期刊
JOURNAL OF NON-CRYSTALLINE SOLIDS
卷 358, 期 10, 页码 1287-1297出版社
ELSEVIER
DOI: 10.1016/j.jnoncrysol.2012.02.035
关键词
Silica aerogel; Porous secondary nanoparticle; Total thermal conductivity; Diffusion-limited cluster-cluster aggregation; 3-D finite volume numerical method
资金
- NSFC [21176133]
- SRFDP [20100002110045]
A 3-D finite volume numerical model based on the porous. secondary nanoparticle random aggregate structure was developed to predict the total thermal conductivity of silica aerogels. An improved 3-D diffusion-limited cluster-cluster aggregation (DLCA) method was used to generate an approximately real silica aerogel structure. The model includes the effects of the random and irregular nanoparticle aggregate structure for silica aerogels, solid-gas coupling, combined conduction and radiation, nanoparticle and pore sizes, secondary nanoparticle porosity and contact length between adjacent nanoparticles. The results show that the contact length and porosity of the secondary aerogel nanoparticle significantly affect the aerogel microstructure for a give density and, thus, greatly affect the total thermal conductivity of silica aerogels. The present model is fully validated by experimental results and is much better than the model based on a periodic cubic array of full density primary nanoparticles, especially for higher densities. The minimum total thermal conductivity for various silica aerogel microstructures can be well predicted by the present model for various temperatures, pressures and densities. (C) 2012 Elsevier B.V. All rights reserved.
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