Theoretical modeling of thermal conductivity of alumina aerogel composites based on real microstructures
Journal
Journal of the Taiwan Institute of Chemical Engineers
Journal Volume
120
Pages
150-160
Date Issued
2021
Author(s)
Abstract
As compared with silica aerogels, alumina aerogels have excellent high-temperature stability, and hence, are regarded as a promising candidate for high-temperature thermal insulation materials. However, heat transfer mechanisms for such materials remain insufficiently explored. In this study, based on real material microstructures, an analytical thermal conductivity model for alumina aerogel-fiber-opacifier composites is developed via a modified parallel-series equivalent electrical circuit approach. The model takes into account solid, gaseous, and solid-gas coupling heat conduction in aerogels, solid heat conduction in both fibers and opacifier particles, and radiation in aerogels, fibers, and opacifier particles. The model is validated by comparing its predictions with measured thermal conductivity data. The model predictions reveal that there are two kinds of solid-gas coupling heat transfer mechanisms, which occur in the corner regions between interconnected secondary particles and in the slit regions between adjacent chains, respectively. Because of this coupling, the contribution of gaseous heat conduction is comparable to that of solid heat conduction and radiation of aerogels, fibers, and opacifier particles, which is well supported by experimentally measured data of thermal conductivity. The model is also used to analyze effects of various parameters on the thermal insulation performance of the composites, such as diameters and volume fractious of both fibers and opacifier particles. ? 2021 Taiwan Institute of Chemical Engineers
Subjects
Alumina; Aluminum oxide; Electric network analysis; Fibers; Heat conduction; Microstructure; Opacifiers; Silica; Silica gel; Thermal conductivity of solids; Thermal insulation; Gaseous heat conductions; Heat transfer mechanism; High temperature stability; Insulation performance; Material microstructures; Solid heat conductions; Thermal conductivity model; Thermal insulation materials; Aerogels
SDGs
Type
journal article