Working fluids in non-steady flows for waste energy recovery systems

Working fluids used in organic Rankine cycle (ORC) recovery systems with Small turbines create problems since the flows are supersonic and consequently special attention is necessary in this respect in the flow study. After a preliminary survey on the ambient compatibility and thermophysical capability of the novel or unconventional fluids, the non-steady flows of some gases and organic vapours are investigated in tests using equipment annexed to a supersonic wind tunnel operating on the 'blowdown' principle. A calculation method is suggested and some equations developed to obtain the outflow parameters. The available wind tunnel reference data confirm the results. For more accurate calculations of non-steady outflow of some vapours, analytically derived values of compressibility factors are given, with which the complete phenomena can be simulated and the flow parameters calculated by the adjusted perfect gas flow equations. Copyright (C) 1996 Elsevier Science Ltd