Abstract: The current design relates back to a twin-screw supercharger invented in the 1930's by Mr. Alf Lysholm who was then Chief Engineer of SRM (Svenska Rotor Maskiner AB) and the design of an expander with specific application objectives that resulted in two patents (U.S. Pat. No. 3,751,673 issued Aug. 7, 1973 and U.S. Pat. No. 3,977,818 issued Aug. 31, 1976). The present design departs from helical rotors used in all prior designs. The present design is more suitable for use as an engine (prime move) for use with lower temperature geothermal hot (warm) waters and brines, waters and brines found in solar salt gradient ponds, and other industrial applications. Thermodynamically speaking, the path through the engine causes isentropic expansion from the saturated liquid line.