scholarly journals Analytical models of heat conduction in fractured rocks

2014 ◽  
Vol 119 (1) ◽  
pp. 83-98 ◽  
Author(s):  
Á. Ruiz Martínez ◽  
D. Roubinet ◽  
D. M. Tartakovsky
Keyword(s):  
Heat Conduction ◽  
Fractured Rocks ◽  
Analytical Models

scholarly journals Heat conduction and thermal convection on thermal front movement during natural gas hydrate thermal stimulation exploitation

2018 ◽  
Vol 73 ◽  
pp. 40 ◽  
Author(s):  
Yongmao Hao ◽  
Xiaozhou Li ◽  
Shuxia Li ◽  
Guangzhong Lü ◽  
Yunye Liu ◽  
...  
Keyword(s):  
Heat Conduction ◽  
Thermal Convection ◽  
Thermal Model ◽  
Hot Water ◽  
Thermal Stimulation ◽  
Analytical Models ◽  
Natural Gas Hydrate ◽  
Thermal Front ◽  
Transfer Mode ◽  
Front Movement

Natural Gas Hydrate (NGH) has attracted increasing attention for its great potential as clean energy in the future. The main heat transfer mode that controls the thermal front movement in the process of NGH exploitation by heat injection was discussed through NGH thermal stimulation experiments, and whether it is reliable that most analytical models only consider the heat conduction but neglect the effect of thermal convection was determined by the comparison results between experiments and Selim’s thermal model. And the following findings were obtained. First, the movement rate of thermal front increases with the rise of hot water injection rate but changes little with the rise of the temperature of the injected hot water, which indicated that thermal convection is the key factor promoting the movement of thermal front. Second, the thermal front movement rates measured in the experiments are about 10 times that by the Selim’s thermal model, the reason for which is that the Selim’s thermal model only takes the heat conduction into account. And third, theoretical calculation shows that heat flux transferred by thermal convection is 15.56 times that by heat conduction. It is concluded that thermal convection is the main heat transfer mode that controls the thermal front movement in the process of NGH thermal stimulation, and its influence should never be neglected in those analytical models.

scholarly journals Uncovering design principles for amorphous-like heat conduction using two-channel lattice dynamics

2020 ◽  
Author(s):  
Riley Hanus ◽  
Janine George ◽  
Max Wood ◽  
Alexander Bonkowski ◽  
Yongqiang Cheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Dynamics ◽  
Rational Design ◽  
Amorphous Materials ◽  
Inelastic Neutron Scattering ◽  
Design Principles ◽  
Analytical Models ◽  
Phonon Modes ◽  
Gas Channel

<pre><pre>The physics of heat conduction puts practical limits on many technological fields such as energy production, storage, and conversion. It is now widely appreciated that the phonon-gas model does not describe the full vibrational spectrum in amorphous materials, since this picture likely breaks down at higher frequencies. A two-channel heat conduction model, which uses harmonic vibrational states and lattice dynamics as a basis, has recently been shown to capture both crystal-like (phonon-gas channel) and amorphous-like (diffuson channel) heat conduction. While materials design principles for the phonon-gas channel are well established, similar understanding and control of the diffuson channel is lacking. In this work, in order to uncover design principles for the diffuson channel, we study structurally-complex crystalline Yb<sub>14</sub>(Mn,Mg)Sb<sub>11</sub>, a champion thermoelectric material above 800 K, experimentally using inelastic neutron scattering and computationally using the two-channel lattice dynamical approach. Our results show that the diffuson channel indeed dominates in Yb14MgSb<sub>11</sub> above 300 K. More importantly, we demonstrate a method for the rational design of amorphous-like heat conduction by considering the energetic proximity phonon modes and modifying them through chemical means. We show that increasing (decreasing) the mass on the Sb-site decreases (increases) the energy of these modes such that there is greater (smaller) overlap with Yb-dominated modes resulting in a higher (lower) thermal conductivity. This design strategy is exactly opposite of what is expected when the phonon-gas channel and/or common analytical models for the diffuson channel are considered, since in both cases an increase in atomic mass commonly leads to a decrease in thermal conductivity. This work demonstrates how two-channel lattice dynamics can not only quantitatively predict the relative importance of the phonon-gas and diffuson channels, but also lead to rational design strategies in materials where the diffuson channel is important. </pre></pre>

