Énergétiquehttp://dspace.univ-tissemsilt.dz/handle/123456789/30142026-05-25T01:25:18Z2026-05-25T01:25:18ZStudy and simulation of complex thermal-hydraulic phenomena in nuclear reactors using the CFD method: Validation of models by reference benchmark experimental dataAYAD, FOUADhttp://dspace.univ-tissemsilt.dz/handle/123456789/30382025-05-26T12:57:04Z2023-01-01T00:00:00ZStudy and simulation of complex thermal-hydraulic phenomena in nuclear reactors using the CFD method: Validation of models by reference benchmark experimental data
AYAD, FOUAD
The current work documents the Computational Fluid Dynamics (CFD) code validation
activity, carried out at the Nuclear Research Center of Birine relevant to Atomic Energy
Commission of Algeria as part of International Atomic Energy Agency (IAEA) Coordinated
Research Project (CRP): Application of CFD Codes for Nuclear Power Plant Design to assess
the current capabilities of these codes and to contribute to technological progress in their
verification and validation. A set of ROCOM CFD-grade test data of Pressurized Thermal
Shock test (PTS) specifications was made available in the framework of this (CRP) by
Helmholtz Zentrum Dresden-Rossendorf, (HZDR) Germany, to perform detailed calculations
of the proposed test. The reference point is the injection of relatively cold core cooling water
(ECC), which can induce buoyant stratification. The data obtained from the PTS experiment
were compared with the results of Ansys-CFX calculations in this paper. The unsteady
Reynolds-Averaged Navier-Stokes (URANS) model is used to examine the buoyancy-
influenced flows in the reactor pressure vessel for condition where natural circulation is a
dominant factor. The Shear Stress Transport (SST k-ω) turbulence model is used to take into
account the turbulence effects on the mean flow. Calculation results show a good qualitative
and quantitative agreement with the experiment data.
2023-01-01T00:00:00ZStudy and analysis of the diϱusion absorption refrigeration machine in search of technological solutions to further extend its limitsRahmani, Zakariahttp://dspace.univ-tissemsilt.dz/handle/123456789/30362025-05-26T12:43:45Z2024-01-01T00:00:00ZStudy and analysis of the diϱusion absorption refrigeration machine in search of technological solutions to further extend its limits
Rahmani, Zakaria
Diϱusion absorption refrigeration (DAR) is a reliable cooling system, especially in
conditions where conventional refrigeration systems are not convenient. Since it operates
without any mechanical components, the DAR refrigerator is silent, making it suitable for
quiet environments. The evaporation process in DAR systems notably aϱects their operation.
However, few studies have focused on this speciϧc issue. In this work, a numerical
investigation was conducted using CONVERGE CFD software and the RANS approach to
analyze the evaporator region of a DAR system operating with an ammonia/water mixture
and using hydrogen or helium as an inert gas. The aim was to validate an accurate CFD model
by analyzing the ϩow behavior and thermal parameters within the evaporator for an
ammonia/hydrogen gas mixture ϧrst, and then to examine the use of helium instead of
hydrogen as the pressure equalizer. For this purpose, an experimental bench was prepared.
The computational results showed high agreement with the experimental data, with slight
deviations often remaining under 3%. The study also investigated the eϱect of ammonia
presence at the hydrogen inlet, speciϧcally at 5% and 10% ratios. The results demonstrated
that the average temperature deviation was less than 1% when using 5% ammonia. A total
pressure of 5 bars was found to be appropriate for the DAR system when helium replaces
hydrogen. This study sheds light on the evaporation process, which is crucial for enhancing
the design and operational eϫciency of DAR systems. The validated numerical model will be
of great use for this purpose.
2024-01-01T00:00:00ZCONTRIBUTION A L’ETUDE DES PERFORMANCES D’UN SYSTEME DE STOCKAGE DE CHALEUR DANS DES MATERIAUX A CHANGEMENT DE PHASECHERIET, Nassirahttp://dspace.univ-tissemsilt.dz/handle/123456789/30152025-05-25T08:30:47Z2025-01-01T00:00:00ZCONTRIBUTION A L’ETUDE DES PERFORMANCES D’UN SYSTEME DE STOCKAGE DE CHALEUR DANS DES MATERIAUX A CHANGEMENT DE PHASE
CHERIET, Nassira
The present numerical study treats the impact of fin shape design on the thermal efficiency of
phase change material (PCM)-based thermal energy storage (TES) unit, focusing on the same surface
area occupied by fins. Comparing two different finned TES units equipped with rectangular and
triangular fin shapes, respectively, showed significant enhancements in PCM melting activity.
Comparative analysis demonstrated that triangular fin shape lowers PCM melting time by 12.64%
for equivalent fin numbers, and by 15.38% for equal fin lengths due to the enlargement of the heat
transfer area provided by the triangular shape. Further examination of fins with triangular shape in
terms of spacing and length, under fixed thickness and size parameters, revealed significant reduction
in melting time with increasing fins length. Notably, 50.75% decrease in melting time was achieved
by decreasing the number of fins to 20 while increasing fin length to 10 mm. Moreover, maintaining
a heat transfer fluid (HTF) temperature 20 K higher than the melting PCM temperature maximizes
TES thermal efficiency. These outcomes emphasize the importance of optimizing fin shape design
for enhancing heat transfer without affecting the energy storage capacity of TES systems, with
potential applications in building thermal management.
2025-01-01T00:00:00Z