Determining Radiative Heat Transfer Through Heterogeneous Multilayer Nonwoven Materials

A theoretical equation of the combined thermal conductive, convective, and radiative heat flow through heterogeneous multilayer fibrous materials is presented. Samples whose properties are analyzed by this equation were constructed from glass and ceramic webs and used in an earlier work to experimentally determine their thermal conductivities. In that experimental work, overall effective thermal conductivities were determined using a guarded hot plate instrument with temperatures ranging from 430 to 480°C. In the theoretical equation presented here, thermal convective heat flow is ignored because of fabric structural conditions, and the conduction component of the overall conductivity is determined by Fricke's equation. Furthermore, the results of Fricke's equation and the overall effective thermal conductivity are used to estimate the radiative thermal conduc tivity of the samples.