Study on thermal efficiency of low- to medium-temperature organic Rankine cycles using HFO−1234yf

HFO−1234yf is a new refrigerant with a nearly zero global warming potential (GWP) and ozone depletion potential (ODP); it exhibits thermodynamic properties similar to HFC−134a. The potential of HFO−1234yf as a working fluid for organic Rankine cycles (ORC) is elucidated through a first-order simulation. A fundamental thermodynamic model of ORC with five types of cycles—trilateral, saturated, superheated, sub-critical, and supercritical—is used to compare the thermal efficiency of HFO−1234yf with that of other working fluids. HFO−1234yf was found to offer a thermal efficiency that was comparable to that of HFC−134a. This paper provides a useful map that clearly shows the best possible thermal efficiency among the five types of cycles for various expander inlet and condensation temperatures. The highest thermal efficiency range (8.8%–11.4%) was obtained when the supercritical ORC was used at an expander inlet temperature of 170 ± 10 °C and a condensation temperature range of 20–40 °C for the given pump and expander efficiency. It is concluded that HFO−1234yf is a potential working fluid for ORC applications, especially for those with low- to medium-temperature heat sources.

► Organic Rankine cycle uses HFO−1234yf with low global warming potential.
► Thermal efficiency of the cycle is comparable to that with HFC-134a.
► Efficiency is over 10% in supercritical cycle at expander inlet temperature 170 °C.
► HFO−1234yf is potential working fluid for organic Rankine cycle power systems.