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    CFD SIMULATION AND OPTIMIZATION OF HEAT TRANSFER ENHANCEMENT IN HEV STATIC MIXERS WITH ROTATED ANGLES FOR TURBULENT FLOWS
    (Vinca Inst Nuclear Sci, 2023) Kaid, Noureddine; Akgul, Ali; Alkhafaji, Mohammed Ayad; Mohsen, Karrar S.; Asad, Jihad; Jarrar, Rabab; Menni, Younes
    Static mixers are becoming increasingly popular because they are energyefficient, cost-effective, and easy to maintain. Mixing is an essential unit operation in many chemical industries. In this study, a modified high efficiency vortex static mixer was used to examine laminar flows in a rectangular duct. To encourage fluid rotation and improve mixing with heat transfer, the modified high efficiency vortex set was rotated by angles of 0 degrees, 5 degrees, 10 degrees, 20 degrees, 25 degrees, and 30 degrees. The Reynolds number varied from 3000 to 8000. The outcomes demonstrated that the performance of the mixing was significantly impacted by the modified high efficiency vortex set. The highest mixing efficiency was achieved with a rotation angle between 15 degrees and 20 degrees. Furthermore, the rotations reduced pressure loss in the system and enhanced heat transfer performance, by creating vortices. These results show how modified high efficiency vortex static mixers can improve mixing and heat transfer efficiency in turbulent flows, with prospective utilization across diverse chemical sectors.
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    COMPARATIVE ANALYSIS OF SOLAR AIR CHANNELS, z-SHAPED OBSTACLES ADDED TO IMPROVE FLOW STRUCTURE
    (Vinca Inst Nuclear Sci, 2022) Afif, Benameur; Salmi, Mohamed; Akgul, Ali; Jarrar, Rabab; Asad, Jihad; Menni, Younes
    This paper's numerical study, which applies the finite volume approach and SIMPLE algorithm, aims to dynamically analyze airflow through a channel with Z-obstacles. Three distinct models were used to place the Z-barriers inside the channel. According to Demartini et al.'s model (2004) and as depicted in example A from the present analysis, the first Z-barrier (fin) is attached to the top wall (heated) and the second (baffle) to the bottom wall (insulated). The Z-barriers, on the other hand, were positioned in the second model on the same wall (in-line arrangement), either on the top surface (two fins in example B) or on the bottom wall (two baffles in example C). With the help of these studies, fluid dynamics in solar air collectors with barriers will be better understood and designed.
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    IMPROVEMENT OF THE PERFORMANCE OF SMALL-SIZED CAVITATING VENTURIS BY INSERTING OBSTACLES
    (Vinca Inst Nuclear Sci, 2023) Rostane, Brahim; Aliane, Khaled; Brayyich, Mohammed; Zearah, Sajad A.; Akgul, Ali; Abdullaeva, Barno; Menni, Younes
    Cavitating Venturis are simple apparatus used as a flow meter over a broad range of mass-flow rates. The main objective of this work is to introduce obstacles in small-sized cavitating Venturis in order to increase their capacity by raising the critical pressure, i.e. widens the phase of the cavitating mode. Four configurations have been tested depending on the location of these obstacles. This study focused on investigating the numerical performance of cavitating Venturis with different downstream pressures by employing the k-. SST turbulence model and the Rayleigh-Plesset equation for modeling cavitation. The governing equations were solved using the finite volume method, employing the Rhie and Chow pressure-velocity coupling scheme. The results showed the void fraction and streamlines contours obtained on the symmetry plane. The mass-flow ratio was presented for all configurations and different pressure ratios. The study showed that the cavitating Venturis equipped with obstacles extend the phase of choked mode from 10.71% to 21.42% and that the best configuration correspond to the case where the obstacles are placed in the converging section.
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    NUMERICAL INVESTIGATION OF THE INTERACTION BETWEEN THE ROUGHNESS AND THE TRIANGULAR OBSTRUCTIONS IN A RECTANGULAR CHANNEL
    (Vinca Inst Nuclear Sci, 2023) Sari Hassoun, Zakaria; Aliane, Khaled; Akgul, Ali; Jarrar, Rabab; Asad, Jihad; Menni, Younes; Ahmad, Hijaz
    The study is conducted around a heat exchanger, its channel is horizontal rect-angular, its upper wall is isothermal, while its lower wall is thermally insulated, containing extended surfaces in the form of triangular obstacles attached in a stag-gered manner periodically. Four models of the channel with various roughnesses were compared in this study. Square, triangular Type 1, triangular Type 2, and triangular Type 3 roughnesses, which are positioned on the hot top part of the channel (absorber), downstream of the last obstacle, are examined to promote heat transfer between the absorber and the heat transfer fluid. The case of triangular roughness (Type 3) is the optimal case in terms of improved heat transfer. More-over, it shows a significant decrease in terms of friction values.
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    THREE-DIMENSIONAL ASSESSMENT OF THERMAL-HYDRAULIC BEHAVIOUR IN HEAT EXCHANGERS FITTED BY WAVY ANNULAR FINS
    (Vinca Inst Nuclear Sci, 2022) Djeffal, Fares; Tahrour, Farouk; Bordja, Lyes; Akgul, Ali; Jarrar, Rabab; Asad, Jihad; Menni, Younes
    In this study, numerical studies to clarify the influence of wave number and amplitude on thermal-flow behavior of wavy annular finned-and-tube heat exchangers are described. For a range of Reynolds number from 4400 to 14300, the influence of wave amplitude, 1.5 <= A <= 4.5 mm, and wave numbers, 2 <= N-w <= 6, on forced convection heat transfer was examined. It was revealed that the wave amplitude and number have an impact on the heat flux, Colburn factor, and friction factor. The wavy annular-fins with a 3 mm amplitude and N-w = 4 waves obtained the highest values at all Reynolds numbers in terms of the overall performance criterion (j/f(1/3)).
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    TURBULENT FLOWS AROUND RECTANGULAR AND TRIANGULAR TURBULATORS IN BAFFLED CHANNELS A Computational Analysis
    (Vinca Inst Nuclear Sci, 2022) Salmi, Mohamed; Afif, Benameur; Akgul, Ali; Jarrar, Rabab; Shanak, Hussein; Menni, Younes; Ahmad, Hijaz
    The present paper highlights a computational analysis of air-flows around rectangular and triangular turbulators inside baffled heat exchanger channels in order to improve heat transfer between the fluid and their heated areas. The dynamic and thermal fields as well as fluid temperature curves at the outlet of the exchanger are studied. The computational study is conducted by utilizing SIMPLE algorithm with FLUENT system based on the finite volumes. The analysis clearly demonstrated the presence of highly turbulent flows and the appearance of many vortices in various regions of the exchanger. By comparing the different heat exchangers, it was found that the baffled channel fitted with rectangular turbulators produced high fluid temperature values at the channel outlet, indicating the significance of using this rectangular form of turbulators in order to enhance the interaction between the hot spaces and the used fluid.