Experimental validation of simplified conduction–radiation models for evaluation of Effective Thermal Conductivity of open-cell metal foams at high temperatures

• Published in: International journal of heat and mass transfer Vol. 78; pp. 112 - 120
• Main Authors: Mendes, Miguel A.A., Skibina, Valeria, Talukdar, Prabal, Wulf, Rhena, Gross, Ulrich, Trimis, Dimosthenis, Ray, Subhashis
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2014
• Subjects: Conduction–radiation; Effective Thermal Conductivity; Foams; Heat conduction; Heat transfer; High resolution 3D CT-scan; High temperature panel test technique; Mathematical analysis; Mathematical models; Metal foams; Open-cell metal foam; Simplified model; Thermal conductivity; Three dimensional; Effective Thermal Conductivity; Simplified model; High temperature panel test technique; Open-cell metal foam; Conduction–radiation; High resolution 3D CT-scan
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2014.05.058

In the present study, the Effective Thermal Conductivity (ETC) of open-cell metal foams at high temperatures is numerically predicted using two different simplified homogeneous models, where relevant effective properties of foams are estimated considering their true geometry obtained from three-dimensional (3D) Computed Tomography (CT)-scan data. The performance of these models is judged by comparing their predictions with experimental results of the ETC measured using the panel test technique in the temperature range of around 130°C–850°C. Two samples of open-cell FeCrAl foams with similar porosity but different characteristic pore dimensions are considered for this purpose. The present results clearly show that both simplified homogeneous models offer efficient alternatives to detailed models for the estimation of ETC at both ambient and higher temperatures. Although Model-2 uses the extremely simplified Rosseland approximation for radiation and hence is expected to be less accurate than Model-1, where the radiation heat transfer is solved with the one-dimensional Radiative Transfer Equation, it may be successfully applied provided the optical thickness of the porous foam is reasonably high. This investigation also shows that effective properties of porous foams, required by these models for both conduction and radiation (i.e. the ETC due to pure heat conduction and the extinction coefficient), can be accurately estimated using simple numerical tools based only upon the information extracted from 3D CT-scan images, which is a cheap alternative as compared to using experimental techniques. Since these simplified models already require the Effective Thermal Conductivity due to pure heat conduction as input, they are not considered self-sufficient as far as the overall modeling is concerned.