Steady temperature fields associated with a moving rod in a medium with nonlinear thermal conductivity

1988 ◽  
Vol 26 (10) ◽  
pp. 1071-1085 ◽  
Author(s):  
C. Atkinson
Keyword(s):  
Thermal Conductivity ◽  
Temperature Fields ◽  
Steady Temperature ◽  
Nonlinear Thermal Conductivity

Method of Lines to Solve 2-D Steady Temperature Field of FGM

2007 ◽  
Vol 353-358 ◽  
pp. 2003-2006 ◽  
Author(s):  
Wei Tan ◽  
Chang Qing Sun ◽  
Chun Fang Xue ◽  
Yao Dai
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Transfer Problem ◽  
Method Of Lines ◽  
Main Idea ◽  
Functionally Graded ◽  
Temperature Fields ◽  
Steady Temperature ◽  
Thermal Transfer ◽  
Steady Temperature Field

Method of Lines (MOLs) is introduced to solve 2-Dimension steady temperature field of functionally graded materials (FGMs). The main idea of the method is to semi–discretized the governing equation of thermal transfer problem into a system of ordinary differential equations (ODEs) defined on discrete lines by means of the finite difference method. The temperature field of FGM can be obtained by solving the ODEs with functions of thermal properties. As numerical examples, six kinds of material thermal conductivity functions, i.e. three kinds of polynomial functions, an exponent function, a logarithmic function, and a sine function are selected to simulate spatial thermal conductivity profile in FGMs respectively. The steady-state temperature fields of 2-D thermal transfer problem are analyzed by the MOLs. Numerical results show that different material thermal conductivity function has obvious different effect on the temperature field.

Nonlinear Steady Temperature Fields in Non—Homogeneous Materials

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.

scholarly journals Thermal Conductivity of High Performance Concrete in Wide Temperature and Moisture Ranges

10.14311/174 ◽  
2001 ◽  
Vol 41 (1) ◽  
Author(s):  
J. Toman ◽  
R. Černý
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Room Temperature ◽  
High Performance Concrete ◽  
Measuring Method ◽  
Point Of View ◽  
Temperature Measurements ◽  
Temperature Fields ◽  
Measured Temperature ◽  
Hot Wire

The thermal conductivity of two types of high performance concrete was measured in the temperature range from 100 °C to 800 °C and in the moisture range from dry material to saturation water content. A transient measuring method based on analysis of the measured temperature fields was chosen for the high temperature measurements, and a commercial hot wire device was employed in room temperature measurements of the effect of moisture on thermal conductivity. The measured results reveal that both temperature and moisture exhibit significant effects on the values of thermal conductivity, and these effects are quite comparable from the point of view of the magnitude of the observed variations.

Adaptive Thermal Conductivity Metamaterials: Enabling Active and Passive Thermal Control

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Austin A. Phoenix ◽  
Evan Wilson
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Passive Control ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Strain ◽  
Thermal Control ◽  
Variable Thermal Conductivity ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Nonlinear Thermal Conductivity

The novel adaptive thermal metamaterial developed in this paper provides a unique thermal management capability that can address the needs of future spacecraft. While advances in metamaterials have provided the ability to generate materials with a broad range of material properties, relatively little advancement has been made in the development of adaptive metamaterials. This metamaterial concept enables the development of materials with a highly nonlinear thermal conductivity as a function of temperature. Through enabling active or passive control of the metamaterials bulk effective thermal conductivity, this metamaterial that can improve the spacecraft's thermal management systems performance. This variable thermal conductivity is achieved through induced contact that results in changes in the F path length and the conductive path area. The contact can be generated internally using thermal strain from shape memory alloys, bimetal springs, and mismatches in coefficient of thermal expansion (CTE) or it can be generated externally using applied mechanical loading. The metamaterial can actively control the temperature of an interface by dynamically changing the bulk thermal conductivity controlling the instantaneous heat flux through the metamaterial. The design of thermal stability regions (regions of constant thermal conductivity versus temperature) into the nonlinear thermal conductivity as a function of temperature can provide passive thermal control. While this concept can be used in a wide range of applications, this paper focuses on the development of a metamaterial that achieves highly nonlinear thermal conductivity as a function of temperature to enable passive thermal control of spacecraft systems on orbit.

scholarly journals Impact of Tunnel Temperature Variations on Surrounding Rocks in Cold Regions

2019 ◽  
Author(s):  
Qingyang Yu ◽  
Chao Zhang ◽  
Zhenxue Dai ◽  
Chao Du ◽  
Mohamad Reza Soltanian ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Insulation Layer ◽  
Cold Regions ◽  
Ambient Temperatures ◽  
Temperature Conditions ◽  
Layer Control

Temperature is an important factor in designing and maintaining tunnels, especially in cold regions. We present three-dimensional numerical simulations of tunnel temperature fields at different temperature conditions. We study the tunnel temperature field in two different conditions with relatively low and high ambient temperatures representing winter and summer of northeast China. We specifically study how these temperature conditions affect tunnel temperature and its migration to surrounding rocks. We show how placing an insulation layer could affect the temperature distribution within and around tunnels. Our results show that the temperature field without using an insulation layer is closer to the air temperature in the tunnel, and that the insulation layer has shielding effects and could plays an important role in preventing temperature migration to surrounding rocks. We further analyzed how thermal conductivity and thickness of insulation layer control the temperature distribution. The thermal conductivity and thickness of insulation layer only affect the temperature of the surrounding rocks which are located at distances below ~20 m from the lining.

Effect of Thermal Conductivity of the Soil Cover on the Air Temperature Dynamics under Natural Conditions and at Anthropogenic Loads

2012 ◽  
Vol 260-261 ◽  
pp. 852-855
Author(s):  
E.E. Kholoden ◽  
O.M. Morina ◽  
S.A. Lobanov
Keyword(s):  
Thermal Conductivity ◽  
Air Temperature ◽  
Soil Cover ◽  
Linear Trend ◽  
Russian Far East ◽  
Far East ◽  
Temperature Fields ◽  
Heat Condition ◽  
Condition Equation ◽  
Natural Mechanism

By the example of the southern Russian Far East territory, it was stated that a sign of the linear trend of the long-term air temperature variations in the warm and cold periods of the year depended essentially on the soil thermal conductivity. It was shown that the mechanism of the soil temperature fields’ formation was controlled by the Fourier heat condition equation. In this case, the modern anthropogenic loads on the soil cover can only slightly enhance or weaken the natural mechanism of forming the temperature fields of soil and air.

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