Experimental and numerical study of heat transfer due to developing flow in a two-pass rib roughened square duct

Abstract

Experimental and numerical study of flow and heat transfer in a two-pass channel featuring different rib geometries has been carried out. The thermal hydraulic performance of four different rib geometries – 45° angled, V, W and M-shaped ribs, have been reported and analyzed. The tests were performed over a Reynolds number range from 19,500 to 69,000. The channel aspect ratio was 1:1 (square), the rib-pitch-to-rib-height ratio (p/e) was 16 and the rib-height-to-channel hydraulic diameter ratio (e/Dh) was 0.125. The detailed Nusselt number distributions on the ribbed wall were obtained using transient liquid crystal thermography. Numerical simulations (using ANSYS Fluent) have been carried out to resolve the complex flow field peculiar to rib turbulator shapes, for detailed understanding of the experimentally measured heat transfer coefficients. For the numerical simulations, realizable version of k-ε model was chosen because of its ability to predict separated flows behind ribs. Also, CFD simulations have been validated with experimentally obtained pressure measurements at several locations in the two pass channel. In addition to flow validation, the numerically obtained heat transfer results are validated and compared with the experiments and discussion has been presented on the role of secondary flows, turbulent kinetic energy etc., on heat transfer augmentation due to the presence of the ribs.