What is the working principle of automobile air dryer?

Dryers generally appear on large passenger cars or trucks, because these cars are braked with high-pressure air. The role of the dryer is to dry the moisture in the high-pressure air, to avoid the corrosion of the brake components due to the moisture in the air. There is a heating rod in the drying tank, which is automatically controlled. I remember it seems that when the temperature is below 5 degrees, the heating rod of the dryer works to dry the moisture in the high-pressure air.
The compressed air enters the air pre-cooler to pre-cool and remove part of the water, and then enters the air cooler to reduce the temperature to 2°C (dew point temperature). The water in the air is precipitated at this temperature, separated by the gas-water separator and separated by The automatic drain valve discharges the water, and the dry low-temperature air enters the air pre-cooler, and then exchanges heat with the untreated compressed air to increase the temperature, which is the treated dry air.