HOLOGRAPHIC-INTERFEROMETRY STUDY OF SPATIALLY PERIODIC HEAT-TRANSFER IN A CHANNEL WITH RIBS DETACHED FROM ONE WALL

The effects of clearance ratio (C/H) and Reynolds number (Re) on the t urbulent heat transfer and friction in a rectangular duct with ribs de tached from one wall were characterized quantitatively using laser hol ographic interferometry and pressure measurements. The investigated fl ow was periodic in space both hydrodynamically and thermally. C/H and Re were varied from 0.25 to 1.5 and 5 x 10(3) to 5 x 10(4), respective ly. The obtained interferograms, local (Nu) and average (($) over bar N ($) over bar u) Nusselt number, and thermal performance (($) over ba r N ($) over bar u(p)/($$$) over bar Nu(s) ($) over bar) allowed the critical C/H characterizing different mechanisms of heat transfer augm entation to be identified and allowed a comparison of Nu, ($) over bar N ($) over bar u, and ($) over bar N ($) over bar u(p)/($$$) over bar Nu(s) ($) over bar among the detached ribbed duct, the attached ribb ed duct, and the smooth duct to be made. It was found that the detache d ribbed geometry has the advantage of eliminating the hot spots behin d the attached ribs. Optimal clearance ratios for heat transfer enhanc ement between the present periodic detached ribs and previous single d etached cylinder were also compared. Furthermore, compact heat transfe r and friction correlations were developed for a detached ribbed duct for the first time.