Flow boiling of environmentally friendly refrigerants inside a compact enhance 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 degrees. The experimental measurements were carried out at a constant mean saturation temperature of 30 degrees 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. (C) 2019 Elsevier Ltd and IIR. All rights reserved.