Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
To generate electricity from biomass combustion heat,
geothermal wells, recovered waste heat from internal
combustion engines, gas turbines or industrial processes, both
the steam cycle and the organic Rankine cycle are widely in
use. Both technologies are well established and can be found
on comparable industrial applications. This paper presents a
thermodynamic analysis and a comparative study of the cycle
efficiency for a simplified steam cycle versus an ORC cycle.
The most commonly used organic fluids have been considered :
R245fa, Toluene, (cyclo)-pentane, Solkatherm and 2 siliconeoils
(MM and MDM). Working fluid selection and its
application area is being discussed based on fluid properties.
The thermal efficiency is mainly determined by the temperature
level of the heat source and the condenser conditions. The
influence of several process parameters such as turbine inlet
and condenser temperature, turbine isentropic efficiency,
vapour quality and pressure, use of a regenerator (ORC), is
derived from numerous computer simulations. The temperature
profile of the heat source is the main restricting factor for the
evaporation temperature and pressure. Finally, some general
and economic considerations related to the choice between a
steam cycle and ORC are discussed.