Browsing by Author "Daimallah, Ahmed"

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3D-Numerical simulation of the effect of radial gap on the stability of taylor-couette flow
(2015) Daimallah, Ahmed; Lebbi, M.; Bouabdallah, A.
We study numerically the effect of the radial gap on the onset of Taylor vortices in Taylor-Couette flow system. The inner cylinder is rotating and the outer is at rest. We interested in the appearance of Taylor vortices for a varied radius of the inner and the outer cylinders while making sure to keep a constant annulus between the cylinders in the aim to examine the influence of centrifugal force on the stability of the flow. The obtained results indicate that the onset of Taylor vortices is delayed when the radial gap is increasing.
Corrigendum to “Thermo-hydrodynamic behavior of an innovative solar chimney” [Renew. Energy 145 (2020) 2074–2090]
(Elsevier, 2020) Kebabsa, Hakim; Lounici, Mohand Said; Lebbi, Mohamed; Daimallah, Ahmed
Effect of Thermal Collector Height and Radius on Hydrodynamic Flow Control in Small Solar Chimney
(Penerbit Akademia Baru, 2020) Daimallah, Ahmed; Lebbi, Mohamed; Lounici, Mohand Said; Boutina, Lyes
Solar chimney power plant (SCPP) is one of the promising technologies for solar energy utilization. It is an interesting system especially in large isolated desert areas due to its basic techniques and low operating costs. In this study, we investigate numerically the collector geometrical parameters effect on the hydrodynamic flow control in a solar chimney. The finite volume method and the SIMPLE algorithm have been used to solve the turbulent flow equations and energy equation. A standard K-ε model is used. The influence of the collector height (0.05m≤Hc≤0.5m) and the collector radius (2.5m≤Rc≤15m) on the flow behavior has been numerically analyzed. The obtained results indicate that increasing the collector height and collector radius affect considerablythe flow behavior and the SCPP performance. The mass flow rate is enhanced by about 27 %, for Rc=12.5m and Hc = 0.25m.
Mass flow rate enhancement inside a solar chimney power plant
(Toronto Metropolitan University, 2023) Daimallah, Ahmed; Lebbi, Mohamed; Lounici, Mohand Said
The Solar chimney power plant is a system that converts solar energy to mechanical energy and then to electrical energy. The present work aims to conduct numerical investigation on the influence of the radius ratio Rt* = Rtout/Rtinlet and the height of the tower-chimney, on the flow behavior inside the SCPP of Manzanares. A 2D axi-symetric turbulent model is adopted. The momentum and energy equations are solved using the finite volume method and the simple algorithm. Results show that velocity and mass flow rate inside the SCPP are affected by the radius ratio Rt*, the height of tower-chimney Ht* and intensity radiation Q. We obtain an enhancement of mass flow rate by about 58.23% for the divergence of the tower-chimney.
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.
Onset of instabilities in Taylor-Dean flow of yield-stress fluid
(2009) Daimallah, Ahmed; Bouabdallah, Ahcene; Nsom, Blaise; Adnane, M.; Alemany, Antoine
Thermo-hydrodynamic behavior of an innovative solar chimney
(Elsevier, 2020) Kebabsa, Hakim; Lounici, Mohand Said; Lebbi, Mohamed; Daimallah, Ahmed
Production 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 numbers