Study of geothermal energy piles performances using CFD (Etude des performances des pieux à énergie géothermique par utilisation de la CFD)
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Date
2025
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Abstract
Geothermal energy piles (GEPs), which integrate structural foundation elements with
ground heat exchangers, represent a sustainable and efficient solution for building heating and
cooling by harnessing the relatively stable subsurface soil temperature. This study offers a
comprehensive parametric and multi-physics investigation into both the thermal and thermomechanical
behavior
of
GEPs
under
seasonal
operating
conditions.
It
is
divided
into
three
main
parts,
using advanced numerical simulations within ANSYS Workbench. In the first part, the
transient thermal response of GEPs during summer and winter is analyzed using Computational
Fluid Dynamics (CFD) in ANSYS Fluent, assessing the impact of varying flow regimes
(Reynolds numbers from 500 to 2000) on outlet temperature and heat transfer rate. Results
indicate that higher flow velocities increase the heat transfer rate but reduce thermal exchange
efficiency due to shorter fluid residence time. The second part focuses on parametric CFD
optimization of key geometric parameters, pile diameter, heat exchanger diameter, pipe-toconcrete
spacing,
and
pipe
angular
orientation.
Supported
by
analytical
modeling,
simulations
identify
the optimal configuration (400 mm pile diameter, 26 mm pipe diameter, 20 mm
spacing, and 30° orientation), yielding improved thermal performance in both heating and
cooling scenarios. Strong correlation between CFD and analytical results confirms the model’s
validity. The third part involves a coupled thermo-mechanical analysis, evaluating the structural
response of GEPs with circular, square, and triangular U-shaped pipe geometries through twoway
coupling between ANSYS Fluent (thermal input) and Static Structural (mechanical
analysis). Findings reveal that pipe geometry significantly influences both heat transfer and
stress distribution. The triangular configuration demonstrates superior cooling efficiency due to
enhanced internal convection but introduces localized stress concentrations that require
structural consideration. Seasonal thermal loads induce geometry-dependent axial and shear
stress patterns, with maximum displacement consistently occurring at the pile base. Overall,