Determination of the anisotropic thermal conductivity of an aerogel-based plaster using transient plane source method

Aerogel-based plasters are composite materials with declared thermal conductivities in the range of traditional insulating materials, i.e. 30-50 mW/(m·K). Based on the results from reported field measurements, aerogel-based plasters can significantly reduce the thermal transmittance of uninsulated walls. However, the in-situ measured thermal conductivities have sometimes been higher than the declared values measured in laboratory and in the main direction of the heat flow. Meanwhile, the anisotropic thermal performance of aerogel-based plasters, i.e., deviating thermal performance in the different directions of heat flow, has not been explored yet. The objective of this study is thus to evaluate the anisotropic thermal conductivity of an aerogel-based plaster. This is done in a set of laboratory measurements using the transient plane source method. Six identical and cubic samples with the dimensions of 10×10×10 cm3 were paired two and two, creating three identical sample sets. In total, 360 measurements of thermal conductivity and thermal diffusivity, and 130 measurements for specific heat capacity were conducted. The results indicate a weak anisotropy of less than ±6.5 % between the three directions (x, y, z). Considering the accuracy of the selected measurement technique, better than ±5 %, supplementary measurements using another technique are recommended.

Experimental Study on Thermal Properties of Hollow Sphere Structures

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

Thermal Properties of Söderberg Electrode Materials

Thermal properties of green Söderberg electrode pastes were measured up to 1073 K (800 °C) using the transient plane source method. Comparison was made to measurements on an electrode material baked beforehand to 1473 K (1200 °C). For the green pastes, thermal conductivity was found to decrease up to 673 K (400 °C) at the onset of baking. After about 873 K (600 °C), thermal conductivity of the material increases with increasing temperature. For previously baked Söderberg material, thermal conductivity continually increases with increasing temperature.