Abstract: A heat exchanger element for exchanging heat between a fluid circulating in the element and a phase-change medium in a reservoir housing the element is formed of a plurality of spiral coils of flexible tubing disposed horizontally, one above the other, in a vertical stack. One end of each spiral coil is in communication with an inlet manifold and the opposite end is in communication with an outlet manifold. Preferably, the manifolds are disposed vertically, extending the height of the stack and side-by-side. Preferably, the manifolds are adjacent the outer periphery of the vertical stack of spiral coils. The spiral coils of the stack are wound alternatively clockwise and counterclockwise from a first radially outermost turn to a last radially innermost turn and arranged in pairs, one above the other. One spiral coil of each pair has the first radially outermost turn connected directly to the inlet manifold and the last radially innermost turn connected directly to the outlet manifold.

Abstract: A large slide valve member concentrically mounts a small slide valve member or slide stop at one end thereof proximate to a helical screw rotary compressor discharge port with the small and large slide valve members movable as a unit for varying the built in volume ratio of the compressor. The small slide valve member is shiftable independently of the large slide valve member to vary the capacity of the machine. A large diameter cylinder fixedly mounted to the end of the compressor casing remote from an outlet port slidably mounts interiorly a smaller diameter cylinder fixed to the large slide valve via a spindle. The small slide valve is fixed to one end of a piston rod which extends through a bore within the large slide valve member and the spindle and terminates internally of the small diameter sliding inner cylinder and has fixed thereto a piston.

Abstract: A turbulator for insertion in a heat exchange pipe in the form of a flattened hollow cylindrical metal tube with adjacent flats offset by 90.degree. and separated by integral tubular transition portions of generally triangular plane configuration. An elongated tab is partially struck out of each flat forming a fluid passage hole leading from one side of the turbulator to the other side.