Huijin Xu

By Huijin Xu, Zhanbin Xing, Fuqiang Wang and Changying Zhao

Metal foams can be well used as ideal materials for various efficient heat transfer devices due to light weight, high specific, and high thermal conductivity. Nanofluids have higher thermal conductivities than traditional fluid, so it can be used as an efficient heat transfer characteristics medium. This paper focuses on heat transfer of nanofluid, metal foam and the combination of the two. The physical properties of nanofluid and metal foam are summarized. The characteristics of flow and heat transfer are introduced. This work creates a close connection between scientific research and practical applications of this dual heat transfer enhancement method.

Part of the book: Novel Nanomaterials

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 Guojun Yu and Huijin Xu

The heat and/or mass transfer is crucial in various energy conversion and storage systems such as heat exchangers and energy storage systems, since they highly affect the efficiency of energy conversion and transport. Enhancing the heat and/or mass transfer within these systems is the most important means to improve system efficiency. Porous media have found wide application in enhancing the heat conduction, mass diffusion, or both, for different energy conversion and storage systems. In this chapter, a brief review on the application of different porous media for transport enhancement in various systems was made, indicating that using porous media is capable of enhancing the transport ability appreciably, sometimes being up to hundreds of times in some physical problems. This review could provide some insight into the transport enhancement design of various energy conversion and storage systems, which is especially important in the background of carbon neutralization.

Part of the book: Transport Perspectives for Porous Medium Applications