Browsing by Author "Aich W."
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Item Jet impingement cooling of a rotating hot circular cylinder with hybrid nanofluid under multiple magnetic field effects(MDPI, 2021) Ayadi B.; Selimefendigil F.; Alresheedi F.; Kolsi L.; Aich W.; Said L.B.The cooling performance of jet impinging hybrid nanofluid on a rotating hot circular cylinder was numerically assessed under the effects of multiple magnetic fields via finite element method. The numerical study was conducted for different values of Reynolds number (100 ≤ Re ≤ 300), rotational Reynolds number (0 ≤ Rew ≤ 800), lower and upper domain magnetic field strength (0 ≤ Ha ≤ 20), size of the rotating cylinder (2 w ≤ r ≤ 6 w) and distance between the jets (6 w ≤ H ≤ 16 w). In the presence of rotation at the highest speed, the Nu value was increased by about 5% when Re was increased from Re = 100 to Re = 300. This value was 48.5% for the configuration with the motionless cylinder. However, the rotations of the cylinder resulted in significant heat transfer enhancements in the absence or presence of magnetic field effects in the upper domain. At Ha1 = 0, the average Nu rose by about 175%, and the value was 249% at Ha1 = 20 when cases with the cylinder rotating at the highest speed were compared to the motionless cylinder case. When magnetic field strengths of the upper and lower domains are reduced, the average Nu decreases. The size of the cylinder is influential on the flow dynamics and heat transfer when the cylinder is rotating. An optimum value of the distance between the jets was obtained at H = 14 w, where the Nu value was highest for the rotating cylinder case. A modal analysis of the heat transfer dynamics was performed with the POD technique. As diverse applications of energy system technologies with impinging jets are available, considering the rotations of the cooled surface under the combined effects of using magnetic field and nanoparticle loading in heat transfer fluid is a novel contribution. The outcomes of the present work will be helpful in the initial design and optimization studies in applications from electronic cooling to convective drying, solar power and many other systems. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Item Impacts of double rotating cylinders on the forced convection of hybrid nanofluid in a bifurcating channel with partly porous layers(Elsevier Ltd, 2021) Kolsi L.; Selimefendigil F.; Öztop H.F.; Hassen W.; Aich W.Impacts of using double rotating cylinders and partly porous layers in the bifurcating channels on the hydro-thermal performance were numerically assessed. Hybrid nanoparticles were used in water and finite element method was selected as the solver. Effects of Reynolds number, rotational speeds of the cylinders and their locations in the bifurcating channels, porous layer sizes and nanoparticle solid volume fractions on the hydro-thermal performance features were explored. The contribution of different hot wall parts was changed with varying Reynolds number and rotational velocity of the cylinders. Depending upon the rotational direction of the cylinders, the vortex occurrence and size at the bifurcations change significantly. Heat transfer considering all hot walls rise with higher rotational speeds in both directions. The amount of improvement in the heat transfer rate becomes 25% and 19% with varying speeds of the cylinders as compared to motionless cylinders. The pressure coefficient reduces with increasing the second cylinder speed in clockwise direction and this is favorable for thermal performance since the heat transfer also increases. The overall impact of the varying horizontal locations of the cylinders on the heat transfer rate is slight. The separated zones at the branching depends on the porous layer sizes. The overall heat transfer behavior becomes opposite when varying the sizes of the porous layers in the horizontal and vertical channels. By using nanoparticles in the base fluid, 35.75% improvement in the heat transfer rate is achieved for vertical wall at Re = 350 while pressure drop coefficient rises by about 8.5%. The overall improvement in the heat transfer rate by using nanofluid is 26%. Owing to diverse use of bifurcating channels in thermal engineering from fuel cells to electronic cooling, the proposed methods of heat transfer enhancement techniques can be considered simultaneously for effective control the thermal performance of those systems. © 2021 The Author(s).Item Thermal and Phase Change Process in a Locally Curved Open Channel Equipped with PCM-PB and Heater during Nanofluid Convection under Magnetic Field(MDPI, 2022) Aich W.; Selimefendigil F.; Alqahtani T.; Algarni S.; Alshehery S.; Kolsi L.Thermal performance and phase-change dynamics in a channel having a cavity equipped with a heater and phase-change material (PCM)-packed bed (PB) region are analyzed during nanoliquid convection under an inclined magnetic field. Curvature of the upper wall above the PCM zone is also considered by using the finite element method. Impacts of curvature of the upper wall (between 0.01H and 0.6H, H-channel height), strength of magnetic field (MGF) (Hartmann number between 0 and 40), height (between 0.1H and 0.4H) and number (between 5 and 17) of heaters on the thermal performance and phase-change dynamics are studied. In the interior and wall near regions of the PCM-PB, the curvature effects become