Calculation of wall heat transfer in pipeexpansion turbulent flows

A new modified low-Reynolds-number k-ε turbulence Chang, Hsieh and Chen (CHC)] model, which possesses the proper near-wall limiting behaviors and is free of the singular defect occurring near the reattachment point when applied to separated flows, is examined for use in wall heat transfer problems in flow with pipe expansion geometry. Another eight low-Reynolds-number k-ε models, found in open literature, are also examined in this study. Attention is specifically focused on the flow region surrounding the reattachment point. Comparative results show that only the CHC model and the model developed by Abe et al. Abe, Kondoh and Nagano (AKN model)] can yield satisfactory distributions of the Nusselt number along the wall. However, the CHC model adopted the same model constants as conventionally used for the standard k-ε model. Thus, the CHC model is more universal than the AKN model.