Power Recovery from Low Grade Heat by Means of Screw Expanders

Power recovery from low grate heat by means of screw expanders gives a generalised overview of how best to recover power from sources, based on thermodynamic considerations.

Ian K Smith (Author), Nikola Stosic (Author), Ahmed Kovacevic (Author)

9781782421894, Elsevier Science

Hardback, published 7 April 2014

272 pages
23.3 x 15.6 x 2.2 cm, 0.56 kg

Current concerns with climate change have resulted in greatly increased interest in power recovery from low grade heat sources. This includes both hot fluid streams which can be expanded directly to produce mechanical power and those which act as a source of heat to closed cycle power generation systems. Power recovery from low grate heat by means of screw expanders with a generalised overview of how best to recover power from such sources, based on thermodynamic considerations, which differs to the approach used in classical thermodynamics textbooks and which includes an introductory description of the types of working fluid that are used in systems used to recover power from such sources and the criteria that must be taken into account in their selection. This is followed by a description of the mathematical modelling of twin screw machine geometry. The modelling of the thermodynamics and fluid flow through such machines is then given, together with how this is used to predict their performance. Finally a detailed description is given of systems currently used or projected both for direct expansion of the source fluid and by recovery of heat from it, which includes those which are particularly suited to the use of screw expanders in place of turbines.

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.

Subject Areas: Mechanical engineering [TGB]