Library Subscription: Guest
ICHMT DL Home Current Year Archives Executive Committee International Centre for Heat and Mass Transfer

COMPUTATIONAL PREDICTION OF RADIATIVE PROPERTIES OF POLYMER CLOSED-CELL FOAMS WITH RANDOM STRUCTURE

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

Jaona Harifidy Randrianalisoa
Centre de Thermique de Lyon, Institut National des Sciences Appliqués, Lyon; GRESPI - EA 4694, University of Reims Champagne-Ardenne, F-51687 Reims, France

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

Abstract

Polymer foams with closed-cells are widely used as insulating material in many applications from building to space launchers. In these applications, the heat transfer within the foam is governed mainly by conduction and radiation. To enhance the insulating system capability, the knowledge of the thermal properties of these materials is indispensable.
From the thermal radiation point of view, polymer foams behave as semitransparent materials. Current knowledge shows that the radiative properties of the foam depend on the optical and surface properties of the solid phase, on the cell size and shape, and on the wall thickness (or relative density). Among these parameters, the influences of the cell morphology are not well understood. This contribution aims to investigate numerically the influences of the cell architecture on their radiative properties.
At first, three-dimensional samples are modeled through the Voronoï tessellation method. Different foam morphologies are considered ranging from the periodic assembly of the famous Kelvin'cells to assemblies of totally random cells.
Secondly, the equivalent radiative properties are determined from a Ray-Tracing (RT) method performed inside the REV [Randrianalisoa 2010, Coquard 2011]. This method consists in tracking the path of a large number of energetic rays (or photon bundles) from their possible emission location to their extinction location. The absorption and scattering coefficients are determined from the history of extinction paths while the scattering phase function is determined from the history of scattering direction distribution.
The radiative properties of the samples are compared with analytical models of the literature. The evolution of these properties with the cell randomness is analysed and discussed. An analysis of the anisotropy of the radiative behaviour is also conducted. For validation purpose, the calculated hemispherical transmittances and reflectances of plan parallel foam slices are compared with the corresponding measurements conducted on XPS foam slices. The agreement between experimental and computed transmittances and reflectance is quite satisfactory, demonstrating the suitability of the numerical approach.

ICHMT Digital Library

Bow shocks on a jet-like solid body shape. Thermal Sciences 2004, 2004. Pulsed, supersonic fuel jets - their characteristics and potential for improved diesel engine injection. PULSED, SUPERSONIC FUEL JETS - THEIR CHARACTERISTICS AND POTENTIAL FOR IMPROVED DIESEL ENGINE INJECTION
View of engine compartment components (left). Plots of temperature distributions in centreplane, forward of engine (right). CHT-04 - Advances in Computational Heat Transfer III, 2004. Devel... DEVELOPMENT AND CURRENT STATUS OF INDUSTRIAL THERMOFLUIDS CFD ANALYSIS
Pratt & Whitney's F-135 Joint Strike Fighter Engine under test in Florida is a 3600F class jet engine. TURBINE-09, 2009. Turbine airfoil leading edge stagnation aerodynamics and heat transfe... TURBINE AIRFOIL LEADING EDGE STAGNATION AERODYNAMICS AND HEAT TRANSFER - A REVIEW
Refractive index reconstructed field. (a) Second iteration. (b) Fourth iteration. Radiative Transfer - VI, 2010. Theoretical development for refractive index reconstruction from a radiative ... THEORETICAL DEVELOPMENT FOR REFRACTIVE INDEX RECONSTRUCTION FROM A RADIATIVE TRANSFER EQUATION-BASED ALGORITHM
Two inclusion test, four collimated sources. Radiative Transfer - VI, 2010. New developments in frequency domain optical tomography. Part II. Application with a L-BFGS associated to an inexa... NEW DEVELOPMENTS IN FREQUENCY DOMAIN OPTICAL TOMOGRAPHY. PART II. APPLICATION WITH A L-BFGS ASSOCIATED TO AN INEXACT LINE SEARCH