Function Of Thermal Conductivity Research Articles

Insights into the thermo-hydraulic properties of compacted MX80 bentonite during hydration under elevated temperature

In high-level radioactive waste geological repositories, compacted bentonite undergoes coupled thermo-hydraulic processes due to heat released from a central waste canister and groundwater imbibition from the surrounding host rock. An understanding of these processes is essential for long-term simulations of radionuclide migration and canister corrosion, which requires an understanding of temperature effects on the coupled thermo-hydraulic properties governing these processes. In this study, a tank-scale radial infiltration test was used to investigate water imbibition processes in compacted bentonite under a central heater temperature of 200 °C that simulates high thermal gradients in a repository. Interpretation of this test focuses on evaluation of the liquid water wetting front during hydration and the interpretation of the temperature-dependent transient soil water retention curve (SWRC), thermal conductivity function (TCF), and hydraulic conductivity function (HCF). The SWRC during imbibition follows a temperature-dependent wetting path. Temperature effects on the hydraulic conductivity of bentonite in saturated conditions had the greatest effect on the shape of the HCF, with minimal temperature effects at higher suctions. The transient thermal conductivity data matched well with a new TCF linked with the SWRC shape. Although the bentonite layer was restrained, local deformations during hydration may have affected the shapes of the TCF and HCF.

Improved Thermal Conductivity Function for Unsaturated Soil with Physics-based Parameters

This paper proposes a new relationship between thermal conductivity and degree of saturation of unsaturated soils, referred to as the thermal conductivity function (TCF). The new sigmoidal relationship between thermal conductivity and degree of saturation was developed so that all parameters have a physical meaning. After calibration of the model using data from the literature and comparison with other available TCFs, the parameters of the new TCF were related to those of the soil-water retention curves for the soils investigated in the calibration process. The linkage between the parameters of the TCF and SWRC indicates that the parameters reflect the point of air entry and pore size distribution of the soil, as well as the maximum and minimum thermal conductivity values encountered at saturated and dry conditions, respectively.

Improved finite element method for flow, heat and solute transport of Prandtl liquid via heated plate

In the current study, a vertical, 3D-heated plate is used to replicate the generation of heat energy and concentration into Prandtl liquid. We discuss how Dufour and Soret theories relate to the equations for concentration and energy. In order to see how effectively particles, interact with heat and a solvent, hybrid nanoparticles are used. It does away with the phenomena of viscous dissipation and changing magnetic fields. The motivation behind the developed study is to optimize solvent and heat storage uses in the biological and industrial domains. This article's major goal is to explore the aspects of thermal energy and mass transfer that influence how nanoparticles, hybrid nanoparticles, and 3D melting surface sheets behave. Variable thermal efficiency and variable mass transfer are combined. The system of generated PDEs (difference equations) includes the concentration, velocity, and heat energy equations. The numerical calculations are done for Silver (Ag), Molybdenum Disulfide (MoS2) nanoparticles with Ethylene glycol (C2H6O2) as the base fluid using a boundary layer approach to the mathematical formulation. The system of ODEs is formulated through transformations in order to find a solution. A Galerkin finite element algorithm (G-FEA) is adopted to analyze various aspects versus different parameters. It has been found that motion into hybrid nanoparticles is reduced by motion into nanoparticles. Additionally, differences in heat energy and solvent particle sizes are associated with modifications in magnetic, Dufour, Eckert, and Soret numbers. In contrast to hybrid nanostructures, the output of thermal energy is usually observed to be substantially higher. The magnetic field parameter decreases the particle velocity. In contradiction to the Eckert number, bouncy parameter, and magnetic parameter set values, the maximum quantity of heat energy is obtained. variable thermal conductivity's function. The 3D heated vertical surface convective heat transfer of nanofluids and hybrid nanofluids under the impact of a heat source, thermal radiation, and viscous dissipation has not yet been studied, as far as the authors are aware.

Study on Calculation of Minimum Thickness of Sample in Thermal Conductivity Measurement

It is found that the true thermal conductivity can be measured only when material reaches a certain minimum thickness, within which the thermal conductivity varies with thickness. Based on the derivative of Fourier's law, it is pointed out that the phenomenon of thermal conductivity varying with thickness is caused by the existence of second derivative of temperature. Both of the FTC (function of thermal conductivity) and the calculation formula of MMT (minimum measured thickness) are established. For materials of GFRP (glass fiber reinforced plastic), neoprene and silicone, their R-squared of FTC are respectively 0.9995, 0.9668 and 0.9976, and their MMTs are 5.2287 mm, 4.7034 mm and 12.7532 mm, respectively. What’s more, their interfacial thermal conductivities are different, which reveals that thermal conductivity of material is a numerical field.

General Thermal Conductivity Function for Unsaturated Soils Considering Effects of Water Content, Temperature, and Confining Pressure

AbstractThe thermal conductivity function (TCF) is an important constitutive function establishing the thermal conductivity–water content relationship in unsaturated soils. The existing TCFs do not...

Measurement of Thermal Conductivity Function of Unsaturated Soil Using a Transient Water Release and Imbibition Method

Thermal conductivity of unsaturated soil depends on soil water content and soil type. A transient water release and imbibition method (TRIM) is modified to include measurement of the thermal conductivity function (TCF) in conjunction with concurrent measurement of the soil water retention curve (SWRC) and hydraulic conductivity function (HCF). Two pairs of dielectric and thermal needle sensors are embedded in the soil specimen to monitor spatial and temporal variation of water content, thermal conductivity, and thermal diffusivity during drying and wetting processes. Three different soils, including pure sand, silt, and clayey sand are used to examine the effectiveness and validity of the new technique. The thermal conductivity data from the modified TRIM technique accords well with other independent measurements. The results show that the modified TRIM technique provides a fast and accurate way of obtaining thermal properties of different types of soils under both drying and wetting states. The typical testing time for a soil going through a full saturation variation is less than 3 weeks. We observe that the hysteresis in thermal conductivity during a wetting and drying cycle is much less pronounced than that of the hydraulic hysteresis.

Approximation of Physical Properties of Steam and Other Arc Plasmas for Anisotropic Model Concerning Gasification Processes

In this paper, the anisotropic model for the dc electric arc was expanded, which allows the obtaining of power function generalized expressions for calculating the characteristics of the electric discharge into the dc plasma torch channel without using a large number of experimental studies. The model is based on the power law approximation of temperature dependence of the plasma electrical conductivity σ with different exponents along the longitudinal and transversal coordinates. The approximation of the dependence for σ of steam plasma was obtained in simple linear forms σ = 0.221 ΔS and as the power approximation σ = 44.51 ΔS <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.484</sup> [where ΔS is increment of thermal conductivity function (TCF)]. The comparison of the obtained dependences with referenced data shows such moderate difference between the calculated approximations for σ of steam and the data of recent publications for this plasma as 15%-25% throughout the vast ranges of the plasma parameters T (temperature) and S (TCF).