Publications Internationales

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    A Numerical Study on the Effect of Radiation on Natural Convection in a Two-Square Duct Annuli Filled with a Semi-Transparent Fluid
    (IJME, 2023) Bouanani, Mohammed; Benbrik, Abderrahmane; Soualmi, Rabiaa; Cherifi, Mohammed
    In the present study, a numerical investigation of natural convection and volumetric radiation interactions has been analysed in an annulus between two isothermal concentric square ducts filled with a semi-transparent medium. Two-dimensional solution was obtained using a discrete ordinates method based on a combined finite volume-immersed boundary method. The fluid is assumed to be gray absorbing-emitting and non-scattering and all walls are gray, diffuse and opaque. The Rayleigh number is fixed to 106 , and a study of the effect of three optical thicknesses τ=0.2-1-5 is performed on the thermal and dynamic fields and consequently on the heat transfer rate has been examined. A pure natural convection case has been shown for a comparative study. It is found that the radiation has a large influence on the flow and surface averaged Nusselt number and especially for high Rayleigh numbers.
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    Numerical investigation of surface evaporation and thermocapillarity effects on natural convection within a contained fluid in cryogenic tank
    (Elsevier, 2022) Rachedi, Kamel; Ragueb, Haroun; Boussaid, Mohammed
    Quantification of liquefied gas surface evaporation in partially filled cryogenic tank is important in both design process and operations control later. This paper focuses on effects of external heat leaks on the surface evaporation and the natural convection of a liquefied gas contained in cryogenic cylindrical tank with consideration of thermocapillarity. The evaporation mass flow rate is assumed negligible; however, the absorbed heat during the process is considered and defined according the Hashemi-Wesson model. The physical problem was formulated in dimensionless form, and then solved numerically using finite volume procedure. The external heat leaks and the surface evaporation heat flux were quantified by means of Nusselt number. Several simulations have been conducted based on the Rayleigh number (10+4 ≤ Ra ≤ 10+5), Marangoni number (0 ≤ Ma ≤ 2000) and the cavity aspect ratio (0.5 ≤ AR ≤ 2). Results showed that as Ra increases, the heat transfer rate from wall to fluid increases as well as the evaporation rate. Large value of Ma can reduce the surface evaporation heat flux up to 5% due to thermocapillary flow. High filling level reduces surface evaporation up to 42% for AR = 0.5, whereas low filling level promotes it to 46% for AR = 1.5, with respect to AR = 1. Free surface and side wall Nusselt numbers are strongly dependent on Ra, Ma and AR, and both have been correlated in simple formulas within engineering tolerance ±5%.
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    Numerical investigation of a novel tower solar chimney concept
    (elsevier, 2020) Kebabsa, Hakim; Lounici, Mohand Said; Daimallah, Ahmed
    Divergent tower solar chimney power plant is an attractive upgrading of the solar chimney system. However, boundary layer separation (BLS) phenomenon can appear when the divergence angle exceeds a specific value, inducing system performance degradation. The present paper proposes a novel solar chimney tower concept, named annular tower solar chimney power plant (ATSCPP), to deal with BLS phenomenon and improve the divergent tower system. Accordingly, the influence of exterior tower radius (ETR) and interior tower radius (ITR) were evaluated, using the Spanish prototype. Simulations were carried out using a 3D model. The results indicate that flow behavior, power output and thermal efficiency shows a strong sensitivity to the change of both ETR and ITR. The best case is obtained when (ETR = 17 m, ITR = 13 m). The new solar chimney tower concept allowed a significant increase in the driving potential. The total improvement in power output reaches 32%. An improved concept which allows a compromise between induced cost and performance gain of the system is also proposed.
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    A hybrid scheme of single relaxation time lattice Boltzmann and finite volume methods coupled with discrete ordinates method for combined natural convection and volumetric radiation in an enclosure
    (2020) Soualmi, R; Benbrik, A.; Lemonnier, D.; Cherifi, M.; Bouanani, Mohammed
    This paper is focused on the application of hybrid Single relaxation time lattice Boltzmann and finite volume methods in conjunction with discrete ordinates method to simulate coupled natural convection and volumetric radiation in differentially heated enclosure, filled with an absorbing, emitting and non - scattering gray medium. In this work, the velocity and temperature fields are calculated using lattice Boltzmann and finite volume methods respectively, whereas the radiative term is computed by the discrete ordinates method. This study is carried out for Pr = 0.71 , a Rayleigh n umber range of 10 3 ≤ Ra ≤ 10 6 , an optical thickness with values 0 ≤ τ ≤ 100, a Planck number ranging in 0.001≤ Pl ≤ 100 and an aspect ratio varying between 0.5 ≤ Ar ≤ 2. Results are presented in terms of streamlines, isotherms, velocity profiles and averag e Nusselt number. Based on the obtained results, it can be concluded that the presence of volumetric radiation is noteworthy. Its effect, as a function of Rayleigh number and the radiative properties, yields significant changes on the behavior of streamlin es and isotherms. In the taller enclosure, the increase of average total Nusselt number with increasing Rayleigh number is less significant than that in the case of the shallow enclosure.
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    Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink
    (2013) Ahmanache, Abdennacer; Zeraibi, Noureddine
    Numerical study of natural convection heat transfer and fluid flow in cylindrical cavity with hot walls and cold sink is conducted. Calculations are performed in terms of the cavity aspect ratio, the heat exchanger length, and the thermo physical properties expressed via the Prandtl and the Rayleigh numbers. Results are presented in the form of isotherms, streamlines, average Nusselt number, and average bulk temperature for a range of Rayleigh number up to 106. It is observed that Rayleigh number and heat exchanger length influences fluid flow and heat transfer, whereas the cavity aspect ratio has no significant effects
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    Laminar natural convection flow in cylindrical cavity application to the storage of LNG
    (Elsevier, 2010) Khelifi-Touhami, M. S.; Benbrik, Abderahmane; Lemonnier, D.; Blay, D.
    The numerical simulation of laminar natural convection in a vertical cylindrical cavity is proposed. The cavity is insulated at the bottom, laterally heated at a uniform heat flux and cooled by a non uniform evaporative heat flux at the top surface obeying the Hashemi–Wesson's law. The equations of mass conservation, momentum and energy are resolved with finite-volume method in fully implicit form. The influence of the characteristic parameters (103≤Ra≤105, Pr=2, 1/3≤Al≤1) on the thermal and dynamic behavior at steady state is analysed and discussed. In particular, the study describes the solutions at Ra=105 and Pr=2 for various aspect ratios. The evaporative heat flux is computed for all the parameters and it is found that its maximum is localized near the lateral wall whereas its minimum is at the free surface center