This paper investigates the thermodynamic and physical properties of some unconventional fluids for use in organic Rankine-cycles supplied by waste energy sources. Energy requirement and recovery system performances are analyzed using realistic design operating conditions. Thermodynamic efficiencies and other useful results have been calculated by varying some recovery system operating parameters at various reference temperatures. With reference to proposed application, equations and graphs are presented which interrelate the recovery system operational parameters for some possible working fluids with computation results.