A simple simulation method for designing fibrous insulation materials

Conductive heat in a fibrous material travels through both the air (interstitial fluid) and the fibers (solid phase). The numerical simulations reported in this paper are devised to study the effective thermal conductivity of fibrous media with different microstructural parameters. Simulations were conducted in 3-D fibrous geometries resembling the microstructure of a fibrous material. Assuming that the heat transfer through the interstitial fluid is independent of the geometrical parameters of the solid phase (for when the porosity is held constant), the energy equation was solved only for the solid structures, and the resulting values were used to predict the effective thermal conductivity of the whole media. This treatment allows us to drastically reduce the computational cost of such simulations. The results indicate that heat conduction through the solid fibrous structure increases by increasing the material’s solid volume fraction, fiber diameter, and fibers’ through-plane orientations. The in-plane orientation of the fibers, on the other hand, did not show any significant influence on the material’s conductivity. It was also shown that the microstructural parameters of fibrous insulations have negligible influence on the material’s performance if the conductivity of the solid phase is close to that of the interstitial fluid.