This article is about the development of a mathematical model for calculating the longwave optical properties of a curved venetian blind.
The calculated optical properties are used to determine the performance of the glass window installed with a venetian blind in terms of thermal
comfort. The blind, whose optical properties are considered nonspecular, is modeled as an effective layer. The effect of slat curvature is
included in the developed model. A six surface enclosure formed by two consecutive slats is used to analyze for the longwave optical properties
of the effective layer. The longwave optical properties, transmittance, reflectance, absorptance and emittance are developed by using
the radiosity method. The steady state energy balance method along with the developed longwave optical properties are used to determine
the surface temperature of the effective layer. The empirical expression for the total heat flux from the indoor glass window surface with an
adjacent venetian blind is adopted in the developed model. The surface temperature of the blind, which is the key parameter for calculating
the thermal performance of glass windows with venetian blinds with respect to thermal comfort, is chosen as the parameter used for the
model validation. The predicted surface temperature of the venetian blind is compared with the surface temperature of the venetian blind
obtained from the measurement. The agreement between the predicted temperature and the measured temperature is good.
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