Publications Internationales
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Item Heat transfer investigation near the onset of nucleate boiling on a single artificial nucleate site: Influence of the wall orientation(Elsevier, 2025) Kharkwal, Himanshi; Zamoum, Mohammed; Barthès, Magali; Lanzetta, François; Combeau, Hervé; Tadrist, LounèsStudying the transition from natural convection to nucleate boiling is crucial for both the efficiency and safety of thermal systems. Present study aims to investigate the heat transfer characteristics at the transition of the natural convection and the nucleate boiling regimes. An experimental setup has been designed and implemented to perform experiments with FC72 on flat heating wall that can be inclined from 0° to 180°. This was possible thanks to the development of a boiling meter mounted on a pivoting axis. This work provides new insights into local wall heat transfer behavior and nucleation dynamics under varying gravitational configurations, contributing novel data on single-site boiling physics. Intermittent behavior with typical heat transfer cycles is evidenced. Two criteria are found to control this intermittency; the wall temperature threshold for bubble nucleation and the heat flux threshold needed to sustain bubble emission. A single isolated bubble leads to a variation in the transfer coefficient. Changing inclination from 0° to 180° increases the heat transfer coefficient in the bubble emission regime from 263 to 489 W/(m2 °C) but decreases it in natural convection from 240 to 176 W/(m2 °C)Item 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, MohammedIn 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.Item 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, MohammedQuantification 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%.Item Natural convection and volumetric radiation interactions in a concentric square annulus(American Institute of Aeronautics and Astronautics, 2021) Bouanani, Mohammed; Benbrik, Abderrahmane; Lemonnier, Denis; Cherifi, Mohammed; Soualmi, RabiaaThis paper focuses on a numerical investigation of steady two-dimensional natural convection and volumetric radiation interactions in a concentric annulus between two square isothermal cylinders. The annulus is filled with a gray absorbing–emitting and non-scattering medium. All the walls are assumed to be gray, diffuse, and opaque. The dynamic and thermal interactions are studied through a finite volume method combined with an immersed boundary technique to handle the square-shaped cylinder, whereas the discrete ordinates method is used to solve the radiative transfer equation. The present study is performed to investigate the effect of volumetric radiation on the flow for a variety of Rayleigh numbers 103 –106, three different optical thicknesses τ 0.2–1–5, a variety of Planck numbers 0.01–1, and three different aspect ratios A 0.2–0.4–0.6. The analysis is based on the dynamic and thermal fields in addition to the heat transfer rate. Results show that radiation affects significantly the flow and temperature distributions for a higher Rayleigh number Ra > 104, depending on the Planck number. The optical thickness and the aspect ratio has an important impact on the Nusselt number and percentage of radiation in heat transferItem Performance evaluation of the combined solar chimney-photovoltaic system in Algeria(Elsevier, 2021) Kebabsa, Hakim; Lounici, Mohand SaidThe demand for solar energy technologies is increasing due to the growing interest in renewable energy. However, these technologies are affected by atmospheric conditions and low overall efficiency. The present study proposes a combined solar chimney-photovoltaic (SC-PV) system to deal with stand-alone system weaknesses. This work evaluates this self-sustainable system's performance and estimates the electric energy generated under the climatic conditions of Algeria using computational fluid dynamics (CFD). The model is first validated using the Spanish prototype experimental data. The simulations show that the proposed system provides several valuable benefits for improving turbine power, solar cell temperature, and PV efficiency. The results indicate the SC in the combined system performs better turbine generated power than a stand-alone system only for an appropriate PV location and width. Using the heat released from the PV to increase the kinetic energy of airflow beneath the collector, the total improvement in turbine power reaches 8.91%. Similar to the optimal PV widths (10 m), other widths, varying from 20 m to 30 m, increase the overall turbine power without degrading SC performance. Using the SC-PV as a cooling method, the solar cell temperature decreases by 12.12% (6.30 °C) compared with cell temperature in the stand-alone system (52 °C). Accordingly, the PV efficiency increases by 3.23% compared with PV efficiency in the stand-alone system (13.18%). The results also indicate the highly intensive solar radiation region (Adrar) has higher monthly turbine power than other areas. The appropriate areas for building such a system will be in the south of the country, where the solar potential is high. In these regions, the SC-PV could contribute to satisfying the electricity demandItem Thermo-hydrodynamic behavior of an innovative solar chimney(Elsevier, 2020) Kebabsa, Hakim; Lounici, Mohand Said; Lebbi, Mohamed; Daimallah, AhmedProduction of electricity through solar systems is a viable alternative, especially for deserted regions where access to electricity is difficult. Solar chimney power plant (SCPP) is one of the promising concepts in renewable energy technology that needs performance enhancement. The objective of this research is to investigate a novel concept, which consists of a horizontal solar chimney power plant with an adapted collector entrance, named sloped collector entrance SCPP (SCESCPP). The effect of the collector entrance shape (slope, sloping distance) is investigated. For each sloping distance, eleven values for the slope are examined. Thus, a numerical investigation is carried out using a 2D axisymmetric chimney model. The model was first validated using experimental results. The influence on air thermo-hydrodynamic behavior of this system is comprehensively studied to enhance the understanding and deepen the analysis in order to improve the performance of the SCPP. The results indicate that the new collector entrance design influences the system performance in a significant manner. It is shown that the best performing configuration (sloping distance of 0.8 and slope of 9.1°) produces an available power reaching 16.36% more than that for zero slope collector roof at same conditions. Moreover, it is found that the optimal slope depends on sloping distance and remains almost the same for different Rayleigh numbersItem Numerical investigation of a novel tower solar chimney concept(elsevier, 2020) Kebabsa, Hakim; Lounici, Mohand Said; Daimallah, AhmedDivergent 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.Item 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, MohammedThis 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.Item Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink(2013) Ahmanache, Abdennacer; Zeraibi, NoureddineNumerical 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 effectsItem 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