Modelling of frozen soil thermal conductivity

2020 ◽  
Author(s):  
Hailong He ◽  
Dong He ◽  
Yuki Kojima ◽  
Gerald Flerchinger ◽  
Miles Dyck
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Transport Processes ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Extensive Literature ◽  
Soil Thermal Conductivity ◽  
Differential Heat ◽  
Steady State Method ◽  
Water Redistribution

<p>Frozen soil thermal conductivity (FSTC), which describes frozen soils’ ability to conduct heat under a unit temperature gradient, is a critical parameter of the partial differential heat conduction equation required for numerical studies of coupled heat and mass transport processes and engineering applications in cold and arid regions. FSTC is complicated because it is affected by factors such as temperature, unfrozen water and ice content, and soil texture. Although many FSTC models are available in literature, many of these models were developed using steady-state method that are subject to errors associated with phase change and water redistribution or not even tested with experiments. In addition, no studies have assessed their applicability and reliability. We conducted an extensive literature review and collated over 30 FSTC models. Their performance was evaluated with a large compiled dataset measured with transient method (e.g., heat pulse method), which is less likely to be affected by phase change and water redistribution at unfrozen or low subfreezing temperatures. In addition, a new FSTC model that is capable of accurately estimating FSTC at both unfrozen and frozen conditions is proposed.</p>

scholarly journals Assessment for Thermal Conductivity of Frozen Soil Based on Nonlinear Regression and Support Vector Regression Methods

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Fu-Qing Cui ◽  
Wei Zhang ◽  
Zhi-Yun Liu ◽  
Wei Wang ◽  
Jian-bing Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Support Vector Regression ◽  
Nonlinear Regression ◽  
Prediction Accuracy ◽  
Prediction Models ◽  
Frozen Soil ◽  
Support Vector ◽  
Soil Thermal Conductivity ◽  
Fine Grained ◽  
Fine Grained Soil

The comprehensive understanding of the variation law of soil thermal conductivity is the prerequisite of design and construction of engineering applications in permafrost regions. Compared with the unfrozen soil, the specimen preparation and experimental procedures of frozen soil thermal conductivity testing are more complex and challengeable. In this work, considering for essentially multiphase and porous structural characteristic information reflection of unfrozen soil thermal conductivity, prediction models of frozen soil thermal conductivity using nonlinear regression and Support Vector Regression (SVR) methods have been developed. Thermal conductivity of multiple types of soil samples which are sampled from the Qinghai-Tibet Engineering Corridor (QTEC) are tested by the transient plane source (TPS) method. Correlations of thermal conductivity between unfrozen and frozen soil has been analyzed and recognized. Based on the measurement data of unfrozen soil thermal conductivity, the prediction models of frozen soil thermal conductivity for 7 typical soils in the QTEC are proposed. To further facilitate engineering applications, the prediction models of two soil categories (coarse and fine-grained soil) have also been proposed. The results demonstrate that, compared with nonideal prediction accuracy of using water content and dry density as the fitting parameter, the ternary fitting model has a higher thermal conductivity prediction accuracy for 7 types of frozen soils (more than 98% of the soil specimens’ relative error are within 20%). The SVR model can further improve the frozen soil thermal conductivity prediction accuracy and more than 98% of the soil specimens’ relative error are within 15%. For coarse and fine-grained soil categories, the above two models still have reliable prediction accuracy and determine coefficient (R2) ranges from 0.8 to 0.91, which validates the applicability for small sample soils. This study provides feasible prediction models for frozen soil thermal conductivity and guidelines of the thermal design and freeze-thaw damage prevention for engineering structures in cold regions.

