Abstract: An apparatus and process including a heat sink exchanger (26) to cool and condense liquid out of a drying gas with a heat transfer surface arranged to exchange heat with a first sub-stream of the drying gas and a heat source heat exchanger (27) arranged to exchange heat with a second sub-stream of a drying gas and arranged in a functionally parallel configuration with said heat sink heat exchanger (26) so that each of said drying gas sub-streams exchanges heat with one of the two said heat transfer surface per cycle through the heat exchange system and a gas movement device (35) for propelling the drying gas through the heat exchanger system in either a forward or reverse flow path direction.