scholarly journals Mesoscopic Finite Element Method of the Effective Thermal Conductivity of Concrete with Arbitrary Gradation

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Pingming Huang ◽  
Yu Zhao ◽  
Yanwei Niu ◽  
Xiang Ren ◽  
Mingfeng Chang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Effective Thermal Conductivity ◽  
Thermal Stresses ◽  
Coarse Aggregate ◽  
Volume Fraction ◽  
Cement Mortar ◽  
Coarse Aggregates ◽  
Element Method

The effective thermal conductivity (ETC) of concrete is the most important parameter in determining the temperature field and thermal stresses. A 2D random polygonal aggregate model and its modified model considering porosity were established in this paper in order to partially replace the experiment for parametric analysis on the ETC of concrete and to save the experiment cost. A mesoscopic finite element method for the ETC of concrete with arbitrary gradation was also proposed. In addition, the influence factors (thermal conductivity of coarse aggregate, cement mortar, and volume fraction of coarse aggregate) of the effective thermal conductivity of concrete were analyzed. The results show that the 2D gradation curve of coarse aggregates is proved to exist, and there is a corresponding relationship between the 2D and 3D gradation curves of coarse aggregates. The effective thermal conductivity of concrete has a positive exponential relationship with the volume fraction of coarse aggregates, a positive logarithm relationship with the thermal conductivity of coarse aggregates, and a positive linear correlation with the thermal conductivity of cement mortar. The most practical way to improve the effective thermal conductivity of concrete is to increase the ETC of the cement mortar, but the most effective way is to replace the aggregate with a material with a high thermal conductivity.

Determination of the Effective Thermal Conductivity Tensor of Heterogeneous Media Using a Self-Consistent Finite Element Method: Application to the Pseudo-percolation Thresholds of Mixtures Containing Nonspherical Inclusions

1999 ◽  
Vol 122 (1) ◽  
pp. 171-175 ◽  
Author(s):  
A. Decarlis ◽  
M. Jaeger ◽  
R. Martin
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Effective Thermal Conductivity ◽  
Heterogeneous Media ◽  
The Finite Element Method ◽  
Self Consistent ◽  
Percolation Thresholds ◽  
Element Method

This paper concerns the determination of the effective thermal conductivity of heterogeneous media with randomly dispersed inclusions. Inclusions of arbitrary shape can be considered since the self-consistent problem is solved numerically with the finite element method. Results for many different cases of heterogeneous media with axially symmetrical inclusions are presented. Moreover, the influence of the inclusion’s shape on the pseudo-percolation threshold is investigated. [S0022-1481(00)00801-X]

scholarly journals A novel method for calculating effective thermal conductivity of particulate fouling

2019 ◽  
pp. 308-308
Author(s):  
Zhong-Bin Zhang ◽  
C Congyu ◽  
Yang Liu ◽  
Li-Hua Cao
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Heat Exchanger ◽  
Effective Thermal Conductivity ◽  
Parametric Design ◽  
The Finite Element Method ◽  
Particulate Fouling ◽  
Novel Method ◽  
Element Method

The accurate thermal conductivity of fouling plays a very significant role in designing heat exchanger. In this paper, a novel method of calculating the effective thermal conductivity (ETC) of particulate fouling is put forward by using Image-Pro-Plus image processing, the finite element method and ANSYS parametric design language (APDL). First of all, according to the analysis on the particulate fouling samples features, the particulate fouling is considered as porous media with fractal characteristics, whose microscopic network model is established using the finite element method, and each unit body material properties are randomly assigned by APDL. Secondly, ETC of particulate fouling model is calculated by the steady state plate method. And then, the influence of particulate fouling microstructure on ETC is explored. Last, it is also show that the calculation resulting of ETC agrees well with available experimental data and empirical correlation. Moreover, it has been shown that ETC of particulate fouling is closely associated with the porosity and pore size. The method can be used to research on the thermal conductivity of fouling, discuss the influence of microstructure on ETC of fouling, and provide the guidelines for designing of heat exchanger on calculating accurate thermal conductivity of fouling.

Thermal analysis of conventional and performance plain woven fabrics by finite element method

2017 ◽  
Vol 48 (4) ◽  
pp. 685-712 ◽  
Author(s):  
Muhammad Owais Raza Siddiqui ◽  
Danmei Sun
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Effective Thermal Conductivity ◽  
Three Dimensional ◽  
Woven Fabrics ◽  
Woven Fabric ◽  
Element Analysis ◽  
Thermal Anisotropy ◽  
Element Method

The research reports the development of geometrical models of woven fabric structures and evaluation of fabric thermal properties by using finite element method. A mesoscopic scale modelling approach was used to investigate the effective thermal conductivity and thermal resistance of woven textile structures. Various techniques, including scanning electron microscopy and experimental methods, have been adopted to obtain the actual three-dimensional parameters of the fabrics for finite element analysis. The research revealed that the thermal anisotropy of fibres, fibres material orientation and temperature-dependent thermal conductivity of fibre has a significant impact on the effective thermal conductivity of fabrics because experimental and simulated results were highly correlated with the consideration of above-mentioned factors.

Effect of Lumen Size on Transverse Thermal Conductivity of Unidirectional Natural Fiber-Polymer Composite via Finite Element Method

2011 ◽  
Vol 675-677 ◽  
pp. 431-434
Author(s):  
Ke Liu ◽  
Hitoshi Takagi ◽  
Zhi Mao Yang
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Polymer Composite ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Cell Model ◽  
Insulation Material ◽  
Transverse Thermal Conductivity ◽  
Element Method

In order to evaluate the effect of natural fiber lumen size on the transverse thermal conductivity of the unidirectional natural fiber-polymer composite, a two-dimensional unit cell model of natural fiber-polymer composite was studied using finite element method (FEM). In this study, the FE cell model was kept in the steady state thermal condition. The results showed that the effective transverse thermal conductivity K has a relationship with the geometrical ratio (α, 0<α<1) of lumen radius (rl) to fiber radius (rf). When the lumen size ratio α is small, K increases with increasing fiber volume fraction Vf, while K decreases as the Vf increases when α is large. It indicates that the thermal property of composites changes with fiber’s lumen size. When a composite is designed for thermal insulation material, we should choose the natural fiber with large lumen, and to design thermal conductive composite, small lumen size should be used. The result from present method was compared with experimental data and shows a good agreement.

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