Numerical model for non-grouted borehole heat exchangers, Part 2—Evaluation

The vertical borehole heat exchangers were surrounded by the heterogeneous multilayered geological environment and groundwater flow that affected the performance of borehole plants. In this paper, the field investigation of vertical borehole ground heat exchangers in capital city Vilnius (Visoriai), Lithuania is presented. The numerical heat transfer model considering seven different geological strata was developed using the cylindrical heat sink model for vertical borehole inside by solving the soil mass and heat transfer equations with groundwater flow. The numerical multilayered ground vertical borehole heat transfer model was calculated and validated by in-situ thermal response test data. The numerical model results were also compared with the homogeneous finite difference model expressed by the temperature response functions (well known as “g-functions”). The practical realization of g-functions was designed in the Earth Energy Designer as a practical tool for geoengineers designing the vertical borehole plants. The temperature profiles at borehole wall at different heating times were presented and explored together with relative errors. The numerical model will be used as a practical tool for the Lithuanian Geological Survey under the Ministry of Environment to estimate the underground conditions for the consumption of shallow geothermal energy.

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A numerical model for transient simulation of borehole heat exchangers

Renewable Energy ◽

10.1016/j.renene.2016.12.010 ◽

2017 ◽

Vol 104 ◽

pp. 224-237 ◽

Cited By ~ 25

Author(s):

Hassan Biglarian ◽

Madjid Abbaspour ◽

Mohammad Hassan Saidi

Keyword(s):

Numerical Model ◽

Heat Exchangers ◽

Transient Simulation ◽

Borehole Heat Exchangers

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Validation of a numerical model for the design of borehole heat exchangers in the presence of groundwater flow

Energy Geotechnics ◽

10.1201/b21938-80 ◽

2016 ◽

pp. 499-503

Author(s):

J Van Steenwinkel ◽

D Simpson ◽

M Degros ◽

W Vienne ◽

G Van Lysebetten ◽

...

Keyword(s):

Numerical Model ◽

Groundwater Flow ◽

Heat Exchangers ◽

Borehole Heat Exchangers

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Enhanced Steady-State Solution of the Infinite Moving Line Source Model for the Thermal Design of Grouted Borehole Heat Exchangers with Groundwater Advection

Geosciences ◽

10.3390/geosciences11100410 ◽

2021 ◽

Vol 11 (10) ◽

pp. 410

Author(s):

Adinda Van de Ven ◽

Roland Koenigsdorff ◽

Peter Bayer

Keyword(s):

Steady State ◽

Numerical Model ◽

Temperature Change ◽

Heat Exchangers ◽

Line Source ◽

Thermal Design ◽

Correction Function ◽

Moving Line Source ◽

Moving Line ◽

Borehole Heat Exchangers

The objective of this study is to assess the suitability of the analytical infinite moving line source (MLS) model in determining the temperature of vertical grouted borehole heat exchangers (BHEs) for steady-state conditions when horizontal groundwater advection is present. Therefore, a numerical model of a grouted borehole is used as a virtual reality for further analysis. As a result of the first analysis, it has been discovered that established analytical methods to determine the borehole thermal resistance as a mean value over the borehole radius can also be applied to BHEs with groundwater advection. Furthermore, the deviation between a finite MLS and the infinite MLS is found to be only less than 5% for BHEs of a depth of 30 m or more, and Péclet numbers greater than 0.05. Finally, the accuracy of the temperature change calculated with the infinite MLS model at the radius of the borehole wall compared to the temperature change at a numerically simulated grouted borehole is addressed. A discrepancy of the g-functions resulting in a poor dimensioning of BHEs by the infinite MLS model is revealed, which is ascribed to the impermeable grouting material of the numerical model. A correction function has been developed and applied to the infinite MLS model for steady-state conditions to overcome this discrepancy and to avoid poor dimensioning of BHEs.

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Borehole Heat Exchangers in aquifers: simulation of the grout material impact

Rendiconti online della Società Geologica Italiana ◽

10.3301/rol.2016.145 ◽

2016 ◽

Vol 41 ◽

pp. 268-271

Author(s):

Luca Alberti ◽

Adriana Angelotti ◽

Matteo Antelmi ◽

Ivana La Licata

Keyword(s):

Heat Exchangers ◽

Borehole Heat Exchangers

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Low enthalpy geothermal energy: borehole heat exchangers (BHE). Geological and geothermal supervision during active construction in support of the energy certification of buildings - ESBE certification plan

Acque Sotterranee-Italian Journal of Groundwater ◽

10.7343/as-009-12-0028 ◽

2012 ◽

Cited By ~ 1

Author(s):

Lorenzo Cadrobbi ◽

Fioroni Daniele ◽

Alessandro Bozzoli

Keyword(s):

Energy Conservation ◽

Heat Exchangers ◽

Energy Efficient ◽

Geothermal Energy ◽

Energy Requirements ◽

Effective Coverage ◽

Correct Execution ◽

Environmental Technologies ◽

Borehole Heat Exchangers ◽

Ongoing Monitoring

This article draws on the experience matured while working with low-enthalpy geothermic installations both in the design and executive phase as well as ongoing monitoring, within the scope of energy conservation as it relates to building and construction. The goal is to illustrate the feasibility of adopting the ESBE certification protocol (Certification of Energy Efficient Low-Enthalpy Probes) aimed at optimizing the harnessing of local geothermic resources to satisfy the energy requirements of a building, measured against the initial investment. It is often the case, in fact, that during the course of a construction project for a given low-enthalpy installation, we verify incompa tibilities with the local geologic and geothermic models, which, if inadequate during construction, can compromise the proper functioning of the installation and its subsequent operation. To this end, the ESBE method, which adheres to the governing environmental regulations, and which takes its cue from technical statutes within the sector, permits us to validate via verification, simulations and tests, the geothermic field probes used in construction in an objective and standardized manner, thereby joining and supporting the most recent protocols for energy certification of buildings (LEED 2010, CASACLIMA 2011, UE 20120/31 Directive). ESBE certification operates through a dedicated Certifying Entity represented by the REET unit (Renewable Energies and Environmental Technologies) of FBK (Bruno Kessler Foundation) of Trento. The results obtained by applying the ESBE method to two concrete cases, relative to two complex geothermic systems, demonstrate how this protocol is able to guarantee, beyond the correct execution in the field of geothermic probes, an effective coverage of the energy requirements of the building during construction adopting the best optimization measures for the probes in keeping with the local geological and geothermic model.

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