Effect of rib orientation and channel rotation on heat transfer in a two-pass square channel with 180degrees sharp turns was numerically investigated by using the large eddy simulation with a Lagrangian dynamic subgrid-scale model. In the stationary condition, the heat transfer in and after the turn was increased, and it was dominated by the sharp-turn induced flow field. In the rotating condition, the highest rotating speed caused deteriorated heat transfer on the pressure surface of the straight pass. The friction factor was much more sensitive to both the rib arrangement and channel rotation than the heat transfer. (C) 2004 Elsevier Ltd. All rights reserved.