Publish Time: 2023-12-14 Origin: Site
In order to further solve the energy crisis, China vigorously advocates the development of new energy, among which the new energy vehicles driven by electricity are the key areas for China to enter the new energy applications on a large scale. New energy vehicles refer to the use of non-fossil energy (such as electricity, solar energy, etc.) as a power source of vehicles, which has the advantages of low-carbon environmental protection, high efficiency and energy saving, and has become an important development direction of the future automotive industry. As one of the core components of new energy vehicles, the performance of the power battery directly affects the performance and safety of the vehicle. However, because the power battery will produce a lot of heat when working, its heat dissipation problem has been one of the important factors restricting its development. In this paper, the current five mainstream heat dissipation technologies - convection heat dissipation, air cooling, liquid cooling, heat pipe cooling and phase change material heat dissipation are reviewed, and their principles, advantages and disadvantages and applications are analyzed and compared, providing certain reference value for the development of new energy vehicle power battery heat dissipation technology.
As an energy storage device, the lithium-ion battery comprises a positive electrode, a negative electrode, an electrolyte, a diaphragm and a shell. The heat production mechanism of power battery mainly includes chemical reaction heat, Joule heat, polarization heat, side reaction heat and so on. Chemical reaction heat is the chemical reaction inside the battery will produce a certain amount of heat, is the main source of power battery heat. When the battery is charged, the chemical reaction between the positive and negative electrodes will produce a lot of chemical reaction heat; Joule heat is the heat generated by the current passing through the battery when the battery is working. The generation of this heat is related to the working state of the battery, for example, when the load of the battery is large, the current passes through the battery for a longer time, and the generated joule heat is more; The heat of polarization is the polarization of the chemical substances inside the battery under the action of an electric field. The size of this heat is related to the working voltage, current of the battery and the temperature of the working environment. In addition to the above three methods of heat production, some side reactions may also occur during the use of the battery, and these side reactions will also release heat. In general, the heat production mechanism of power batteries is complex, and it needs to be considered comprehensively according to the specific use environment and conditions.
Power battery convection heat dissipation technology is a technology that uses the natural convection of air to dissipate the heat generated inside the battery through the radiator. Convection heat is dissipated by the transfer of heat between the battery pack and the bottom thermal material, while the side of the battery pack is dissipated by air. The technology has the advantages of high heat transfer efficiency and good stability, which can effectively reduce the operating temperature of the battery and improve the service life and safety of the battery. In addition, the convection heat dissipation technology also has the effect of isolation and shock absorption, which can avoid the occurrence of problems such as short circuit and wear between batteries.
When the battery is working, a lot of heat will be generated, and if this heat is not dissipated in time, it will adversely affect the performance and life of the battery. Therefore, this heat needs to be dissipated through a radiator. The principle of convective heat dissipation technology is to increase the heat transfer efficiency between the battery pack and the bottom of the battery. At the same time, the side of the battery pack through air flow to achieve heat dissipation effect. The choice of thermal conductive silicone sheet is also very important for the effect of convection heat dissipation. At present, the commonly used thermal conductive silicone sheet materials are silicone rubber, polyurethane elastomer and so on. Thermal conductive materials have good thermal conductivity and high temperature resistance. In addition, the shape and size of the thermal conductive silicone sheet also need to be adjusted and optimized according to the actual situation.
The advantages of convective heat dissipation technology are high heat transfer efficiency and good stability. At the same time, it also has the advantage of isolation and shock absorption. However, the disadvantage of this technology is that it needs to increase certain hardware facilities to achieve convective heat dissipation function. In order to achieve better cooling effect in actual use, it is often necessary to increase special parts such as fins to expand the area of heat dissipation contact [3]. At the same time, it is also necessary to optimize the design and adjust the plan for different models and the needs of the use environment. Power battery convection heat dissipation technology is mainly used in some low-end electric vehicles, but with the development of technology, convection heat dissipation technology has also begun to be applied in some mid-end electric vehicles.
Air-cooled heat dissipation is a way to strengthen the flow of air inside the battery under the action of the fan and take away the heat dissipated by the battery. The technology has the advantages of simple structure and low cost, and is suitable for some small battery packs or mobile battery packs. However, the heat transfer efficiency of air-cooled heat dissipation technology is low, and it is easily affected by the external environment, such as temperature, humidity and other factors will affect its heat dissipation effect.
