Aerogel blankets: From mathematical modeling to material characterization and experimental analysis

Abstract

One of the most feasible solutions for reducing the global energy consumption and associated CO2 emissions, is through usage of more efficient insulation systems in buildings and refrigeration units. Commercialization of high-performance thermal insulation will significantly contribute to environmentally sustainable future development. Aerogel composites provide superior thermal resistance and enable new design approaches for high performance insulation systems. This paper presents a theoretical and experimental study on the effective thermal conductivity of aerogel composites. The analytical model represents aerogel composites with a unit cell consisting of a cylindrical fiber surrounded by a packed bed of aerogel particles. The model accounts for various heat transfer mechanisms, namely conduction in the solid, gas conduction, and radiation. The properties and microstructure of two types of aerogel composites (Cryogel® Z and ThermalWrap™) were studied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and Fourier transform infrared spectroscopy (FTIR). The apparent thermal conductivity of the samples of aerogel blanket were measured using heat flow meter (HFM) at mean temperature ranging from −20°C to 80°C and the results polished thorough two-thickness method to de-convolute the effect of thermal contact resistance (TCR), between the sample and HFM hot and cold plates, from the apparent thermal conductivity values. The effective thermal conductivity results were found to increase from 0.0135 to 0.0175Wm−1K−1 for Cryogel® Z and 0.0188 to 0.0271Wm−1K−1 for ThermalWrap™ at mentioned temperature range. The analytically predicted variation in the effective thermal conductivity as a function of temperature agreed well with the experimental data. Using the proposed model, parametric studies were performed to investigate the effect of blanket porosity and fiber thermal conductivity on the effective thermal conductivity of aerogel composites.