Reticulated porous ceria undergoing thermochemical reduction with high-flux irradiation. (April 2017)

• Record Type: Journal Article
• Authors: Ackermann, Simon; Takacs, Michael; Scheffe, Jonathan; Steinfeld, Aldo
• Is Part Of: International journal of heat and mass transfer. Volume 107(2017:Apr.)
• Page Start: 439
• Page End: 449
• Publication Date: 2017-04
• Subjects: Solar -- Thermochemistry -- Redox cycle -- Porous ceria; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2016.11.032
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: The solar-driven thermochemical reduction of ceria is applied for splitting H2 O/CO2 . Transient heat and mass transfer numerical model is implemented. Transport properties of porous ceria are obtained by direct pore-level simulations. Model is experimentally validated with samples exposed to high-flux irradiation. Structure with two pore-size regions exhibits superior heat transfer and oxygen yield. Abstract: A numerical and experimental analysis is performed on the solar-driven thermochemical reduction of ceria as part of a H2 O/CO2 -splitting redox cycle. A transient heat and mass transfer model is developed to simulate reticulated porous ceramic (RPC) foam-type structures, made of ceria, exposed to concentrated solar radiation. The RPC features dual-scale porosity in the mm-range and μm-range within its struts for enhanced transport. The numerical model solves the volume-averaged conservation equations for the porous fluid and solid domains using the effective transport properties for conductive, convective and radiative heat transfer. These in turn are determined by direct pore-level simulations and Monte-Carlo ray tracing on the exact 3D digital geometry of the RPC obtained from tomography scans. Experimental validation is accomplished in terms of temporal temperature and oxygen concentration measurements for RPC samples directly irradiated in a high-flux solar simulator with a peak flux of 1200 suns and heated to up to 1940 K. Effective volumetric absorption of solar radiation was obtained for moderate optically thick structures, leading to a more uniform temperature distribution and a higher specific oxygen yield. The effect of changing structural parameters such as mean pore diameter and porosity is investigated.