摘要

The effects of three different turning configurations; i.e., (a) straight-comer turn, (b) rounded-corner turn, and (c) circular turn, on the flowfield and heat transfer in a square duct with a 180-degree sharp turn are modeled numerically. The present study employs a non-staggered grid, pressure-based, finite-difference method to solve three-dimensional transport equations in curvilinear coordinates. The computed results reveal detailed information concerning secondary flow patterns and local heat transfer with severe flow turning. Secondary flow in the post-turn region displays combined features of a bend-induced, Dean-type circulation and a form-induced separation behind the partition wall. This phenomenon varies significantly with different turn configurations. At the turn, the straight-corner case has the strongest turn-induced heat transfer enhancement, while the circular turn has the weakest. However, in the post-turn region, heat transfer with circular turn surpasses that of the other two configurations, by almost the same difference in the turning region. Average heat transfer results from the present numerical modeling agree favorably with experimental data.