Thermal Conductivity of Frozen Soil at Cryogenic Temperatures

1995 ◽  
pp. 655-661
Author(s):  
J. J. Cloessner ◽  
R. F. Barron
Keyword(s):  
Thermal Conductivity ◽  
Frozen Soil ◽  
Cryogenic Temperatures

scholarly journals Improved Copper–Epoxy Adhesion by Laser Micro- and Nano-Structuring of Copper Surface for Thermal Applications

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1721
Author(s):  
Mario Mora ◽  
Hippolyte Amaveda ◽  
Luis Porta-Velilla ◽  
Germán F. de la Fuente ◽  
Elena Martínez ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Bonding Strength ◽  
Copper Surface ◽  
Heat Sinks ◽  
Electrical Insulation ◽  
Cryogenic Temperatures ◽  
Shear Tests ◽  
Patterned Structures ◽  
Different Temperatures ◽  
Mechanical Tensile

The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryogenic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures.

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.

Measuring Thermal Conductivity of Insulators at Cryogenic Temperatures

2000 ◽  
pp. 1919-1924 ◽  
Author(s):  
B. P. M. Helvensteijn ◽  
L. J. Salerno ◽  
P. R. Roach ◽  
P. Kittel ◽  
S. M. White
Keyword(s):  
Thermal Conductivity ◽  
Cryogenic Temperatures

Stress Analysis of Buried Pipelines Under Thaw Settlement of Permafrost Zone Based on Moisture-Heat-Stress Coupled Analysis

2020 ◽  
Author(s):  
Jinxu Jiang ◽  
Hong Zhang ◽  
Jianping Liu ◽  
Pengchao Chen ◽  
Xiaoben Liu
Keyword(s):  
Thermal Conductivity ◽  
Vertical Displacement ◽  
Frozen Soil ◽  
Ground Temperature ◽  
Permafrost Zone ◽  
Insulation Material ◽  
Longitudinal Stress ◽  
Buried Pipelines ◽  
Safe Operation ◽  
Thaw Settlement

Abstract Permafrost thawing caused by the hot crude pipeline is a major threat to the safe operation of buried pipelines in permafrost zone. In this paper, the process of thawing and consolidation of frozen soil is considered, and a three-dimensional (3D) finite element model of buried pipelines in permafrost zone is established using ABAQUS. The calculation of thaw settlement displacement of frozen soil based on moisture-heat-stress coupled was carried out, and the deformation and stress of buried pipelines were analyzed. The effects of ground temperature, oil temperature, thermal conductivity of insulation material and soil distribution along the pipeline on the vertical displacement and longitudinal stress of buried pipelines in frozen soil were studied. Research results show that in thaw-unstable soil, the vertical displacement and stress of the pipeline increase significantly with the increase of the average ground temperature, and change on ground temperature amplitude has a little effect on the vertical displacement and longitudinal stress of the pipeline in thaw settlement zone. It is 1/3 of the vertical displacement of the pipeline without a heat insulating layer. When the thermal conductivity of the insulation material is less than 0.4 W/m °C, the vertical displacement of the pipeline in the thawing zone can be further reduced by reducing the thermal conductivity of the insulation material. When clay and sand appear alternately along the pipeline, the vertical displacement and longitudinal stress of the pipeline can be reduced by reducing the length of clay section. This study has certain reference value for optimizing the design parameters of buried pipelines in permafrost zone and reducing the impact of differential thaw settlement of frozen soils on the safe operation of pipelines.

scholarly journals Theoretical Studies of Ice Segregation in Soil

1966 ◽  
Vol 6 (44) ◽  
pp. 255-260 ◽  
Author(s):  
Kiyoshi Arakawa
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Mathematical Theory ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Heat Of Fusion ◽  
Theoretical Studies ◽  
Latent Heat Of Fusion ◽  
Two Parameters ◽  
Ice Segregation

Abstract The mathematical theory of heat conduction is applied to the analysis of ice segregation processes in soil. A diffusion equation is first employed for the flow of soil moisture. Two new quantities, the rate of ice segregation,σ and the segregation efficiency, E, are introduced. The first is the rate of ice growth measured as mass per area per time. The latter is defined as E = σL/(K 1 ∂T 1/∂x−K 2 ∂T 2/∂x), where L is the latent heat of fusion of ice, T 1and K 1are the temperature and thermal conductivity of frozen soil, and T 2 and K 2 are the temperature and thermal conductivity of unfrozen soil. Three types of soil freezing can be classified in terms of E: freezing of non-frost-susceptible soil (E = 0), perfect segregation (E = 1) and imperfect segregation (0 < E < 1). Finally, the mathematical boundary conditions at an advancing frost line are obtained in freezing, frost-susceptible soil (E ≠ 0). Two parameters related to the structure of soil are pointed out, which seem to be valid criteria of frost susceptibility. The amount of frost-heaving is derived under special conditions.

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