Abstract: An improved compressed air dryer unit having an air-to-air heat exchanger and an air-to-refrigerant heat exchanger separately mounted on a common base plate and connected in series for air flow therethrough in succession. Each exchanger comprises a tubular housing containing a bundle of tubing disposed longitudinally in the housing and extending through holes in a stack of closely spaced parallel sheet metal fins substantially coextensive in area with the cross-sectional area of the chamber in the housing. Longitudinally spaced baffles on the interior walls of the housing direct the flow of air therethrough in a succession of oppositely directed passes around and between the fin sheets. Water vapor, oils and particulates are deposited on the fin sheets and flow due to gravity to the bottom of the housing producing a self-cleaning function on the fin sheets. Water collected in the housing is removed via drain tubes controlled by automatic drain valves.