Heat transfer, friction factor and thermal performance of three sides artificially roughened solar air heaters

This paper presents the experimental results on heat transfer, friction factor and thermal performance of a novel type of three sides artificially roughened and glass covered solar air heater under fully developed turbulent flow conditions. The results on heat transfer and friction factor compare well with analytical values (Prasad et al., 2014), for the range of the values of operating parameters. Such solar air heaters have higher value of heat transfer coefficient than those of one side artificially roughened solar air heaters in the range of 21-78% for the same values of operating parameters. The values of performance parameters, FRUL and F-R(tau alpha) and consequently those of F-R and F', have been found to be superior to those of one side roughened solar air heaters. Thermal performance equations in terms of the performance parameters have been derived. Enhancement of about 40-48% in thermal performance over those of one side artificially roughened solar air heaters has been achieved. (C) 2016 Elsevier Ltd. All rights reserved.