Evaluation of soil thermal conductivity models

2015 ◽  
Vol 52 (11) ◽  
pp. 1892-1900 ◽  
Author(s):  
D. Barry-Macaulay ◽  
A. Bouazza ◽  
B. Wang ◽  
R.M. Singh
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Detailed Analysis ◽  
Soil Parameters ◽  
Soil Thermal Conductivity ◽  
Moisture Contents ◽  
Saturated Sands ◽  
Good Agreement ◽  
Different Soils ◽  
Conductivity Models

Numerous models have been developed to predict the thermal conductivity of soils at a range of different densities and moisture contents. This paper evaluates four thermal conductivity models, developed by various researchers, by comparing their performance against experimental results obtained on 27 different soils prepared at a range of saturation levels and densities. The results demonstrate that, in general, all four models show good agreement between experimental thermal conductivity and modelled thermal conductivity. The only significant shortfall is observed in low-saturated sands when using two of the models. A detailed analysis of the empirical soil parameters used in three of the recent models is presented. It shows that the accuracy of the three models can be improved by modifying the empirical soil parameters to fit the experimental data.

scholarly journals Relationship between the Transport Coefficients of Polar Substances and Entropy

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 13
Author(s):  
Ivan Anashkin ◽  
Sergey Dyakonov ◽  
German Dyakonov
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Diffusion Coefficient ◽  
High Pressures ◽  
Thermal Conductivity Coefficient ◽  
Good Description ◽  
Transport Coefficients ◽  
Viscosity Coefficient ◽  
Wide Region ◽  
Good Agreement

An expression is proposed that relates the transport properties of polar substances (diffusion coefficient, viscosity coefficient, and thermal conductivity coefficient) with entropy. To calculate the entropy, an equation of state with a good description of the properties in a wide region of the state is used. Comparison of calculations based on the proposed expressions with experimental data showed good agreement. A deviation exceeding 20% is observed only in the region near the critical point as well as at high pressures.

The Prediction of Thermal Conductivity of Agricultural Residues from Straw for Biomass Energy

2013 ◽  
Vol 779-780 ◽  
pp. 1419-1422 ◽  
Author(s):  
Lin Lu ◽  
Li Jiang ◽  
Qing Feng ◽  
He Ping Wang
Keyword(s):  
Thermal Conductivity ◽  
Rice Straw ◽  
Agricultural Residues ◽  
Biomass Energy ◽  
Thermal Probe ◽  
Moisture Contents ◽  
Proposed Model ◽  
Wire Method ◽  
The Relationship ◽  
Good Agreement

Agricultural residues from straw are widely used for energy and other applications. The thermal conductivity is one of the most important thermophysical properties considered when using agricultural residues, such as rice straw, in renewable energy engineering. In this paper, the thermal conductivity of rice straw was measured using a thermal probe by the transient hot wire method at selected moisture contents, temperatures and dry densities. The moisture contents of the samples ranged from 0 to 21.47 percent wet basis and the dry densities ranged from 90.7 to 136.4 kg/m3 and the temperature ranged from 0 to 170°C. Under those conditions, the thermal conductivity was measured and analyzed. Experiment results showed that the thermal conductivity increases with the increases of the density, moisture content and temperature, and the relationship among them is approximately described in a linear way. A new model to predict the thermal conductivity of agricultural residues from straw was proposed. The calculated results by the proposed model are in good agreement with the experimental data.

Dual Role of Nanoparticles in the Thermal Conductivity Enhancement of Nanoparticle Suspensions

2005 ◽  
Author(s):  
Calvin H. Li ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Theoretical Models ◽  
Conductivity Enhancement ◽  
Nanoparticle Suspensions ◽  
The Difference ◽  
Physical Phenomena ◽  
Good Agreement

Experimental evidence exists that the addition of a small quantity of nanoparticles to a base fluid, can have a significant impact on the effective thermal conductivity of the resulting suspension. The causes for this are currently thought to be due to a combination of two distinct mechanisms. The first is due to the change in the thermophysical properties of the suspension, resulting from the difference in the thermal conductivity of the fluid and the particles, and the second is thought to be due to the transport of thermal energy by the particles, due to the Brownian motion of the particles. In order to better understand these phenomena, a theoretical model has been developed that examines the effect of the Brownian motion. In this model, the well-known approach first presented by Maxwell, is combined with a new expression that incorporates the effect of the Brownian motion and describes the physical phenomena that occurs because of it. The results indicate that the enhanced thermal conductivity may not in fact be due to the transport of energy by the particles, but rather, due to the stirring motion caused by the movement of the nanoparticles which enhances the heat transfer within the fluid. The resulting model shows good agreement when compared with the existing experimental data and perhaps more importantly helps to explain the trends observed from a fundamental physical perspective. In addition, it provides a possible explanation for the differences that have been observed between the previously obtained experimental data, the predictions obtained from Maxwell’s equation and the theoretical models developed by other investigators.

scholarly journals Thermal Conductivity of Al2O3 and CeO2 Nanoparticles and Their Hybrid Based Water Nanofluids: An Experimental Study

2020 ◽  
Vol 65 (1) ◽  
pp. 50-60
Author(s):  
Mohammed Saad Kamel ◽  
Otabeh Al-Oran ◽  
Ferenc Lezsovits
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Volume Concentration ◽  
Experimental Models ◽  
Deionized Water ◽  
Thermal Conductivity Enhancement ◽  
Hybrid Nanofluid ◽  
Step Method ◽  
Conductivity Enhancement ◽  
Good Agreement

