Spectral Radiative Properties and Apparent Thermal Conductivity of Expanded Polystyrene Foam Insulation

Abstract

Heat transfer in foam insulations is primarily due to conduction and radiation. In order to predict the heat transfer in expanded polystyrene foams the determination of reliable spectral radiative properties is important since radiation accounts for up to 27% of the overall heat transfer at moderate temperatures (250 to 350 K). Most of the previous work done on the determination of the spectral radiative properties of foam insulations employed direct transmission measurements and Beer's law to invert the extinction coefficients. This paper utilizes directional-hemispherical reflectance data in the wavelength range from 4 to 20 μm to invert the spectral radiative properties of a standard reference material, namely 20.7 kg/m3 expanded polystyrene foam insulation. Apparent thermal conductivity values are predicted using the inverted radiative properties. The non-linear least squares method was used to invert the spectral radiative scattering and absorption coefficients from the experimental reflectance data and a numerical model.