The structure and working principle of the battery
thermal management system-2
A major difference between the battery thermal management independent unit and the ordinary air conditioner is the different structure of the evaporator. The ordinary air conditioner evaporator is used for heat exchange between the air conditioner refrigerant and the air, but the internal evaporator of the independent unit is used for heat exchange between the air conditioner refrigerant and the antifreeze. This special heat exchanger generally adopts a sleeve structure, and the heat exchange pipe is divided into two layers. The refrigerant is in the inner pipe and the cooling water is in the outer pipe. Some fins are distributed between the two pipes to increase the heat exchange area. The evaporator and condenser of the independent unit are available in two forms: integrated design and split design.
The independent unit requires a separate refrigeration system. When the system receives a refrigeration signal, the fan and water pump start working. The refrigerant completes the heat exchange with the antifreeze in the system through the plate heat exchanger in the unit, and then the antifreeze is sent to the heat exchanger inside the battery through the water pump, thereby achieving the purpose of lowering the battery temperature. When the heating signal is received, the PTC electric liquid heater and water pump inside the unit start working to heat the antifreeze in the system. The same as the principle of the refrigeration cycle, the heat exchange between the antifreeze and the heat exchange plate inside the battery is used to achieve the purpose of heating the battery.
Independent units can be designed with different powers according to needs, matching compressors, evaporators and other components with corresponding powers, so they can meet the needs of different cooling powers and have a wider range of uses. Compared with non-independent units, independent units respond more quickly to changes in the temperature inside the battery, do not need to consider the requirements of the passenger area for air conditioning refrigeration performance, and the layout is relatively flexible.
Compared with non-independent unit systems, independent units have an additional set of compressors and condensers for independent refrigeration, which is more expensive. However, because it is an independent system, the control logic is simpler than that of non-independent units. The cooling capacity of the independent unit system can be selected according to needs, generally above 2 kW, and is suitable for hybrid buses and pure electric buses using fast-charging batteries with high battery charge and discharge rates.
