Experimental and numerical pore-scale characterization of multi-mode heat transfer in porous ceramics exposed to a transverse heat flux

We present experimental and computational approaches to characterize the multimode heat transfer in an open-cell Si-SiC foam exposed to a transverse heat flux. The experimental setup consists of a 5×5×10 cm3 parallelepipedal 10ppi foam (83% porosity) placed within a rectangular channel, in which airflow (0-8 g.s-1) was established. The pressure drop across the foam was measured and infrared cameras were used to obtain the temperature of the heater plate and the thermal maps of the foam at the outlet and on the top. The computational approach is a 3D pore scale model of flow and multi-mode heat transfer in the channel subjected to the same conditions. A X-ray tomography technique (50 μm resolution) was used to scan the foam structure and subsequent segmentation and binarization of the data resulted to a digitalized volume of the 1000×1000×2000 voxels and about 101 million cells after meshing. The computations were performed using ANSYS Fluent. Laminar or k-ϵ turbulence models with enhanced wall treatment were used depending on the airflow rate. Finally, the comparison of the numerical results with experimental data shows that the relative deviation of pressure drop is less than 7.1% and that of outlet foam temperature is less than the experimental uncertainties (5-20%). Using similarity with fins, the effectiveness of foam is evaluated around 2.2.