opposite, while phase completion time (tF) rises by about 42% at the highest radius of the curvature. Imposing MGF and increasing its strength has positive impacts on the phase change and thermal performance. There is a reduction in tF by about (Formula presented.) and (Formula presented.) when MGF is imposed at Ha = 40 for pure fluids and nanofluids. When thermal performance for all different cases is compared, using MGF+nanofluid+PCM provides the most favorable case. When the reference case (only pure fluid without MGF and PCM) is used, including nanoparticles results in an improvement of 33.7%m while it is further increased to 71.1% when PCM-PB is also installed. The most favorable case by using MGF, nanofluid and PCM-PB results in thermal performance improvement of about 373.9% as compared to the reference configuration. © 2022 by the authors.Item Performance Optimization of a Thermoelectric Device by Using a Shear Thinning Nanofluid and Rotating Cylinder in a Cavity with Ventilation Ports(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Ben Khedher N.; Selimefendigil F.; Kolsi L.; Aich W.; Said L.B.; Boukholda I.The combined effects of using a rotating cylinder and shear thinning nanofluid on the performance improvements of a thermoelectric generator (TEG)-installed cavity with multiple ventilation ports are numerically assessed. An optimization algorithm is used to find the best location, rotational speed and size of the cylinder to deliver the highest power generation of the TEG. The power generation features with varying Rew are different for the first nanofluid (NF1) when compared to the second one (NF2). The power rises with higher Rew when NF1 is used, and up to 49% enhancement is obtained. The output power variation between nanofluids NF1 and NF2 is the highest at Rew = 0, which is obtained as 68.5%. When the cylinder location is varied, the change in the output power becomes 61% when NF2 is used. The optimum case has 11.5%-and 161%-higher generated power when compared with the no-object case with NF1 and NF2. The computational effort of using the high-fidelity coupled system is reduced when optimization is considered. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Item Jet impingement cooling using shear thinning nanofluid under the combined effects of inclined separated partition at the inlet and magnetic field(Springer Science and Business Media Deutschland GmbH, 2022) Selimefendigil F.; Kolsi L.; Ayadi B.; Aich W.; Alresheedi F.; Borjini M.N.Combined effects of using inclined partition and magnetic field on the cooling performance of double slot jet impingement are analyzed with finite element method. Two different shear thinning nanofluids are used while experimental data is available for the rheological properties. Different values of of Reynolds number (Re between 100 and 1000), velocity ratio (VR, between 0.2 and 1), opening ratio (OR, between 0.05 and 0.95), magnetic field strength (Ha, between 0 and 30) and inclination of partition (Ω , between 0 and 40) are used. It is observed that varying VR of the jets, size/inclination of the partition, magnetic field strength and nanfluid type, can be used to control the local and average convective heat transfer and cooling performance features effectively. The average Nusselt number (Nu) rises with higher VR while at the highest VR the amount of increments are 23.5% and 28.5% with first (NF1) and second (NF2) nanofluid (NF). When magnetic field is imposed, effects of OR becomes important with NF1 at the lowest strength of magnetic field. Average Nu reduces with higher magnetic field strength for NF1 while 14.4 % reduction for the highest strength at OR = 0.95 is achieved. However, for NF2 the trend is opposite and 18.8 % increment is obtained. Variations in the average Nu becomes 7.6 % and 1.8 % for NF1 and NF2 when inclination of the partition is changed. The cooling performance is estimated by using a feed-forward network modeling approach in terms of average Nu for NF1 and NF2 by using 25 neuron in the hidden layer. © 2022, The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature.Item Application and CFD-Based Optimization of a Novel Porous Object for Confined Slot Jet Impingement Cooling Systems under a Magnetic Field(MDPI, 2022) Aich W.; Selimefendigil F.; Ayadi B.; Ben Said L.; Alshammari B.M.; Kolsi L.; Betrouni S.A.; Gasmi H.A novel porous object for the control of the convective heat transfer of confined slot nanojet impingement is offered under magnetic field effects, while optimization-assisted computational fluid dynamics is used to find the best working conditions to achieve the best performance of the system. The flow, thermal patterns, and heat transfer characteristics were influenced by the variation in rotational Reynolds number (Rew), Hartmann number (Ha), permeability of the porous object (Da) and its location (Mx). There was a 14.5% difference in the average Nusselt number (Nu) at the highest Rew when motionless object configuration at Ha = 5 was compared, while it was less than 2% at Ha = 25. At Rew = −600, the average Nu variation was 22% when cases with the lowest and highest magnetic field strength were compared. The porous object provides an excellent tool for convective heat transfer control, while the best performance was achieved by using optimization-assisted computational fluid dynamics. The optimal sets of (Rew, Da, Mx, AR) for porous object were (−315.97, 