The venetian blinds used for investigation in this study have optical properties as shown in Table 1.
The slat curvature radius is chosen to be 50 mm which gives a slat curvature radius to projected slat width ratio about 2.
The slat thickness is 0.3 mm.
The optical properties for direct radiation (transmittance,reflectance and absorptance) of the effective layer having the slat reflectance of 0.5 are shown in Figs. 7–9 for slat angle of +45, 0 and 45 degree.
The optical properties for the same venetian blind with flat slat of negligible thickness,which are calculated by using the 6 surface closed enclosure method, are also shown in Figs. 7–9 to show the effect of slat curvature and thickness.
It is found that for the slat angle of +45 degree (the leading edge of the slat points toward the ground) the front direct-to-direct transmittance,