At present, in China, the air conditioning device rate of domestically produced sedans has approached 100%, and the device rate on other car models is also increasing year by year. The air conditioning device in automobiles has become a crucial functional component, but the air conditioning brings many headaches to car owners. In addition to maintenance and upkeep issues, it is also very important to use air conditioning correctly.

What are the systems of car air conditioning

Car air conditioning is generally composed of four major parts: refrigeration system, heating system, gas distribution system, and control system. It can not only regulate the temperature and humidity inside the car, but also adjust the airflow direction and flow rate, and improve the air quality inside the car through filters.

What is the working principle of car air conditioning

The refrigeration system is mainly composed of components such as a compressor, condenser, liquid storage dryer, expansion valve, evaporator, and blower. After the compressor sucks in the low-temperature and low-pressure refrigerant in the evaporator, it compresses it into a high-temperature and high-pressure gas and is discharged into the condenser. The high-temperature and high-pressure refrigerant in the condenser is condensed into a low-temperature and low-pressure liquid, and a large amount of heat is discharged into the expansion device. In the expansion device, the refrigerant pressure and temperature drop sharply, while being discharged in a mist like manner from the expansion device. The mist like refrigerant enters the evaporator and evaporates into gas, absorbing a large amount of heat during the evaporation process to achieve refrigeration of the air conditioner.

The heating system and the cooling system are two different working principles. The engine dissipates a large amount of heat during operation, and in order to cool the engine, cooling is necessary. This provides the best heat source for the warm air. The cold air is heated through the car radiator and blown into the car through a blower.

Heating systems can be divided into waste heat heating systems and independent heating systems based on the heat source used. Generally, cars use a waste heat (water heating) heating system. The engine generates residual heat during operation, which is circulated and cooled by the coolant. The waste heat heating system uses the heat from the engine coolant as the heat source and introduces a heat exchanger (heater core). The air inside or outside the vehicle is blown by a blower to heat up the exchanger, which is a quite economical and environmentally friendly heating method. At present, the commonly used heating system for cars is the water heating system.

In addition, many vehicles now use PTC electric heaters to assist in heating during the early stages of vehicle startup in order to enhance winter heating performance, which can significantly improve the heating speed. The heating system of pure electric vehicles relies entirely on PTC electric heaters for heating.

How did the hot and cold air come from

The air distribution system generally consists of three parts: the first part is the air inlet section, mainly composed of switching dampers, blowers, and air conditioning filters used to control fresh air and indoor circulating air; The second part is the air mixing section, mainly composed of evaporator, air mixing damper, and heater; The third part is the air distribution section, mainly composed of mode switching dampers and various branch air ducts.

Cold air (coldest) distribution process: external air+internal air - blower - evaporator (cooling, drying) - air mixing damper (closed state) - mode switching damper - each branch duct.

Hot air (hottest) distribution process: external air+internal air - blower - evaporator (cooling, drying) - air mixing damper (fully open) - heater - mode switching damper - each branch duct.

Proper use of air conditioning

Correct defogging

In rainy and snowy weather, due to the high humidity inside the vehicle and the temperature difference between the inside and outside of the vehicle (cold outside and hot inside), fog will be generated on the inner surface of the car glass, which greatly affects driving safety. How to correctly remove fog and eliminate safety hazards is one of the skills that car owners must master.

From the diagram of the hot air distribution process, it can be seen that the air inside and outside the car is forced to circulate through a blower, and the necessary path for the air is the evaporator installed in the air duct. If there is refrigerant flowing through the evaporator, it will absorb heat and dehumidify the air, and then heat it up through the heater. This will blow out dry hot air.

When fog is generated from the interior glass of the vehicle, the blower should be turned on and the damper mode should be adjusted to the defogging position. At this time, most vehicles' air conditioning systems will force external circulation and forced AC to open. If the vehicle does not have this function, it is necessary to manually turn on the AC switch and press the inner and outer circulation button to reach the outer circulation state. The purpose is to allow the evaporator to dehumidify the air and then blow it onto the inside of the glass to achieve dehumidification.

In winter, when the temperature drops below zero, the car air conditioner cannot cool, thus losing its dehumidification function. The purpose of the external circulation is to introduce dry air from the outside into the car for defogging.

Correct use of internal and external circulation

The airflow ducts inside and outside the car are interconnected, and regardless of whether the air conditioning system is turned on or not, air will continue to flow in and out. If the fan is turned on at this time, it will accelerate the air exchange and circulation speed. When driving in mountainous or seaside areas, using the external circulation mode can mostly fill the car with fresh air and improve the air quality inside the car. However, if using the external circulation mode on congested roads, it will suck all the car exhaust and dust into the car, causing a significant decrease in the air quality inside the car. In severe cases, it may even cause discomfort to the passengers inside the car. Therefore, when driving on congested commuting roads, please try not to use the external circulation mode as much as possible, To avoid affecting the respiratory health of members.

In contrast to the external circulation, the airflow ducts inside and outside the car are in a closed state, and all the flowing air comes from inside the car and is constantly reused. Therefore, the temperature inside the car can be quickly reduced in summer and can also be used to maintain warmth and constant temperature in winter. However, there are still drawbacks to internal circulation. The air inside the car is continuously recycled, and over time, the air quality will still decrease, especially when there are many passengers in the car. At this time, it is recommended to occasionally switch to external circulation or open the windows on open roads with few cars, and quickly update the air inside the car to maintain good quality.

In addition, many vehicles are in reverse mode, with the air conditioning blower in operation and the cycle set to external circulation. At this time, the air conditioning system will automatically switch to internal circulation to prevent exhaust gas from flowing back into the vehicle.