In Situ Experiment and Numerical Model Validation of a Borehole Heat Exchanger in Shallow Hard Crystalline Rock

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Janiszewski , M , Hernandez , E C , Siren , T , Uotinen , L , Kukkonen , I & Rinne , M 2018 , ' In Situ Experiment and Numerical Model Validation of a Borehole Heat Exchanger in Shallow Hard Crystalline Rock ' Energies , vol. 11 , no. 4 , 963 . https://doi.org/10.3390/en11040963

Title: In Situ Experiment and Numerical Model Validation of a Borehole Heat Exchanger in Shallow Hard Crystalline Rock
Author: Janiszewski, Mateusz; Hernandez, Enrique Caballero; Siren, Topias; Uotinen, Lauri; Kukkonen, Ilmo; Rinne, Mikael
Contributor: University of Helsinki, Department of Physics
Belongs to series: Energies
ISSN: 1996-1073
Abstract: Accurate and fast numerical modelling of the borehole heat exchanger (BHE) is required for simulation of long-term thermal energy storage in rocks using boreholes. The goal of this study was to conduct an in situ experiment to validate the proposed numerical modelling approach. In the experiment, hot water was circulated for 21 days through a single U-tube BHE installed in an underground research tunnel located at a shallow depth in crystalline rock. The results of the simulations using the proposed model were validated against the measurements. The numerical model simulated the BHE's behaviour accurately and compared well with two other modelling approaches from the literature. The model is capable of replicating the complex geometrical arrangement of the BHE and is considered to be more appropriate for simulations of BHE systems with complex geometries. The results of the sensitivity analysis of the proposed model have shown that low thermal conductivity, high density, and high heat capacity of rock are essential for maximising the storage efficiency of a borehole thermal energy storage system. Other characteristics of BHEs, such as a high thermal conductivity of the grout, a large radius of the pipe, and a large distance between the pipes, are also preferred for maximising efficiency.
URI: http://hdl.handle.net/10138/236733
Date: 2018-04
Subject: underground thermal energy storage
borehole heat exchanger
in situ experiment
numerical modelling
model validation
finite element method
COMSOL Multiphysics
crystalline rock
FINITE-ELEMENT FORMULATION
SYSTEMS
FLOW
MASS
114 Physical sciences
1171 Geosciences
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