Nikola Stosic - Böcker

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.

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.

The first part of Screw Compressors gives a review of recent developments in screw compressor design. The second part presents a generalized mathematical definition of screw machine rotors and describes some well known lobe shapes in detail. The third part treats the mathematical modelling of the thermodynamics and fluid mechanics of compression and expansion processes. This includes discussion of the issues addressed in order to be able to predict the optimum rotor size and speed and built-in volume ratio and, in the case of oil flooded machines, the injection position and jet diameter. The fourth and fifth parts discuss the principles used and describe the application of the analytical procedures and rotor profiling techniques, presented in the earlier chapters, to the design of a number of twin screw compressors, currently manufactured including the examples of combining expansion and compression in the same machine.

This book presents the most up-to-date methods of three-dimensional modeling of the fluid dymanics and the solid-fluid interaction within these machines, which are still being developed. Adding modeling to the design process makes it possible not only to predict flow patterns more accurately, and also to determine distorting effects on rotors and casing of pressure and temperature distribution within the compressor. Examples outline the scope of the applied mathematical model.

The first part of Screw Compressors gives a review of recent developments in screw compressor design. The second part presents a generalized mathematical definition of screw machine rotors and describes some well known lobe shapes in detail. The third part treats the mathematical modelling of the thermodynamics and fluid mechanics of compression and expansion processes. This includes discussion of the issues addressed in order to be able to predict the optimum rotor size and speed and built-in volume ratio and, in the case of oil flooded machines, the injection position and jet diameter. The fourth and fifth parts discuss the principles used and describe the application of the analytical procedures and rotor profiling techniques, presented in the earlier chapters, to the design of a number of twin screw compressors, currently manufactured including the examples of combining expansion and compression in the same machine.