Abstract

Porous coating over hybrid elliptical tubes are 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 tubes 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 coated hybrid elliptical tube compared to the uncoated circular tube, regardless of the orientation angle or coating thickness. The uncoated and porous coated hybrid elliptical tube provided a greater coefficient of heat transmission at 0° than at 90°. At 0° orientation angle, the coating with a thickness of 66 µm improve 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.

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