Browsing by Author "Ghachem K."
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Item Effects of magnetic field, binary particle loading and rotational conic surface on phase change process in a PCM filled cylinder(Elsevier Ltd, 2021) Ghachem K.; Selimefendigil F.; Öztop H.F.; Almeshaal M.; Alhadri M.; Kolsi L.In the present work, coupled effects of forced convection, rotational conic surface and magnetic field on the phase change dynamics are numerically explored by using finite element method for a phase change material (PCM) filled 3D cylindrical reactor. The PCM filled region has a conic shape and it is rotating. The study is conducted for various values of rotational Re number (between 0 and 2500), magnetic field strength (Hartmann number between 0 and 30) and conic surface aspect ratio (between 1 and 2). It is observed that the coupled interactions between the rotational surface and magnetic field significantly affect the phase change process dynamics and convective heat transfer between different phases. Optimum value of rotational Reynolds number for minimum complete phase transition time is achieved at Rew = 1000. The magnetic field has a positive impact on the phase change process while it is impact is profound without surface rotation. There are 98% and 65% reductions in the complete phase transition times when configurations at Rew = 1000 are compared with motionless conic surface case in the absence and presence of magnetic field. The effects of rotation are profound when different aspect ratios of the PCM filled region is considered. The transition time is increased up to 553% without rotation while this value is only 86% when cases with lowest and highest aspect ratio are compared. A modal analysis with 30 mode is used to capture the phase change dynamics and coupled interactions between the rotational surface and magnetic field on the variation of liquid fraction. © 2021 The AuthorsItem Exergy and environmental analysis of an active greenhouse dryer with Al2O3 nano-embedded latent heat thermal storage system: An experimental study(Elsevier Ltd, 2022) Selimefendigil F.; Şirin C.; Ghachem K.; Kolsi L.In this study, influences of integrating nanoparticles into paraffin-based latent heat thermal energy storage system on the thermal and drying behaviors of a greenhouse dryer have been analyzed. The major goal of this survey is improving the drying performance of a greenhouse dryer by employing nano-embedded latent heat storage unit. In this regard, two even-span greenhouse dryers have been produced and modified with paraffin-based and Al2O3 nano-embedded paraffin-based thermal energy storage units. Tests have been conducted at two flow rates that are 0.010 kg/s and 0.016 kg/s. According to the findings, average specific moisture extraction rates for the systems with and without nanoparticles were attained between 1.01 and 1.37 and 0.83–1.20 kg/kWh, respectively. Average exergy efficiency metrics were found as 3.45% and 2.74%, respectively in the test done at 0.016 kg/s flow rate for the greenhouse dryers with and without nanoparticles. These values were found as 3.01% and 2.40%, respectively in the test conducted at 0.010 kg/s. In addition, energy payback time, mean annual CO2 emission and net CO2 mitigation in lifetime values were obtained between 2.34 and 2.92 years, 33.04–34.28 kg/year and 8.45–9.08 tons, respectively. Results indicated the successful utilization of Al2O3 nanoparticle-embedded latent heat storage unit in a greenhouse dryer. © 2022 Elsevier LtdItem Coupled Effects of Using Magnetic Field, Rotation and Wavy Porous Layer on the Forced Convection of Hybrid Nanoliquid Flow over 3D-Backward Facing Step(MDPI, 2022) Ghachem K.; Selimefendigil F.; Alshammari B.M.; Maatki C.; Kolsi L.In the present study, the effects of using a corrugated porous layer on the forced convection of a hybrid nanofluid flow over a 3D backward facing step are analyzed under the coupled effects of magnetic field and surface rotation. The thermal analysis is conducted for different values of the Reynolds number (Re between 100 and 500), the rotational Reynolds number (Rew between 0 and 2000), the Hartmann number (Ha between 0 and 15), the permeability of the porous layer (the Darcy number, Da between (Formula presented.) and (Formula presented.)) and the amplitude (ax between 0.01 ap and 0.7 ap) and wave number (N between 1 and 16) of the porous layer