Automotive air conditioning and refrigeration systems are divided into two categories

One type is the expansion valve system, and the other type is the orifice tube system.

The difference between them is the structure of the throttling expansion device used and the installation position of the liquid storage dryer.
The characteristics of the automobile air conditioning expansion valve system are: as long as the driver turns on the air conditioner, the electromagnetic clutch is always engaged and never disconnected. The compressor is always running, and the evaporator temperature is controlled by the suction throttle valve or the absolute pressure valve. Around 0°C.
The characteristics of the orifice tube system are: the electromagnetic clutch is sometimes combined and sometimes disconnected, and the compressor sometimes runs and sometimes stops running according to the ambient temperature of the cabin, so it is also called a circulating clutch system. Circulating clutch systems also use expansion valves, but only as a throttling device. The expansion valve system is also called a traditional air conditioning system.
All automobile air conditioning systems must not only ensure that the evaporator does not freeze, but also achieve the highest cooling efficiency.