0.0188, −1.456, 0.235), (−181.167, 0.0167, −1.441, 0.2), and (−483.13, 0.0210, −0.348, 0.2) at Ha = 5, 10, and 25, respectively. At the optimal operating point, the local Nu enhancements were 19.46%, 44.86%, and −0.54% at Ha = 5, 10, and 15, respectively, when the no-object case was compared, while the average values were 7.87%, 8.09% and 5.04%. © 2022 by the authors.Item Recent Advances in Nanoencapsulated and Nano-Enhanced Phase-Change Materials for Thermal Energy Storage: A Review(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Khlissa F.; Mhadhbi M.; Aich W.; Hussein A.K.; Alhadri M.; Selimefendigil F.; Öztop H.F.; Kolsi L.Phase-change materials (PCMs) are becoming more widely acknowledged as essential elements in thermal energy storage, greatly aiding the pursuit of lower building energy consumption and the achievement of net-zero energy goals. PCMs are frequently constrained by their subpar heat conductivity, despite their expanding importance. This in-depth research includes a thorough categorization and close examination of PCM features. The most current developments in nanoencapsulated PCM (NEPCMs) techniques are also highlighted, along with recent developments in thermal energy storage technology. The assessment also emphasizes how diligently researchers have worked to advance the subject of PCMs, including the creation of devices with improved thermal performance using nano-enhanced PCMs (NEnPCMs). This review intends to highlight the progress made in improving the efficiency and efficacy of PCMs by providing a critical overview of these improvements. The paper concludes by discussing current challenges and proposing future directions for the continued advancement of PCMs and their diverse applications. © 2023 by the authors.Item Numerical Study of Thermo-Electric Conversion for TEG Mounted Wavy Walled Triangular Vented Cavity Considering Nanofluid with Different-Shaped Nanoparticles(MDPI, 2023) Selimefendigil F.; Omri M.; Aich W.; Besbes H.; Ben Khedher N.; Alshammari B.M.; Kolsi L.The effects of the combined utilization of wavy wall and different nanoparticle shapes in heat transfer fluid for a thermoelectric generator (TEG) mounted vented cavity are numerically analyzed. A triangular wave form of the cavity is used, while spherical and cylindrical-shaped alumina nanoparticles are used in water up to a loading amount of 0.03 as solid volume fraction. The impacts of wave amplitude on flow and output power features are significant compared to those of the wave number. The increment in the generated power is in the range of 74.48–92.4% when the wave amplitude is varied. The nanoparticle shape and loading amount are effective in the rise of the TEG power, while by using cylindrical-shaped nanoparticles, higher powers are produced as compared to spherical ones. The rise in the TEG power by the highest loading amount is achieved as 50.7% with cylindrical-shaped particles, while it is only 4% with spherical-shaped ones. Up to a 194% rise of TEG power is attained by using the triangular wavy form of the wall and including cylindrical-shaped nanoparticles as compared to a flat-walled cavity using only pure fluid. © 2023 by the authors.Item Pulsating multiple nano-jet impingement cooling system design by using different nanofluids for photovoltaic (PV) thermal management(Elsevier Ltd, 2023) Maatoug S.; Moulahi A.; Bazuhair N.; Alqarni S.; Selimefendigil F.; Aich W.; Kolsi L.; Mhimid A.The present work proposes a new cooling system for thermal management and cooling of photovoltaic (PV) systems. Pulsating flow with multiple jet impingement is considered by using different fluid types. Hybrid nanofluid and alumina-water nanofluid having cylindrical ans spherical shaped nanoparticles are used as the cooling medium. The study is conducted by using finite volume method for various values of pulsating amplitude (between 0 and 1), Strouhal number (between 0.01 and 1), solid volume fraction of nanoparticles (between 0 and 2%) and slot number of the impinging jet (between 1 and 13). It is observed that pulsating amplitude is more effective on the cooling performance enhancement as compared to frequency while average Nusselt number (Nu) rises by about 63.5% while temperature drop of 2.16 °C can be achieved when pulsation amplitude is increased from 0 to 1. Nanofluid with cylindrical shaped nanoparticles and hybrid nanofluid show very similar trends while temperature drop of 2.6 °C is achieved when cooling system with nanofluid-cylinder in pulsating flow case is compared with pure-fluid in non-pulsating flow configuration. When nanoparticles loading amount on the thermal improvement is compared, the most favorable cases are obtained for nanofluid-cylinder and hybrid nanofluid case. The average Nu increments become 3.5%, 22.8% and 22.9% for nanofluid-spherical, nanofluid-cylinder and hybrid nanofluid when lowest and highest nanoparticle loading amount cases are compared. Increasing the slot number in pulsating flow case significantly rises the Nu and drops the average panel surface temperature. When different systems are compared pulsating nano-jets cooling system using alumina-water nanofluid with cylindrical shaped nanoparticles provides the most effective cooling system while while temperature drop of ΔT=37.30 °C is achieved at the highest amplitude and highest loading of nanoparticles in the pure fluid as compared to uncooled PV system. © 2022 The Authors.