Influence of turn geometry on turbulent fluid flow and heat transfer in a stationary two-pass square duct

摘要

The turbulent flow and heat transfer in a two-pass smooth square duct were studied experimentally and numerically. Four different turn configurations (cases-1,2,3, and 4) having various divider and outer turn geometries were considered in this study. A thin stainless steel foil is used as heater and infra-red ther-mography (IR) technique has been employed to obtain the local temperature distribution on the heated surface for three different Reynolds numbers namely, 25,000, 35,000, and 45,000. In addition, all four cases were investigated numerically using CFD commercial code FLUENT~®. A realizable k-ε model with a two-layer near-wall formulation is employed to simulate the turbulent flow and heat transfer field. The numerical result shows that the bend induced secondary flow structure and its effect on local heat transfer distribution varies significantly with different turn configurations. Comparison of averaged Nusselt number and friction factors of various turn configurations reveals that the numerical simulations follows the similar behavior as experimentally observed but the selected turbulence model underpredict the heat transfer augmentation in the bend region. The overall thermal performance of case-3 (sharp 180° bend with circular divider) is better than that of other three cases.