Computational fluid dynamics (CFD) is employed in the design and optimization of a novel high-temperature solar chemical reactor. The reaction considered is the thermal reduction of metal oxides, as part of a two-step water-splitting cycle for hydrogen production. The solar reactor uses a flow of metal oxides particles under concentrated solar radiation, that serve simultaneously as energy absorbers and chemical reactants. CFD simulation offers the possibility to calculate velocity, temperature and pressure fields, and particle trajectories, which cannot be measured under the severe flux radiation (above 3000 kW/m(2)) and high-temperature (above 1500 K) environment of solar furnace experiments. CFD validation is accomplished by comparison with experimental results in cold operating conditions.