Effect of Surface Roughness on Pool Boiling Characteristics under Variable Heat Supply

Abstract

An experimental investigation of critical heat flux (CHF) for boiling heat transfer from the rough copper sample under steady and quasi-steady exponentially varying heat supply is presented in this paper. The unidirectional scratches are made on the 20 mm diameter copper sample to obtain a wide range of surface roughness, ranging from Ra=0.106 μm to Ra=4.03 μm. The boiling characteristics for steady and transient-state conditions are compared by considering the onset of boiling (ONB) and CHF. The effect of surface roughness on the surface wettability and CHF are also studied. The enhancement in the transient CHF for the roughest sample (Ra=4.03 μm) is found to be 98.88%. The Rohsenow correlation for heat transfer coefficient (HTC) is modified, which predicts the present experimental data of HTC with mean absolute error (MAE) of 10.36%. The hydrodynamic model with capillary wicking force predicts the CHF for a wide range of Ra with a mean absolute error of 4.14%. © 2019, Toronto Metropolitan University. All rights reserved.