Performance analysis of different working fluids for use in organic Rankine cycles

TLDR

This study performs a second‑law analysis of organic Rankine cycles to convert low‑grade waste heat into power, examining how fluid boiling point temperature affects performance. The authors evaluate seven organic fluids (R134a, R113, R245ca, R245fa, R123, isobutane, propane) spanning boiling points 48–243 °C, compare their performance to water, and conduct a combined first‑ and second‑law analysis across varied operating parameters and reference temperatures. Results show R113 yields the highest efficiency above 430 K, R123, R245ca, and R245fa excel between 380–430 K, while isobutane performs best below 380 K, confirming that the working fluid boiling point strongly determines system thermal efficiency.

Abstract

This article presents a second-law analysis for the use of organic Rankine cycle (ORC) to convert waste energy to power from low-grade heat sources. The organic working fluids were selected to investigate the effect of the fluid boiling point temperature on the performance of ORCs. The working fluids under investigation are R134a, R113, R245ca, R245fa, R123, isobutane, and propane, with boiling points between 243 and 48 °C. The results are compared with those of water under similar conditions. A combined first- and second-law analysis is performed by varying some system operating parameters at various reference temperatures. Some of the results demonstrate that ORC using R113 shows the maximum efficiency among the evaluated organic fluids for temperatures >430 K; R123, R245ca, and R245fa show the best efficiencies for temperatures between 380 and 430 K; and for temperatures <380 K, isobutane shows the best efficiency. Also, it is shown that the organic-fluid boiling point has a strong influence on the system thermal efficiency.