(345e) Geometry design and thermodynamic analysis of an epitrochoidal rotary reactorfor solar hydrogen production via ceria redox cycle

In this study, a conceptual epitrochoidal rotary reactor is designed for solar-driven hydrogen production based on the redox cycle of ceria. Compared to the state-of-the-art solar reactors for two-step redox cycles of metal oxides, the epitrochoidal rotary reactor has the advantages of (1) convenient conveying of the metal oxides between the reduction and oxidation chambers, (2) performing solid-phase heat recovery in the form of mechanical energy via isentropic compression and expansion, and (3) providing satisfactory gas sealing between the reduction and oxidation chambers.

The reactor consists of an eccentric shaft, a rotor in the shape of a regular polygonal prism with curved side surfaces, and a case in the shape of the outer conjugate profile of the rotor. The rotor, meshed with the eccentric shaft through a cam, performs an epitrochoidal movement. The apexes of the rotor are in constant and dynamic contact with the housing, dividing the cavity into multiple reaction chambers. Due to the epitrochoidal movement of the rotor, gases in the reaction chambers are periodically compressed and expanded. Ceria in the form of reticulate porous ceramic is mounted on the curved side surfaces of the rotor. During the rotation, the ceria is not in contact with the housing. Inert gas enters a reaction chamber at the oxidation temperature. As the rotor rotates, the isentropic compression of the inert gas raises the temperature of both the ceria and the gas to the reduction temperature. After the irradiated ceria is isothermally reduced, the inert gas and oxygen generated are expanded, allowing for the recovery of the sensible heat in the form of mechanical energy and reducing the temperature of ceria and the gases to around the oxidation temperature.

This study explores the kinematic synthesis of the epitrochoidal solar reactor, which is based on the planetary motion of a regular polygonal prism with curved side surfaces. A detailed thermodynamic analysis is performed to elucidate the effects of the key geometrical parameters on the solar-to-fuel efficiency of the reactor.