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A numerical and experimental study of near surface ground energy systems including the use of adaptable insulation layer

Mobarek, Hassanein 2017. A numerical and experimental study of near surface ground energy systems including the use of adaptable insulation layer. PhD Thesis, Cardiff University.
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Abstract

Unfortunately, the global conventional fuels in reserves are running out while the world energy consumption is increasing unruly. Therefore, innovative methods for providing sustainable heating and cooling through thermal energy storage (TES) have gained increasing attention. This study presents a numerical and experimental investigation of near surface ground energy systems including the use of adaptable insulation layers. The experimental set up involves the development of an innovative technique that is proposed to regulate the transfer of heat energy to the storage regions of the soil mass. Furthermore, a theoretical framework to represent the transient processes of such systems was developed and 1D and 2D numerical models were established to simulate ground energy system behaviour. The finite element method was utilised for spatial discretization and the finite difference method for time-stepping. The resulting model took into account conductive and convective heat transfer between the fluid inside pipe heat exchangers and the surrounding soil. Key additions were introduced to the recent model work which allowed it to take into account surface snow and ground freezing presence in the system, the amount of thermal energy available in the system and the ability to represent porous layer thermal properties of a multi layered system through considering its components (i.e. air, water and solids particles). The proposed new experimental setup was used to investigate the practical implementation of adaptable insulation layers with the experimental data then used to validate the numerical model. Further validation of the modelling of the surface snow and ground freezing was achieved via comparison against an experimental case study performed by others. In the analysis performed, particular attention was 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. Additionally, the developed models were applied to explore the use of the adaptable insulation layer in different systems in comparison to typical designs. Three case scenarios were chosen to represent different type of systems, a comparisons analysis was then introduced which shows the potential effectiveness of using the adaptable insulation layer.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Underground thermal energy systems; Insulation layer; Inter-seasonal heat transfer; Adaptable layer; Shallow geothermal systems; Thermal storage systems.
Date of First Compliant Deposit: 17 May 2018
Last Modified: 17 May 2018 09:15
URI: http://orca-mwe.cf.ac.uk/id/eprint/111512

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