Liquid cooling technology introduction
The liquid cooling system refers to the cooling system in which the cooling liquid directly or indirectly contacts the power battery module, and then takes away the heat generated by the battery through the continuous circulation of the cooling liquid. Due to the higher heat transfer coefficient of the coolant, it is more efficient and effective than an air-cooled system. The liquid cooling system can be divided into direct contact and indirect contact according to the contact mode between the cooling liquid and the battery. The direct contact liquid cooling system completely immerses the lithium-ion battery in the cooling liquid, which has a good effect on the temperature uniformity of the battery pack. However, the sealing requirements for battery packs are stricter. Due to the insulation requirements of the battery, the direct contact method requires a coolant with insulating properties, such as silicone oil, mineral oil, etc. The indirect liquid cooling system mainly consists of condenser, evaporator, compressor, cold plate and battery. The principle is to arrange a cold plate or water jacket on the surface of the battery, and the coolant flows through the surface of the battery through the flow channel to achieve the purpose of circulation and heat exchange. Commonly used coolants for indirect contact are ethylene glycol and water, which have a lower viscosity than direct liquid cooling. Although the liquid cooling thermal management system technology is quite mature and has been widely used in the cooling system of new energy vehicles, there is still a lot of room for development. The key to liquid cooling technology is the increase of effective cooling area and the enhancement of turbulence intensity. Therefore, the research on the liquid cooling technology of electric vehicles at home and abroad mainly focuses on the structural design of the cooling medium flow channel.
Integrated battery thermal management system
At present, the mainstream cooling method of the battery thermal management system is still liquid cooling, and its technology is relatively mature, but the weight and the poor heat dissipation effect of traditional cooling media are the main reasons that limit the development of liquid cooling systems, so it is necessary to study cooling media with higher heat transfer efficiency . In addition, under the premise that the development of cooling media is limited, research on high-efficiency cooling structures is also one of the future development directions. With the continuous development of new energy vehicles in the direction of high energy density and high integration, the hybrid battery thermal management system will be applicable to more working conditions, such as liquid cooling-phase change materials, air cooling-phase change materials, liquid cooling- High-efficiency integrated cooling-heating systems such as high-frequency heating will be one of the main development trends of thermal management systems in the future.
The direct cooling technology based on the air-conditioning system uses compressed steam for cooling, and removes heat from the battery through the evaporation of the working medium to achieve battery cooling. It efficiently utilizes the existing heat management structure and reduces the cost and structural complexity. Compared with liquid cooling technology, the safety of direct cooling technology is higher. At the same time, the vehicle air conditioning system is also based on direct cooling technology. Therefore, combining the air conditioning system and battery cooling system into one, that is, the vehicle integrated thermal management system, will also be one of the best solutions for future battery cooling technology, and it is also one of the development directions of the future vehicle thermal management system.