Automotive air conditioning works as a self-contained looping process within the vehicle that changes the state of the refrigerant to both a gas and liquid. A high- and low-pressure system completes the process and blows cool air to the vehicle's passenger cabin.
Automotive air conditioning has both a high- and low-pressure side that runs in a nearly closed loop. The high-pressure side starts with a compressor which forces the refrigerant in a gas form to the condenser where it forms a liquid used to cool the passengers. The liquid enters a receiver-dryer containing desiccants that remove water particles which could form ice and damage the air conditioning system.
The low-pressure side begins with a thermal expansion valve that allows the high-pressure liquid refrigerant to flow from the receiver-dryer and expand. The expanded liquid enters the evaporator at around 32 degrees Fahrenheit. The evaporator absorbs heat and converts the liquid refrigerant back to a gas. This is done easily because the refrigerant has a very low boiling point. A fan blows over the coil of the evaporator to force cool air into the cabin. Remaining gas and warm air transfers from the passenger compartment back to the compressor where the process starts again.