EXPERIMENTAL INVESTIGATION FOR ENHANCEMENT HEAT TRANSFER IN A CHANNEL WITH ANGLE-RIBBED TAPE AT VARIOUS ATTACK ANGLE

Abstract

This paper presents the results of an experimental investigation for heat transfer and pressure drop characteristics in a square duct inserted with angle-ribbed straight diagonal tape. The straight tape used in the current study inserted in diagonal side of 44 mm hydraulic diameter square test section duct has uniform heat-fluxed walls. Different angled ribs were repeatedly placed at similar locations on both opposite sides of the inserted tape. The investigation covers a range of Reynolds numbers from (3400 to 20,800) according to hydraulic diameter and air is employed as working fluid. For studying the heat transfer dependency on ribs inclination angle, six different inclination angles (α) of 10°, 20°, 30°, 45°, 60°, 90° are examined at constant value for both rib blockage ratio (BR) and pitch spacing ratio (PR) of 0.2 and 1 respectively. The angle-ribbed diagonal tape generate a pair of longitudinal vortex flow through the heated duct and it is apparent that these vortices helps to induce impingement flows on the duct walls leading to drastic increase in heat transfer rate over the duct. The experimental results showed that the insertion of ribbed diagonal tape leads to a significant increase in Nu and f over smooth duct with no tape. Ribs at α= 45° provides higher heat transfer and friction losses as compared with other angles about (77.78, 98.42)% respectively more than smooth duct while ribs at 10° provides higher thermal enhancement factor (TEF) by about 1.297 at lower Re.

Keywords

• square duct
• angled ribs
• pressure drop
• heat transfer