Method for determining the transmission of a garret window from a direct sun component

. Based on the experimental studies using the method of physical modeling under an artificial horizon NIISPh Moscow and the method of mathematical planning of the experiment, an analytical dependence of the light transmission coefficient on the direct component of sunlight, which characterizes the relationship between the height of the sun, geometric and lighting parameters of point skylights, was obtained.


Introduction
Unlike a cloudy sky, with a clear sky, the luminous flux incident on the entrance cavity of the light opening consists of two components: the flux coming from the sky (the scattered component) s F and the stream coming from the sun (direct component) F  (Figure 1).
The total luminous flux entering the room is determined by the formula (1) where . . c s  is the coefficient of light transmission from the scattered component of the luminous flux, is determined by [1,2];   s the coefficient of light transmission from the direct component of the luminous flux.
Given the complexity of the redistribution of the luminous flux from the direct component, when passing through the opening of the garret window, the determination of the light transmission coefficient was carried out on the basis of the experimental research, at the working site of the installation of a small "Artificial horizon" NIISPH. The experimental setup (Fig. 2) consisted of a searchlight moving across the sky -5 searchlights with a parabolic mirror -3, a tube-cylinder -7, a box -2 of 1 х 1 х 1 m size, the inner surface of which was evenly coated with white paint with a reflectivity   0 85 , and scattering light according to Lambert's law. Two holes were cut in the box lid. A model of a light opening or a diaphragm -4 was installed in a large hole, in another -a photocell -1 with a screen -8. The photocell was connected to a galvanometer -6. E after passing the light flux through the diaphragm.
To display the functional dependence of the light transmission coefficient, which characterizes the relationship between the height of the sun H  , index of the skylight of the garret window i and the reflection coefficient of the garret window walls  the method of mathematical planning of the experiment was applied [3]. The measurements were carried out according to the D-optimal design for three independent variables, ( ) In accordance with the adopted D-optimal plan for the three-factor process study, a rectangular matrix of the experiment was compiled for I and II plans for 14 experiments, which is presented in Table 1. The controllable factors were normalized by linear transformations in the matrices of the plans for the experiments. The transition from real values to normalized variables is made according to the formula. The results of the experimental studies are presented in Table 2. The application correctness of the statistical estimates for processing the results obtained was carried out using  distribution. The test for reproducibility of the studied process was carried out according to the Cochran criterion. The construction of mathematical models was carried out by the least squares method. The significance of the regression equations' obtained coefficients was checked according to the Student's criterion, the adequacy of the obtained mathematical models and results -according to Fisher's criterion with a confidence level of 95%. After

Conclusion
The proposed method will make it possible, to more fully take into account the natural light energy resources of the construction site, when calculating natural illumination in spaces with garret windows which is important in the transition from the average accounting of the light climate to a differentiated one.