APPLICATION OF THE KUBELKA-MUNK THEORY FOR THE DETERMINATION OF THE OPTICAL-PROPERTIES OF SOLAR ABSORBING PAINTS

The possibility to predict the solar absorptance gradient by colorimet ry is described. The study is performed on black spectrally selective paints used as absorber in photothermal conversion of solar energy. Th e Kubelka-Munk absorption and scattering coefficients of all considere d paints are determined. The relation between the degree of dispersion in the paint and Kubelka-Munk coefficients in the visible spectral re gion is discussed. The coefficients an used further to calculate the t ransparency values according to principles of colorimetry. The measure d solar absorptance gradient for a very thin paint layer reversibly de pends upon calculated transparency for different types of paints. This result helps to express the solar effectiveness of spectrally selecti ve paint by the transparency in the visible. (C) 1997 Elsevier Science S.A.