Conduction and Radiation Heat Transfer in High-Porosity Fiber Thermal Insulation

An improved theoretical model for the prediction of radiative properties of, and radiative heat transfer in, high-porosity fiber thermal insulations is presented. The validity of the model is demonstrated via comparison of numerical predictions with a comprehensive data base of experiments described in the literature prior to the development of the present model. The radiation model produced excellent agreement with experimental heat-transfer data for a variety of fiber material that contain bonded fibers, unbonded fibers, with and without an absorbing matrix, and fibers randomly or preferentially oriented. The success of the model is due to the rigorous formulations of the fiber radiative properties and the modified exinction coefficient that include the effect of fiber orientation. (AIAA)