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A COMBINED ANALYTICAL-NUMERICAL MODEL TO DETERMINE RADIATIVE PROPERTIES OF TETRAKAIDECAHEDRA CELL STRUCTURE

DOI: 10.1615/ICHMT.2017.CHT-7.390
pages 339-350

Vipul M. Patel
Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India

Prabal Talukdar
Institute of Textile & Clothing

Аннотация

In the present work, radiative properties of representative porous media are estimated using pore structure modelling along with radiation interaction with the solid matrix. This approach is found to be more useful as it enables to understand the physics of the radiation propagation. The tetrakaidecahedra unit cell structure is found to be a close approximation of actual foam structure and hence in the present work, it is considered as a representative unit cell structure. An analytical model based on zonal method is developed to determine effective reflectance (ρe,c) and transmittance (τe,c) of the considered unit cell structure. The results of unit cell are then extended to multi-layered unit cell structures using recurrence relationships. The radiative properties of an equivalent homogeneous participating medium are determined using inverse method. The radiative transfer equation (RTE) in a homogeneous participating medium is solved using the finite volume method (FVM). The genetic algorithm (GA) required in the inverse method is integrated to the FVM code. The obtained results of recurrence relationships are used in the FVM-GA code to determine extinction coefficient (β*) and scattering albedo (ω*) of an equivalent homogeneous participating medium. Effects of solid reflectivity (ρs) and pore density on the radiative properties of the porous media have been studied using the proposed model. Results obtained from this study show that the β* decreases with ρs while ω* shows increasing trend with ρs. With increase in pore density, β* increases. However, ω* is found to be insensitive to pore density values.

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