Numerical study of cell morphology effects on convective heat transfer in reticulated ceramics

Understanding the influence of foam morphology on the heat transport mechanism is an essential task for the design engineers. The assessment of foam thermal properties was performed using experimental techniques or simulation approaches such as Finite Elements analysis and/or computational fluid dynamics and was, up to now, mainly focused on describing the influence of some average parameters, such as cell size and porosity. Recent numerical analysis have instead demonstrated that local cell morphological structures can strongly influence thermal conduction in ceramic foams. Therefore, in the present work, the effect of morphological characteristics, namely ligament radius, cell inclination angle and ligament tapering, on the convective heat transfer of ceramic foams were studied. The approach used is Computational Fluid Dynamics (CFD) and foam geometries were schematically represented with tetrakaydecahedra geometries. The numerical simulations, performed with ANSYS/Fluent on different tetrakaydecahedra geometries, aimed at evaluating pressure drop and heat exchange through the foam. A heat exchanger efficiency parameter was defined and then evaluated for the different foam geometries at several air flow velocities. Results show the influence of the different morphological parameters and, in particular, that the heat exchanger efficiency of the foams decreases when increasing the air flow velocity.