Thermal Management Technology Overview 2
1.2 Thermal management of motors and electronic controls
The thermal management of electric vehicle motors and electronic control systems is an important part of ensuring long-term stable operation of vehicles, extending component life, and improving energy efficiency. Motors and electronic control components generate a lot of heat during operation. Excessive temperatures will not only reduce system performance, but may even cause safety hazards. For the thermal management of pure electric vehicle motors and electronic controls, heat dissipation is currently mainly achieved through air cooling systems, liquid cooling systems, and heat pipe technology. Some systems also recycle the waste heat of motors and electronic control systems.
1) Air cooling system. As a traditional motor heat dissipation method, the air cooling system uses the airflow generated when the vehicle is driving to dissipate heat, and removes the excess heat generated by the motor through natural convection or forced convection. The air cooling system has a relatively simple structure and low cost. It does not require additional cooling media and is suitable for situations where the power density is not high. However, as electric vehicle drive motors develop towards high power density, especially under continuous high load conditions, the heat dissipation capacity of air cooling has gradually become insufficient.
2) Liquid cooling technology. Liquid cooling technology plays an important role in the thermal management of electric vehicle motors. This technology uses coolant (such as water, ethylene glycol solution, etc.) as a heat transfer medium, and is closely attached to the motor winding or housing surface through a circulation pipeline, thereby effectively absorbing and removing heat. The liquid cooling system can quickly and evenly cool all parts of the motor, and is particularly suitable for high-performance electric vehicles. At the same time, in order to prevent safety risks caused by coolant leakage, materials and technologies with good sealing performance need to be used, and monitoring and alarm devices need to be added.
3) Heat pipe technology. Heat pipe technology can help conduct heat evenly and improve heat dissipation efficiency. Thermal sensors and intelligent control algorithms can achieve real-time monitoring and adjustment of system temperature. In addition, the use of high thermal conductivity materials and optimized design can also improve the heat exchange efficiency of heat dissipation components.
1.3 Passenger compartment thermal management system
Electric vehicle passenger compartment thermal management is one of the key technologies to ensure the comfort of drivers and passengers, improve vehicle energy efficiency and extend driving range. It mainly covers summer cooling, winter heating and intelligent control of temperature regulation. For summer cooling, evaporative cycle refrigeration system is mostly used. The difference lies mainly in the winter heating method. The main passenger compartment thermal management system heating methods are as follows:
1) PTC heater is a heating solution widely used in electric vehicles in the early days. In low temperature environment, PTC heater can quickly provide heat to the passenger compartment, but its energy conversion efficiency is relatively low, and the heating process directly consumes battery power, which may have a certain impact on the endurance of electric vehicles.
2) Heat pump air conditioning system plays an important role in the thermal management of electric vehicle passenger compartments, especially in winter heating. The system uses the reverse Carnot cycle to recover waste heat from the external environment or internal components, and converts low-grade heat energy into high-grade heat energy through components such as compressors, evaporators, and condensers to achieve efficient heating. Compared with traditional PTC heaters, heat pump systems have higher energy efficiency ratios, which reduces the demand for on-board battery energy to a certain extent. With the development of technology, dual-source or multi-source heat pump systems (such as integrated motor waste heat recovery function) have gradually attracted attention, further improving the performance of heat pumps in extreme low temperature environments. However, the performance of heat pump air conditioning systems will be significantly reduced in low temperature environments. The main reason is that the evaporation pressure and heat absorption of the refrigerant at low ambient temperature are reduced, resulting in a decrease in the coefficient of performance (COP) and difficulty in normal operation. To solve this problem, technologies such as air replenishment and enthalpy increase, defrosting, and waste heat recovery are usually used for improvement.
Some emerging passenger compartment thermal management technologies are also gradually being developed and tried to be applied in the field of electric vehicles. For example: phase change material energy storage technology can absorb excess heat when the temperature in the passenger compartment is too high, and release the stored heat when the temperature is too low; solar gain capture technology can collect solar radiation energy through solar panels installed on the roof and convert it into electrical energy or heat energy for use by the air conditioning system; in addition, the intelligent thermal management system uses advanced sensor networks and control algorithms to monitor the temperature inside and outside the cabin and passenger needs in real time, and dynamically adjust the thermal management strategy to achieve the best energy utilization effect.
