http://dspace.univ-tissemsilt.dz/handle/123456789/3014 2026-05-25T02:03:25Z http://dspace.univ-tissemsilt.dz/handle/123456789/3038 Study 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. 2023-01-01T00:00:00Z http://dspace.univ-tissemsilt.dz/handle/123456789/3036 Study 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. 2024-01-01T00:00:00Z http://dspace.univ-tissemsilt.dz/handle/123456789/3015 CONTRIBUTION 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