Experimental validation of a TRC model for a double U-tube borehole with two independent circuits

Marcotte, Bruno; Bernier, Michel

doi:10.1016/j.applthermaleng.2019.114229

Cited by 14 publications

(10 citation statements)

References 24 publications

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“…Other effects on performance are due to the anti-freeze solution. Such values of thermal resistance are slightly higher than the typical range observed in the literature (∼ 0.1 mk/W); however, the authors calculate them by theoretical models specific for the single [123], and double U-tube [124] configuration and then validate their numerical method against the experimental results in [125].…”

Section: Temperature Optimizationmentioning

confidence: 95%

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

2021

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Geothermal heat pumps have a widespread diffusion as they are able to deliver relatively higher energy output than other systems for building air-conditioning. The exploitation of low-enthalpy geothermal energy, however, presents crucial sustainability issues. This review investigates the primary forms of the environmental impact of geothermal heat pumps and the strategies for their mitigation. As life-cycle analyses shows that the highest impacts arise from installation and operation stages, most optimization studies focus on system thermodynamics, aiming at maximizing the energy performance via the optimization in the design of the different components interacting with the ground and serviced building. There are environmental studies of great relevance that investigate how the climate and ground properties affect the system sustainability and map the most suitable location for geothermal exploitation. Based on this review, ground-source heat pumps are a promising technology for the decarbonization of the building sector. However, a sustainable design of such systems is more complex than conventional air-conditioning systems, and it needs a holistic and multi-disciplinary approach to include the broad environmental boundaries to fully understand the environmental consequences of their operation.

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Section: Temperature Optimizationmentioning

confidence: 95%

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

2021

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“…To validate the developed model, the simulation result was compared with experimental data presented by Marcotte and Bernier (2019) on a fully instrumented small-scale borehole for the validation of the thermal capacitance resistance model developed for the double U-tube BHE with two independent circuits. The experimental setup was a laboratory model of double U-tube borehole (90.39 cm long with 9.45 cm diameter) placed in a sand tank with known properties.…”

Section: Validation Of the Current Workmentioning

confidence: 99%

“…For the validation of the recent model, the test with a step change in inlet temperature where a step change of 26.4 °C is imposed in both circuits for the period of 3 min, was considered. For the sake of comparison, the same working fluid conditions, borehole characteristics and parameters presented by Marcotte and Bernier (2019) Since the model utilized is numerical model, selection of discritization scheme is crucial. As a result, scheme descritisation adopted for the borehole and the surrounding ground is provided by performing grid sensitivity analysis.…”

Section: Validation Of the Current Workmentioning

confidence: 99%

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Transient Heat Transfer Modeling, Simulation and Performance Analysis of Single and Double U-Tube Borehole Heat Exchanger

Kerme

2024

Preprint

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<p>Ground source heat pump systems (GSHPs) are currently being widely applied to space heating and cooling due to their high efficiency and reduced environmental impact and running cost. Borehole heat exchanger (BHE) is the key component that determines the performance and total cost of the GSHPs. This thesis primarily focuses on transient heat transfer modeling, simulation, and performance analysis of single and double U-tube borehole heat exchanger with two independent circuits. Numerical heat transfer model that predicts the transient heat transfer of the BHE with single and double U-tube configuration was developed. The model developed is then used to perform simulation and analysis of transient heat transfer and thermal performance of single U-tube BHE (sBHE) as well as double U-tube BHE (dBHE) with two independent circuits for different cases of operating conditions: simultaneous charging, discharging, and charging-discharging. Using developed model, detailed comparison of thermal performance between single and double U-tube BHE was also made. Furthermore, comprehensive parametric analysis was performed to identify the major factors that affects the thermal performance of the sBHE and dBHE. It was concluded that the developed model was successfully applied for the analysis of short time thermal performance of sBHE and dBHE with two independent circuits where different borehole operating conditions with the same or different mass flowrate, inlet temperature and working fluid can be taken into consideration. The obtained result revealed that the heat injected and extracted by the double U-tube BHE at steady state is 21.8 (77%) and 10.2 W/m (71.8%) more than that of the sBHE, respectively. The simulation results also indicate that the thermal effectiveness of sBHE and dBHE at steady state are 0.24 and 0.31, respectively. The obtained results also revealed that the dBHE is preferable to transfer more heat when used in shallow borehole depth; while with deep borehole depth, sBHE is better to transfer more heat than dBHE particularly for high grout and soil thermal conductivities. The performed simulation and analysis are important as quick a reference for the design and system optimization of BHE integrated with GSHPs.</p>

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“…Ground initial temperature distribution, soil thermal characteristic and insulation of borehole heat exchanger all played an important role in heating exchange efficiency of BHEs [32,[34][35][36], in which, ground heat conductivity and borehole heat resistance are the two most important parameters [37][38][39]. Ground heat conductivity reflects the heat physical properties of the soil and is related to soil density, water content, groundwater, and other factors [11] (Li et al, 2020); the borehole heat resistance reflects the heat transfer effect between the U-pipe and the borehole wall, and is related to factors such as backfill material, U-pipe material, U-pipe shapes, and distribution position.…”

Section: Introductionmentioning

confidence: 99%

Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

et al. 2021

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For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

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Experimental validation of a TRC model for a double U-tube borehole with two independent circuits

Abstract: Ce fichier a été téléchargé à partir de PolyPublie, le dépôt institutionnel de Polytechnique MontréalThis file has been downloaded from PolyPublie, the institutional repository of Polytechnique Montréal http://publications.polymtl.ca

Cited by 14 publications

References 24 publications

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

Transient Heat Transfer Modeling, Simulation and Performance Analysis of Single and Double U-Tube Borehole Heat Exchanger

Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

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