Holographic Interferometry Study of Spatially Periodic Heat Transfer in a Channel With Ribs Detached From One Wall

Abstract

The effects of clearance ratio (C/H) and Reynolds number (Re) on the turbulent heat transfer and friction in a rectangular duct with ribs detached from one wall were characterized quantitatively using laser holographic interferometry and pressure measurements. The investigated flow was periodic in space both hydrodynamically and thermally. C/H and Re were varied from 0.25 to 1.5 and 5 × 103 to 5 × 104, respectively. The obtained interferograms, local (Nu) and average (Nu) Nusselt number, and thermal performance (Nup/Nus*) allowed the critical C/H characterizing different mechanisms of heat transfer augmentation to be identified and allowed a comparison of Nu, Nu, and Nup/Nus* among the detached ribbed duct, the attached ribbed duct, and the smooth duct to be made. It was found that the detached ribbed geometry has the advantage of eliminating the hot spots behind the attached ribs. Optimal clearance ratios for heat transfer enhancement between the present periodic detached ribs and previous single detached cylinder were also compared. Furthermore, compact heat transfer and friction correlations were developed for a detached ribbed duct for the first time.

A numerical study of particle deposition in ribbed duct flow with different rib shapes

“…According to the literatures of heat transfer enhancement by surface ribs [28,29], the maximum enhancement of heat transfer with lowest pressure increase occurs when the rib spacing to rib height ratio p/e is around 10. Moreover, the rib height to duct diameter ratio is usually from 0.02 to 0.1 in heat transfer enhancement by surface ribs [28,29].…”

“…Moreover, the rib height to duct diameter ratio is usually from 0.02 to 0.1 in heat transfer enhancement by surface ribs [28,29]. In this study, the ratio of the rib spacing to height p/e was also chosen as 10.…”

Enhancement of heat transfer from a flat surface in a channel flow by attachment of rectangular blocks

“…These can be classi"ed into two main groups: (i) passive techniques not requiring additional power sources and (ii) active techniques requiring additional external power inputs (Bergles and Webb, 1985;Reay, 1991). In the case of the passive techniques, convection heat transfer from surfaces with attachments of di!erent shapes with di!erent geometry, such as "ns, ribs, blocks, have been widely exploited (Ledezma et al, 1996;Goldstein et al, 1994;Tahat et al, 1994;Jurban et al, 1993;Babus'Haq et al, 1993;Naik et al, 1987;Liou and Hwang, 1992a, b;Hong and Hsieh, 1993;Hwang and Liou, 1994;Hwang and Liou, 1995;Liou et al, 1995;Han, 1988;Zhang et al, 1994;Molki and Mostou"zadeh, 1989;Molki et al, 1995). Heat transfer enhancement with such arrangements is achieved by the increase in the surface area and also by the turbulence (or the mixing) generated due to the attachments.…”

Numerical investigation of turbulent heat transfer in channels with detached rib‐arrays

“…For the range examined, the bar pitch-to-height of 10 was recommended for heat transfer augmentation. Liou et al [8] employed a detached rib array to the internal cooling passage of a gas turbine blade. They reported that the detached rib array possessed a better performance than the attached one when the clearance ratio was less than 0.58.…”