R1233zd(E) and R245fa Flow Boiling Heat Transfer and Pressure Drop inside a 4.2 mm ID Microfin Tube

This paper presents R1233zd(E) and R245fa flow boiling heat transfer and pressure drop measurements inside a mini microfin tube with an internal diameter at the fin tip equal to 4.2 mm, having 40 fins, 0.15 mm high, and a helix angle of 18°. The tube was brazed inside a copper plate and electrically heated from the bottom. The experimental measurements were carried out at a constant mean saturation temperature of 30 °C, by varying the refrigerant mass velocity between 100 and 300 kg m-2 s-1, the mean vapor quality from 0.1 and 0.95, and the heat flux from 15 to 90 kW m-2. The experimental results are here presented in terms of two-phase heat transfer coefficient and frictional pressure drop. In this paper, the performance of the two fluids is compared under different working conditions and commented. Finally, the experimental measurements were used to assess some models for boiling heat transfer coefficient and frictional pressure drop estimations available in the open literature.