Modelling and evaluation of groundwater filled boreholes subjected to natural convection

Johnsson, Josef; Adl‐Zarrabi, Bijan

doi:10.1016/j.apenergy.2019.113555

Cited by 17 publications

(13 citation statements)

References 11 publications

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“…The boreholes are drilled with an equal spacing of 10 m to a depth of 210 m. According to previous geological surveys, the boreholes are drilled in clay slate covered by an approximately 10 m of glacial till. In 2018, thermal response tests were performed, and the ground thermal conductivity was determined to be 3.15 W/mK with a volumetric thermal capacity of 2.8 MJ/m 3 K [17].…”

Section: Measuring Harvested Energymentioning

confidence: 99%

A numerical and experimental study of a pavement solar collector for the northern hemisphere

Johnsson

Adl‐Zarrabi

2020

Applied Energy

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Section: Measuring Harvested Energymentioning

confidence: 99%

A numerical and experimental study of a pavement solar collector for the northern hemisphere

Johnsson

Adl‐Zarrabi

2020

Applied Energy

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“…Their method is valid for little or no fractured bedrock (no groundwater advection) and relies on the calculation of the corresponding Rayleigh and Nusselt numbers in contact with borehole annulus, experimentally fitted to measured data of five TRT tests of groundwater-filled boreholes located in the Swedish Chalmers University of Technology. Johnsson and Adl-Zarrabi [12] utilized Spitler's correlations and substituted the calculated values for groundwater-filled boreholes instead of those calculated for grouted boreholes, used within the GHE simulation toolbox Pygfunction [13]. In grouted boreholes, it is acknowledged that lower borehole effective thermal resistance is achieved with higher thermal conductivity of the backfilling material (grout).…”

Section: Introductionmentioning

confidence: 99%

“…In grouted boreholes, it is acknowledged that lower borehole effective thermal resistance is achieved with higher thermal conductivity of the backfilling material (grout). Johnsson highlighted that the effect of natural convection in groundwaterfilled boreholes was equivalent to grout material with 2-3 times better (higher) thermal conductivity than water [12].…”

Section: Introductionmentioning

confidence: 99%

Different Approaches for Evaluation and Modeling of the Effective Thermal Resistance of Groundwater-Filled Boreholes

et al. 2021

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Groundwater-filled boreholes are a common solution in Scandinavian installations of ground source heat pumps (GSHP) due to the particular hydro-geological conditions with existing bedrock, and groundwater levels close to the surface. Different studies have highlighted the advantage of water-filled boreholes compared with their grouted counterparts since the natural convection of water within the borehole tends to decrease the effective thermal resistance Rb*. In this study, several methods are proposed for the evaluation and modeling of the effective thermal resistance of groundwater-filled boreholes. They are based on distributed temperature sensing (DTS) measurements of six representative boreholes within the irregular 74-single-U 300 m-deep borehole field of Aalto New Campus Complex (ANCC). These methods are compared with the recently developed correlations for groundwater-filled boreholes, which are implemented within the python-based simulation toolbox Pygfunction. The results from the enhanced Pygfunction simulation with daily update of Rb* show very good agreement with the measured mean fluid temperature of the first 39 months of system operation (March 2018–May 2021). It is observed that in real operation the effective thermal resistance Rb* can vary significantly, and therefore it is concluded that the update of Rb* is crucial for a reliable long-term simulation of groundwater-filled boreholes.

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“…g-Functions, introduced by Eskilson [27], offered a nondimensional relation between the heat extracted from the ground at the borehole wall and the borehole wall temperature, thus making it fast-to-compute and practical in GSHP analyses. A few new contributions to the original g-function were made to adapt shorttime responses [28], various boundaries [29,30], and the effect of natural convection in the groundwater [31]. Another type of hybrid model couples analytical solution with numerical algorithm.…”

Section: Introductionmentioning

confidence: 99%

An Analytical Model for Transient Heat Transfer with a Time-Dependent Boundary in Solar- and Waste-Heat-Assisted Geothermal Borehole Systems: From Single to Multiple Boreholes

Hefni

Hassani

et al. 2021

Applied Sciences

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With the increasing engineering applications of geothermal borehole heat exchangers (BHEs), accurate and reliable mathematical models can help advance their thermal design and operations. In this study, an analytical model with a time-dependent heat flux boundary condition on the borehole wall is developed, capable of predicting the thermal performance of single, double, and multiple closed-loop BHEs, with an emphasis on solar- and waste-heat-assisted geothermal borehole systems (S-GBS and W-GBS) for energy storage. This analytical framework begins with a one-dimensional transient heat conduction problem subjected to a time-dependent heat flux for a single borehole. The single borehole scenario is then extended to multiple boreholes by exploiting lines of symmetry (or thermal superposition). A final expression of the temperature distribution along the center line is attained for single, double, and multiple boreholes, which is verified with a two-dimensional finite-element numerical model (less than 0.7% mean absolute deviation) and uses much lesser computational power and time. The analytical solution is also validated against a field-scale experiment from the literature regarding the borehole and ground temperatures at different time frames, with an absolute error below 6.3%. Further, the thermal performance of S-GBS and W-GBS is compared for a 3-by-3 borehole configuration using the analytical model to ensure its versatility in thermal energy storage. It is concluded that our proposed analytical framework can rapidly evaluate closed-loop geothermal BHEs, regardless of the numbers of boreholes and the type of the heat flux on the borehole wall.

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Modelling and evaluation of groundwater filled boreholes subjected to natural convection

Cited by 17 publications

References 11 publications

A numerical and experimental study of a pavement solar collector for the northern hemisphere

A numerical and experimental study of a pavement solar collector for the northern hemisphere

Different Approaches for Evaluation and Modeling of the Effective Thermal Resistance of Groundwater-Filled Boreholes

An Analytical Model for Transient Heat Transfer with a Time-Dependent Boundary in Solar- and Waste-Heat-Assisted Geothermal Borehole Systems: From Single to Multiple Boreholes

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