An aftercooler was the cooler whose outlet fed the engine. Some systems had a cockpit control for opening or closing a damper to the intercooler/aftercooler, providing another way to control temperature.
Aftercoolers are heat exchangers for cooling the discharge from a air compressor. They use either air or water and are an effective means of removing moisture from compressed air.
Aftercoolers control the amount of water vapor in a compressed air system by condensing the water vapor into liquid form. In a distribution or process manufacturing system, liquid water can cause significant damage to the equipment that uses compressed air. An aftercooler is necessary to ensure the proper functionality of pneumatic or air handling devices that are a part of process manufacturing systems. Aftercoolers can use either air-cooled or water-cooled mechanisms.