Experimental investigation of low GWP alternative R1233zd(E) for use in organic rankine cycle condensers

Simulated and experimental system level investigations of Organic Rankine Cycle (ORC) systems have shown that R1233zd(E) can be considered a low global warming potential (GWP) alternative to R245fa, with higher system thermal efficiencies. In addition to thermodynamic considerations, the heat transfer performance and resulting component size of this alternative must be considered. Thus, in this study, we experimentally investigate in-tube condensation heat transfer coefficients and pressure drop of R1233zd(E) at representative ORC conditions, and compare the results with R245fa data and correlations from the literature. Experiments are conducted in a smooth round tube with inner diameter of 4.7 mm, mass fluxes from 100 to 400 kg m^-2 s^-1, and saturation temperatures of 45 °C to 60 °C. The results are then used to design and compare the size and pressure drop of an air-cooled condenser using the two different refrigerants. Replacing R245fa with R1233zd(E) leads to 2.7% reduction in size but an 18.9% increase in the refrigerant pressure drop for equivalent power production.