Call number:
AWI G3-23-95005
Description / Table of Contents:
In this thesis processes and parameters associated with heat and mass transfer in frozen porous media both on a theoretical and empirical basis are studied. To obtain the required measurements some existing measuring methods needed to be improved.
Firstly, an improved model has been developed for the measurement of thermal conductivity with use of the nonsteady-state probe method. The measurements of thermal conductivity indicate four separate effects caused by the freezing process. The second improved measuring method is the measurement of bulk electrical conductivity with use of time-domain r e flectometry. And the third improvement is the use of the dispersion theory in the description of relations between water content and bulk electrical conductivity or dielectric constant.
This thesis shows that time-domain reflectometry can be used to measure the unfrozen water content and bulk electrical conductivity simultaneously under frozen conditions and that from the latter parameter solute redistribution can be monitored. From the measured heat flows a time delay in the forming of pore ice can be
concluded. From the measured moisture transport (resulting in frost heave) a relation with some soil properties could be established. For some of the materials studied a minimum temperature gradient has been observed at which heave starts . From this and other results an effort was made to come to a synthesis of the rigid ice concept and the segregation potential concept.
The thesis finishes with some recommandations in connection with the improvement of soil structure by freezing, frost heave and artificial ground freezing.
Type of Medium:
Dissertations
Pages:
8, 204 Seiten
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Illustrationen
URL:
https://library.wur.nl/WebQuery/wurpubs/fulltext/201303
Language:
English
Note:
Dissertation, Landbouwuniversiteit Wageningen, Wageningen, 1991
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1 INTRODUCTION
1.1 Fields of interest
1.2 Macroscopic freezing test
1.3 Microscopic model
1.4 Aim of the thesis
1.5 Overview of the thesis
2 THEORY
2.0 Introduction to the chapter
2.1 Theory of different soil analyses
2.1.1 Particle size distribution
2.1.2 Specific surface area
2.1.3 Cation exchange capacity
2.1.4 Zeta potential
2.1.5 Water retention
2.1.6 Hydraulic conductivity
2.1.7 Thermal conductivity
2.2 Determination of soil water content by time-domain reflectometry
2. 2.1 Transmission line theory
2.2.2 Water content
2.2.3 Bulk electrical conductivity
2.3 Transfer of heat and mass
2.3.1 Moisture transport
2.3.2 Heat transport
2.3.3 Solute transport
3 NEW MODELS AND METHODS
3.0 Introduction to the chapter
3.1 A new model for the nonsteady-state probe method to measure thermal properties of porous media
3.1.0 Abstract
3.1.1 Introduction
3.1.2 Present approach
3.1.3 Experimental set-up
3.1.4 The perfect line source model
3.1.5 The modified Jaeger model
3.1.6 Gauss-Newton iteration
3.1.7 Calibration measurements
3.1.8 Conclusions
3.2 A new method to measure bulk electrical conductivity in soil using time-domain reflectometry
3.2.0 Abstract
3.2.1 Introduction
3.2.2 Measurement theory
3.2.3 Materials and methods
3.2.4 Results and discussion
3.2.5 Conclusions
3.3 Application of dispersion theory to time-domain reflectometry in soils
3.3.0 Abstract
3.3.1 Introduction
3.3.2 Dielectric constant as a function of water content
3.3.2.1 Soil as a two phase dielectric medium
3.3.2.2 Unfrozen soils
3.3.2.3 Frozen soils
3.3.3 Bulk electrical conductivity as a function of water content
3.3.4 Materials and methods
3.3.5 Results and discussion
3.3.5.1 Validation of the model for bulk electrical
conductivity
3.3.5.2 Comparison with other models
3.3.6 Conclusions
3.3.7 Appendix
3.4 Description of the experiments to measure heat and mass transfer in freezing porous media
3.4.1 Experimental set-up
3.4.2 Used materials
3.4.3 Relations between soil physical and electrochemical properties
4 RESULTS AND DISCUSSION
4.0 Introduction to the chapter
4.1 Thermal conductivity of unsaturated frozen sands 4. 1.0 Abstract
4.1. 1 Introduction
4.1. 2 Experimental set-up
4.1. 3 Theoretical approach
4. 1.4 Properties of the used sands
4.1.5 Measured heat flows
4.1. 6 Measured thermal conductivities
4.1. 7 Discussion
4.2 Heat transfer
4.2.1 Heat capacity
4.2.2 Thermal conductivity
4.2.2.1 Influence of the temperature dependence of the pore ice versus unfrozen water content
4.2.2.2 Contribution of the apparent thermal conductivity
4.2.2.3 Segregated ice content
4.2.2.4 Presence of the freezing front close to the measuring probe
4.2.3 Latent heat of in situ freezing
4.2.4 Heat balances
4.2.5 Temperature fields
4.2.6 Dynamics of heat flows in frozen porous materials
4.3 Moisture transfer
4.3.1 Segregation potential
4.3.2 Influence of soil physical and electrochemical properties
4.4 Application of time-domain reflectometry to measure solute concentration during soil freezing
4.4.0 Abstract
4.4.1 Introduction
4.4.2 Materials and methods
4.4.3 Results and discussion
4.4.3.1 Influence of temperature
4.4.3.2 Influence of liquid water content
4.4.3.3 Redistribution of solutes
4.4.4 Conclusions
4.5 Influence of added solutes on moisture transfer
5 CONCLUSIONS AND FINAL DISCUSSION
5.1 General discussion
5.2 Recommandations in connection with frost in porous media
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Zusammenfassung in niederländischer Sprache
Location:
AWI Reading room
Branch Library:
AWI Library
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