Flow boiling of environmentally friendly refrigerants inside a compact enhanced tube

R1233zd(E) has been proposed as low GWP alternative to R245fa. This paper compares the R1233zd(E) and R245fa performance during flow boiling inside a small diameter microfin tube having internal diameter at the fin tip equal to 4.2 mm, 40 fins, 0.15 mm high, and a helix angle of 18°. The experimental measurements were carried out at a constant mean saturation temperature of 30 °C, by varying the refrigerant mass velocity between 100 kg m−2 s−1 and 300 kg m−2 s−1, the mean vapor quality from 0.1 to 0.95, and the heat flux from 15 to 90 kW m− 2. The experimental results showed that R1233zd(E) presented almost similar flow boiling heat transfer coefficients at all the investigated mass velocities but slightly higher two-phase frictional pressure drops. The experimental measurements were compared against the calculated values of boiling heat transfer coefficients and frictional pressure drops from several models selected from the open literature.