Effect of Net Geometry on the Nusselt Number Distribution for Channel Flow

For channel flow between two parallel plates, obstacles may take the form of ordered asymmetrical porous nets. The dimensions of this net will affect the resulting variations in the laminar velocities and the local heat and mass transfer coefficients. This article presents a numerical study of the effect of an inert insulating net and its geometry on the heat transfer characteristics in such a system. The governing equations for momentum, continuity, and energy equation were solved in a three-dimensional domain using a commercial CFD software for fully developed flow with constant temperature boundary conditions. The local Nusselt number was calculated from the resulting temperature distribution. The effects of location, spacing, and number of the longitudinal and transverse ribs of the net on the distributions and on the mean Nusselt number of the two plates are analyzed. Enhancement factors of the mean Nusselt number were found to increase between 13 and 330% as the number of transverse ribs increased from four to 29 for typical nets with a 0.27mm thickness. However, for the same nets, the enhancement factors of the mean Nusselt number were found to decrease between 16 and 50% as the number of longitudinal ribs increased from four to 14.