Air Conditioning System for New Energy Vehicles
At present, there are two main air-conditioning systems for new energy vehicles, PTC air-conditioning and heat pump air-conditioning.
The basic principle of PTC technology is to energize thermal materials such as ceramics/resistance wires to generate heat to heat the cabin. If the heat is not enough, the heat production can be increased by increasing the number of resistors or increasing the power.
The PTC air conditioner has the characteristic of constant temperature heating. The principle is that after the PTC heating plate is powered on, the self-heating temperature rises to make the resistance value rise and enter the transition zone, and the surface temperature of the PTC heating plate will maintain a constant value. It is related to the applied voltage, but basically has nothing to do with the ambient temperature. The PTC ceramic heating element used in the PTC air conditioner is composed of several single pieces connected in parallel and then bonded with corrugated aluminum strips at high temperature.
This type of PTC heater has the advantages of small thermal resistance, high heat transfer efficiency and low power attenuation in long-term use, and has good safety performance. It will automatically drop sharply. At this time, the surface temperature of the heater is maintained at around the Curie temperature (generally around 250°C), so as not to cause the surface "redness" of the heater such as electric heating tubes, and the probability of safety accidents is low.
PTC is characterized by low cost, simple structure, fast heat generation, and little influence from the external environment, so it is widely used in entry-level cars to high-end cars. The overall shape of the PTC heater is light and compact, and it is extremely convenient to assemble in the machine.
The disadvantage of PTC air conditioner is that it obviously affects the battery life of the vehicle. Because it needs power consumption and heat generation, it directly affects the battery life of the vehicle. As the outside temperature decreases, the resistance value of PTC decreases accordingly, and the current passes through the resistance to generate heat. The heating energy efficiency ratio ( The maximum value of COP) does not exceed 1, that is to say, 1kW of electricity can generate 1kW of heat at most. The test shows that when the heater is turned on when driving in winter, at least one-third of the electricity will be consumed in the whole process. The greater the power, the greater the energy consumption, and the longer the time The greater the performance, the greater the mileage in winter will be greatly affected. This deficiency is particularly obvious in new energy vehicles with poor battery life.
When the heat pump system is heating/cooling, the low-temperature and low-pressure gaseous refrigerant is compressed into a high-temperature and high-pressure state in the compressor, and the refrigerant flows into the internal/external heat exchanger, releases heat to the air in the car/outside the car, and becomes a high-pressure liquid , and then flow through the liquid storage drying bottle to remove moisture and impurities, then pass through the expansion valve into a low-temperature and low-pressure gas-liquid mixed state, and finally pass through the external/inside heat exchanger to absorb heat from the outside/inside of the car into a low-temperature and low-pressure gas state and Entering the next cycle, the air in the car flows through the heat exchanger in the car to absorb heat and heat up/release heat to cool down, realizing the heating/cooling function in the car.