The air-cooled radiator is the core component of the air-cooled heat dissipation technology of power battery, which is mainly composed of fan, heat sink, heat shield and so on. The role of the fan is to blow air towards the radiator, creating a airflow that takes the heat away. The heat sink is an important medium that transfers heat to the air, and its shape, size, and material will affect the heat dissipation effect. The heat sink is used to protect the battery and radiator from the external environment, such as dust, rain and so on. The principle of air-cooled heat dissipation technology is to increase the air flux, thereby taking away the heat of the power battery. The choice of fan is also very important for the effect of air cooling heat dissipation. At present, there are two types of fans commonly used: axial fans and centrifugal fans. Axial-flow fans are suitable for low-speed operation. Centrifugal fans are suitable for high-speed operation scenarios. In addition, the design of the ventilation hole also needs to take into account the spatial layout and structural characteristics of the battery pack.
The advantage of air-cooled heat dissipation technology is that it has the advantages of simple structure and low cost, and it is suitable for the heat dissipation requirements of some small battery packs or mobile battery packs. However, the heat transfer efficiency of air-cooled heat dissipation technology is low, and it is easily affected by the external environment, such as temperature, humidity and other factors will affect its heat dissipation effect. In addition, due to the limited space inside the battery pack, the number and size of the ventilation holes also need to be adjusted and optimized according to the actual situation. The air-cooled heat dissipation technology also has some shortcomings such as loud noise. Due to the existence of fans, the air-cooled radiator will have some noise during operation. Power battery air cooling technology is mainly used in some low-end electric vehicles and small energy storage systems. In these systems, due to cost and space constraints, other heat dissipation methods cannot be used, so only air-cooled heat dissipation technology can be used. However, with the development of technology, air-cooled heat dissipation technology has also begun to be applied in some high-end electric vehicles.
Liquid cooling heat dissipation is a new type of heat dissipation, its working principle is under the action of the liquid medium through convection heat transfer to release the battery heat, reduce the battery temperature. The technology has the advantages of high heat transfer efficiency and good heat dissipation effect, which can effectively reduce the working temperature of the battery and improve the service life and safety of the battery. In addition, liquid cooling technology also has the advantages of high reliability and low maintenance costs, so it has been widely used in the field of new energy vehicles.
The principle of liquid cooling cooling technology is to inject coolant into the battery pack, and then dissipate heat through the cooling aluminum tube. The choice of coolant is very important for the effect of liquid cooling. At present, the commonly used coolants are mineral oil, synthetic oil and water-based coolants. Among them, mineral oil has the characteristics of good thermal conductivity and high temperature resistance, but it has a certain pollution to the environment; The synthetic oil has better environmental protection performance and high temperature stability; Water-based coolant has the advantages of non-toxic and harmless, good environmental protection and so on. When selecting coolant, comprehensive consideration should be made according to the specific application scenario. At present, the research of liquid cooling cooling technology is mainly focused on the design of the cooling plate structure, and the design of the cooling plate is focused on the design of the flow channel, often by changing the shape of the flow channel, the number of flow channels to achieve the impact on the power battery heat dissipation. The more complex the design of the flow channel, the better the general heat dissipation effect, but the processing is often extremely complex, the cost is higher, and even some flow channels can not be completed in the actual processing and manufacturing, so the flow channel is designed to fully consider the difficulty of manufacturing, and then the comprehensive heat dissipation effect to develop a program.
The advantages of liquid cooling technology are obvious. First of all, it can effectively reduce the operating temperature of the battery, thereby improving the service life and safety of the battery. Secondly, the liquid cooling device has a simple structure and is easy to maintain and replace. In addition, the liquid cooling technology also has high reliability and stability, and can work normally in harsh environments. However, liquid cooling technology also has some disadvantages. For example, its cost is high, and more funds need to be invested in equipment renovation and maintenance; At the same time, problems such as liquid leakage also need attention.
Heat pipe cooling is a new way of heat dissipation of power battery, which has strong thermal conductivity and good application prospect. Heat pipe cooling technology is a technology that uses the principle of heat pipes to dissipate heat, mainly used for cooling battery systems. A heat pipe is an efficient heat-transfer element consisting of a slender tube and two metal fins connected at the ends. When the heat inside the battery is conducted to the heat pipe, the liquid inside the heat pipe will absorb heat and evaporate, producing a large amount of steam, which will flow along the tube and take away the heat inside the battery. Eventually, the steam cools into a liquid in the radiator, releasing latent heat and thus dissipating heat. Heat pipe radiator is one of the core components of power battery heat pipe cooling technology, which is mainly composed of heat pipe, fin, fan and so on. The role of the heat pipe is to transfer the heat inside the battery to the radiator, and the fin is an important component used to increase the heat dissipation area and improve the heat dissipation efficiency. The fan is used to accelerate the flow of air, thereby improving the heat dissipation effect of the radiator. In some high-end battery systems, heat pipe cooling technology has been widely used, such as new energy vehicles, drones and other industries. With the continuous development of technology and the reduction of cost, it is believed that heat pipe cooling technology will be applied in more fields.
