An Experimental Study of Porous Coated Hybrid Elliptical Heating Tubes in Phase Change Heat Transfer

Abstract

Porous coating over hybrid elliptical heating tubes (HETs) is presented as the state-of-the-art in heat transmission during phase change maintaining its wide-ranging applicability. The saturated nucleate boiling heat transfer performance of porous coated hybrid elliptical heating tubes (CHETs) exposed to varying orientation angles is compared to that of conventional circular tubes in an accompanying experimental study conducted at atmospheric pressure. Four different copper porous coating thicknesses are varied from 34 μm to 128 μm with a heat flux range of 14.87–94.82 kW/m2. A greater coefficient of heat transfer is claimed for the CHET compared to the uncoated circular tube, regardless of the orientation angle or coating thickness. The uncoated and porous CHET provided a greater coefficient of heat transmission at 0 deg than at 90 deg. At 0 deg orientation angle, the coating with a thickness of 66 μm improves heat transmission by 1.27–1.5 times than that of uncoated surface, while minimum enhancement about 1.16–1.24 times is found in 34 μm. Furthermore, a dimensionless semi-empirical correlation is established to predict own heat transmission coefficient findings within ±12%, independent of coating thicknesses and orientation angles.