corrugation. When rotations are activated, the average Nusselt number (Nu) and pressure coefficient values rise, while the increment of the latter is less. The increment in the average Nu is higher for the case with a higher permeability of the layer. When the corrugation amplitude and wave number are increased, favorable impacts of the average Nu are observed, but at the same time pressure coefficients are increased. Successful thermal performance estimations are made by using a neural-based modeling approach with a four input-two output system. © 2022 by the authors.Item Enhancing the performance of a greenhouse drying system by using triple-flow solar air collector with nano-enhanced absorber coating(Elsevier Ltd, 2022) Selimefendigil F.; Sirin C.; Ghachem K.; Kolsi L.; Alqahtani T.; Algarni S.In this research, the impacts of utilizing nano-embedded absorber coating in an auxiliary heater of a greenhouse drying system on the thermal and drying performances have been surveyed empirically. In this context, triple-flow solar air collectors with and without CuO nano-enhanced absorber coating have been designed and manufactured. Designed collectors then integrated to even-span greenhouse dryers to be used as an auxiliary heating device. In the experiments, greenhouse dryers have been tested with and without auxiliary heaters at constant flow rate which is 0.014 kg s-1. According to the experimental findings, utilizing triple-flow solar air heating device with and without nano-embedded paint decreased the drying time as 35.71% and 26.66%, respectively. Thermal and exergetic efficiencies for newly developed collectors were found between the range of 70.39-75.11% and 9.05-10.18%, respectively. In addition, specific energy consumption values were decreased by using collectors with and without nano-enhanced modification from 2.51 to 2.11 and from 2.61 to 2.18 kWh/kg, respectively. Attained outcomes of this study showed the successful utilization of nano-enhanced absorber coating in the auxiliary heating system of the greenhouse dryer. © 2022 The Authors.Item Impacts of rotating surface and area expansion during nanofluid convection on phase change dynamics for PCM packed bed installed cylinder(Elsevier B.V., 2022) Ghachem K.; Selimefendigil F.; Öztop H.F.; Alhadri M.; Kolsi L.; Alshammari N.Phase change dynamics under the rotational surface effects, area expansion and nanoparticle loading in the base fluid are explored for forced convective flow of hybrid nanofluid in a phase change packed bed installed cylindrical reactor. The study is performed with finite element method for different parameters of rotational Reynolds number, fluid stream Reynolds number and concentration of nanoparticle. The hybrid nanofluid properties are based on experimental data for binary particle of Al2O3-TiO2 in 40% ethylene–glycol. Complete phase transition time is estimated with ANFIS based model. The recirculation zone due to the area expansion within the phase change installed region is controlled by the complex interactions between the forced flow, rotation of the surface and nanoparticle amount. Higher values of Reynolds number and nanoparticle concentration result in fast phase change process at rotational Reynolds number of 0 while the effects become reverse in the presence of rotations. Complete phase transition time reduces by about 49% and 10.5% at the highest Reynolds number and at the highest concentration in the absence of rotation while it is increased by about 88% and 6.5% when rotational effects are considered at the highest rotational speed. When only rotational effects are considered, phase change process completion time reduces by about 60% at the highest speed. © 2021 THE AUTHORSItem Pulsating nanofluid flow in a wavy bifurcating channel under partially active uniform magnetic field effects(Elsevier Ltd, 2022) Kolsi L.; Selimefendigil F.; Ghachem K.; Alqahtani T.; Algarni S.Separated flow and thermal performance characteristics by combined utilization of surface corrugation, partially active magnetic field, nanoparticle loading in the base fluid and flow pulsations are analyzed numerically in a bifurcating channel by using finite element method. Size and number of vortices are affected by the variation corrugation height and wave numbers while the vortices are damped by using partially active magnetic field in different domains. When various methods are compared, by