PTC heating system: integrated heat pump air conditioning will become the mainstream
The cockpit air-conditioning system mainly has two technical routes: PTC heating and heat pump air-conditioning heating. Both have their own advantages and disadvantages. PTC has good heating effect under low temperature working conditions, but consumes electricity. The heat pump air-conditioning system has poor heating capacity at low temperature and good power saving effect, which can effectively improve the battery life of new energy vehicles in winter.
In terms of heating principles, the essential difference between the PTC system and the heat pump system is that the heat pump system uses refrigerant to absorb heat from the outside of the vehicle, while the PTC system uses water circulation to heat the vehicle. Compared with PTC heaters, heat pump air-conditioning systems involve technical difficulties such as gas-liquid separation during heating, refrigerant flow pressure control, etc. The technical barriers and difficulties are significantly higher than those of PTC heating systems.
The cooling and heating of the heat pump air-conditioning system use the electric compressor as the core and adopt a set of systems. In the PTC heating mode, the PTC heater is the core, and in the cooling mode, the electric compressor is the core, and two different system modes operate. Therefore, the heat pump air conditioner has a specific mode and a higher degree of integration. In terms of heating efficiency, in order to obtain 5kW of output heat, the electric heater needs to consume 5.5kW of electric energy due to resistance loss. A system with a heat pump requires only 2.5kW of electrical energy. The compressor uses electrical energy to compress the refrigerant to generate the required output heat in the heat pump heat exchanger.
In the future space, the upper limit of PTC electric heating is limited by heater power and heat conduction loss. At present, the heating efficiency of this technology has reached the upper limit and it is difficult to improve. The principle of heat pump system transfer heat makes its heating efficiency depend on two factors: the power of the electric compressor and the heat conduction power of the refrigerant. The shift from freon to carbon dioxide and other environmentally friendly refrigerants has room for further improvement in heating efficiency.
At present, new refrigerants such as R744 heat pump (carbon dioxide heat pump) and R1234yf (tetrafluoropropylene) replace R142b (freon).
In the comparison of auto parts, the parts of PTC heating system and heat pump system are roughly the same. However, the operating pressure of the heat pump is relatively high, and high-pressure resistant components are required, such as high-pressure resistant pipelines, high-voltage resistant electronic expansion valves, and high-pressure resistant air compressors. This leads to a significant increase in cost compared with PTC.
