Experimental Study of Free Convection at an Indoor Glazing Surface with a Venetian Blind

Abstract

A Mach-Zehnder interferometer was used to measure the laminar free convective heat transfer rate from an isothermal vertical surface adjacent to a set of aluminum Venetian blinds. Local and average heat transfer data were obtained at three different blind-to-plate spacings, and at four different blade angles. Data are presented up to a Rayleigh number of Ra =3 × 10⁷, based on the distance from the leading edge. Flow visualization results that illustrate the cellular flow patterns between the blades are also presented. Overall, it was found that the flow field and local heat transfer distribution on the surface can be significantly affected by the presence a Venetian blind. When placed close to the surface, the blind causes a strong periodic variation in the local Nusselt number distribution. However, for all cases studied the average Nusselt number was within 13% of an isolated vertical flat plate at the same Rayleigh number.