Browsing by Author "Rachedi, Kamel"

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Analysis of natural convection heat transfer in a rectangular cavity with discrete heat flux: Implications for building thermal management using artificial neural networks
(Taylor and Francis Ltd., 2024) Rachedi, Kamel; Ragueb, Haroun; Behnous, Dounya; Tahiri, Antar; Manser, Belkacem; Ait Chikh, Mohamed Abdessamed
This study numerically investigates free convection within a rectangular air-filled cavity, simulating real-romm conditions. The top, bottom, and one sidewall are at constant temperatures, while the opposite sidewall has a constant discrete heat flux, akin to heater appliances. The impact of heating intensity, length, and position on temperature distribution is explored. Artificial Neural Networks (ANN) are utilized to correlate the average Nusselt number, providing a model for engineering applications in building thermal management. The dataset includes 2436 simulation runs with varying parameter: Rayleigh number (103 to 106), aspect ratio (0.5 to 2), heating surface length (0.1 to 1), and elevation (0.05 to 0.95). Results show increased Rayleigh numbers intensify the stream function and promote uniform temperature distribution. The elevation of the heating surface influences temperature distribution, with placement closer to the floor or ceiling optimizing heat transfer. ANN modeling predicts the average Nusselt number with high precision (±3%).
Contribution à l'étude des paliers de moteurs thermiques en régime transitoire
(1994) Rachedi, Kamel
Etude numérique des effets d'évaporation et de thermo-capillarité sur la convection naturelle aux sein des réservoirs cryogéniques
(Université M'Hamed Bougara : Faculté de Technologie, 2022) Rachedi, Kamel; Nour, Abdelkader(Directeur de thèse)
La quantification de l'évaporation de surface du gaz liquéfié dans un réservoir cryogénique partiellement rempli est importante à la fois dans le processus de conception et dans le contrôle ultérieur des opérations. Cette thèse se concentre sur les effets des pertes de chaleur externes sur l'évaporation de surface et la convection naturelle d'un gaz liquéfié contenu dans un réservoir cylindrique cryogénique en tenant compte de la thermo-capillarité (de l’effet de Marangoni). Le débit massique d'évaporation est supposé négligeable ; cependant, la chaleur absorbée pendant le processus est prise en compte et définie selon le modèle de Hashemi-Wesson. Le problème physique a été formulé sous forme adimensionnelle, puis résolu numériquement en utilisant la procédure des volumes finis. Les pertes de chaleur externe et le flux de chaleur d'évaporation de surface ont été quantifiés au moyen du nombre de Nusselt. Plusieurs simulations ont été réalisées en fonction du nombre de Rayleigh (10+4 ≤ Ra ≤ 10+5), du nombre de Marangoni (0 ≤ Ma ≤ 2000) et du rapport d'aspect de la cavité (0,5 ≤ AR ≤ 2). Les résultats ont montré que lorsque Ra augmente, le taux de transfert de chaleur de la paroi vers le fluide augmente ainsi que le taux d'évaporation. Une grande valeur de Ma peut réduire le flux de chaleur d'évaporation de surface jusqu'à 5% en raison du flux thermo-capillaire. Un niveau de remplissage élevé réduit l'évaporation de surface jusqu'à 42 % pour AR = 0,5, tandis qu'un faible niveau de remplissage la favorise jusqu'à 46 % pour AR = 1,5, par rapport à AR = 1. Les nombres de Nusselt de la surface libre et de la paroi latérale dépendent fortement de Ra, Ma et AR, et les deux ont été corrélés dans des formules simples avec une tolérance technique de ±5%.
Irreversibilities and heat transfer in magnetohydrodynamic microchannel flow under differential heating
(Elsevier, 2023) Ragueb, Haroun; Tahiri, Antar; Behnous, Dounya; Manser, Belkacem; Rachedi, Kamel; Mansouri, Kacem
This study investigates heat transfer and entropy generation in a microchannel subjected to differential heating, viscous dissipation, and Joule heating within a magnetohydrodynamic (MHD) fluid flow. A finite difference method with a fully implicit scheme is employed to accurately model temperature distribution and entropy generation. A comparison between the average Nusselt numbers (Nu) calculated using the classical method and the Bennett Formula reveals a notable discrepancy, particularly at the entry length (up to 14%). It has been found that when one plate is heated while the other is cooled and the Hartmann number (Ha) is low, the average Nu for both plates converges to 2. However, at high Ha values considering viscous dissipation and Joule heating, there is an 8% deviation between the Nu values of the two plates, with the higher Nu found on the cooling plate. Sensitivity analyses explore the impact of control parameters on entropy generation, emphasizing the significance of η as a key parameter that reflects the system's resistance to entropy generation. Increasing η from 0.1 to 0.5 results in a 32% reduction in entropy generation. In particular, for microchannels, substantial η high values imply reduced entropy generation, highlighting their efficiency in heat transfer.
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%.