%0 Journal Article
%T Aerogels as Promising Thermal Insulating Materials: An Overview
%A Prakash C. Thapliyal
%A Kirti Singh
%J Journal of Materials
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/127049
%X Aerogels are solids with high porosity (<100£¿nm) and hence possess extremely low density (¡«0.003£¿g/cm3) and very low conductivity (¡«10£¿mW/mK). In recent years, aerogels have attracted more and more attention due to their surprising properties and their existing and potential applications in wide range of technological areas. An overview of aerogels and their applications as the building envelope components and respective improvements from an energy efficiency perspective including performance is given here. This overview covers thermal insulation properties of aerogels and studies regarding structural features which will be helpful in buildings envelope. The improvements of thermal insulation systems have future prospects of large savings in primary energy consumption. It can be concluded that aerogels have great potential in a wide range of applications as energy efficient insulation, windows, acoustics, and so forth. 1. Introduction Short supply, limited availability, and increasing energy costs all around the world emphasize the need for immediate energy conservation in both oil rich and oil producing countries. An effective way towards saving energy is to improve the thermal insulation of buildings especially in hot climates where the energy demand for cooling by air conditioning is comparatively higher. In addition to the need for energy saving, high insulating materials are further justified by improved comfort levels and increased building life. Thermal characteristics depend largely on the thermal conductivity of the cell walls and the cell matrix, as well as radiation and convection, with the cell matrix being the most significant factor in determining the overall heat transfer characteristics. Thermal properties of some commonly available insulating materials are given in Table 1. Table 1: Commonly available thermal insulation materials. Thermal conductivity varies with time due to changes in the composition of the cell matrix. The ambient air and external building surface temperatures in hot climates of Asia and Africa are much higher than in cold climates of a Australia, Europe and America, temperature of 38¡ãC should be taken into account while calculating thermal conductivities at ageing. In addition to the product specific parameter of the change of the thermal conductivity, mean temperature and water absorption are also other important influencing factors. As per IUPAC, aerogel is defined as a gel comprised of a microporous solid in which dispersed phase is a gas [1]. Aegerter et al. defined aerogels as gels in which the liquid has been
%U http://www.hindawi.com/journals/jma/2014/127049/