3D numerical modeling of vertical geothermal heat exchangers

Ozudogru, Tolga Y.; Olgun, C. Güney; Şenol, Aykut

doi:10.1016/j.geothermics.2014.02.005

Cited by 115 publications

(41 citation statements)

References 17 publications

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“…In order to verify the accuracy of the model in predicting the long-term operation and restoration process, the model was also validated with the numerical model presented by Ozudogru et al [37]. A test was performed in a borehole with a single loop, by applying a constant heat rate of 50 W¨m´1 for the duration of 100 h. After loading, the temperatures were recorded for a recovery period of 150 h. The ground surface was kept at a constant temperature, equal to the undisturbed temperature, in both the model presented here and the numerical model from the literature.…”

Section: Experiments and Validationmentioning

confidence: 99%

Analysis of Geo-Temperature Restoration Performance under Intermittent Operation of Borehole Heat Exchanger Fields

Mao

Xing

et al. 2015

Sustainability

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Intermittent operation can improve the coefficient of performance (COP) of a ground source heat pump (GSHP) system. In this paper, an analytical solution to analyze the geo-temperature restoration performance under intermittent operation of borehole heat exchanger (BHE) fields is established. For this purpose, the moving finite line source model is combined with the g-function and the superposition principle. The model takes into account the heat transfer along the borehole, thermal interference between BHEs, and the influence of groundwater flow. The accuracy of the model is validated through comparison with an experiment carried out under intermittent operation. The model makes it possible to analyze the geo-temperature restoration performance and its influencing factors, such as BHE spacing, heat flow rate, operation mode, and groundwater flow. The main conclusions of this work are as follows. The heat transfer along the borehole should be considered when analyzing the geo-temperature restoration performance. When the BHE spacing increases, the soil temperature change decreases and the heat recovery improves. Therefore, adequate borehole separation distance is essential in the case of a multiple BHE system with unbalanced load. The presence of groundwater flow is associated with interference between the BHEs, which should not be ignored. In the case of long-term operation, the groundwater flow is beneficial to the geo-temperature recovery process, even for downstream BHEs. Finally, a greater groundwater flux leads to a better geo-temperature recovery.

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Section: Experiments and Validationmentioning

confidence: 99%

Analysis of Geo-Temperature Restoration Performance under Intermittent Operation of Borehole Heat Exchanger Fields

Mao

Xing

et al. 2015

Sustainability

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“…A commonly used technique is to build a swept mesh consisting of prisms for the meshing of the BHE domain [13,14,17]. This allows the geometry of the cross-section to be represented accurately.…”

Section: Numerical Model Set-upmentioning

confidence: 99%

“…Other simplified numerical approaches were presented by Ozudogru et al [14] and Holzbecher and Rauschel [15] with the U-tube pipes being also represented as 1D elements, but with a slightly modified approach. The former introduced the so-called pseudo-pipes to overcome the absence in the pipe's heat capacity, and the latter presented a method to discretise the pipes using the extruded linear element to simplify the geometry and limit the number of elements.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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.

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“…However, the effect of groundwater was neglected by Florides et al [16]. A similar approach was used by Ozudogru et al [17], who coupled the commercial software COMSOL ® for the description of the heat transfer in the borehole with a 1D description of heat and water transport in the pipe. In another study, Han et al [18] developed a 3D coupled Finite Element Model, which was then utilized to simulate steady-state and transient behaviors of a geothermal heat exchanger.…”

Section: Introductionmentioning

confidence: 99%

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

Brunetti

Saito

et al. 2017

Applied Energy

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3D numerical modeling of vertical geothermal heat exchangers

Cited by 115 publications

References 17 publications

Analysis of Geo-Temperature Restoration Performance under Intermittent Operation of Borehole Heat Exchanger Fields

Analysis of Geo-Temperature Restoration Performance under Intermittent Operation of Borehole Heat Exchanger Fields

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

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

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