A theoretical octet-truss lattice unit cell model for effective thermal conductivity of consolidated porous materials saturated with fluid

The evaluation of effective material properties in heterogeneous materials (e.g., composites or multicomponent structures) has direct relevance to a vast number of applications, including nuclear fuel assembly, electronic packaging, municipal solid waste, and others. The work described in this paper is devoted to the numerical verification assessment of the thermal behavior of porous materials obtained from thermal modeling and simulation. Two-dimensional, steady state analyses were conducted on unit cell nano-porous media models using the finite element method (FEM). The effective thermal conductivity of the structures was examined, encompassing a range of porosity. The geometries of the models were generated based on ordered cylindrical pores in six different porosities. The dimensionless effective thermal conductivity was compared in all simulated cases. In this investigation, the method of manufactured solutions (MMS) was used to perform code verification, and the grid convergence index (GCI) is employed to estimate discretization uncertainty (solution verification). The system response quantity (SRQ) under investigation is the dimensionless effective thermal conductivity across the unit cell. Code verification concludes an approximately second order accurate solver. It was found that the introduction of porosity to the material reduces effective thermal conductivity, as anticipated. This approach can be readily generalized to study a wide variety of porous solids from nano-structured materials to geological structures.

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Validity of Finite Element Unit Cell Model for Studying Yield Condition of Isotropic Porous Materials.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.61.2435 ◽

1995 ◽

Vol 61 (591) ◽

pp. 2435-2441

Author(s):

Tomoyuki Sasaki ◽

Moriaki Goya ◽

Kiyohiro Miyagi ◽

Shousuke Itomura ◽

Toshiyasu Sueyoshi

Keyword(s):

Finite Element ◽

Porous Materials ◽

Cell Model ◽

Yield Condition ◽

Unit Cell ◽

Unit Cell Model

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A unit cell model for predicting the thermal conductivity of a granular medium containing an adhesive binder

International Journal of Heat and Mass Transfer ◽

10.1016/s0017-9310(83)80011-8 ◽

1983 ◽

Vol 26 (1) ◽

pp. 87-99 ◽

Cited By ~ 16

Author(s):

K.W. Jackson ◽

W.Z. Black

Keyword(s):

Thermal Conductivity ◽

Granular Medium ◽

Cell Model ◽

Unit Cell ◽

Unit Cell Model ◽

Adhesive Binder

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Influence of Some Parameters on Effective Thermal Conductivity of Nano-Porous Aerogel Super Insulator

Heat Transfer: Volume 1 ◽

10.1115/ht2005-72192 ◽

2005 ◽

Cited By ~ 3

Author(s):

Xinxin Zhang ◽

Gaosheng Wei ◽

Fan Yu

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Elevated Temperature ◽

Porous Structure ◽

Effective Thermal Conductivity ◽

Cell Model ◽

High Specific Surface Area ◽

Unit Cell ◽

Infrared Light ◽

Key Factors

Based on the open-cell nano-porous structure features, a cubic array of nano-spheres unit cell model describing the coupled conduction of gas and solid in aerogel super insulator is developed. By one-dimensional heat conduction analysis in the unit cell, the effective thermal conductivity expression is obtained. The results show that the model matches well with the experimental data and nano-porous structure, nanometer size effect of solids as well as the very high specific surface area are the key factors make aerogel have very low thermal conductivity. There exists an optimal density value where the thermal conductivity of aerogel is minimum. Thermal radiative heat transfer is the dominating heat transfer mechanism of aerogel at an elevated temperature. It can decrease the thermal conductivity value of aerogel effectively at an elevated temperature by doping carbon or other matters which can strongly absorb infrared light at 3∼8 μm.

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