The function of vehicle air conditioning system is to make indoor temperature, relative humidity, airflow speed and cleanliness meet the design requirements and create a comfortable riding environment for passengers.
General automobile air conditioning system is mainly composed of ventilation system, refrigeration system, heating system, humidification system and control system. Considering the climatic conditions in the actual operation area, some vehicles do not need special heating and humidification systems, such as the subway in southern cities without heating systems.
As for its working principle, the air conditioner will send some fresh air and return air into the carriage through the tuyere after refrigeration, which is also a source of "wind" in the carriage. Another source is the ventilation system. The ventilation system sucks in fresh air outside the car and mixes it with the return air inside the car. After the dust and impurities are filtered, they are transported and distributed to all parts of the car, so that the air distribution in the car can be reasonable. At the same time, the dirty air in the car is discharged out of the car, so that the air parameters in the car are kept within a reasonable range.
There are two ways of ventilation system: mechanical ventilation and natural ventilation. The mechanical ventilation system is in a long-term working state. Through the work of the ventilator, the treated air is transported out through the air supply pipeline in the car, so as to achieve the purpose of ventilation.
There is a certain distance between the interior trim panel of the body side wall and the vehicle shell at the window partition. In this way, the air in the car passes through the ventilation plate hole under the passenger seat → the space between the window partition and the vehicle shell → the space between the roof and the ceiling → the air conditioning air return port or the roof ventilator → the external space.
Finally, to sum up, the two air conditioning units on the roof send the treated cold air into the roof air duct through two vibration and noise reduction transition air ducts connected to the car body, and then into the passenger compartment through the air outlet on the roof of the passenger compartment. The cold air radiated to the passenger compartment takes away the heat of the passenger compartment, and then flows to the air return duct on the roof through the vent hole under the seat and the gap on the side wall of the car body. Part of the hot air is discharged from the car through the air outlet, and the other part is returned to the air conditioning unit through the air return duct to be mixed with the inhaled fresh air, then cooled by the air filter and evaporator, and sent to the roof air duct by the centrifugal fan. In this way, air circulation is formed in the passenger room, which is the so-called "wind". In the season when air-conditioning refrigeration is not needed, the air-conditioning compressor does not work, and the ventilation system continues to work, but it does not produce cold air. )
When vehicles are running and passengers are moving, air flow will also occur, which involves fluid mechanics. In addition, the through passage at the vehicle connection is not sealed, which will also produce "wind", which will not be described in detail here.