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RADIATIVE PROPERTIES OF CELLULAR FOAMS

DOI: 10.1615/ICHMT.2008.CHT.470
14 pages

Aurelie Kaemmerlen
Centre de Thermique de Lyon (CETHIL), UMR CNRS 5008, INSA-Lyon, F-69621, France

Remi Coquard
Société "Etude Conseils Calcul Modélisation" (EC2-MODELISATION), 66 Boulevard Niels Bohr, F69603 Villeurbanne, France

Dominique Baillis
LaMCoS, INSA-Lyon, CNRS UMR 5259,18-20 Rue des Sciences, F69621 Villeurbanne, France

Abstract

A better understanding of the heat transfer mechanisms in polystyrene foams will enable substantial improvements in their thermal insulation performance. Heat transfer in polystyrene foams consists of two components: conduction through the solid polymer and the gaseous phase, and thermal radiation. The convection component is negligible due to the very small size of cells. The impact of foam morphology on thermal insulation performance was established by several studies, however the effects of polymer refractive index and cell wall thickness are not fully understood yet. We model in this study the radiative properties of expanded polystyrene foams (EPS) using two recently developed models: one is based on a ray-tracing procedure and the other one is based on the integration of the radiative properties around the different orientations of walls in space. We assume that the cell walls are randomly oriented in space. The analysis of the results obtained with these two models pointed out the significant influence of the real part of the refractive index on the optimum cell wall thickness. Furthermore, our study shows that the deviation of the results concerning radiative properties of both mono and polydispersed cell wall thickness is very weak. Finally, we show that a very good agreement is obtained between the two models. Nevertheless the ray-tracing method is slower but it is expendable for non-random morphologies, while the integration method could only be applicable when the hypothesis of random orientated walls is applied.

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