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Finite element modeling of borehole heat exchanger systems: Part 1. Fundamentals

Diersch, H.-J. G. and Bauer, D. and Heidemann, W. and Rühaak, W. and Schätzl, P. (2011):
Finite element modeling of borehole heat exchanger systems: Part 1. Fundamentals.
In: Computers & Geosciences, pp. 1122-1135, 37, (8), [Online-Edition: http://www.sciencedirect.com/science/article/B6V7D-51FNPD8-1...],
[Article]

Abstract

Single borehole heat exchanger (BHE) and arrays of BHE are modeled by using the finite element method. The first part of the paper derives the fundamental equations for BHE systems and their finite element representations, where the thermal exchange between the borehole components is modeled via thermal transfer relations. For this purpose improved relationships for thermal resistances and capacities of BHE are introduced. Pipe-to-grout thermal transfer possesses multiple grout points for double U-shape and single U-shape BHE to attain a more accurate modeling. The numerical solution of the final 3D problems is performed via a widely non-sequential (essentially non-iterative) coupling strategy for the BHE and porous medium discretization. Four types of vertical BHE are supported: double U-shape (2U) pipe, single U-shape (1U) pipe, coaxial pipe with annular (CXA) and centred (CXC) inlet. Two computational strategies are used: (1) The analytical BHE method based on Eskilson and Claesson's (1988) solution, (2) numerical BHE method based on Al-Khoury et al.'s (2005) solution. The second part of the paper focusses on BHE meshing aspects, the validation of BHE solutions and practical applications for borehole thermal energy store systems.

Item Type: Article
Erschienen: 2011
Creators: Diersch, H.-J. G. and Bauer, D. and Heidemann, W. and Rühaak, W. and Schätzl, P.
Title: Finite element modeling of borehole heat exchanger systems: Part 1. Fundamentals
Language: English
Abstract:

Single borehole heat exchanger (BHE) and arrays of BHE are modeled by using the finite element method. The first part of the paper derives the fundamental equations for BHE systems and their finite element representations, where the thermal exchange between the borehole components is modeled via thermal transfer relations. For this purpose improved relationships for thermal resistances and capacities of BHE are introduced. Pipe-to-grout thermal transfer possesses multiple grout points for double U-shape and single U-shape BHE to attain a more accurate modeling. The numerical solution of the final 3D problems is performed via a widely non-sequential (essentially non-iterative) coupling strategy for the BHE and porous medium discretization. Four types of vertical BHE are supported: double U-shape (2U) pipe, single U-shape (1U) pipe, coaxial pipe with annular (CXA) and centred (CXC) inlet. Two computational strategies are used: (1) The analytical BHE method based on Eskilson and Claesson's (1988) solution, (2) numerical BHE method based on Al-Khoury et al.'s (2005) solution. The second part of the paper focusses on BHE meshing aspects, the validation of BHE solutions and practical applications for borehole thermal energy store systems.

Journal or Publication Title: Computers & Geosciences
Volume: 37
Number: 8
Uncontrolled Keywords: Finite elements;Borehole heat exchanger;Thermal resistances;Local problem;Static condensation
Divisions: 11 Department of Materials and Earth Sciences > Earth Science > Geothermal Science and Technology
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences
Date Deposited: 06 Nov 2014 13:29
Official URL: http://www.sciencedirect.com/science/article/B6V7D-51FNPD8-1...
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