Spectral Radiative Properties of Fiberglass Insulation

Abstract

An inversion method was used to determine the spectral radiative properties (scattering and absorption coefficients) of fiberglass insulation from directional-hemispherical reflectance data. The experimental reflectance data were obtained with a Willey 318S Fourier transform spectrophotometer (FTS) in the wavelength range of 4-19 jim. The theoretical reflectance values were computed from the discrete ordinates solution to the radiative transport equation. Both isotropic and anisotropic scattering were considered. The experimental data and theory were coupled via the nonlinear least squares method to invert the radiative properties. In the wavelength range of 20-80 /im, the extinction coefficient was inverted from specular reflectance data via Beer's law and the nonlinear least squares method. Heat fluxes were computed using these properties and compared to existing steady-state heat-transfer measurements.