PREDICTION OF THERMAL CONDUCTIVITY OF FIBER/AEROGEL COMPOSITES FOR OPTIMAL THERMAL INSULATION

A numerical model for predicting the effective thermal conductivity of fused silica fiber/aerogel composites by simultaneously considering the effects of the fiber volume fraction and fiber diameter is presented. The predicted effective thermal conductivity of the fiber/aerogel composites agreed well with the existing measured and predicted results. The effects of the volume fraction (0−25%) and diameter (0.3−10 µm) of fibers on the effective thermal conductivity of aerogel composites were investigated under a large range of temperatures (300−1300 K). The results indicated that the minimum effective thermal conductivity of the fiber/aerogel composites by simultaneously considering the optimized fiber volume fraction and diameter was significantly lower than when individually considering the optimized fiber volume fraction and diameter values. For instance, the minimum effective thermal conductivity by simultaneous optimization was 0.0262 W/m−1 K−1 at 1000 K, which was much lower than 0.0327 W/m−1 K−1 by individually optimizing the fiber volume fraction at a diameter of 8 µm and 0.0532 W/m−1 K−1 by individually optimizing the fiber diameter at a volume fraction of 3%. Moreover, the quantitative relations between the minimum effective thermal conductivity of the fiber/aerogel composites and the temperatures are presented, with the aim of identifying the optimal thermal insulation for applications in aeronautics and astronautics, construction, and other industrial fields.