Effect of providing gap in multiple-arc rib-roughened solar air heater - Part 1

Roughness is an effectual way to augment heat transfer in solar air heater (SAH). Multiple arcs (with gap) type of roughness has considered in this work and experimentation is performed to determine their effect on thermo-hydraulic performance of rectangular channel SAH duct. The experimentation is performed to analyze the effect of different parameters (both roughness as well as flow). Roughness parameters; number of gaps ( N g ) and rib gap width (g) has considered with fixed value of pitch ( p ), rib width (w) , rib height (e), arc angle (or). The effect of considered parameters was investigated experimentally on Nusselt number (Nu) and friction penalty ( f ). Strong impact of roughness parameters is observed on the Nusselt number ( Nu ) and frictional penalty ( f ). In comparison to smooth duct, 5.57 times higher Nusselt number is obtained along with increase of frictional penalty by 4.46 times at number of gaps ( N g ) of 3. The domination of Nusselt number ( Nu ) over frictional penalty ( f ) resulted tremendous increment in thermo-hydraulic performance (TPP) with the highest value of 3.46 at N g = 3 and relative-roughness-width ( g/e ) = 1.0.