a water loop through which water passes, the other set of snakelike refrigeration pipes is a refrigerant loop through which refrigerant passes, each set of snakelike refrigeration pipes comprises a plurality of refrigeration loops corresponding to a plurality of areas respectively, and the plurality of refrigeration loops refrigerate in parallel; in the battery discharging operation process, the temperature measuring device obtains temperature data of different areas in real time and transmits the temperature data to the control module in real time, the control module regulates and controls battery thermal management based on the real-time temperature data, accurate temperature control can be achieved, the battery temperature can be rapidly reduced, and the thermal management efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal management, and particularly to a battery thermal management system and a control method combining liquid cooling and phase change immersion cooling. Background Art

[0002] Lithium batteries are the core components of new energy vehicles and energy storage systems. The normal operating temperature range of most electric vehicle batteries is a temperature difference threshold of -20°C to 55°C, and the battery has the best performance when the battery temperature is within 45°C. Once the battery temperature reaches or exceeds 60°C, the chemical substances inside the battery may react violently, the electrolyte may decompose and burn, and the separator may melt, thus triggering thermal runaway, posing serious safety risks such as fire and explosion. In addition, in order to ensure the best working performance of the battery, the temperature difference of the battery module needs to be controlled within the temperature difference threshold.

[0003] In recent years, liquid cooling has been increasingly widely used in fields such as new energy vehicles. The liquid cooling system is in direct contact with the battery module through cooling plates or cooling pipes, and uses a coolant to absorb the heat generated by the battery to maintain the battery within the best operating temperature range. However, with the increase in battery power, due to its low heat removal capacity, liquid cooling is increasingly difficult to meet the requirements, and the flow of the coolant in the pipes or cooling plates may be uneven, resulting in uneven temperature distribution inside the battery pack.

[0004] Composite phase change materials can absorb a large amount of heat when the temperature reaches the phase change point, and at the same time change from a solid to a liquid, absorbing a large amount of heat. However, the thermal conductivity of composite phase change materials is usually low, and the heat absorption process of composite phase change materials depends on the phase change temperature, and precise temperature control cannot be achieved.

[0005] Therefore, how to comprehensively consider temperature uniformity and cooling speed to perform efficient and precise thermal management on the battery urgently needs research and development. Summary of the Invention

[0006] To solve the above problems raised in the background art, the present invention provides a battery thermal management system and a control method combining liquid cooling and phase change immersion cooling.

[0007] The technical solution of the present invention is as follows:

[0008] A battery thermal management system combining liquid cooling and phase change immersion cooling includes: a heat-conducting housing with an open top, a heat-conducting upper cover arranged on the top of the heat-conducting housing, and composite phase change materials filled in the voids of the battery.

[0009] The composite phase change materials are divided into several regions with the same area, and a temperature measuring device is arranged in the composite phase change materials of each region. The temperature measuring device is communicatively connected to a controller arranged outside the heat-conducting housing.

[0010] The bottom surface and the outer sides around of the heat-conducting housing are closely provided with a refrigeration device. The refrigeration device includes two sets of independently arranged and spaced serpentine refrigeration pipes. One set is for water circulation as a water circuit, and the other set is for refrigerant circulation as a refrigerant circuit; each set of serpentine refrigeration pipes includes several parallel refrigeration circuits, and each refrigeration circuit corresponds to a region;

[0011] At the water inlet of each refrigeration circuit in the water circuit, a first flow regulating member is provided. At the refrigerant inlet of each refrigeration circuit in the refrigerant circuit, a second flow regulating member is provided. The first flow regulating member and the second flow regulating member are both communicatively connected to the controller;

[0012] Control module: During the battery discharge operation, based on the temperature data of different regions obtained by the temperature measuring device in real time, it is used to regulate the battery thermal management. The regulation process is as follows:

[0013] Take the average value of the temperatures of each region to obtain the average temperature. If the average temperature is less than or equal to the first temperature, control all the first flow regulating members to open with a fixed opening degree, and the water circuit passes water with the first water flow; if the average temperature is greater than the first temperature and less than or equal to the second temperature, dynamically regulate the opening degrees of all the first flow regulating members according to the set water flow regulation rule;

[0014] If the average temperature is greater than the second temperature, control all the first flow regulating members to be adjusted to the maximum opening degree, and at the same time control all the second flow regulating members to open with the maximum opening degree until the average temperature is less than the second temperature.

