Heat Transfer Enhancement of Solar Air Heater Having Twisted V-Shaped Staggered Roughness Over Absorber Plate

The present experimental work is dedicated to establish the effect of novel twisted V-shaped staggered ribs provided on the absorber plate of solar air heater on the Nusselt number, friction factor and thermo-hydraulic performance parameter. The liquid crystal thermography technique is employed to measure the distribution of Nusselt number over the absorber plate. Experimentations have been done for all configurations of varied roughness parameters termed as relative roughness pitch ranging from 7 to 11, relative roughness length in the range of 4.39–10.26 and Reynolds number varying from 3000 to 21,000. The Nusselt number and friction factor of the roughened plate are compared with the smooth absorber plate under similar flow conditions. The optimum roughness parameters based on thermo-hydraulic performance parameter index are as relative roughness pitch of 9 and relative roughness length of 6.15. The maximum thermo-hydraulic performance parameter index obtained is 2.59.