Based on the open-cell nano-porous structure features, a cubic array of nano-spheres unit cell model describing the coupled conduction of gas and solid in aerogel super insulator is developed. By one-dimensional heat conduction analysis in the unit cell, the effective thermal conductivity expression is obtained. The results show that the model matches well with the experimental data and nano-porous structure, nanometer size effect of solids as well as the very high specific surface area are the key factors make aerogel have very low thermal conductivity. There exists an optimal density value where the thermal conductivity of aerogel is minimum. Thermal radiative heat transfer is the dominating heat transfer mechanism of aerogel at an elevated temperature. It can decrease the thermal conductivity value of aerogel effectively at an elevated temperature by doping carbon or other matters which can strongly absorb infrared light at 3∼8 μm.

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