A Spherical Steady-State Method to Measure Soil Thermal Conductivity

2019 ◽  
Vol 52 (12) ◽  
pp. 1572-1576
Author(s):  
S. M. Mahdavi ◽  
M. R. Neyshabouri ◽  
H. Fujimaki
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Soil Thermal Conductivity ◽  
Steady State Method ◽  
State Method

Soil thermal conductivity dataset

2021 ◽  
Author(s):  
Hailong He
Keyword(s):  
Thermal Conductivity ◽  
Land Surface ◽  
Pulse Method ◽  
Time Domain Reflectometry ◽  
Soil Thermal Conductivity ◽  
Thermal Probe ◽  
Line Heat Source ◽  
Steady State Method ◽  
Needle Probe ◽  
Transient Heat Flow

<p>Soil thermal conductivity (STC) is required parameter for coupled water and heat transport for land surface models. However, unlike soil hydraulic properties, no global dataset is available for STC. The objective of this study was to collate literature data and to take new measurements in order to establish a big STC dataset that would facilitate the evaluation and development of STC models. We collected over 8000 STC measurements made on over 400 soil types around the world following rigid filtering criteria and processes. All the STC data in the dataset were based on transient-heat-flow methods (e.g., non-steady-state method, line-heat source, needle probe, thermal probe, dual and single probe heat pulse method, thermo-time domain reflectometry). Each soil contains at least five water contents in addition to known soil physical properties such as texture and bulk density. This presentation will give a brief introduction about the STC dataset as well as call for contributions to it.</p>

scholarly journals Coupled cellular automata for frozen soil processes

SOIL ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 103-116 ◽  
Author(s):  
R. M. Nagare ◽  
P. Bhattacharya ◽  
J. Khanna ◽  
R. A. Schincariol
Keyword(s):  
Cellular Automata ◽  
Phase Change ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Potential ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Unfrozen Water ◽  
First Order ◽  
Unfrozen Water Content

Abstract. Heat and water movement in variably saturated freezing soils is a strongly coupled phenomenon. The coupling is a result of the effects of sub-zero temperature on soil water potential, heat carried by water moving under pressure gradients, and dependency of soil thermal and hydraulic properties on soil water content. This study presents a one-dimensional cellular automata (direct solving) model to simulate coupled heat and water transport with phase change in variably saturated soils. The model is based on first-order mass and energy conservation principles. The water and energy fluxes are calculated using first-order empirical forms of Buckingham–Darcy's law and Fourier's heat law respectively. The liquid–ice phase change is handled by integrating along an experimentally determined soil freezing curve (unfrozen water content and temperature relationship) obviating the use of the apparent heat capacity term. This approach highlights a further subtle form of coupling in which heat carried by water perturbs the water content–temperature equilibrium and exchange energy flux is used to maintain the equilibrium rather than affect the temperature change. The model is successfully tested against analytical and experimental solutions. Setting up a highly non-linear coupled soil physics problem with a physically based approach provides intuitive insights into an otherwise complex phenomenon.

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

Phase Change Effects on Transport Processes in Resistance Spot Welding

2011 ◽  
Vol 27 (1) ◽  
pp. 19-26 ◽  
Author(s):  
P. S. Wei ◽  
T. H. Wu ◽  
S. S. Hsieh
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Specific Heat ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Surface Condition ◽  
Transport Processes ◽  
Resistance Spot ◽  
Faying Surface ◽  
Working Parameters

ABSTRACTThe effects of distinct properties during phase change on mass, momentum, energy, species, and magnetic field intensity transport in workpieces and electrodes in the course of heating, melting, cooling and freezing periods in AC (alternative current) resistance spot welding are realistically and extensively investigated. Resistance spot welding has been widely used in joining thin workpieces due to its light weight and easy manufacturing. This study accounts for electromagnetic force, heat generations at the electrode-workpiece interface and faying surface between workpieces, and dynamic electrical resistance taking the sum of temperature-dependent bulk resistance of the workpieces and contact resistances at the faying surface and electrode-workpiece interface. The contact resistance is a function of hardness, temperature, electrode force, and surface condition. Instead of dealing with specific materials, this work is a general dimensionless investigation of resistance spot welding of materials with different specific heat and thermal conductivity ratios subject to realistic working parameters. The computed results show that nugget formation is delayed and heat transfer is reduced by increasing solid-to-liquid thermal conductivity and liquid-to-solid specific heat ratio. The corresponding thermal fields and flow patterns are also presented.

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