The Thermal Diffusivity of Glass Sieves: II. Gas-saturated Frits

Abstract

AbstractThe thermal diffusivity of gas-saturated glass sieves (frits) of porosities between 20 % and 48 % is presented as measured at room temperature and ambient pressure. The saturants cover a range in thermal diffusivity from 20.63 × 10–6 m2⋅s−1 to 172 × 10–6 m2⋅s−1. The experiments were carried out using a transient hot-bridge instrument of an expanded uncertainty of 5 % to 10 %. It turned out that all measured thermal diffusivities of the gas-saturated frits (1) are smaller than that of the borosilicate glass the frits are made from and (2) are completely different from the thermal diffusivities of the liquid-saturated frits. Both these discrepancies can be attributed to characteristic properties of the matrix and not directly to the saturants. The first divergence results from thermal tortuosity that lengthens the pathway of heat through the matrix, whereas the second arises from dissolved He that enhances the transport of heat through the matrix.