| Abstract: | The thermal losses of a monolithic low-density SiO2 aerogel tile (thickness d = 9 mm, density = 80 kg/m3) have been determined in our evacuable guarded hot plate system LOLA II. The measurements were performed for two values of boundary emissivities ( ≈ 0.05 and 0.9) under variation of temperature and of gas pressure for several types of gases. From our results we conclude that low-density silica aerogel tiles about 10 mm thickness provide excellent thermal insulation with overall loss coefficients k 0.7 W/(m2 · K) at ambient temperatures (10°C or 283 K) and pressures 10 mbar. Their use in window systems and covers for passive use of solar energy thus is extremely promising. From the change of thermal losses with gas pressure, a mean free path within the (evacuated) skeleton of about 120 nm can be derived. |
