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Öğe 3D numerical study and comparison of thermal-flow performance of various annular finned-tube designs(Shanghai Jiaotong University, 2022) Tahrour, Farouk; Ahmad, Hijaz; Ameur, Houari; Saeed, Tareq; Abu-Zinadah, Hanaa; Menni, YounesWith the increase of heat transfer problems in marine vehicles and submerged power stations in oceans, the search for an efficient finned-tube heat exchanger has become particularly important. The purpose of the present investigation is to analyze and compare the thermal exchange and flow characteristics between five different fin designs, namely: a concentric circular finned-tube (CCFT), an eccentric circular finned-tube (ECFT), a perforated circular finned-tube (PCFT), a serrated circular finned-tube (SCFT), and a star-shaped finned-tube (S-SFT). The fin design and spacing impact on the thermal-flow performance of a heat exchanger was computed at Reynolds numbers varying from 4,300 to 15,000. From the numerical results, and when the fin spacing has been changed from 2 to 7 mm, an enhancement in the Colburn factor and a reduction in the friction factor and fin performances were observed for all cases under study. Three criteria were checked to select the most efficient fin design: the performance evaluation criterion PEC, the global performance criterion GPC, and the mass global performance criterionMG. Whatever the value of Reynolds number, the conventional CCFT provided the lowest performance evaluation criterion PEC, while the SCFT gave the highest amount of PEC. The most significant value of GPC was reached with the ECFT; however, GPC remained almost the same for CCFT, PCFT, SCFT, and S-SFT. In terms of the mass global performance criterion, the S-SFT provides the highest MGpcas compared with the full fins of CCFT (41–73% higher) and ECFT (29–54% higher). Thus, the heat exchanger with S-SFT is recommended to be used in the cooling of offshore energy systems.Öğe Combination of the Parallel/Counter Flows Nanofluid Techniques to Improve the Performances of Double-Tube Thermal Exchangers(Springer Science and Business Media Deutschland GmbH, 2022) Lahmer, Djelloul; Benamara, Nabil; Ahmad, Hijaz; Ameur, Houari; Boulenouar, AbdelkaderThe Al2O3 (aluminum oxide)-water nanofluid is utilized in this study to improve the overall performance of a parallel flow thermal exchanger with two coaxial tubes. Numerically, the impacts of hot fluid flow, flow direction, and nanoparticle volume fraction on thermal fields, Nusselt number, and device performance are investigated. The hot fluid’s Reynolds number ranges between 3054 and 7636, whereas the cold fluid’s is set at 3000. The two-equation k-? SST turbulence model is used to accomplish the numerical simulation. The validation of numerical findings reveals a satisfactory match with the experimental reported values. The obtained results reveal positive effects of increasing fluid flow rates and nanoparticles concentration on the performance of the double-tube thermal device and Nusselt number, especially in the counter flows configuration.Öğe Different scenarios to enhance thermal comfort by renewable-ecological techniques in hot dry environment(Elsevier Ltd, 2022) Sakhri, Nasreddine; Ahmad, Hijaz; Shatanawi, Wasfi; Menni, Younes; Ameur, Houari; Botmart, ThongchaiRecently, building thermal studies have focused more and more on providing the right living conditions inside buildings, houses, schools, hospitals, etc., especially in hot-dry regions to defeat energy consumption dilemmas generally coming from fossil fuels source by renewable energy. In this paper, a field of experiments in actual conditions is conducted to investigate the influence of external parameters on the occupant's thermal comfort inside a typical dry region house. The obtained results are projected directly on the psychometric chart to position the real thermal comfort current situation. The results confirm the direct influence and indirect influence of external climatic conditions (temperature and humidity, respectively) on internal comfort. Two scenarios with renewable techniques are investigated experimentally based on the obtained results. An earth-to-air heat exchanger (EAHE) and solar chimney (SC) are connected separately to a similar building, and parameters affecting thermal comfort are discussed. The results show that both techniques improve thermal comfort inside the structure with efficiently saving energy. Renewable energy can enhance thermal comfort with significant power- and cost-saving in hot-dry regions.Öğe Optimal backstepping-fopıd controller design for wheeled mobile robot(International Information and Engineering Technology Association, 2022) Euldji, Rafik; Batel, Noureddine; Rebhi, Redha; Kaid, Noureddine; Tearnbucha, Chutarat; Sudsutad, Weerawat; Lorenzini, Giulio; Ahmad, Hijaz; Ameur, Houari; Menni, YounesA design of an optimal backstepping fractional order proportional integral derivative (FOPID) controller for handling the trajectory tracking problem of wheeled mobile robots (WMR) is examined in this study. Tuning parameters is a challenging task, to overcome this issue a hybrid meta-heuristic optimization algorithm has been utilized. This evolutionary technique is known as the hybrid whale grey wolf optimizer (HWGO), which benefits from the performances of the two traditional algorithms, the whale optimizer algorithm (WOA) and the grey wolf optimizer (GWO), to obtain the most suitable solution. The efficiency of the HWGO algorithm is compared against those of the original algorithms WOA, GWO, the particle swarm optimizer (PSO), and the hybrid particle swarm grey wolf optimizer (HPSOGWO). The simulation results in MATLAB–Simulink environment revealed the highest efficiency of the suggested HWGO technique compared to the other methods in terms of settling and rise time, overshoot, as well as steady-state error. Finally, a star trajectory is made to illustrate the capability of the mentioned controllerÖğe Study of the effect of ACL anode catalytic layer porosity on the efficiency of a direct methanol fuel cell(International Information and Engineering Technology Association, 2022) Medkour, Mihoub; Kaid, Noureddine; Ameur, Houari; Tearnbucha, Chutarat; Sudsutad, Weerawat; Lorenzini, Giulio; Ahmad, Hijaz; Menni, YounesThe current work investigates the efficiency of a Direct Methanol Fuel Cell (DMFC) by using COMSOL. The set-up model takes into consideration the electrochemical kinetics and chemical reactions. The anode catalyst layers are a main element in the PEM fuel cell; their porosity significantly affects the fuel cell efficiency. We focus on the impact of catalytic layers porosity on the battery efficiency. As claimed by the results, the porosity of catalytic layer greatly affects the performance of the battery. In addition, better output performance of µDMFC may be obtained when the catalytic layer porosity is chosen as ?ACL=0.009-0.1. The distributions of methanol, carbon dioxide, water, oxygen, polarization, and the current density are plotted to highlight the impact of porosity on the global performances.
