Various Ways of Adiabatic Expansion in Organic Rankine Cycle (ORC) and in Trilateral Flash Cycle (TFC)

For energy production and conversion, the use of thermodynamic cycles is still the most common way. To find the optimal solution is a multiparametric optimization problem, where some parameters are related to thermodynamic and physical chemistry, while others are associated with costs, safety, or even environmental issues. Concerning the thermodynamic aspects of the design, the selection of the working fluid is one of the crucial points. Here, we are going to show different types of adiabatic expansion processes in various pure working fluids, pointing out the ones preferred in Organic Rankine Cycles or in Trilateral Flash Cycles. The effect of these expansions on the layout of the cycles will also be presented. Finally, we are giving a few thumb-rules, derived from thermodynamic studies, useful for energy engineers to select the proper working fluid for a given thermal system.