Mixed convection and radiation heat transfer in porous media for solar thermal applications

This chapter provides a guide on radiation convection coupling methodologies within
the framework of porous solar receivers. Solid materials, contrarily to most gasses,
are capable of absorbing light in the visible range. Electromagnetic waves in this
spectral range propagate into the medium via the pores and interacts with the
solid-gas interface at the pore boundaries. For this reason porous media can be used
as efficient volumetric solar receivers. If high temperatures are involved, the solid
matrix also emits thermal radiation allowing a "long-range" heat transport which
substantially modies the temperature proles of the medium. Therefore, the influence of radiation on the heat transfer in a porous medium is of high importance for
efficient energy applications. In this chapter the identification of effective radiative
properties of the porous media and the most used numerical solution approaches of
the radiative transfer equation are described. It also provides a short summary of
the effect of radiation on heat transfer in porous media, as found in the literature,
and describes the challenges associated with designing a porous medium volumetric
solar absorber.