Operating Principle of Automotive Air Conditioning

Automotive air conditioning is a device installed in vehicles that can cool, heat, ventilate, and purify the air inside the car cabin. Since a car is a relatively enclosed space, prolonged poor air circulation can cause occupants to feel fatigued. This is not only a nuisance for drivers, affecting their driving performance, but can also pose serious safety hazards. Therefore, air conditioning systems have now become one of the key indicators for measuring the completeness of a vehicle’s functions.

The layout of different types of air conditioning systems varies. Currently, the integrated heating and cooling air conditioning system is widely adopted in passenger cars. Its layout integrates components such as the evaporator, heater core, centrifugal blower, and control mechanism into a single unit, known as the air conditioning assembly.

An air conditioning system generally consists of the following five subsystems:

1. Refrigeration System: Cools or dehumidifies the air inside the cabin or the fresh air drawn into the cabin, making the indoor air cool and comfortable.

2. Heating System: Mainly used for heating, it warms the air inside the cabin or the incoming fresh air to achieve heating and dehumidification purposes.

3. Ventilation System: Draws fresh outside air into the cabin to achieve ventilation and air exchange. Meanwhile, ventilation also plays an excellent role in preventing windshield fogging.

4. Air Purification System: Removes dust, odors, smoke, and toxic gases from the cabin air, ensuring clean air inside the vehicle.

5. Control System: Regulates the temperature and pressure of the refrigeration and heating systems, and also controls the temperature, air volume, and airflow direction of the cabin air, ensuring the proper operation of the air conditioning system.

The automotive air conditioning refrigeration system is mainly composed of a compressor, expansion valve, condenser, evaporator, and blower. All components are connected by high-pressure rubber hoses and steel pipes to form a sealed system. When the refrigeration system is in operation, the refrigerant circulates in this closed space in different states, and the cycle consists of four processes:

1. Compression Process: The compressor sucks in the low-temperature, low-pressure refrigerant vapor from the outlet of the evaporator, compresses it into high-temperature, high-pressure vapor, and then discharges it.

2. Heat Dissipation Process: The high-temperature, high-pressure superheated refrigerant vapor enters the condenser. As the pressure and temperature drop, the refrigerant vapor condenses into a liquid and releases a large amount of heat.

3. Throttling Process: The high-temperature, high-pressure refrigerant liquid passes through the expansion device, where its volume expands sharply, causing the pressure and temperature to drop drastically, and finally exits the expansion device in the form of a mist (fine liquid droplets).

4. Heat Absorption Process: The misty refrigerant liquid enters the evaporator. At this point, the boiling point of the refrigerant is much lower than the temperature inside the evaporator, so the refrigerant liquid evaporates into vapor. During the evaporation process, it absorbs a large amount of heat from the surroundings. After that, the low-temperature, low-pressure refrigerant vapor re-enters the compressor. This cycle repeats continuously, thereby reducing the temperature of the air around the evaporator.