Radiative properties of fibrous insulations: Theory versus experiment

The validity of an exact theoretical model for calculation of the radiative properties of high porosity, randomly oriented fiber media is examined by comparing experimental measurements with theoretical predictions for spectral reflectance and transmittance. Spectral hemispherical reflectances and spectral normal transmittances were calculated at wavelengths from 1.5 to 10.0 mu m for several thicknesses of three types of thermal insulating materials having randomly oriented sillca fibers of different size distributions, Theoretical results are compared with experimental measurements made on each of the three materials. The theoretical methodology, analytical results, and experimental characterizations of geometric parameters and radiative properties of the test materials are presented. The comparison shown between theory and experiment is excellent. Thus, the model is considered to be a valid tool for prediction of radiative properties of high-porosity, randomly oriented fibrous media.