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Power Recovery from Low Grade Heat by Means of Screw Expanders - 1st Edition - ISBN: 9781782421894, 9781782421900

Power Recovery from Low Grade Heat by Means of Screw Expanders

1st Edition

Authors: Ian Smith Nikola Stosic Ahmed Kovacevic
Hardcover ISBN: 9781782421894
eBook ISBN: 9781782421900
Imprint: Chandos Publishing
Published Date: 1st April 2014
Page Count: 272
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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.

Key Features

  • A novel generalised approach to the thermodynamics of power recovery from low grade heat systems
  • Gives criteria for working fluid selection
  • Provides details of, and how to model, screw expander geometry
  • Details how to estimate screw expander performance
  • Surveys types of system used for power recovery from low grade heat and where this can be improved by the use of screw expanders.


All those interested in the recovery of power from low grade heat sources, the design of twin screw expanders and the teaching of thermal power plant theory.

Table of Contents

  • List of figures
  • Preface
  • Acknowledgements
  • Notation
    • Subscripts
  • About the authors
  • Introduction: power from low-grade heat
  • 1. Expanders for power recovery
    • Abstract:
    • 1.1 Turbines
    • 1.2 Positive displacement machines
  • 2. Power plant thermodynamics
    • Abstract:
    • 2.1 Maximum work
    • 2.2 Some observations
    • 2.3 Practical considerations
    • 2.4 Working fluids other than water
    • 2.5 Fluid properties
  • 3. Geometry and manufacture of screw expander rotors
    • Abstract:
    • 3.1 Introduction
    • 3.2 Review of contemporary rotor profiles
    • 3.3 Screw expander rotor geometry
    • 3.4 Features of ‘N’ rotor profiles
    • 3.5 Geometry of rotor manufacturing tools
    • 3.6 Design of screw expander housings and choice of bearings
  • 4. Modelling and performance calculation of screw expanders
    • Abstract:
    • 4.1 The screw expander process and mathematical modelling
    • 4.2 Equations governing the screw machine processes
    • 4.3 Flow through the admission and discharge ports
    • 4.4 Flow through the leakage paths
    • 4.5 Injection of oil and other liquids
    • 4.6 Solution procedure for the screw machine thermodynamics
    • 4.7 Calculation of thermodynamic properties of working fluids
    • 4.8 Calculation of machine performance parameters
    • 4.9 Results of modelling and experimental investigations
    • 4.10 Calculation of pressure forces acting on screw machine rotors
    • 4.11 Radial, axial rotor loads, torque and bearing reactions
    • 4.12 Rotor deflections
    • 4.13 Recent advances in screw machine development
  • 5. Applications for screw expanders
    • Abstract:
    • 5.1 Screw expander lubrication
    • 5.2 Systems
    • 5.3 Cycles
    • 5.4 Cycle optimisation
  • Appendix 1: Properties of commonly used working fluids
  • Appendix 2: Estimation of working fluid properties
    • A2.1 The Redlich-Kwong-Soave equation of state
    • A2.2 Thermodynamic property estimation
  • Bibliography
  • Index


No. of pages:
© Chandos Publishing 2014
1st April 2014
Chandos Publishing
Hardcover ISBN:
eBook ISBN:

About the Authors

Ian Smith

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.

Affiliations and Expertise

City University, London, UK

Nikola Stosic

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.

Affiliations and Expertise

City University, London, UK

Ahmed Kovacevic

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

Affiliations and Expertise

City University, London, UK

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