Classification of power battery thermal management system
The power battery thermal management system can mainly realize functions such as cooling, heating, and temperature balance. Currently, electric vehicle thermal management systems at home and abroad mainly include air cooling, liquid cooling, direct cooling and other forms.
1. Air-cooled thermal management system The structure of the air-cooled thermal management system can be divided into natural cooling and forced air cooling according to whether there is a fan. Natural cooling means that the power battery has no additional device for heat exchange, and the heat of the battery pack is completely balanced by the surrounding environment. Its advantages are simple structure and low cost, but the heat dissipation performance is weak. Forced air cooling is to cool the battery pack by fans. Compared with the natural cooling mode, the cooling effect is obvious, but in high temperature environment, the cooling effect is not good, and it cannot maintain the consistency of the battery cell temperature well.
2. Compared with the air-cooled thermal management system, the liquid-cooled structure has higher heat dissipation efficiency and more precise temperature control of the battery pack, which can well ensure the consistency of the battery pack. At the same time, the liquid-cooled structure can better protect the battery and enable the battery to provide better performance output in any environment. The liquid cooling system can be divided into a direct cooling liquid cooling system and an air-cooled/water-cooled mixed cooling system according to whether there is a low-temperature radiator. The direct cooling liquid cooling system has the advantages of compact system, good cooling performance but high compressor load. The air-cooled/water-cooled mixed cooling system has the advantages of compact system, good performance and economic energy saving in low temperature environment, but the system is complex, costly, complex to control and has high reliability requirements. At present, large-tonnage pure electric commercial vehicles and pure electric buses mostly use this structure.
3. Direct cooling system The direct cooling system uses refrigerant (phase change material) as the heat exchange medium. The refrigerant can absorb a large amount of heat during the gas-liquid phase change process. Compared with the refrigerant, the heat exchange efficiency can be increased by more than three times, and the heat inside the battery system can be taken away more quickly. However, the direct cooling system cannot achieve battery heating, there is no condensed water protection, and the refrigerant temperature is not easy to control. Although the direct cooling system has great potential, its shortcomings such as poor thermal conductivity need further exploration.
