Abstract
The purpose of this paper is to give a general calculation method of illuminance on the working plane in interior from a two-dimentional window with a Venetian blind system, and to get the available data for the average luminances of slats and the transmittances of blind system. In this paper, Part l, it is assumed that the slats are of negligible thickness, uniformly diffusing surfaces and part of circle on the two-dimentional cross section. In Part I the blind system is illuminated by diffuse light from the sky and ground with uniform luminance. Reduction ratio of direct transmittance of blind system due to the slatcurvature is investigated with relation to t:be slat angle of inclination and the incident angle of daylight to blind system. Next, integral equations for interreflection in unit-cell of curved slats are developed to obtain illuminance distributions on the slats, and the numerical solution of these equations gives the average luminances of slat surfaces and the transmittances of downward and upward fluxes to interior. These results are examined as compared with values on the same louver system except that slats are flat. It is concluded that the formula for louver system with flat slats can be available to calculation of direct illuminance on the working plane from Venetian blind in normal case of the slat angle of inclination and the formula of split-flux at the working plane by MATSUURA is useful in practice to calculate the indirect illuminance using data of the above-mentioned transmittances of blind system.
