Bilateral estimates of thermal conductivity characteristics of anisotropic heat-shielding materials

An integrated approach to determine the rational design of wall ceramic products based on modeling their behavior under operating conditions is proposed. This approach was used in the development of technology for heat–efficient insulating construction ceramic materials for energy–saving construction. For two models of porous–hollow ceramic products with a porous frame (40 % of voids) and a dense frame (60 % of voids), a predictive assessment of their heat–shielding and mechanical properties was carried out. Calculations of the equivalent coefficient of thermal conductivity of models based on Fourier’s law established that with a decrease in the voidness of products with a porous wall, the coefficient of their thermal conductivity decreases by 12 %, which improves the heat–shielding properties. Based on the results of computer simulation of the behavior of models under the influence of static power loads, it was determined that porosity of the ceramic framework of products leads to degradation of mechanical strength almost proportionally to a decrease in voidness. The stress–strain state of 3D models of ceramic structures with different pore geometry (spherical, globular, ellipsoidal) is analyzed and it is shown that stresses are concentrated in the contact zones of a ceramic matrix with pores. It is shown that the most durable is the structural model with spherical pores. The expediency of organizing such a structure, the need to strengthen the ceramic matrix of materials and zones surrounding the pores, as the most vulnerable structural sites, is shown. The results of predictive calculations have been experimentally confirmed in the development of technology for structural and heat–insulating composite–type ceramic materials based on low–melting loam and ash microspheres, which provide a given structural picture of the ceramic material.

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Nonlinear Steady Temperature Fields in Non—Homogeneous Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.1957 ◽

2007 ◽

Vol 561-565 ◽

pp. 1957-1960

Author(s):

Yao Dai ◽

Qi Sun ◽

Wei Tan ◽

Chang Qing Sun

Keyword(s):

Thermal Conductivity ◽

Differential Equations ◽

Method Of Lines ◽

Variable Coefficients ◽

Temperature Fields ◽

Gradient Material ◽

Original Form ◽

Steady Temperature ◽

Heat Shielding ◽

Parameter Values

Functionally gradient material (FGM) developed for heat-shielding structure is often used in the very high temperature environment. Therefore, the material property parameters are not only functions of spatial coordinates but also ones of temperature. The former leads to partial differential equations with variable coefficients, the latter to nonlinear governing equations. It is usually very difficult to obtain the analytical solution to such thermal conduction problems of FGMs. If the finite element method is adopted, it is very inconvenient because material parameter values must be imputed for each element. Hence, a semi-analytic numerical method, i.e., method of lines (MOLs) is introduced. The thermal conductivity functions do not need to be discretized and remain original form in ordinary differential equations. As a numerical example, the nonlinear steady temperature fields are computed for a rectangular non-homogeneous region with the first, the second and the third kinds of boundary conditions, where three kinds of functions, i.e. power, exponential and logarithmic ones are adopted for the thermal conductivity. Results display the important influence of non-linearity on temperature fields. Moreover, the results given here provide the better basis for thermal stress analysis of non-homogenous and non-linear materials.

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THEORETICAL METHOD ALLOWING CALCULATING AND ANALYZE THE EFFECTIVE COEFFICIENT OF THERMAL CONDUCTIVITY, NONWOVEN HEAT-SHIELDING MATERIALS

Theoretical & Applied Science ◽

10.15863/tas.2017.07.51.5 ◽

2017 ◽

Vol 51 (07) ◽

pp. 21-27

Author(s):

Viktir Yureivich Mishakov ◽

◽

Dimitry Anatolievich Sovetnikov ◽

Maxim Andreevich Pavlov ◽

Elena Aleksandrovna Kirsanova ◽

...

Keyword(s):

Thermal Conductivity ◽

Theoretical Method ◽

Effective Coefficient ◽

Coefficient Of Thermal Conductivity ◽

Heat Shielding

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Thermal Analysis of a New Neutron Shielding Vacuum Multiple Glass

Sustainability ◽

10.3390/su12083083 ◽

2020 ◽

Vol 12 (8) ◽

pp. 3083

Author(s):

Shanwen Zhang ◽

Min Kong ◽

Saim Memon ◽

Hong Miao ◽

Yanjun Zhang ◽

...

Keyword(s):

Thermal Conductivity ◽

Element Model ◽

Organic Glass ◽

Neutron Shielding ◽

Transfer Path ◽

Vacuum Insulation ◽

The Common ◽

Maximum Temperatures ◽

Heat Shielding ◽

Good Heat

The neutron shielding glass is widely used in nuclear/fusion plants. To improve its temperature resistance and heat insulation, a Gadolinium (Gd)-containing laminate vacuum multiple glass is proposed by using the vacuum insulation method. A 3D finite element model validated by theoretical calculation was developed to analyse the heat transfer path and numerical simulation of the multiple glass was carried out to obtain the temperature distribution and the maximum temperatures of the organic glass in relation to dynamic working temperatures, the sealing agent width, view size, and vacuum thermal conductivity. The results show that the vacuum layer between common glasses can make the work temperature of neutron shielding glass increase. The multiple glass has good heat-shielding performance and it is expected to work in a high-temperature environment. In addition, the vacuum layer between the common glasses and the sealing agent width decay with respect to the view size and vacuum thermal conductivity show an increase in the working temperature of the neutron shielding glass. It was concluded that the order of affecting the temperatures of the organic glass follows the pattern of: view size > vacuum thermal conductivity > sealing agent width.

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