The mathematical model for determining the shortwave optical properties of the effective layer for the curved venetian blind with the effect of thickness is developed.
The optical properties of the effective layer are mainly dependent on the slat optical properties, slat angle and profile angle of the incident radiation.
The optical properties of the effective layer can be divided into optical properties for direct radiation and optical properties for diffuse radiation.
The transmittance of the effective layer for direct radiation can be further separated into two components.
The first component is the transmittance due to the direct radiation which is directly passing through the blind without touching the slat surfaces (direct-to-direct transmittance).
The second component is the transmittance due to the part of direct radiation which is inter reflected between two adjacent
slats (direct-to-diffuse transmittance).
The direct-to direct transmittance is determined from the incident direction of the direct radiation and the geometry of the blind.
The optical properties in the part of direct radiation which is interreflected between two adjacent slats are determined
by using the radiosity method on closed enclosure composed from the cell between the two adjacent slats.
The model is based on the perfect diffuse surface.