The air-conditioning dryer is often also called air-conditioning filter and is connected via the air-conditioning conduct. It filters the cooling agent with each flow and absorbs particulate material and rubbed-off parts.
Furthermore the air-conditioning dryer extracts the humidity from the air-conditioning circuit due to the hygroscopic material.
Thus the unit is protected from corrosion.
Here the cooling agent is stored for the transport to the expansion valve. Thus the air-conditioning dryer has also a store- and-forward function.