using corrugations highest heat transfer improvement is achieved followed by the flow pulsations and magnetic field. By utilization of nanofluids, thermal performance is further improved. When corrugation height is considered, enhancement up to 248.3% is obtained for wave number of 8 while variation in the average Nusselt number (Nu) becomes only 22.9% with varying wave number. The enhancement amount with pulsating flow amplitude depends upon the nanoparticle loading amount in the base fluid. At solid volume fraction of 0.02%, the average Nu increases by about 79.8% with pulsating flow at the highest amplitude as compared to steady flow case. Dynamic models with system identification are constructed for predictions of time dependent Nu variations for different pulsating amplitudes in the absence and presence of magnetic field for the bifurcating channel. The potential improvement of convective heat transfer in bifurcation channels is explored by combining different novel enhancement methods together. The results of the present analysis will be beneficial for performance improvement and optimization studies of bifurcating channel applications appeared in microelectromechanical systems, fuel cells and thermal management of diverse thermal systems. © 2022 Elsevier LtdItem Multiple Impinging Jet Cooling of a Wavy Surface by Using Double Porous Fins under Non-Uniform Magnetic Field(MDPI, 2022) Kolsi L.; Selimefendigil F.; Ghachem K.; Alqahtani T.; Algarni S.Coupled effects of double porous fins and inhomogeneous magnetic field on the cooling performance of multiple nanojet impingement for a corrugated surface were numerically analyzed. Different values of magnetic field parameters (strength, inclination, and amplitude of spatially varying part) and double porous fin parameters (inclination and permeability) were used, while finite element method is used as the solution method. When parametric computational fluid dynamics (CFD) simulations were performed, there were 162.5% and 34% Nusselt number (Nu) enhancement with magnetic field for flat and wavy surfaces, respectively. The variations of average Nu became 36% and 24% when varying the inclination and amplitude of inhomogeneous magnetic for a flat surface, while the amounts were 43.7% and 32% for a corrugated one. The vortex distribution in between the jets and cooling performance was affected by the variation of double porous fin permeability and inclination. An optimization method was used for the highest cooling performance, while the optimum set of parameters was obtained at (Ha, Amp, Da, Ω) = (0.224, 0.5835, 7.59 × 10−4, 0.1617). By using the double porous fins and inhomogeneous magnetic field, excellent control of the cooling performance of multiple impinging jet was obtained. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Item Thermal and phase change process of nanofluid in a wavy PCM installed triangular elastic walled ventilated enclosure under magnetic field(Elsevier Ltd, 2023) Selimefendigil F.; Ghachem K.; Albalawi H.; Alshammari B.M.; Labidi T.; Kolsi L.Coupled interactions between magnetic field, wall elasticity and corrugation of the packed bed container on the phase change and thermal process are analyzed during nanofluid convection in a triangular shaped vented cavity. The numerical analysis is performed considering Cauchy number (Ca between 10−7 and 5×10−5), Hartmann number (Ha between 0 and 50), number of waves (N between 1 and 8) and nanoparticle solid volume fraction (SV-F between 0 and 2%). Higher values of Ca and Ha contributes positively to the phase change and thermal process. The reduction of phase transition time (TP) reduces by 23% at the highest Ca while heat transfer improvements of 22.8% are obtained. The optimum value of wave number is found as N = 2. The optimum configuration is found for elastic wall case at the parameters (50, 2, 2%). The heat transfer enhancement factor is found as 13.8 while the TP reduction is 5% as compared to worst case which is found at (Ha, N, SV-F) = (0, 8, 0) with rigid wall. © 2023 The Author(s)Item Multiple slot nano-jet impingement cooling of a sinusoidal hot surface by using active rotating cylinders under magnetic field(Elsevier Ltd, 2023) Selimefendigil F.; Ghachem K.; Alwadai N.; Alshammari B.M.; Kolsi L.In this study, cooling performance of a multi-slot jet impingement system for a wavy surface are explored under the triple combined