The measurement of anisotropic thermal conductivity in snow with needle probes
| dc.contributor.author | Holbrook, Joshua | |
| dc.date.accessioned | 2020-10-16T22:31:43Z | |
| dc.date.available | 2020-10-16T22:31:43Z | |
| dc.date.issued | 2011-05 | |
| dc.identifier.uri | http://hdl.handle.net/11122/11363 | |
| dc.description | Thesis (M.S.) University of Alaska Fairbanks, 2011 | en_US |
| dc.description.abstract | A new method for measuring thermal conductivity is being adapted from the method of measuring isotropic thermal conductivity in snow with needle probes as used by Sturm, Johnson and others, in order to enable the determination of anisotropic thermal conductivities. This method has particular relevance to measuring thermal conductivity of natural snowpacks where conductivity can be strongly anisotropic due to structures that develop from vapor transport-induced metamorphism, self-compaction and other mechanisms, and where there are known discrepancies between density-conductivity relations empirically derived from guarded hot plate and needle probe methods. Both analytically-based solutions and finite element numerical solutions to the anisotropic case are used to calculate the expected effective thermal conductivity as a function of anisotropic thermal conductivity and needle orientation. Additionally, preliminary measurements of both anisotropic salt/sugar layered samples and of snow were taken. Both suggest that detecting anisotropy in such materials is possible, though made difficult by variability between measurements and the requirement of multiple measurements at various angles. These studies suggest that anisotropy in snow may be able to explain in part the discrepancies between guarded hot plate and needle probe measurements in certain cases. | en_US |
| dc.description.sponsorship | Cooperative Institute For Alaska Research | en_US |
| dc.description.tableofcontents | 1. Introduction -- 1.1. Why snow's conductivity matters -- 1.2. Thermal conductivity measurements of snow -- 1.3. Snow metamorphic principles -- 1.4. Anisotropic behavior in snow -- 1.5. Motivation for measuring snow anisotropy -- 1.6. Anisotropic model -- 1.7. Document outline -- 2. Analytical needle probe approach -- 2.1. Introduction -- 2.2. The isotropic case -- 2.3. Difficulties in the anisotropic case -- 2.4. Posing the problem in two coordinates -- 2.5. Coordinate transformation -- 2.6. From temperature distribution to effective thermal conductivity -- 2.7. Finding effective conductivity as a function of needle orientation -- 2.8. Conclusions -- 3. Numerical needle probe approach -- 3.1. Introduction -- 3.2. Geometry and domain properties -- 3.3. MATLAB in geometry-based parametric studies using COMSOL 3.5a -- 3.4. Automatic calculation of conductivity from simulated time/temperature data -- 3.5. Convergence study -- 3.6. Conclusions -- 4. Experimental measurements -- 4.1. Introduction -- 4.2. Needle probe measurement fundamentals -- 4.3. Snow conductivity measurements -- 4.4. Benchtop tests -- 4.5. Raw materials for the anisotropic composite -- 4.6. Apparatus for containing anisotropic composite -- 5. Results and interpretation -- 5.1. Parameters and nondimensionalization -- 5.2. Numerical vs. analytical predictions -- 5.3. Benchtop measurements -- 5.4. In-situ snow measurements -- 5.5. Ramifications -- 6. Future work -- 6.1. Introduction -- 6.2. Assumptions in the analytical approach -- 6.3. Extended convergence study -- 6.4. Improved benchtop method -- 6.5. Comprehensive benchtop measurements -- 6.6. Comprehensive in-situ measurements -- 6.7. Exploration of the cooling curve -- 6.8. A method for determining anisotropic thermal conductivity from measurements -- 7. Conclusions -- Bibliography. | en_US |
| dc.language.iso | en_US | en_US |
| dc.subject | snow | en_US |
| dc.subject | thermal properties | en_US |
| dc.title | The measurement of anisotropic thermal conductivity in snow with needle probes | en_US |
| dc.type | Thesis | en_US |
| dc.type.degree | ms | en_US |
| dc.identifier.department | Department of Mechanical Engineering | en_US |
| refterms.dateFOA | 2020-10-16T22:31:44Z |