The heat pipe cooling technology has the advantages of high efficiency and energy saving, high reliability, wide application range and low maintenance cost. High efficiency and energy saving: heat pipe cooling technology can quickly transfer the heat generated by the battery, avoiding the waste of energy and improving the efficiency of energy utilization; High reliability: heat pipe cooling technology uses a closed pipe structure, will not be affected by the external environment, with high stability and reliability; Wide range of application: heat pipe cooling technology is suitable for various types of battery systems, including lithium-ion batteries, lead-acid batteries, etc. Low maintenance cost: heat pipe cooling technology has simple structure, low maintenance cost and long-term stable operation.
The shortcomings of heat pipe cooling technology are also very obvious, mainly with large volume, high cost, large fluid resistance and other unfavorable factors. Large volume: Because the heat pipe needs to occupy a certain space, compared with the traditional air cooling method, the heat pipe cooling technology needs more installation space; High cost: The manufacturing cost of heat pipe cooling technology is relatively high, and high-quality materials and processes are required to ensure its performance and life. Large fluid resistance: liquid flow inside the heat pipe will produce a certain resistance, which will affect the heat transfer efficiency of the heat pipe; Heat pipe cooling technology also has a big noise problem, because of the existence of fans, heat pipe radiator will produce a certain noise during operation; Heat pipe cooling technology temperature control is difficult, its heat dissipation effect is greatly affected by environmental factors, so the temperature control is relatively difficult.
Power battery phase change material cooling technology is a technology that uses phase change materials for heat dissipation, which is mainly used for cooling battery systems. The basic principle of power battery phase change material heat dissipation technology is to use phase change materials for heat dissipation. Phase change material is a kind of material that can absorb or release a lot of heat within a certain temperature range. When the heat inside the battery is conducted to the phase change material, the liquid part of the phase change material will absorb heat and expand, becoming a gas. The solid part, on the other hand, emits heat and contracts. In this way, the phase-change material can quickly transfer the heat inside the battery to the radiator, thus achieving the cooling of the battery. Phase change material heat sink is one of the core components of power battery phase change material heat dissipation technology, which is mainly composed of phase change material, fin, fan and so on.
Photo material cooling technology has the advantages of high efficiency and energy saving, high reliability, wide application range and low maintenance cost. High efficiency and energy saving: phase-change material cooling technology can quickly transfer the heat generated by the battery, avoiding the waste of energy and improving the efficiency of energy utilization; High reliability: the phase change material cooling technology uses stable phase change materials, has high stability and reliability, and can run stably for a long time; Wide range of application: Phase change material cooling technology is suitable for various types of battery systems, including lithium-ion batteries, lead-acid batteries, etc. Low maintenance cost: Phase change material cooling technology has simple structure, low maintenance cost, and long-term stable operation.
The disadvantages of photo material cooling technology are large volume, high cost and limited temperature range. Large volume: Because the phase change material needs to occupy a certain space, so compared with the traditional air cooling method, the phase change material cooling technology needs a larger installation space; High cost: The manufacturing cost of phase change material cooling technology is relatively high, and high-quality materials and processes are required to ensure its performance and life. Limited temperature range: the temperature range of phase change materials is narrow, and can only be dissipated within a certain range, and can not adapt to the needs of all working conditions.
In summary, convection heat dissipation technology, air cooling heat dissipation technology, liquid cooling heat dissipation technology, heat pipe cooling heat dissipation technology and phase change material cooling heat dissipation technology are the five mainstream new energy vehicle power battery heat dissipation technology. The liquid cooling technology has the advantages of high heat transfer efficiency and good heat dissipation effect. The air-cooled cooling technology has the advantages of simple structure and low cost. Convective heat dissipation technology has the advantages of high heat transfer efficiency and good stability. Heat pipe cooling technology has the advantages of high efficiency and energy saving, high reliability, wide application range and low maintenance cost. In the future development, the appropriate heat dissipation technology scheme should be selected according to the needs of different models and the use of the environment, and the existing heat dissipation technology should be continuously optimized and improved to improve the performance and reliability of the new energy vehicle power battery.
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