Experimental study of parametric influence on heat transfer and friction in a rectangular duct having V-down baffle blocks with staggered racetrack-shaped openings

Abstract

ABSTRACT This paper presents the detailed study of parameter’s effect on Nusselt number (Nu), friction factor (f), and thermohydraulic performance parameter (η) of a rectangular duct through experiments using 45° V-down baffle blocks with staggered racetrack-shaped perforation geometry. The parameters investigated are the relative roughness height (e/H), relative pitch (p/e), and flow Reynolds number (Re). The results show that the secondary air jets issuing through racetrack-shaped perforations of baffle blocks with staggered holes strongly affect the duct’s flow pattern. The Nusselt number values show ups and downtrend with variation in the relative pitch and relative roughness height of the baffle blocks at all Reynolds number. The friction factor decreases with increased spacings but with variations up to a p/e value of 6 for different e/H of baffle blocks. The baffle block having e/H of 0.7 at p/e of 2 shows a maximum 456% rise in Nusselt number and an increase of 39 times in friction factor over the smooth duct. Baffle blocks having e/H of 0.5 and p/e of 4 obtain a 100% rise in thermohydraulic performance parameter value than the value for e/H of 0.6.