[0015] Specifically, the water flow regulation rule when the average temperature is greater than the first temperature and less than or equal to the second temperature is expressed by the following formula:

[0016]

[0017] where N i is the opening degree of all the first flow regulating members at different average temperatures T i , Q i is the water flow regulated corresponding to different average temperatures T i , Q max is the maximum water flow, Q1 is the first water flow, T i is the different average temperatures obtained in real time, T1 < T i <<T2; T1 is the first temperature, and T2 is the second temperature.

[0018] During the regulation process of battery thermal management, if the average temperature is less than or equal to the first temperature and the maximum temperature difference between any two regions is greater than the temperature difference threshold, then based on the first water flow rate, the maximum temperature difference, and the set flow rate adjustment amount, the region with the highest temperature is adjusted for flow rate with the second partition flow rate, and the other regions are all fixed to pass water with the first water flow rate. The second partition flow rate adjustment formula is as follows:

[0019]

[0020] Among them, Q v is the second partition flow rate. When the calculated Q v is greater than 100%, take Q v as 100%; Q1 is the first water flow rate, ΔT is the maximum temperature difference, ΔT th is the temperature difference threshold, and q is the flow rate adjustment amount.

[0021] Specifically, the first flow rate adjustment component is an electric flow control valve, and the second flow rate adjustment component is a solenoid valve.

[0022] Specifically, a thermal conductive sealant is provided between the composite phase change material and the thermal conductive upper cover inside the thermal conductive housing.

[0023] The temperature measuring device is a thermocouple.

[0024] Furthermore, it further includes an alarm module communicatively connected to the controller, which is arranged outside the thermal conductive housing and gives an early warning when the average temperature is greater than the second temperature.

[0025] The phase change temperature of the composite phase change material is 37°C.

[0026] The first temperature is less than the second temperature.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. A battery thermal management system and regulation method combining liquid cooling and phase change immersion cooling provided by the present invention uses a water circuit and a refrigerant circuit for dual-channel refrigeration and regulation on the basis of the heat absorption of the composite phase change material. Based on the real-time acquired temperature data, by adjusting the opening degrees of the first flow rate adjustment components provided on the water inlet pipe corresponding to different regions and the second flow rate adjustment components provided on the refrigerant circuit corresponding to different regions, it is convenient to achieve precise temperature control, can quickly reduce the battery temperature, effectively improve the thermal management efficiency, and ensure that the battery operates within the optimal temperature range.

[0029] 2. According to the real-time temperature data, when the maximum temperature difference between any two regions is greater than the temperature difference threshold, the present invention can reduce the temperature difference between different regions by performing partition adjustment of the water flow rate, make the temperature distribution in each region inside the battery uniform, thereby improving the battery performance, extending the battery life, and enhancing the safety. Description of the Drawings

[0030] In the drawings:

[0031] Figure 1 is a schematic diagram of the hierarchical expansion of the battery thermal management system in the embodiment;

[0032] Figure 2 is a schematic layout diagram of a single set of serpentine refrigerant pipes in the embodiment;

[0033] The components represented by the reference numerals in the drawings are as follows:

[0034] 1, heat-conducting housing; 2, heat-conducting upper cover; 3, composite phase change material; 4, battery; 5, temperature measuring device; 6, water circuit; 7, refrigerant circuit; 8, flow regulating member; 801, first flow regulating member; 802, second flow regulating member; 10, heat-conducting sealant. Detailed Embodiment

[0035] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the drawings.

[0036] Embodiment

[0037] This embodiment provides a battery thermal management system combining liquid cooling and phase change immersion cooling. Refer to Figure 1 、 Figure 2 , including: a heat-conducting housing 1 with an open top, a heat-conducting upper cover 2 provided on the top of the heat-conducting housing 1, and a composite phase change material 3 filled in the gaps of the battery 4,

[0038] The composite phase change material 3 is divided into several regions with the same area, and a temperature measuring device 5 is arranged in the composite phase change material 3 of each region. The temperature measuring device 5 is communicatively connected to a controller arranged outside the heat-conducting housing 1;

[0039] The bottom surface and the outer sides of the four weeks of the heat-conducting housing 1 are closely provided with a refrigeration device. The refrigeration device includes two sets of serpentine refrigerant pipes that are independent of each other and arranged at intervals. One set passes water as the water circuit 6, and the other set passes refrigerant as the refrigerant circuit 7; each set of serpentine refrigerant pipes includes several parallel refrigeration circuits, and each refrigeration circuit corresponds to a region;

[0040] A first flow regulating member 801 is arranged at the water inlet of each refrigeration circuit in the water circuit 6, and a second flow regulating member 802 is arranged at the refrigerant inlet of each refrigeration circuit in the refrigerant circuit 7. The first flow regulating member 801 and the second flow regulating member 802 are both communicatively connected to the controller;

[0041] Control module: used for regulating the thermal management of the battery 4 based on the temperature data of different regions obtained by the temperature measuring device 5 received in real time during the discharge operation of the battery 4. The regulation process is as follows:

[0042] Take the average value of the temperatures of each region to obtain the average temperature. If the average temperature is less than or equal to the first temperature, control all the first flow regulators 801 to open with a fixed opening degree, and the water circuit 6 to pass water with the first water flow rate; if the average temperature is greater than the first temperature and less than or equal to the second temperature, dynamically adjust the opening degrees of all the first flow regulators 801 according to the set water flow regulation rules.