In many heat exchange systems, there is a demand to improve the thermal conductivity of the working fluids to make those fluids more efficient, and this can be done by dispersing solid nanomaterials into conventional liquids. In the present work, the thermal conductivity of alumina, ceria, and their hybrid with ratio (50:50) by volume-based deionized water nanofluids was experimentally measured. The nanofluids were prepared by two-step method with a range of dilute volume concentration (0.01-0.5 % Vol.), and measured at various temperatures (35, 40, 45, and 50 ºC). The experimental data for basefluid and nanofluids were verified with theoretical and experimental models, and the results have shown good agreement within the accuracy of the thermal conductivity tester. The results demonstrated that the higher thermal conductivity enhancement percentages for Al2O3, CeO2, and their hybrid nanofluids were (5.3 %, 3.3 %, and 8.8 %) at volume concentration (0.5 % Vol.) and temperature (50 ºC) compared to deionized water, respectively. Moreover, a correlation was proposed for the thermal conductivity enhancement ratio of the hybrid nanofluid and showed good accuracy with measured experimental data.

Phonon Thermal Conductivity of Superlattice Nanowires for Thermoelectric Applications

2003 ◽  
Vol 793 ◽  
Author(s):  
C. Dames ◽  
M. S. Dresselhaus ◽  
G. Chen
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Size Effects ◽  
Three Dimensional ◽  
Small Diameter ◽  
Particle Model ◽  
Phonon Thermal Conductivity ◽  
Alloy Scattering ◽  
Classical Size ◽  
Good Agreement

ABSTRACTAn incoherent particle model has been developed to predict the phonon thermal conductivity of nanowires and superlattice nanowires. It is argued that the surface roughness of most real nanowires prevents the formation of idealized confined dispersion relations for typical temperatures and diameters. Instead, the three-dimensional bulk dispersion is used, thus addressing only classical size effects. Four adjustable parameters capture the effects of diameter, superlattice, Umklapp, impurity, and alloy scattering. Predictions are compared with experimental data for nanowires and superlattice nanowires down to 22 nm diameter and 20 K, and are in good agreement above ∼40 nm diameter. The analysis suggests that ideal low thermal conductivity nanowires for thermoelectric applications would have small-diameter, alternating alloy segments that are acoustically dissimilar but electrically similar.

scholarly journals Extension of soil thermal conductivity models to frozen meats with low and high fat content

2005 ◽  
Vol 28 (6) ◽  
pp. 840-850 ◽  
Author(s):  
V.R. Tarnawski ◽  
D.J. Cleland ◽  
S. Corasaniti ◽  
F. Gori ◽  
R.H. Mascheroni
Keyword(s):  
Thermal Conductivity ◽  
Fat Content ◽  
Soil Thermal Conductivity ◽  
High Fat ◽  
Conductivity Models

scholarly journals Thermal Conductivities of Unidirectional Materials

1967 ◽  
Vol 1 (2) ◽  
pp. 166-173 ◽  
Author(s):  
George S. Springer ◽  
Stephen W. Tsai
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Model ◽  
Longitudinal Shear ◽  
Unidirectional Composite ◽  
Shear Loading ◽  
Square Packing ◽  
Good Agreement ◽  
Thermal Conductivities

In this paper the composite thermal conductivities of unidirec tional composites are studied and expressions are obtained for pre dicting these conductivities in the directions along and normal to the filaments. In the direction along the filament an expression is presented based on the assumption that the filaments and matrix are connected in parallel. In the direction normal to the filaments composite thermal conductivity values are obtained first by utiliz ing the analogy between the response of a unidirectional composite to longitudinal shear loading and to transverse heat transfer; second by replacing the filament-matrix composite with an idealized ther mal model. The results of the shear loading analogy agree reason ably well with the results of the thermal model particularly at filament contents below about 60%. These results were also com pared to experimental data reported in the literature and good agreement was found between the data and those theoretical re sults that were derived for circular filaments arranged in a square packing array.

scholarly journals Evaluation of 14 frozen soil thermal conductivity models with observations and SHAW model simulations

Geoderma ◽  
2021 ◽  
Vol 403 ◽  
pp. 115207
Author(s):  
Hailong He ◽  
Gerald N. Flerchinger ◽  
Yuki Kojima ◽  
Dong He ◽  
Stuart P. Hardegree ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Frozen Soil ◽  
Soil Thermal Conductivity ◽  
Model Simulations ◽  
Conductivity Models

Significance of Thermal Conductivity of Molten Polyethylene in Cable Extrusion Process

Volume 3 ◽  
2004 ◽  
Author(s):  
Birgitta Ka¨llstrand ◽  
Carl-Olof Olsson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
High Voltage ◽  
Outer Layer ◽  
Extrusion Process ◽  
Temperature Profiles ◽  
Line Speed ◽  
Conductor Temperature ◽  
Good Agreement

The dominating parameter for heat transfer during continuous curing of extruded high voltage cables is the thermal conductivity of molten polyethylene. Literature on thermal conductivity has been reviewed, and it is found that there are differences of order 50% between different investigations. From numerical simulations it is found that 20% increase in thermal conductivity corresponds to 8 °C increase in maximum conductor temperature for constant line speed or 16% increase in line speed for optimized crosslinking. The calculated conductor temperature profile is compared with experimental data from the cable manufacturing. The conductor temperature was measured continuously, using an optical fiber embedded in the outer layer of the conductor, while the conductor passed through the extrusion line. The comparison between measured and simulated conductor temperature profiles show good agreement provided that an appropriate value of the thermal conductivity is chosen.

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