Numerical quantification of coupling effects for radiation-conduction heat transfer in participating macroporous media: Investigation of a model geometry

Abstract

a b s t r a c tRadiative-conductive heat transfer in porous media is usually investigated by decoupling the heat transfer modes and solving the volume-averaged continuum equations using effective transport properties. However, both modes are naturally coupled and coupling effects might significantly affect the results. We aim at providing quantitative understanding of the coupling effects occurring in a model geometry. This is an important first step towards improving the accuracy of heat transfer predictions in engineering applications.We developed a numerical method using a structured mesh, cell centered finite volumes and Monte Carlo ray tracing techniques in order to simulate the 3-dimensional and unsteady coupled radiativeconductive heat transfer in semitransparent macroporous media. We have optimized the numerical method with regards to memory and computational requirements leading to optimal performance and allowing to perform a parameter variation study for various steady state cases.We conducted a parameter study considering different optical and thermal material properties and boundary conditions in order to quantify the coupling effect between conduction and radiation, and to demonstrate its dependencies. In terms of thermal properties, it was found that the ratio of bulk thermal conductivities is governing the coupling effect. A distinct peak at a given conductivity ratio was found. The influence of optical properties is discussed in details. It was found that a significant coupling effect exists, reaching up to 15% of the total thermal heat flux.The verified modeling framework in conjunction with our non-dimensionalization offers a tool to investigate the importance of radiation-conduction coupling in a quantitative manner. It is an important step towards understanding the detailed mechanisms of radiation and conduction coupling and provides engineering guidelines on the importance of these effects.

Analytical Solution of Problems about the Radiative and Radiative–Conductive Stationary Heat Transfer in a Medium with an Arbitrary Dependence of the Scattering and Absorption on Frequency Boundary Conditions

“…This formula entirely coincides with Formulas (4) and (5). In addition, we found that the radiant thermal conductivity approximation is valid with the condition (22) and with the accuracy (26).…”

“…Most of the problems of radiative-conductive heat transfer in a medium are solved based on "the radiation transfer equation" [4][5][6][7][8][9]. Recall that the law of conservation of energy is not enough to solve such problems.…”

Conductive-radiative heat transfer within SiC-based cellular ceramics at high-temperatures: A discrete-scale finite element analysis

“…Involvement of high-temperature physics implicates accurate prediction of heat transport as one of the primary factors for optimizing the global performance of these systems. As such, many researchers have focused on studying (numerically or experimentally) the behavior of open-cell cellular ceramics at high temperatures, especially at temperatures beyond 1200 K [7,8,9,10]. Complementary to these researches, the current article focuses on analyzing coupled conductive-radiative heat transport of topologically different open-cell cellular ceramics up to 1800 K.…”

“…However, when conjugate heat transfers are being investigated, the present-day numerical approaches are limited to 3D images with modest volumes. This is due to important computational cost required to reproduce the underlying heat transfers [18,10]. Detailing and solving accurately discrete problems on these complex geometries requires meshes with large number of elements.…”

Finite element framework for modeling conducto-radiative transfers within heterogeneous media at both discrete and continuous scales

“…Such a discrete-scale approach, finely described in a previous work [19], makes it possible to achieve a good level of details in terms of three-dimensional temperature fields, conductive flux fields, and radiative flux fields. This is important because, at high temperature, heat transfer modes are coupled in such a way that a given heat transfer mode is affected by the other modes, making their effective contribution non linear [20].…”