Simulation and Investigation of Heat Transfer in Structurally Graded Silica Aerogels with Pores Diameter Changing

In graded structure aerogels, change of pores diameter through the thickness affects the effective thermal conductivity. As the pores diameter is reversely correlated to the density, the effective thermal conductivity of aerogel is often normalized to the density and it is expressed as the B parameter. Lower values of B would be the optimum conditions for the resulting aerogel. The objective of this work is to simulate the heat transfer of the optimum structure and to compare it with structures that pore diameter vary through the thickness. For this purpose, the structure characteristics and properties of silica aerogel along with the effect of coupling thermal conductivity have tobe taken into consideration. Using the COMSOL Multiphysics® software, the heat transfer was modeled for an optimum structure (OPT) having a minimum value of the B parameter. The results were compared to the structurally graded aerogels in which the density was varied in two fashions, from higher values to lower (HtL) and from lower to higher values (LtH). The change of temperature with time was tracked for all the cases. Results indicated that the minimum value of heat transfer was obtained for the structurally graded aerogel of the type of LtH (a 2-percent increase of efficiency for LtH when compared to the optimum structure (OPT)). Therefore, this structure introduce as the best candidate for producing a thermal insulator.

Keywords:

Silica Aerogel , Gradient Structure , Heat Transfer , Simulation