Heat Transfer Predictions in Rotating Radial Smooth Channel: Comparative Study of k-ε Models With Wall Function and Low-Re Model

Abstract

The two-equation models (k-ε) have been employed to predict turbulent flow and heat transfer for radially outward flow in a cooling duct rotating in orthogonal mode. The low-Reynolds-number model, which permits integration of the Navier-Stokes equations to the wall, has been used. The results from the low-Re model and the high-Re model with “Wall Function” are compared with the experimental data available in literature. Computations have been made for a range of Reynolds numbers (2500 to 25000) and a range of rotation numbers (0.088 to 0.24). Different conditions such as uniform wall temperature, uniform wall heat flux and uneven wall temperatures have been used as boundary conditions for heat transfer. The low-Re model does not perform as well as the Wall Function model in predicting heat transfer for flows at high Reynolds number. However, the low-Re model predictions are better than those from the high-Re Wall Function model for flows at low Reynolds number. In fact, for the geometry considered (1.27 cm × 1.27 cm duct) it becomes necessary to use the low-Re model for flows at low Reynolds number because of the limitation of the Wall Function. Heat transfer predictions from the low-Re model are within 10–40% for flows at low Reynolds number. The disadvantage of the low-Re model, in addition to the large number of cells requirement, is the slow convergence rate.