Effect of the working fluids critical temperature on thermal performance for trilateral flash cycle and organic Rankine cycle

•Investigation effect of the critical temperature of working liquids on thermal performance at the low-grade heat source using 13 alkanes and 10 halogenated alkanes.•The critical temperature has strong limitations in working fluid evaluations not only in ORC, but this statement is also valid for cycles similar to ORC.•Better thermal performance is not necessarily to be a monopoly for high Tcr working fluids when using the same external conditions. The critical temperature (Tcr) is one of the important thermophysical properties of the working fluid, and it has a crucial effect on the output parameters of thermodynamic cycles used for power generation. This study aims to show the effect of the working fluids Tcr on the cycle thermal performance (thermal efficiency (ηth) and net-work output (Wnet) at the same heat source/heat sink temperature. For this purpose, 13 alkanes and 10 halogenated alkanes working fluids were investigated. Two different kinds of subcritical cycles, namely the Organic Rankine Cycle (ORC) and Trilateral Flash Cycle (TFC), were investigated. Pure and mixed (with various compositions) working fluids were used. Finally, it has been shown that although the critical temperature is an important factor, it can be correlated with output parameters only by using chemically similar working fluids.