effects of using magnetic field (MG-F), double active rotating cylinders and nanofluid. Double rotating cylinders which provide additional cooling are used while Galerkin weighed residual finite element method is used for the solution of the governing equations. Effects of Rew (rotational Reynolds number, between −1000 and 1000), Ha (MG-F strength between 0 and 30), MG-F inclination (between 0 and 90) and sub-cooling temperature of the active cylinders (dT between 0 and 10) on the cooling performance are assessed. Rotations of the double cylinders generally provide higher Nusselt number (Nu) while 41% and 18.9% increment in the Nu is obtained when using pure fluid and nanofluid. The average Nu behavior is different when using MG-F depending upon the rotations are active or not. Average Nu is sharply reduced by about 25.1% without rotations but it rises by about 89% at Ha = 10 by using rotations. The impacts of sub-cooling is very effective when rotations are active while up to 37.9% rise of Nu is obtained at Rew = −1000. When no cylinders are used, using MG-F reduced the average Nu by about 15.4%. The best cooling performance case in the absence of MG-F with cylinders is obtained at Rew = −1000 and dT = 10. © 2023 The Author(s)Item Convective Heat Transfer and Entropy Generation for Nano-Jet Impingement Cooling of a Moving Hot Surface under the Effects of Multiple Rotating Cylinders and Magnetic Field(MDPI, 2023) Kolsi L.; Selimefendigil F.; Larguech S.; Ghachem K.; Albalawi H.; Alshammari B.M.; Labidi T.In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher. © 2023 by the authors.Item Effects of a conductive T-shaped partition on the phase change dynamics in a channel equipped with multiple encapsulated PCMs under different magnetic fields(Elsevier Ltd, 2024) Selimefendigil F.; Ghachem K.; Albalawi H.; Alshammari B.M.; Labidi T.; Kolsi L.For enhanced thermal management and energy storage, an understanding of the phase change process and how to control it is crucial in many different engineering applications. In this study, effects of using a T-shaped conductive partition on the phase change process in a multiple phase change material-installed three dimensional cylinder are explored by using finite element method. In the computational domain, a uniform magnetic field with varying strengths is applied. The investigation is conducted for various Reynolds numbers (Re:200–500), Hartmann number of the first and second domains (Ha1: 0–50 and Ha2: 0–50), partitions sizes (Lp: 0.05L–0.5L), and conductivity ratios (KR:0.01–100). The entire transition times (trF) of the left and right phase change materials decrease with increasing Re and Ha. At Ha1=0, the reduction amounts of trF with Re for phase change materials P1 and P2 are 24.40% and 27.45%, respectively. When magnetic field is imposed at Ha1=50, the amounts are 19.4% and 22.7%. The size of the conductive partition affects the size of the vortex established within the phase change material zone. When the partition size is altered, the tr-F variation for P1 and P2 in the absence of magnetic field is 11% and 8.5%, respectively, but in the presence of magnetic field it is 26.5% and 7%. The partition's conductivity has an impact on the dynamics of phase changes as well. The phase completion times of the various phase change materials differ most at KR=0.1, and at that moment, P1's trF is 42% higher than P2's. When modeling the time-dependent variation of liquid fraction for various phase change materials and conductivity ratios, a polynomial type regression model is employed. The findings are useful for the initial design, thermal management and the optimization studies of phase change material embedded systems in a variety of applications, such as heat recovery systems, convective heat transfer applications, and the cooling of electronic equipments. © 2024 The Author(s)Item Magneto-convection of nanofluid flow over multiple rotating cylinders in a confined space with elastic walls and ventilated ports(Elsevier Ltd, 2024) Selimefendigil F.; Ghachem K.; Albalawi H.; AlShammari B.M.; Labidi T.; Kolsi L.In this study, convective heat transfer for nanofluid flow over multiple rotating cylinder in a confined space is analyzed under magnetic field while enclosure has one inlet and one outlet port. Three identical circular cylinder are used and the two walls of the cavity are considered to be elastic. The coupled