[0043] If the average temperature is greater than the second temperature, control all the first flow regulators 801 to be adjusted to the maximum opening degree, and at the same time control all the second flow regulators 802 to open with the maximum opening degree until the average temperature is less than the second temperature.

[0044] Specifically, for a battery thermal management system combining liquid cooling and phase change immersion cooling provided in this embodiment, the materials of the heat-conducting housing 1 and the heat-conducting upper cover 2 are both copper metal, with high heat-conducting performance. The heat-conducting housing 1 serves as an external structural support, and a composite phase change material 3 is arranged inside it. A heat-conducting sealant 10 is arranged between the composite phase change material 3 and the heat-conducting upper cover 2. The composite phase change material 3 used in this embodiment is graphene aerogel enhanced paraffin, with a phase change temperature of 37°C. Under a graphene aerogel (HGA) filler loading of only 12.5 wt%, the thermal conductivity before phase change is 0.719 W / m·K, and the thermal conductivity after phase change is 30.75 W / m·K, significantly higher than that of traditional composite phase change materials (such as 0.2 - 0.5 W / m·K for pure paraffin), and the latent heat of phase change is 200 J / g.

[0045] The composite phase change material 3 absorbs heat when the battery 4 operates and generates heat, undergoes a phase change at the phase change temperature, absorbs heat and melts, changing from a solid state to a liquid state. The heat absorbed by the composite phase change material 3 is transferred to the heat-conducting housing 1 through heat conduction, and then dissipated from the housing to the outside. A number of batteries 4 are arranged at equal intervals inside the composite phase change material 3. The number of batteries 4 is arranged at equal intervals to achieve uniform distribution of heat and avoid heat concentration. A number of batteries 4 are all in close contact with the composite phase change material 3, enabling the heat generated by the batteries 4 to be quickly transferred into the composite phase change material 3, improving the heat transfer efficiency.

[0046] The bottom surface and the outer sides around the heat-conducting housing 1 are provided with refrigeration devices. The refrigeration devices include two independent and spaced-apart serpentine refrigeration pipes. Each serpentine refrigeration pipe is integrally connected and arranged closely against the outer surface of the heat-conducting housing 1. The two refrigeration pipes are independent of each other, providing a redundant design, which can improve the reliability of the system. The two refrigeration pipes can take away the heat transferred to the heat-conducting housing through the circulating cooling working medium to achieve active cooling. In order to increase the contact area between the refrigeration pipes and the outer surface of the heat-conducting housing 1 and improve the heat dissipation efficiency, both of the two refrigeration pipes adopt a serpentine design. At the same time, both of the two liquid-cooling pipes adopt a countercurrent arrangement. The diameter of the liquid-cooling pipe is 20 mm and the wall thickness is 0.2 mm. It is set that each serpentine liquid-cooling pipe is spaced 30 mm from each other at the bottom surface of the heat-conducting housing and 40 mm from each other on the outer surfaces around.

[0047] The present invention realizes dual heat dissipation by combining the passive heat absorption ability of the composite phase change material 3 and the active cooling ability of the refrigeration pipes. At the same time, two refrigeration pipes are designed, which can significantly improve the efficiency and reliability of the thermal management of the battery 4. The phase change latent heat of the composite phase change material 3 can absorb a large amount of heat, significantly reducing the battery temperature. At the same time, the uniform distribution of the composite phase change material 3 and the heat conduction performance of the heat-conducting housing contribute to achieving temperature uniformity and avoiding local overheating. The two refrigeration pipes can achieve fine temperature control through the flow regulating components, making up for the disadvantage of insufficient temperature control accuracy of the composite phase change material.

[0048] The present invention further considers zoning regulation based on temperature differences on the basis of dual heat dissipation. Based on the arrangement of the battery 4, the composite phase change material 3 is divided into several regions with the same area. A temperature measuring device 5 is arranged in the composite phase change material 3 of each region. The temperature measuring device 5 can be a thermocouple. The temperature measuring device 5 is communicatively connected to a controller arranged outside the heat-conducting housing 1 for transmitting the measured temperature data to the controller in real time.

