Influence of Rib Height on Heat Transfer Augmentation – Application to Aircraft Turbines

Abstract

This paper presents the influence of rib height on heat transfer and friction factor augmentation in convergent rectangular channel with bottom rib-roughened walls has been conducted in experimentally. In this experiment the square sized ribbs at three different height were (3, 6 and 9 mm) used. A specified constant heat-flux is applied to the bottom surface of the test section and the ribs are arranged in the form of a staggered array. Measurements were taken of a convergent rectangular channel with an inlet aspect ratio of 1.25 and an exit aspect ratio of 1.35. This yields a rib height (e) to mean hydraulic diameter of the duct (Dm) ratio of 0.0348, 0.0697 and 0.1046 respectively, with a fixed rib pitch (p) to test the section inlet height (hin) ratio of 0.6 along the sloped surface of the test section. The Reynolds number based on the mean hydraulic diameter (Dm) of the channel was kept in a range of 20,000 to 60,000. The results from the ribbed channel are compared with that of the smooth convergent rectangular channel, to estimate the heat transfer enhancements from the ribbed channel. The comparison shows that among the tested convergent smooth channel, 3, 6 and 9 mm ribbed channel; the heat transfer from the channel with 6 mm rib height is better and showed comparatively lower friction loss than the other ribbed channels.