Soutenance de thèse : Ahmed RAHMA
Titre : Numerical Simulation of Two-Phase Closed Thermosiphon Systems for Cooling and Heat Recovery in Data Centers
Date et heure : Jeudi 1er Octobre 2026 à 14h00
Lieu : Amphi Alain Beretz, campus d'esplanade
Lien visio : https://visio.numerique.gouv.fr/dnp-geay-vco
La soutenance est ouvert à tous et aura lieu en anglais.
Jury
- Prof. Yannick Hoarau — University of Strasbourg — Jury President
- Dr. Denis Funfschilling — University of Strasbourg — Thesis Director
- Prof. Abdellah Ghenaim — INSA Strasbourg — Thesis Co-director
- Dr. Abderahmane Marouf — University of Strasbourg — Thesis Co-supervisor
- Prof. Eric Goncalves — ISAE-ENSMA — Rapporteur
- Prof. Nicolas Rimbert — University of Lorraine — Rapporteur
- Dr. Cécile Lemaitre — University of Lorraine — Examiner
- Dr. Rainier Hreiz — University of Lorraine — Examiner
Abstract:
The rapid growth of artificial intelligence, cloud computing, and digital services has significantly increased the cooling and energy demands of data centers. Two-Phase Closed Thermosiphon (TPCT) systems offer a promising passive cooling solution by using natural circulation and phase-change heat transfer without mechanical components. This thesis presents a theoretical and numerical investigation of TPCT systems for data center cooling. The study combines a multi-criteria evaluation of refrigerants with two- and three-dimensional numerical simulations in STAR-CCM+, using the Volume of Fluid method coupled with phase-change modeling. The numerical model was validated under different operating conditions before conducting parametric studies on geometry, heat input, filling ratio, and confinement.
The results identified water as the most suitable working fluid among the refrigerants considered, while the proposed phase-change modeling approach provided improved prediction accuracy. The simulations showed that TPCT flow behavior and thermal performance are strongly influenced by confinement, heat input, and filling ratio. Higher filling ratios generally improved flow stability and thermal conductance, while confinement strongly affected the operating regime and thermal limits of small-diameter TPCTs. Overall, the study provides a validated numerical framework for the analysis and optimization of TPCT systems and demonstrates their potential for efficient passive cooling in data center applications.
