Heat Transfer Enhancement Mechanism in Rectangular Channels with V- and A shaped Ribs

Abstract

Heat transfer measurement and flow visualization test were performed to investigate heat transfer enhancement mechanism of angled ribs mounted on two opposite walls of a rectangular duct with turbulent flow. Seven rib configurations were studied: 90 deft, rib, 60 deg oblique rib, 60 deg V-shaped rib, 60 deft, A-shaped rib, and their discrete ribs. It was found that the rotational direction of secondary flow induced by ribs plays a dominant role in determining the heat transfer performance. If the rotational direction of the secondary flow is to convey fluid from central core region of a duct directly to the heat transfer wall, the heat transfer performance of the wall is augmented appreciably. This is attributed to (1) transportation of colder fluid from the core region to the heat transfer wall, and (2) suppression of separated region behind a rib through the introduction of higher momentum fluid from the core region of the duct. The mechanism clearly accounted for the heat transfer characteristics of each rib, for example, heat transfer superiority of V-shaped rib over A-shaped rib.