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Three-dimensional thermomechanical modeling of geothermal energy piles with U-tube heat exchangers of different cross-sectional shapes
(2025) Samia Boudjaza
This study explores the thermomechanical performance of a three-dimensional (3D) geothermal energy pile (GEP) system, emphasizing the optimization of heat exchanger (HE) geometry to improve both thermal efficiency and structural integrity. As GEPs offer a promising avenue for integrating renewable geothermal energy into building foundations, their design must balance energy performance with mechanical stability. A finite volume-based numerical model is developed, employing second-order spatial and temporal discretization and the Pressure-Implicit with Splitting of Operators (PISO) algorithm for pressure–velocity coupling. A segregated solution strategy with under-relaxation is used to ensure numerical stability and convergence. The model simulates a concrete-encased U-shaped HE embedded in clayey soil, with three cross-sectional geometries: circular, square, and triangular. Simulation outcomes are validated against analytical predictions and benchmarked with experimental and numerical data from the literature. Among the tested geometries, the triangular HE demonstrates superior thermal and structural performance under both mechanical and thermomechanical loading conditions. Compared to the circular configuration, the triangular U-pipe enhances cooling efficiency by reducing outlet temperature by 1.2 % and increasing heat extraction by 8.6 %. In heating mode, it raises the outlet temperature by 0.6 % but lowers the heat transfer rate by 4.8 %, underscoring the need for season-specific or hybrid designs. Thermomechanically, the triangular configuration exhibits the highest axial compressive stress in summer, increasing by 6.36 %, while in winter, it shows a 4.75
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Study of geothermal energy piles performances using CFD (Etude des performances des pieux à énergie géothermique par utilisation de la CFD)
(2025) BOUDJ AZA samia
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,
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First Term Exam in Academic Writing Level: Master One
(UNIVERSITY OF ABBES LAGHROUR-KHENCHELA, 2025) Kacha ASMA
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Methodology in Molecular and Cellular Biology
(Abbes Laghrour University- Khenchela-, 2025) Lamia BENREDJEM
This handout is designated for Master's students in Applied Microbiology. It aims to provide students with in-depth knowledge of the experimental approach, using the concepts and techniques of modern biology: biochemistry, cell biology, molecular biology, immunology, genetics and microbiology. The aim of this course is twofold: first, to equip the students with the technical skills needed to design and execute experiments, and second, to foster critical thinking about biological systems at the molecular level. By understanding how each technique works and recognizing its strengths and limitations, the students will be prepared to analyze data rigorously and adapt protocols to real‑world challenges.