Chen Yang

By Chen Yang, Huijin Xu and Akira Nakayama

A volumetric solar receiver receives the concentrated radiation generated by a large number of heliostats. Turbulent heat transfer occurs from the solid matrix to the air as it passes through the porous receiver. Such combined heat transfer within the receiver, including radiation, convection and conduction, is studied using a local thermal non-equilibrium model. Both the Rosseland approximation and the P1 model are applied to consider the radiative heat transfer through the solar receiver. Furthermore, the low Mach approximation is exploited to investigate the compressible flow through the receiver. Analytic solutions are obtained for the developments of air and ceramic temperatures as well as the pressure along the flow direction. Since the corresponding fluid and solid temperature variations generated under the Rosseland approximation agree fairly well with those based on the P1 model, the Rosseland approximation is used for further analysis. The results indicate that the pore diameter must be larger than its critical value to obtain high receiver efficiency. Moreover, it has been found that optimal pore diameter exists for achieving the maximum receiver efficiency under the equal pumping power. The solutions provide effective guidance for a novel volumetric solar receiver design of silicon carbide ceramic foam.

Part of the book: Foams

By Yixiong Lin, Chen Yang and Ting Qiu

Dry reforming of methane (DRM) is one of the feasible strategies for carbon capture and utilization. However, DRM has a high tendency toward coking, which is restricted to industrial applications. The primary cause of coking in DRM is the limitation of mass transfer inside porous catalysts. To overcome this limitation, optimizing the pore structure of the porous catalyst becomes crucial. Hierarchical pore structure has received considerable attention in recent years due to its superior mass transfer performance. Therefore, this chapter focuses on the structure-performance relationship of hierarchical porous catalysts in DRM. Specifically, two types of porous catalysts, namely porous pellet and open-cell foam, are examined. The impacts of various hierarchical pore structure parameters on the catalytic activity and coke resistance are investigated. The findings offer a theoretical foundation and technical guidance for the design of porous catalysts with hierarchical pore structures.

Part of the book: Transport Perspectives for Porous Medium Applications [Working title]

By Zhongmin Wan, Yun Sun and Chen Yang

Metal foam as flow field for proton exchange membrane fuel cell (PEMFC) has demonstrated substantial promise for enhancing the distribution uniformities of reactants and temperature. In different types of PEMFC, however, the influence of metal foam flow field on cell performance is diverse. For liquid-cooled PEMFC, employing metal foam flow field encounters challenges in water removal. For air-cooled PEMFC, employing metal foam can help retain a certain amount of liquid water to avoid membrane dehydration. In an effort to further enhance the cell performance and practical application potential of metal foam in different types of PEMFC, the design strategy for metal foam flow field in PEMFCs is studied through this chapter. Experimental results revealed that for liquid-cooled PEMFC, the cathode side employing metal foam flow field raises the potential for water flooding and instability of operational voltage, which can be addressed through reasonably designing the structural characteristics of metal foam. Furthermore, the thermal management capability of air-cooled PEMFC can be boosted through adopting metal foam flow field, owing to the synergic improvement of forced convective heat transfer of reactant gas and electrochemical performance, which is the main factor of the thermal management improvement at high current.

Part of the book: Transport Perspectives for Porous Medium Applications [Working title]