Fluid flow and heat transfer analysis for heat transfer enhancement in three sided artificially roughened solar air heater

• Fluid flow and heat transfer analysis in three sided artificially roughened solar air heater has been made.
• Friction factor and Nusselt number correlation has been developed for fully developed turbulent flow.
• Friction factor and Nusselt number both increase as compared to one sided roughened solar air heaters.
• For range of parameters analysed percentage increase is 2–34% for friction and 20–75% for Nusselt number.

Analytical results are available in plenty for heat transfer and friction factor for artificially roughened solar air heaters. Provision of artificial roughness of various geometries and orientations on the absorber plate in solar air heaters have remained limited to only one side (top side) of the solar air heater duct which results in higher values of heat transfer and associated pressure drop. The present paper deals with the analysis with respect to fluid flow and heat transfer in a novel solar air heater having artificial roughness on three sides (the two side walls and the top side) of the rectangular solar air heater duct, with three sides glass covers. Equations for friction factor and heat transfer parameter have been developed. The analytical values of friction factor and heat transfer parameter have been found to be 2–40% more and 20–75% more than those of the respective values of (Prasad and Saini, 1988) for the same range of the values of operating parameters p/e, e/D and Re and fixed values of W and B. The present novel type of solar air heater would be superior to those of only one side artificially roughened solar air heaters with respect to heat transfer.