Abstract
This paper represents the synthesis of our investigations towards a better understanding of radiative heat transfer through fiberglass insulating materials from 1985 to 1990.
Both a theoretical and experimental approach are proposed in order to predict the thermal resistance of fibrous insulants, and to determine the influence of the chemical composition of the bulk glass, of the insulant morphology (porosity, specific surface, anisotropy) and of the temperature of use (T < 600°C).
The fibrous material is treated as a semi-transparent medium that absorbs, scatters and emits radiation; the radiative heat transfer equation is solved by the Shuster- Schwartzchild approximation. The radiative coefficients of the fiberized glass that ap pear in the equations (scattering, absorption and backscattering coefficients) are derived from spectral reflection and transmission measurements performed on the bulk glass as a function of temperature (determination of the complex index and use of Kerker Mie theory).
Theoretical predictions of the total heat transfer through different types of fiberglass insulants are presented and validated by experimental results.
The emphasis is put on the effect of the chemical composition of glass. Special at tention is given to boron oxide (B2O 3). A close look at the infrared spectra (on both bulk and fiberized glass) allows us to understand the influence of this oxide on the thermal resistance of fiberglass insulating materials.
The effects of the insulant morphology and temperature are also discussed.
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