Temperature and pressure dependent effective thermal conductivity of fibrous insulation

In present paper, a numerical model combined radiation and conduction heat transfer was developed to predict the effective thermal conductivity of fibrous insulation at various temperatures and pressures. Effective thermal conductivities of the fibrous insulation were measured over a wide range of temperature (300-973 K) and pressure (10(-2)-10(5) Pa) using a developed apparatus. The transmittance spectra in the wavelength range of 2.5-25 mu m were also measured at temperatures up to 973 K using a Fourier Transform Infrared Spectrometer. From transmittance data, the spectral extinction coefficients and Rosseland mean extinction coefficients were obtained at various temperatures to investigate the radiative heat transfer in fibrous insulation. The numerical and experimental data were compared. It was found that the calculated values corresponded with the experimental values within an average of 14.7 percent. Numerical results were consistent with experimental results throughout the investigated environmental conditions. (C) 2008 Elsevier Masson SAS. All rights reserved.