Velocity and temperature profiles, wall shear stress and heat transfer coefficient of turbulent impinging jets

摘要

The purpose of this work is to present a set of empirical equations that can be used to predict the flow dynamics and the heat transfer properties of impinging jets over a wide range of Reynolds number, nozzle-to-plate spacing and radial position along the impingement plate. The parametrization scheme proposed by Loureiro and Silva Freire (Int. J. Heat Mass Transfer, 55 (2012), 6400-6409) is used here for the prediction of the mean flow field properties. In particular, the scaling for maximum velocity distribution along the impingement plate is extended to account for nozzle-to-plate distance and Reynolds number dependence. A new methodology for the calculation of the wall shear stress is also presented. The experimental data set of Guerra et al. (Int. J. Heat Mass Transfer, 48 (2005), 2829-2840) is used to propose a description of the full mean temperature profile for the wall jet region that follows a Weibull distribution. In all, eleven different experimental data sets are considered to propose working expressions that include a piecewise Nusselt number expression that furnishes a solution valid over the whole domain of the impingement plate, including the stagnation point and the wall jet region. New values are proposed for the power indexes and multiplicative parameters. The parametric analysis considers that the flow properties can be determined in terms of gross parameters like the free-jet momentum flux.