[0049] For the two sets of serpentine refrigeration pipes, one set of serpentine refrigeration pipes is filled with water as the water circuit 6, and the other set of serpentine refrigeration pipes is filled with refrigerant as the refrigerant circuit 7. Each set of serpentine refrigeration pipes includes several refrigeration circuits corresponding to several regions respectively, and the several refrigeration circuits perform parallel refrigeration.

[0050] At the connection between the bottom of the refrigeration circuit in each region and its inlet pipe in the water circuit 6, a first flow regulating component 801 is arranged. The first flow regulating component 801 is an electric flow regulating valve. In the refrigerant circuit, at the connection between the bottom of the refrigeration circuit in each region and its inlet pipe, a second flow regulating component is arranged. The second flow regulating component 802 is a solenoid valve.

[0051] During the discharge operation of the battery 4, the temperature measuring device 5 obtains the temperature data of the composite phase change material 3 in different regions in real time and transmits the temperature data to the control module in real time. Based on the received temperature data, the control module conducts the regulation of the thermal management of the battery 4, and the regulation process is as follows:

[0052] Take the average value of the temperatures in each area to obtain the average temperature. If the average temperature is less than or equal to the first temperature, control all the first flow regulators 801 to open with a fixed opening degree, and the water circuit 6 passes water with the first water flow rate; if the average temperature is greater than the first temperature and less than or equal to the second temperature, dynamically adjust the opening degrees of all the first flow regulators 801 according to the set water flow regulation rules.

[0053] If the average temperature is greater than the second temperature, control all the first flow regulators 801 to be adjusted to the maximum opening degree, and at the same time control all the second flow regulators 802 to open with the maximum opening degree until the average temperature is less than the second temperature.

[0054] In this embodiment, the phase change temperature of the composite phase change material 3 is set as the first temperature, the first temperature is 37 °C, the first temperature is set to be less than the second temperature, and the second temperature is 45 °C. Generally, that is, when the maximum temperature difference in each area is not greater than the temperature difference threshold, the temperature difference threshold can be set to 5 °C, and all the flow regulators are uniformly adjusted to have the same opening degree, which can reduce the operation burden of the system and improve the reliability and response speed of the system.

[0055] When the average temperature is less than or equal to the first temperature, control all the first flow regulators to open with a fixed opening degree, and the water circuit 6 passes water with the first water flow rate to avoid excessive cooling and energy consumption waste, and the first water flow rate can be set to 60%.

[0056] When the average temperature is greater than the first temperature and less than or equal to the second temperature, dynamically adjust the opening degrees of all the first flow regulators according to the set water flow regulation rules. By dynamically adjusting the water flow rate, ensure the balance between the cooling effect and the energy consumption. The water flow regulation rules are expressed by the following formula:

[0057]

[0058] Among them, N i is the opening degree of all the first flow regulators at different average temperatures T i ; Q i is the water flow rate adjusted correspondingly at different average temperatures T i ; Q max is the maximum water flow rate, Q1 is the first water flow rate, T i is the different average temperature obtained in real time, T1 < T i << T2; T1 is the first temperature, and T2 is the second temperature.

[0059] If the average temperature is greater than the second temperature, control all the first flow regulators 801 to be adjusted to the maximum opening degree, and at the same time control all the second flow regulators 802 to be opened at the maximum opening degree until the average temperature is less than the second temperature. The second temperature is the warning temperature. When the average temperature is greater than the second temperature, by controlling all the first flow regulators 801 and the second flow regulators 802 to be opened at the maximum opening degree, the temperature of the battery 4 can be rapidly reduced.

[0060] The present invention further includes an alarm module communicatively connected to the controller, which is disposed outside the heat-conducting housing 1 and gives a warning when the average temperature is greater than the second temperature.

[0061] Further, during the regulation process of battery thermal management, if the average temperature is greater than the first temperature and less than the second temperature, and the maximum temperature difference between any two regions is greater than the temperature difference threshold, then based on the water flow rate corresponding to different average temperatures, the maximum temperature difference, and the set flow rate adjustment amount, the region with the highest temperature is adjusted with the first partition flow rate, and other regions are adjusted based on the water flow rate adjustment rule. The first partition flow rate adjustment formula is expressed as follows:

[0062]

[0063] Among them, Q u is the first partition flow rate. When the calculated Q u is greater than 100%, take Q u as 100%; Q i is the water flow rate corresponding to different average temperatures, ΔT is the maximum temperature difference, ΔT th is the temperature difference threshold, and q is the flow rate adjustment amount.

