This thesis presents a numerical, analytical and experimental investigation of inter-seasonal heat transfer processes in soils. Particular attention is given to the energy balance at the soil surface and its impact on the performance of thermal energy storage devices in shallow regions of the ground. For this purpose, a transient three-dimensional theoretical framework representing the relevant processes has been developed. A numerical solution has also been developed using the finite element method for spatial discretization and the finite difference method for time-stepping. The resulting model takes into account conductive and convective heat transfer between the fluid inside pipe heat exchangers and the surrounding soil. An alternative simplified 2D approach has also been developed and compared to the full 3D model. The determination of representative initial conditions and far-field (bottom) boundary conditions for the simulation of shallow ground heat storage facilities has also been investigated. To this end, a novel (1D) analytical approach has been developed to estimate realistic soil temperature profiles and seasonal thermal energy storage variations that can be used as input for more comprehensive analysis. Comparisons have been made to 1D numerical analysis. The proposed numerical model has been used to study a full-scale experiment undertaken by others involving the use of an inter-seasonal heat storage facility. As part of this study, key material properties have been measured using soil samples recovered from the experimental site. The results have revealed the importance of correctly representing the energy balance at the soil surface. Inclusion of soil/atmosphere interaction has been shown to be of critical importance for the correct assessment of buried heat transfer devices. The region of thermal influence and its seasonal variation have been established and the main limitations of the proposed model identified. General guidance for the design and installation of inter-seasonal heat transfer facilities has been provided based on the obtained results.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:646315 |
| Date | January 2014 |
| Creators | Muñoz Criollo, José |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/73226/ |
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