Artificially roughened solar air heater: Experimental investigations

Solar air heater is the cheapest and extensively used solar energy collection device for drying of agricultural products, space heating, seasoning of timber and curing of industrial products. The use of an artificial roughness on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the duct of a solar air heater. Use of artificial roughness in solar air heater has been topic in research for the last thirty years. In the present article an attempt has been made to present holistic view of different kinds of roughness geometry used for creating artificial roughness in solar air heater for performance enhancement by experimental approaches. In this article thirty eight experimental studies have been reported on solar air heater, roughened with different kinds of roughness geometry. However, no comprehensive comparative study has been carried out or found in the literature so far, in order to investigate the relative performance of different types of artificially roughened solar air heater. The objective of this article is to perform such a study. In this article twenty known different shapes and orientations of roughness elements are considered for comparative analysis. In order to obtain the results numerically, codes are developed in MATLAB-7. Correlations for heat transfer and friction factor, developed by various investigators for artificially roughened solar air heaters have been reported in this article. The effects of various rib parameters on heat transfer and fluid flow processes are also discussed.