A computational study of flow and heat transfer in a channel with an array of novel surface roughness element

A novel surface roughness element is derived from the combination of dimple and protrusion elements. In the present study, the flow characteristics and heat transfer performance of a rectangular channel with this surface roughness element are computationally investigated and compared with hemispherical dimple and protrusion. The surface roughness element is a combination of dimple and protrusion such that it requires the same area of a flat surface but increases the available area for heat transfer. Various angular positions of this surface roughness element are considered for analysis and the thermal characteristics are compared with the dimpled channel for a fixed Reynolds number. The main geometric parameter considered is the relative location of the dimple and protrusion in the combination and its orientation with respect to the streamwise direction. Twelve different arrangements of this roughness element are compared and all flow and thermal results were obtained using computational fluid dynamics with a validated explicit algebraic Reynolds stress turbulence model. From this investigation, it is found that a particular combination (a double 45 dimple configuration) of this roughness element greatly improves the averaged local heat transfer of the corresponding surface and also creates a strong secondary flow, resulting in high heat transfer augmentation. The objective of this study was to determine the most optimal configuration in order to augment the heat transfer rates at same pumping power and to provide flow and thermal details of this new roughness element.