Abstract: A gas drying apparatus is provided having at least two desiccant-containing towers which alternately receive moisture-saturated air from an inlet to be dried during a drying phase, and then receive dry air during a regeneration phase to regenerate the desiccant which had previously adsorbed moisture from saturated air during the drying phase. The apparatus diverts a portion of dry air flowing along one of two flow paths including a first flow path having a heater and a pulse purge regeneration control valve for selectively enabling delivery of heated dry air to the tower being regenerated, and a second flow path which bypasses the first flow path and includes a bypass valve for selectively permitting delivery of unheated dry air to the tower being generated so as to cool the desiccant therein. A temperature sensing arrangement is provided for monitoring and maintaining the internal temperature of heated dry air delivered into the tower being regenerated.

Abstract: An improved self-contained air drying unit utilizes a single fan to draw air across an aftercooler, a condenser and a reheater, all of which are located within a single housing.