Heat and Mass transport properties of reticulated porous ceramic structures

Reticulated porous ceramic (RPC) foam-type structures are employed in solar reactors for the thermochemical splitting of H₂O and CO₂. Optimization of the thermochemical redox cycle demands the development of numerical heat and mass models. However, 3D geometrical resolving the porous structures in transient heating and reduction simulations would lead to enormous computational requirements. Thus, the unsteady mass, momentum, and energy conservation equations are numerically solved by applying the volume-averaging theory for porous media. In this work, a 1D volume-averaged heat and mass transfer model was implemented in a commercial computational fluid dynamics (CFD) software (ANSYS® Academic Research, release 15.0) for characterisation of the heating and reduction performance of complex dual-scale porous ceria structures directly exposed to concentrated solar radiation.

The RPC features dual-scale porosity: mm-size pores for volumetric radiative absorption and effective heat transfer during the reduction step and micron-size interconnected pores within the struts for increased specific surface area leading to enhanced reaction kinetics during the oxidation step. Additionally, spectroscopic measurements were performed for a high range of wavelengths for the accurate determination of the surface reflectivity of ceria as a function of the reduction extent.