Heat transfer and fluid flow analysis of artificially roughened solar air heater

Abstract

This study aims for computational investigation of roughened solar air heater (SAH) using artificial roughness in the form of double concave ribs. Solar air heater is a type of heat exchanger that utilises the solar radiation to generate heat energy. Smooth solar air heaters are found inefficient due to low convective heat transfer coefficient from absorber plate to air, thus to enhance the heat transfer rate artificial roughness in the form of double concave ribs is employed. Relative roughness height (e/D), relative roughness pitch (P/e) and relative arc radius (r/e) are chosen as geometric variables and analysed at five different values of Reynold’s number (Re) and their effect on heat transfer, friction factor and thermohydraulic performance parameter (THPP) is studied using commercial CFD software Ansys fluent v.15.0. It has been found that the maximum value of THPP is 1.725 for studied range of parameters. Nusselt number increases with increase in Reynold’s number and vice a versa happens for friction factor but in case of relative arc radius (r/e) both Nusselt number and friction factor decreases with increase in r/e.