부산대학교 도서관

Several calculation methods of coefficients of utilization are used in the world, and now it is required to choose the optinum one and unify the calculation. In Italy, Czechoslovakia, Switzerland and the other countries including Japan, the Three Curve Method based upon the Rairison and Anderson experimental results is generally used in practice. In the United States and the Great Britain, however, newly developed methods have been adopted with the progress of lighting calculation theories. The authors also reported these calculation methods, which have been gradually adopted recently in Japan.In view of the present situation limitations of each method are examined and experiments on the validity of these methodes, are made inorder to select a suitable method for adoption.The discussed subjects in this paper are as follows:(1) The Three Curve Method (T. C. M.), the Zonal Factor Method F. M. and the Zonal Cavity Method (Z. C. M.) are choren as the representative methods of calculation and their characteristics and limitations are examined.(2) Experimental investigations are made to support the fact that the Z. C. M. has the highest validity, where three types of fluorescent fittings and an incandescent fitting were used in a model room about one forth of the real dimensions.(3) This experiment indicates that the calculated coefficients of utilization on the basis of the Z. C. M. and the Z. F. M. are slightly conservative but close to the measured values thin the room index is larger than 1. 0. However, the values calculated by the Z. C. M. and the T. C. M. are close to the measured ones where the room index in smaller than 1. O.(4) Difference between measured and calculated values seemes to be mainly caused by the assumption that initial luminous emittance on each surface element is uniform. Therefore, the calculated values wiell become closer to the measured ones of interflected components taking into account the more detailed specifications of initial luminous emittance. It in concluded that the Z. C. M. is the most valid method at present theoretically as well as experimentally.