Thermodynamics Cycle Analysis

In the last years, several fluids have been proposed to replace steam as working fluid in power cycle for con-verting thermal power into electricity. This paper describes the procedure to be adopted for the selection of any
innovative fluid which can be even mixtures of fluids. The first step consists of the working fluid characterization
in terms of thermodynamic properties through equations of state. The equations of state have to be calibrated on
experimental Vapour-Liquid Equilibrium measurements while, in the second step, the maximum operating
temperature is identified through thermal stability tests. Finally, the impact of the fluid thermodynamic prop-erties on the performance of the power cycle in which it is implemented must be assessed through modelling
tools. In this work, the procedure is discussed for the mixture of CO2and C6F14as a potential working fluid for
gas thermodynamic cycles with liquid phase compression. Results of the application of this mixture in a closed
cycle show the benefit of using a CO2/C6F14mixture which provides 3% points efficiency increase at 400 °C with
respect to the pure CO2together with a preliminary design of the expander.