Simulation of a scroll expander using R1233zd(E), R1234ze(Z) and their mixtures as drop-in replacements for R245fa

This paper presents simulations of the performance of a 2 kW hermetic scroll expander, based on a model reported in literature, when replacing the original working fluid (R245fa) with fourth-generation refrigerants. Calculations of micro organic Rankine cycles, equipped with the selected expander, show a slightly better performance when using R1234ze(Z) or R1233zd(E), as drop-in replacements of R245fa. Binary mixtures, characterized by a non-isothermal phase-change behavior, are considered as well. In particular, results of mixtures depend on the fluid temperature at the expander inlet. The most relevant result is that the mixture process for some hydrofluoroolefins causes a decrease of the maximum cycle temperature, after setting a fixed expander power output, and therefore the possibility of exploiting heat sources at lower temperatures.