The effects of an internal isolated plate on natural convective heat transfer inside an industrial oven

Abstract

This paper concerns with the problem of natural convection heat transfer inside an industrial oven with an internal plate. The model is simulated numerically as a square cavity with an isolated plate laid horizontally or vertically inside it. Different ranges of Rayleigh number from laminar to turbulent flow regimes were investigated numerically and inherent flow structures and the amount of transferred heat were obtained. The governing Reynolds-averaged Navier-Stokes and energy equations are discretized and solved applying finite-volume method. Moreover, a two-layer zonal model is applied for near-wall turbulent properties. Comparing the present results with similar previous studies and experimental data shows that the employed zonal model is more accurate than other existing turbulent models. Our results also demonstrate that the total rate of heat transferred by a cavity with internal isolated plate is always lower than that of a bare cavity. As the distance of internal plate from the cavity wall decreases, its effect on the reduction of overall heat transfer increases accordingly. We also determined a distance between the plate and the cavity wall with less than 2% change in relative Nusselt number and deduced that the maximum distance of vertical plate is always greater than that of the horizontal plate at each Rayleigh number. Furthermore, a dead zone is created between the hot wall and the plate with low velocities, the temperatures close to the hot wall temperature, and very weak circulation, which can significantly reduce the overall heat transfer in the cavity. The results of this work can be used in glass industries and reduction of heat loss in industrial ovens by placing the glass sheets inside them in appropriate position.