Power Recovery from Low Grade Heat by Means of Screw Expanders

Ian K Smith is professor of Applied Thermodynamics at City University London, UK, and has been contributing to systems for the recovery of power from low grade heat for more than 40 years. Nikola Stosic is professor of Positive Displacement Compressor Technology at City University, London, UK, and is widely recognised as a world authority on twin screw machines. Ahmed Kovacevic is Howden Professor of Engineering Design at City University, London, UK, and has wide experience in the design of screw compressors and expanders

Expanders for power recovery: Turbines; Positive displacement machines; Power plant thermodynamics: Maximum work; Some observations; Practical considerations; Working fluids other than water; Fluid properties; Screw expander rotors geometry and manufacture: Introduction; review of contemporary rotor profiles; Screw expander rotor geometry; Features of ‘N’ rotor profiles; Geometry of rotor manufacturing tools; Design of screw expander housings and choice of bearings; Modelling and performance calculation of screw expanders: The screw expander process and mathematical modelling; Equations governing the screw machine processes; Flow through the admission and discharge ports; Flow through the leakage paths; Injection of oil and other liquids; Solution procedure for the screw machine thermodynamics; Calculation of thermodynamic properties of working fluids; Calculation of machine performance parameters; Results of modelling and experimental investigations; Calculation of pressure forces acting on screw machine rotors; Radial, axial rotor loads, torque and bearing reactions; Rotor deflections; Recent advances in screw machine development; Applications for screw expanders: Screw expander lubrication; Systems; Cycles; Cycle optimisation; Bibliography.