Abstract: A scroll type device for operating on a fluid provided thereto that includes, as a unit, a housing with two interleaved scroll plates that are installed within such housing and that are operably movable relative to one another in an eccentric orbit, with such scroll plates including interleaved spiral projections, spiral projections include first and second portions, which portions will operate for expansion and the other of which portion will operate for compression as the unit operates in a given normal direction of movement.