fluid-structure interaction and magneto-convection problem is solved by finite element method. Impacts of rotational Reynolds number (Rew between -100 and 100), Hartmann number (Ha between 0 and 50), cylinder size (R between 0.001H and 0.11H) and Cauchy number (Ca between 10−8 and 10−3) on the flow and thermal performance features are explored. The flow field and recirculation inside the cavity are significantly affected by the activation of rotation and magnetic field. The vortices are suppressed by increasing the strength of magnetic field and thermal performance is improved. Thermal performance of 56.6% is achieved by activation of magnetic field at the highest strength with rotations of the circular cylinders. When rotations are active, heat transfer rate is reduced while up to 40% reduction is obtained without magnetic field. Cylinder size has the highest impact on the overall thermal performance improvement while up to 132% enhancements are achieved. The contribution of elastic walls on the thermal performance is slight while less than 5% improvements in the average heat transfer is obtained. An optimization study leads to 12.7% higher thermal performance improvements as compared to best case of parametric computational fluid dynamics simulation results while the optimum values of (Rew, Ha, R) is obtained as (-80.66, 50, 0.11H). © 2024 The Author(s)Item Single-channel cooling system design by using perforated porous insert and modeling with POD for double conductive panel(Walter de Gruyter GmbH, 2024) Selimefendigil F.; Benabdallah F.; Ghachem K.; Albalawi H.; Alshammari B.M.; Kolsi L.In this study, a single cooling channel system is suggested for conductive double panel systems. The cooling channel for the vertical component uses perforated porous insert (PP-I) and porous insert (P-I), while cylinders are used in the PP-I case. The permeability of the porous channel (Da between 1 0-5 and 1 0-1, size of the cylinders (Rc between 0 and 0.25), and location of the PP plate (Yp between 1 and 4.5) are all taken into account when calculating the effectiveness of the cooling system using finite element method. It is found that PP-I can effectively control the vortex size and enhance cooling performance, particularly for vertical plate. Nusselt number is enhanced in the absence of cylinders in the vertical channel by 92% as contrasted to 51% in the presence of cylinders. When cylinders are used for the vertical channel, the temperature drop of 1 3 ° is computed. The flow field noticeably changes when the permeability of the P-I and PP-I is altered. The equivalent temperature increases for P-I and PP-I with setups at Da = 1 0-5 and Da = 1 0-2 are 7.7 ° and 4.4 ° C, respectively. The performance of cooling for the vertical plate is influenced favorably by the higher values of the porous plate's vertical placement. By moving the porous object, it is possible to reduce the temperature by 8 ° C. For panel surface temperature, a proper orthogonal decomposition (POD)-based reconstruction model with 12 POD modes is used. The POD-based model accurately captures the effects of utilizing P-I and PP-I on the panel temperature. © 2024 the author(s), published by De Gruyter.Item Effects of using magnetic field and double jet impingement for cooling of a hot oscillating object(Elsevier Ltd, 2024) Selimefendigil F.; Ghachem K.; Albalawi H.; Alshammari B.M.; Labidi T.; Kolsi L.Efficient cooling system design with impinging jets becomes an important topic due to its higher cooling performance applicable to engineering systems such as in electronic cooling, photovoltaic panels and material processing. In the present study, cooling of an oscillating hot object is considered by using a double slot jet impingement system in the presence of a uniform inclined magnetic field. The oscillation of body and magnetic field can be present in the system or they can be considered as methods for flow and convective heat transfer control for the slot-jet impingement system. Analysis is done for a range of values for the jet Reynolds number (Re ranging from 100 to 500), Hartmann number (Ha, ranging from 0 to 10), inclination of magnetic field (γ, ranging from 0 to 90), and oscillation amplitude (Amp, between −3 and 3) by using finite element method with Arbitrary Lagrangian–Eulerian technique. It is observed that due to the hot object's oscillating nature, cooling is either increased or worsened