Papers by Keyword: Effective Conductivity

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Authors: Thomas Fiedler, Ekaterina Pesetskaya, Andreas Öchsner, José Grácio
Abstract: In this paper, the geometrical effective thermal conductivity of porous materials is investigated based on two different approaches: the finite element method as a representative for numerical approximation methods and an analytical method for 2D homogenised models based on a solution of the respective boundary value problem. It is found that the relative conductivity is practically independent of the specific shape or topology of the inclusions. Only the morphology (closed-cell or open-cell) of the structure slightly influences the conductivity. Furthermore, it is shown that a small perturbation of the circular inclusions of 2D models increases the effective conductivity.
Authors: Jean Michel Hugo, Frédéric Topin
Abstract: We determine thermal dispersion in metal foams using a pore scale numerical approach. Samples are contained in a channel crossed by a steady fully established fluid flow. The size of the foam sample is chosen according to a Representative Elementary Volume (REV).Two configurations are tested with several foam structures, pore size and pore shape. In the first configuration, heat and mass fluxes are in the same direction, in the second one, fluxes are perpendicular such as in heat exchanger. Results obtained on apparent fluid phase conductivity are discussed along with pressure drop data and compared to available literature data.
Authors: Hong Bo Xie, Wei Bin Ma
Abstract: 3-D heat transfer behaviors in two types of concrete perforated bricks used in external walls were numerically simulated. Air density was modeled both with Boussinesq assumption and ideal gas model, and air thermal properties were calculated alternatively with constant and polynomial parameters. Results of four different inputs shown us that there had little difference between them and they agreed well with Guard hot box tests. The effective conductivity of bricks decreased with increase of the air interlayer thickness at first and then increased as it continued to increase, which meant that thickness of the air interlayer was crucial to insulation effect of bricks. This was because of the cooperation of the conduction and natural convection. Under the same condition, effective conductivity is proportional to concrete conductivity.
Authors: Robert W. Zimmerman, Melanie P. Lutz
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