Spectral radiative properties of open-cell foam insulation

A method to determine radiative properties of open-cell foam insulation is described. The spectral volumetric absorption and scattering coefficients and the spectral phase function are predicted from the dimensions and hemi spherical reflectivity of particles that constitute the solid structure by applying to these particles a combination of geometric optics laws and diffraction theory. Three types of carbon foam of different porosities are studied. Particle dimensions and porosity can be obtained from microscopic analysis, but solid hemispherical spectral reflectivity is very difficult to obtain directly. It is determined by the Gauss method of linearization, applied to bidirectional spectral transmittance data obtained from an experimental device using Fourier-transform infrared spectroscopy. Results obtained from this approach are consistent. Good agreement is observed between the experimental results of transmittance and reflectance and the theoretically predicted values computed from the identified values of particle hemispherical reflectivity.