EFFECT OF VARIOUS ARTIFICIAL ROUGHNESS PARAMETERS ON HEAT TRANSFER AND FRICTION CHARACTERISTICS FOR FLOW INSIDE RECTANGULAR DUCTS OF SOLAR AIR HEATER

Abstract: Heat transfer and friction correlations are developed for fully developed turbulent flow in rectangular ducts having repeated integral wire ribbed roughness on the absorber plate. Computer program is developed using 'C++' programming language to determine the effect of various wire roughness parameters on heat transfer and friction for flow inside rectangular ducts with roughened absorber. The study covers wide range of different parameters of wire ribbed roughness such as relative roughness pitch (p/e) from 10 to 40, relative roughness height (e/Dh) from 0.01 to 0.04 and angle of attack of flow (a) from 20? to 90?. Flow parameter Reynolds number (Re) is varied from 5,000 to 30,000 and duct aspect ratio (W/B) is varied from 2 to 10. Program can be used for iterative work to identify the optimum parameters of roughness and duct to enhance thermal performance.

Keywords: Heat Transfer; Friction factor; Wire ribbed absorber; Stanton number; Nusselt number; Efficiency index.