[0064] During the regulation process of battery thermal management, if the average temperature is less than or equal to the first temperature, and the maximum temperature difference between any two regions is greater than the temperature difference threshold, then based on the first water flow rate, the maximum temperature difference, and the set flow rate adjustment amount, the region with the highest temperature is adjusted with the second partition flow rate, and other regions are all fixed to pass water with the first water flow rate. The second partition flow rate adjustment formula is expressed as follows:

[0065]

[0066] Among them, Q v is the second partition flow rate. When the calculated Q v is greater than 100%, take Q v as 100%; Q1 is the first water flow rate, ΔT is the maximum temperature difference, ΔT th is the temperature difference threshold, and q is the flow rate adjustment amount.

[0067] Through the adjustment of differential partition cooling intensity, the refined control of the uneven problem of battery heat release temperature distribution is realized, ensuring the uniform temperature distribution in each area of the battery pack, thereby improving battery performance, extending battery life, and enhancing the use safety.

Claims

1. A battery thermal management system combining liquid cooling and phase change immersion cooling, characterized in that: include: A heat-conducting shell with an opening at the top, a heat-conducting upper cover arranged on the top of the heat-conducting shell, and a composite phase change material filled in the gap of the battery. The composite phase change material is divided into a plurality of regions of equal area, a temperature measuring device is arranged in the composite phase change material of each region, and the temperature measuring device is communicatively connected to a controller arranged outside the heat-conducting housing; The bottom surface and the outer sides of the heat-conducting shell are closely provided with a refrigeration device, which includes two sets of serpentine refrigeration pipes that are independent of each other and arranged at intervals, one set of which is a water circuit for water flow, and the other set of which is a refrigerant circuit for refrigerant flow; each set of serpentine refrigeration pipes includes a plurality of parallel refrigeration circuits, and each refrigeration circuit corresponds to one area; A first flow regulating member is provided at the water inlet of each refrigeration circuit in the water circuit, and a second flow regulating member is provided at the refrigerant inlet of each refrigeration circuit in the refrigerant circuit, and the first flow regulating member and the second flow regulating member are both communicatively connected to the controller; Control module: used to control the thermal management of the battery during the battery discharge operation based on the temperature data of different areas obtained by the real-time receiving temperature measuring device. The control process is as follows: Taking an average of the temperatures of each area to obtain an average temperature, if the average temperature is less than or equal to the first temperature, all first flow regulating elements are controlled to be opened at a fixed opening, and the water circuit flows water at a first water flow rate; If the average temperature is greater than the first temperature and less than or equal to the second temperature, dynamically adjusting the openings of all first flow regulating members according to the set water flow regulating rule; If the average temperature is greater than the second temperature, all first flow regulating elements are controlled to be adjusted to the maximum opening, and all second flow regulating elements are controlled to be opened at the maximum opening, until the average temperature is less than the second temperature.

2. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1 is characterized in that: The water flow rate regulation rule when the average temperature is greater than the first temperature and less than or equal to the second temperature is expressed by the following formula: Among them, N i For different average temperatures T i The opening of all first flow regulating components, Q i For different average temperatures T i Corresponding to the regulated water flow, Q max is the maximum water flow, Q1 is the first water flow, T i Different average temperatures obtained in real time, T1 <T i <<T2; T1 is the first temperature, T2 is the second temperature.

3. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1 is characterized in that: During the regulation of battery thermal management, if the average temperature is less than or equal to the first temperature, and the maximum temperature difference between any two areas is greater than the temperature difference threshold, based on the first water flow rate, the maximum temperature difference, and the set flow adjustment amount, the flow rate of the area with the highest temperature is adjusted at the second partition flow rate, and the other areas are fixed with the first water flow rate. The second partition flow adjustment formula is expressed as follows: Among them, Q v is the flow rate of the second partition, and Q is calculated v When it is greater than 100%, take Q v is 100%; Q1 is the first water flow rate, ΔT is the maximum temperature difference, ΔT th is the temperature difference threshold, and q is the flow adjustment amount.

4. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: The first flow regulating component is an electric flow regulating valve, and the second flow regulating component is a solenoid valve.

5. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: A heat-conducting sealant is arranged between the composite phase-change material and the heat-conducting upper cover in the heat-conducting housing.

6. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: The temperature measuring device is a thermocouple.

7. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: It also includes an alarm module that is connected to the controller for communication and is arranged outside the heat-conducting housing to issue an early warning when the average temperature is greater than the second temperature.

8. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: The phase change temperature of the composite phase change material is 37°C.

9. The battery thermal management system combining liquid cooling and phase change immersion cooling according to claim 1, characterized in that: The first temperature is lower than the second temperature.

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