Experimental study of pool boiling on a novel reentrant cavity tube surface with R134a.

Highlights • The experimental data of R134a pool boiling on a novel reentrant cavity tube was obtained. • The heat transfer enhancement factor for the enhanced tube peaked in the heat flux range was founded. • The boiling Nusselt number and Reynolds number was used to describe the heat transfer characteristics. • Correlations were developed to predict the experimental data within 4%. Abstract This study experimentally investigated pool boiling heat transfer performance on horizontal copper tubes with refrigerant R134a. Experiments were conducted at saturation temperature of 5.6℃, while heat flux varied from 5 to 65 kW/m2 with an interval of 5 kW/m2. A plain tube and a reentrant cavity tube (enhanced tube) were tested. The nominal outside diameter of test tube was 25.14 mm and the length in test section was 1000 mm. Tubes were water heated by 15% volume faction water-ethylene glycol mixture with an insert bar in the fluid passage. The experimental data of the plain tube were compared against the Cooper correlation with deviation of −3% to −10%. The boiling heat transfer coefficient of the enhanced tube increased with the increasing heat flux in the experimental range. The heat transfer enhancement factor, the ratio of boiling Nusselt number for enhanced tube to that for plain tube, varied from 1.66 to 2.64 and reached the maximum at Re o = 0.38(heat flux q = 20 kW/m2). The boiling Nusselt number was correlated with boiling Reynolds number with predicting the experimental data within ±4%. [ABSTRACT FROM AUTHOR]