Numerical Study of Convective and Radiative Heat Transfer from a Window Glazing with a Venetian Blind

Abstract

A two-dimensional numerical solution has been obtained of the effect of a venetian blind on the conjugate heat transfer at an indoor window glazing. A solution has been obtained to the coupled laminar free convection and radiation heat transfer problem, including conduction along the blind slats. The local convective Nusselt number distributions were found to compare well with published experimental data for an aluminum blind. Also, there was good qualitative agreement with temperature and flow field visualization photographs. The results show that, over a wide range of Rayleigh numbers, an aluminum venetian blind can have a strong effect on the heat transfer rate from the indoor window glazing. Depending upon the specific conditions, the average convective heat transfer rate can either increase or decrease. However, for all cases studied, the blind was found to substantially reduce the radiative heat transfer rate from the window, even when the slats were fully open.