Modeling the Transport of Low-Molecular-Weight Penetrants Within Polymer Matrix Composites

2006 ◽  
Vol 59 (5) ◽  
pp. 249-268 ◽  
Author(s):  
David A. Bond ◽  
Paul A. Smith
Keyword(s):  
Heat Conduction ◽  
Environmental History ◽  
Polymer Matrix ◽  
Polymer Matrix Composites ◽  
Analytical Models ◽  
Fickian Diffusion ◽  
Matrix Composites ◽  
Scientists And Engineers ◽  
Structural Engineers ◽  
Kinetics Of

In 1855 Fick reported on the diffusion of liquid through a membrane and proposed that there was an analogy between this process and that of heat conduction allowing him to transcribe the mathematical equation for heat conduction derived in 1822 by Fourier into a form to represent this diffusion of liquid. This model, known as Fickian diffusion, has become the baseline against which the characteristics of liquid diffusion are measured to the point where anomalous diffusion is known generically as non-Fickian. Numerous authors have attempted to develop models to cover all aspects of non-Fickian diffusion resulting in a very large number of models that consider the effect of parameters as varied as the chemical makeup, geometric dimensions, environmental history, stress state, and damage status of the material, as well as the likelihood of multiple diffusion mechanisms being responsible for transport of the water molecules. Of particular interest to structural engineers is the transport of moisture in polymer matrix composites owing to the plasticizing effect the moisture may have on the composite and the potential for the moisture to induce localized damage. This paper reviews analytical models that are relevant to the transport of moisture in structural composites. In doing so the benefits and limitations of the various models and techniques are presented in order to provide a reference for scientists and engineers attempting to describe the kinetics of moisture in composites accurately. There are 160 references cited in this review article.

scholarly journals Uncovering design principles for amorphous-like heat conduction using two-channel lattice dynamics

2020 ◽  
Author(s):  
Riley Hanus ◽  
Janine George ◽  
Max Wood ◽  
Alexander Bonkowski ◽  
Yongqiang Cheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Dynamics ◽  
Rational Design ◽  
Amorphous Materials ◽  
Inelastic Neutron Scattering ◽  
Design Principles ◽  
Analytical Models ◽  
Phonon Modes ◽  
Gas Channel

<pre><pre>The physics of heat conduction puts practical limits on many technological fields such as energy production, storage, and conversion. It is now widely appreciated that the phonon-gas model does not describe the full vibrational spectrum in amorphous materials, since this picture likely breaks down at higher frequencies. A two-channel heat conduction model, which uses harmonic vibrational states and lattice dynamics as a basis, has recently been shown to capture both crystal-like (phonon-gas channel) and amorphous-like (diffuson channel) heat conduction. While materials design principles for the phonon-gas channel are well established, similar understanding and control of the diffuson channel is lacking. In this work, in order to uncover design principles for the diffuson channel, we study structurally-complex crystalline Yb<sub>14</sub>(Mn,Mg)Sb<sub>11</sub>, a champion thermoelectric material above 800 K, experimentally using inelastic neutron scattering and computationally using the two-channel lattice dynamical approach. Our results show that the diffuson channel indeed dominates in Yb14MgSb<sub>11</sub> above 300 K. More importantly, we demonstrate a method for the rational design of amorphous-like heat conduction by considering the energetic proximity phonon modes and modifying them through chemical means. We show that increasing (decreasing) the mass on the Sb-site decreases (increases) the energy of these modes such that there is greater (smaller) overlap with Yb-dominated modes resulting in a higher (lower) thermal conductivity. This design strategy is exactly opposite of what is expected when the phonon-gas channel and/or common analytical models for the diffuson channel are considered, since in both cases an increase in atomic mass commonly leads to a decrease in thermal conductivity. This work demonstrates how two-channel lattice dynamics can not only quantitatively predict the relative importance of the phonon-gas and diffuson channels, but also lead to rational design strategies in materials where the diffuson channel is important. </pre></pre>

On Heat Conduction in Highly Rarefied Air

1881 ◽  
Vol 11 (270supp) ◽  
pp. 4307-4307
Author(s):  
William Crookes
Keyword(s):  
Heat Conduction
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