Assessment of the thermal efficiency of subcritical power generation cycles using environmentally friendly fluids at various heat source temperatures

This study aims to investigate the effect of the various heat source temperature (Tmax) on thermal efficiency (ηth) for the organic rankine cycle (ORC), trilateral flash cycle (TFC), and partial evaporator (PE‐ORC). For this purpose, HFE7000, HFE7100, and HFE7500 were used as working fluids (WFs). The results indicate that by using HFE7000, the maximum ηth was obtained for all used power cycles and temperature ranges. Compared to HFE7100, HFE7500 has higher ηth at TFC, and PE‐ORC at low Tmax, while HFE7100 has the maximum value at high Tmax. The ηth at Tmax = 353 K for TFC were 8.71%, 8.34%, and 8.59%, while for ORC 12.38%, 11.82%, and 11.71% for HFE7000, HFE7100, and HFE7500, respectively. At Tmax = 423 K for TFC were 17.65%, 16.26%, and 16.52%, while for ORC were 18.56%, 17.38%, and 16.59% for HFE7000, HFE7100, and HFE7500, respectively. The ηth results indicate that the maximum improvement at TFC by using HFE7000, and the minimum was at HFE7100, while for ORC, the maximum was at HFE7000, and the minimum was at HFE7500. Therefore, the HFE7000 fluid behaves as normal dry fluids at any used temperature, while HFE7100 as normal dry WFs at low Tmax while behaving as very dry WFs at Tmax extremely close to its Tcr. HFE7500 behaves as very dry working fluids. The ηth intersections temperature was at Tmax = 425.2 K and Tmax = 455.9 K for HFE7500 and HFE7100, respectively. However, there is no ηth intersection for HFE7000. Studying the effect of heat source temperature on the power generation cycles (organic rankine cycle [ORC], trilateral flash cycle [TFC], and partial evaporator [PE‐ORC]), by using hydrofluoroethers categories, which are considered one of the most environmentally friendly fluids. Also, used to replace strong greenhouse gases such as hydrochlorofluorocarbons and hydrofluorocarbons.