Numerical mesh generation tool for thermal conductivity simulations of nanoparticle filled inorganic plates

Abstract

Since regulations on insulation building materials become more stringent, particular interest is growing in thermal low conductive composite building materials. By adding very expensive, low thermal conductive nanoparticles in widely used inorganic solid materials, a new high performance building material can be developed. To sufficiently balance the production cost and the use of the nanofillers, an automatic tool, PreCon, was developed to provide sufficient process information and to generate a general purpose numerical model which can be used for thermal insulation simulations. It is expected that a total random distribution of the particles in the inorganic matrix will not result in a significant increase in insulation properties and hence will not enhance the performance. PreCon is used to investigate the influence of a random distributed nanomaterial combined with a more normal distribution through thickness. Based on this information, one can gauge the efforts needed to localize the nanoparticles in particular regions. However, accurate and repetitive thermal conductivity measurements of real dispersions are very difficult and precarious to obtain. Nevertheless, combining PreCon with Siemens simulation software provides appropriate nanofiller distributions with respect to cost. The realized tool is also able to introduce fibrous material distributions as a composite reinforcement. POLYM. ENG. SCI., 58:568-585, 2018.

Comparative study of a cubic, Kelvin and Weaire-Phelan unit cell for the prediction of the thermal conductivity of low density silica aerogels

“…By applying the desired steady state boundary constraints on this lump volume, a 3D matrix of partial differential equations is determined. Proper inverse matrix calculations provide the flux and hence the total thermal conductivity of the model [2].…”

“…The main characteristics of the proposed unit cell structures in this work, which are based on foams, are used to set-up a tetrahedral element mesh for use in finite element simulations. However, it has been concluded previously that the prediction of the thermal conductivity of silica aerogels based on a simple cubic unit cell model could already be reliable and moreover required limited computational resources compared to the approaches listed above [2]. The results, on the other hand, were only valid for high densities (ρ > 150 kg.m -³) because of the pore size distribution effect which indicates the presence of randomly distributed larger, is of minor importance.…”

“…Widely used construction materials such as concrete or plaster typically possess high thermal conductivities in the range of 1-10 W.m -1 .K -1 which do not provide sufficient thermal resistance for heat transfer. From a thermal performance perspective, adding super insulating materials in an appropriate way can decrease the total thermal conductivity up to one order of magnitude [2]. These types of insulating materials have an effective thermal conductivity lower than that of quiescent air (0.025 W.m -1 .K -1 [3]) at room temperature.…”

“…These assumptions will have their influences but were not yet estimated in this work. The values for the thermal conductivity were benchmarked against available experimental values obtained from literature for a density ρ between 80 kg.m -3 and 120 kg.m -3 [2]. In addition, a comprehensive parametric study was carried out to investigate the individual influences of geometric parameters such as skeletal bead dimensions and neck sizes, contact length between the beads and void dimensions as a function of the aerogel density.…”

“…where D is the void dimension [nm], Vpore, the pore volume, Sext, the external specific surface area [m2 .kg], dp, the bead diameter and ρs, the density of the solid backbone [kg.m-3 ]. Combining equations A.7-A.9, the 'state-of-the-art' empirical relation between D, dp and the density can be rewritten as follows[15]:If is known (in this work, as mentioned, the beads are considered full silica, = 2278 kg.m -3[15]), Eq.…”