for different time steps based. When Re is raised from the lowest to highest value, average Nusselt number (Nu) increases by a factor of 2.4. In the cooling system with impinging jets, strength of magnetic field and its inclination may be employed to regulate the vortex size and distribution. In comparison to the absence of magnetic field, the average Nu falls by around 73% to 75.5% at the greatest magnetic field strength. When oscillation is enabled, cooling performance is increased adopting the time step. By comparing the oscillating object with stationary one, cooling performance improvements of 28% and 8.3% are obtained at (Re, Ha)=(500, 0), and (500, 10) parametric combinations. © 2024 The Author(s)Item Effects of using sinusoidal porous object (SPO) and perforated porous object (PPO) on the cooling performance of nano-enhanced multiple slot jet impingement for a conductive panel system(KeAi Communications Co., 2024) Selimefendigil F.; Benabdallah F.; Ghachem K.; Albalawi H.; Alshammari B.M.; Kolsi L.Cooling system design for thermal management of electronic equipment, batteries and photovoltaic (PV) modules is important for increasing the efficiency, safety operation, and long life span the products. In the present study, two different cooling systems are proposed with nano-enhanced multiple impinging jets for a conductive panel. The present cooling systems can be used in electronic cooling and PV modules. Perforated porous object (PPO) and sinusoidal porous object (SPO) are used in the jet cooling system. 2D numerical analysis using finite volume method is conducted considering different values of permeability of the objects (Darcy number (Da) between 10−6 and 10−1). When PPO is used in the cooling system, number of cylinders (between 1 and 6), and size of the cylinders (between 0.015 and 0.075) are considered. In the case of using SPO, amplitude (between 0.1 and 2) and wave number (between 1 and 12) are varied. Alumina-water nanofluid with cylindrical shaped nanoparticles is used as the heat transfer fluid. When permeability is changed for PPO, the average temperature increases by roughly 3.89 °C for a single cylinder and drops by roughly 0.57 °C for a six-cylinder cases. Increasing the size of the cylinder in the PPO case at highest permeability results in temperature drop of 5.3 °C. When changing the number of cylinders, cooling rate varies by about 3.6%. Wave number of SPO is more influential on the cooling performance enhancement as compared to amplitude and permeability of the SPO. The average surface temperature drops by 12.4 °C when the wave number is increased to 12. As compared to reference case of jet impingement cooling without porous object, using PPO and SPO along with the nanofluid result in temperature drop of 12.3 °C and 14.4 °C. © 2024 The AuthorsItem Nanofluid cooling of a hot rotating circular cylinder employing cross-flow channel cooling on the upper part and multi-jet impingement cooling on the lower part(American Institute of Physics, 2024) Selimefendigil F.; Larguech S.; Ghachem K.; Albalawi H.; Alshammari B.M.; Labidi T.; Kolsi L.This study explores the convective cooling features of a hot rotating cylinder by using the combined utilization of cross-flow on the upper part and multi-jet impingement on the bottom part. The analysis is performed for a range of jet Reynolds number (Re) values (between 100 and 500), cross-flow Re values (between 100 and 1000), rotational Re values (between −1000 and 1000), cylinder size (between 0.25wj and 3wj in radius), and center placement in the y direction (between −1.5wj and 1.5wj). When the cylinder is not rotating, the average Nu increment becomes 102% at the highest jet Re, while it becomes 140.82% at the highest cross-flow Re. When rations become active, the impacts of cross-flow and jet impingement cooling become slight. As compared to a motionless cylinder, at the highest speed of the rotating cylinder, the average Nu rises by about 357% to 391%. For clockwise rotation of the cylinder, a lager cylinder results an increase in the average Nu by about 86.3%. At the lowest and highest cross-flow impinging jet Re value combinations, cooling performance improvement becomes a factor of 8.1 and 2, respectively. When the size of the cylinder changes, entropy generation becomes significant, while the vertical location of the cylinder has a slight impact on entropy generation. © 2024 Author(s).