Where does the hot air from the car come from?

About the landlord's concern about "where does the hot wind of the car come from?" The following is my personal opinion:

The hot air of the car is formed by the heat dissipation after the engine works. The heat collected by the engine cooling system is blown into the car through a small fan in the engine compartment, that is, it is directly heated by the heat of the engine. It uses the thermal cycle process inside the car, so there is no need to start the compressor of the car at all. Automobile heating system is one of the functions of automobile air conditioning system, which is mainly used to heat the automobile, adjust the temperature and humidity, defrost and so on. In classification, it mainly includes water heating system, air heating system, independent combustion heating system and comprehensive preheating heating system.