Heat transfer augmentation in a rectangular channel with a vee-shaped vortex generator

The unsteady flow and heat transfer are simulated using LES and DNS for a channel with two angled ribs as a vee-shaped vortex generator to augment heat transfer. The vortex generators are attached on the bottom wall of the channel and their angles in respect to the main flow are between 10 degrees and 30 degrees. The Prandtl number is 0.71 and the Reynolds numbers based on the inflow velocity and the height of channel are from 200 to 2000. Based on the results of this work, the variations of the Nusselt number, pressure coefficient, bulk temperature, friction factor and Colburn factor with the Reynolds numbers and the incidence angles are provided. The relation between the key parameters of the velocity (friction factor f) and thermal (Colburn factor J) boundary layers is calculated for all cases and their values are compared with the predicted values by the Chilton-Colburn analogy. A comparison between the DNS and LES results is performed and it is found that relatively similar results are obtained from a LES simulation with fine grid and a DNS simulation with finer grid. Thermal performance parameter, JF, is used as a measure for the amount of the heat transfer enhancement relative to the pressure drop. The JF value increases as the Reynolds number or the incidence angles increase. The structure of the heat transfer and fluid flow are studied using the kinetic energy, pressure, velocity and temperature fluctuations. (c) 2006 Elsevier Inc. All rights reserved.