Heat transfer and friction characteristics of impinging jet solar air heater

Abstract

This paper presents an experimental investigation on heat transfer and friction characteristics to study the effect of streamwise and spanwise jet to jet spacing due to inline arrangement of circular jets in a duct flow of solar air heater. The effect of geometrical parameters, especially the streamwise and spanwise pitch has been investigated. The rectangular duct has an aspect ratio of 11.6. The streamwise and spanwise spacing of jets has been varied from 0.435 to 1.739 and 0.435 to 0.869, respectively, and Reynolds number range covered is 3800-16000. The heat transfer and friction factor data obtained is compared with that of smooth duct under similar geometrical and flow conditions. Results show that increase in streamwise pitch and spanwise pitch increases the heat transfer coefficient from the absorber surface to the flowing fluid, as the distance between the jets increases the interference between the jets prior to impingement decreases which leads to development of very thin impingement boundary layer in the vicinity of the heat transferring surface thus enhances heat transfer. As compared to smooth duct, maximum enhancement in heat transfer and friction factor is 2.67 and 3.5 times, respectively. © 2012 American Institute of Physics.