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Thermal radiation is likely to play an important role in the calculation of the energy balance in solid oxide fuel cells (SOFCs), due to their high operating temperatures (600°–1000°C). However, the majority of previous studies dealing with this issue have used room-temperature radiative data for determining the overall heat transfer process within a given cell, which could lead to an inexact appreciation of the role played by the thermal radiation. Consequently, the thermal field within the cell could also be incorrectly determined; however, accurate knowledge of the thermal field is important in order to understand the mechanical behavior of SOFCs. Several parameters, including chemical composition, texture, thickness, and of course operating temperature, have a large effect on the radiative properties of a given compound. As a first step to elucidate the temperature-dependent behavior of SOFCs, we deposited an La2NiO4+δ cathodic layer on a planar ZrO2–8% Y2O3 electrolyte-supported SOFC and investigated its radiative properties using high-temperature infrared emissivity spectroscopy (100°–900°C). Additional X-ray diffraction, thermo-gravimetric analysis, and environmental scanning electron microscopy measurements were also made to study the role played by both the chemical composition and texture on the radiative properties of the cell.

International audience; A multiscale numerical model is developed to predict the thermal radiative properties (TRP) of rough La2NiO4+δ coatings. The model integrates intrinsic and extrinsic contributions related to the chemical composition and the texture, respectively. High-temperature infrared reflectivity and thermogravimetric measurements on a La2NiO4+δ single crystal make it possible to understand the role of the excess oxygen in the intrinsic TRP. We show that dense ceramics with thicknesses higher than 4 μm are optically thick, and that one can adjust the surface roughness parameters to predict their TRP.

A numerical model based upon a Monte Carlo Ray Tracing (MCRT) code was developed to predict the thermal radiative properties (reflectance, transmittance, emittance) of a family of virtual alumina ceramics with prescribed textural features. The numerical samples were constituted of polydisperse spherical pores [20–120 μm] embedded in a continuous and homogenous alumina matrix. The texture of the alumina ceramics were numerically settled, allowing, in our case, to fix their porosity, their volumetric surface and their radii size distribution. The MCRT code was applied at T = 300 K and T = 1300 K since, at the local scale, the complex indices of refraction of the alumina matrix were known. The comparisons of the emittance spectra of the numerical samples with the ones acquired by infrared emittance spectroscopy on a single crystal of alumina (T = 300 K and T = 1300 K) allow to discuss the effects played by the temperature and by each textural parameters.Copyright © 2010 by ASME

A parallel C++ numerical code was implemented to quickly and accurately calculate the radiative properties (reflectance and transmittance) of metallic foams that had scattering domains (pores, struts) with mean sizes larger than the wavelengths associated with thermal radiation. For application, the code required experimental knowledge of the material characteristics on several length scales ranging from the microscopic (approximately one micrometer) to macroscopic (approximately one centimeter). In particular, the 3D voxelized image of the investigated material was used, which was previously acquired using x-ray μ-tomography. The radiative properties were obtained by tracking a large number of rays within the numerical medium. On the local scale, rays interacted directly with the fluid/solid interface, which was obtained prior to the calculation by the application of a robust marching cubes algorithm to the entire set of voxels. The code was applied to aluminum foam samples, for which the experimental radiative properties were previously measured at room temperature with a customized instrument based on an infrared spectrometer. The code performance is discussed and the results enabled determination of the effects caused by the fluid/solid interface on the interfacial reflection.