EXPERIMENTAL INVESTIGATION OF TURBULENT HEATED FLOW IN AN ANNULAR SECTOR DUCT

Abstract

The continuing interest in compact heat exchangers has created the need for ¥ studying the effect of heat transfer parameters for different passage shapes . It has been recognized that generally circular tubes results are not applicable to non-circular passages even when the hydraulic diameter (D,) is used as the characteristic dimension , therefore , design data should be generated for each passage shape individually . The new flow passage shape under investigation in the present work is the annular sector duct which is a non circular passage . The major difference between the annular sector duct and non circular ducts of other geometry is that , the annular sector duct has both concave and convex boundaries. The combination ofthese combined boundaries would significantly affect the secondary flow pattern in the centrifugal force field . In the current research, an annular sector duct of diameter ratio of 0.5 and a sector angle of 60 degrees is studied experimentally . The experimental test rig was of total length of 113 D,, designed to have a starting unheated length of 65 D;, in order to ensure hydrodynamically fully developed flow in the downstream passage. It is followed by 48 D; heated length to ensure thermally fully developed flow at the exit of the test section . Twelve experimental runs were performed for measuring wall temperature , air mixing cup temperature and air velocity at several locations along the test section . Fluid velocity was measured at three axial locations , namely , at lengths equal to 48 D,, 65 D, (before the entrance to the test section) and 113 D, (at the exit of the test section).