Computational fluid dynamics (CFD) analysis of decomposition reaction inside the solar fluid wall reactor

A solar thermo-chemical reactor has been designed and modeled to study the flow of decomposition reactions. The reaction considered in this case is the thermal reduction of metal oxide, as part of a two-step water splitting cycle for hydrogen generation and methane decomposition, which directly generates hydrogen in a single step reaction. The reaction takes place at 2000 K to 2500 K using concentrated solar energy as the source. In this model, the reactor is comprised of two concentric cylinders, which are made of graphite. The input zinc oxide is assumed to be uniform in particle size during the simulation. The inert argon gas passes through the inner porous medium, acts as a fluidized bed for the reactor that prevents reaction between oxygen and graphite wall. A mixture of Zn(g), O2(g) and Ar(g) comes out as the output.;The suitable initial and boundary conditions have been specified and analysis has been done using FLUENT, under unsteady state laminar conditions. The chemical reaction rate constant was calculated based on the Arrhenius equation. Various parametric studies have been examined for optional design of this thermo-chemical reactor, and a full understanding the behavior of the fluid flow and reaction has been obtained.;A variable solar heat flux has been assumed to be on the wall of the reactor, and the effects of wall temperature on the reaction have been studied. The results indicate that pore diameter, inlet temperature of argon gas and the reactor material significantly affect the flow behavior. Increasing the inlet temperature of argon gas drastically improves the fluid flow profile. This simulation also provides the detailed information about the mole fractions of species which are involved in the chemical reactions.