(396b) Non-Thermal Equilibrium Heat Transfer Model of a Thermochemical Solar Reactor Based on Porous Media

The production of energy vectors, such as hydrogen and syngas, through thermochemical solar cycles is a promising option due to their potential high efficiencies, whose theoretical values are around 35% and 50%, respectively. To perform this process with concentrated solar energy it is necessary to develop solar reactors capable to operate with high radiative flux. An attractive reactor configuration consists on using ceramic porous media that are made or coated with the redox material. This type of reactor exhibit several advantages, which include higher volumetric yield. However, measuring temperatures inside the porous media is complicated, therefore it is necessary to develop models that allow to predict such temperatures.

In this work, a one-dimensional transient heat transfer model is proposed to evaluate the thermal behavior of a zirconium oxide foam-type porous medium exposed to concentrated solar radiation provided by the IER-UNAM Solar Furnace. The developed model considers a non-thermal equilibrium situation, in which the temperature of the porous media is different from that of the fluid. In this model an effective conductivity is used, which combines the Archie model, for the conduction contribution on the solid, and the Rosseland diffusion model, for the thermal radiation conductivity. The parameters used for the effective conductivity have been corroborated experimentally for the analyzed porous media.

The model allows calculating temperature profiles inside the porous media, which are evaluated at different values of operation parameters, such as concentrated irradiance, air flowrate, etc. The model was validated with experimental results obtained by using a 10 kW solar reactor prototype with a configuration similar to the simulated system.