An interferometric study of free convection at a window glazing with a heated venetian blind

The free convective heat transfer rate from a vertical isothermal plate adj acent to a heated aluminum venetian blind has been measured using a Mach-Ze hnder interferometer. The blind was heated electrically to simulate solar h eating, and the plate was heated above the room temperature to simulate an indoor window glazing. Local and average heat transfer data were obtained f or three blind heat flux levels, two blind-to-plate spacings, and four slat angles in the laminar flow regime. For most cases, data were obtained up t o a plate Rayleigh number of Ra-L = 2.8 x 10(6) based on the distance from the leading edge. Infinite fringe interferograms were taken for temperature field visualization. The results show that blind heat flux has a strong in fluence on local and average heat transfer coefficients on the plate. It wa s also found that the spacing between the inner tips of the slats and the p late had a substantial impact on the convection. For close spacings, the he ated slats were found to produce a strong periodic variation in the local h eat transfer distribution on the plate. For all cases studied, as the blind heat flux increased, the convective heat transfer rate from the plate decr eased dramatically. In addition, as the blind heat filer increased, the ave rage convection coefficient became more dependent on both the blind-to-plat e spacing and slat angle.