Browsing by Author "Selimefendigil, F"
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Item Experimental analysis and dynamic modeling of a photovoltaic module with porous finsSelimefendigil, F; Bayrak, F; Oztop, HFIn this study, experimental analysis and performance predictions of solar photovoltaic (PV) module equipped with porous fins were performed. The experimental setup was tested in Technology Faculty of Firat University, Elazig of Turkey which is located at 36 and 42 North latitudes. The PV module was oriented facing south and tilted to an angle of 36 with respect to the horizontal in order to maximize the solar radiation incident on the glass cover. Experimental analysis was conducted for configurations where PV module is equipped with porous metal foams. A multi-input multi-output dynamic system based on artificial neural networks was obtained for the PV configuration with and without fin by using the measured data (ambient temperature, PV panels back surface temperatures, current, voltage, radiation and wind velocity) from the experimental test rig. It was observed that adding porous fins to the PV module results in performance enhancements. The developed mathematical model based on dynamic neural networks can be used for further development and performance predictions of these systems. (C) 2018 Elsevier Ltd. All rights reserved.Item MHD Free Convection and Entropy Generation in a Corrugated Cavity Filled with a Porous Medium Saturated with NanofluidsChamkha, AJ; Selimefendigil, FMHD free convection inside a triangular-wave-shaped corrugated porous cavity with Cu-water nanofluid is numerically studied with the finite element method. The influences of the Grashof number (104Gr106), Hartmann number (0Ha50), Darcy number (10-4DaItem Effects of elasticity and waviness of the conductive panel surface on the cooling performance and entropy generation by using nano-enhanced multiple impinging jetsSelimefendigil, F; Öztop, HFThe design of cooling systems is crucial for the thermal management of many energy systems including batteries, microelectro-mechanical systems, photovoltaics and many others. In this study, cooling system for elastic curved conductive panel is developed by using nano-enhanced multiple jet impingement. ALE finite element modeling of the entire coupled fluid-structure conjugate heat transfer system is employed for assessment, which considers both elastic flat and wavy panels. Type of the panel and operating parameters affect the cooling performance and entropy generation. Different effects and contributions of varying parameters such as Cauchy number (Ca), jet-cooling spacing (to the target plate and between the slots), wave amplitude and number of the conducive panel and nanoparticle loading amount in the pure fluid on the cooling performance and entropy generation features are analyzed. Increases in the Cauchy number, waveform amplitude, slot-slot distance, and slot-plate distance reduce the effectiveness of cooling, whereas increases in the nanoparticle loading have the reverse effect. When varying the Ca, there is 12.1% decrease of average Nusselt number (Nu) while average panel temperature rise becomes 3.1 & DEG;C by using nanofluid. The average Nu deteriorates by 7.7% and 6.6% when amplitude and wave number are varied while the corresponding temperature rises are achieved as 1.4 & DEG;C and 1 & DEG;C. When wavy and flat surfaces are used, using nanofluid provides 2.8 & DEG;C and 2.5 & DEG;C temperature drops. Lower entropy generation (EG) is obtained with flexible panel while higher amplitude of the wave form and increasing the nanoparticle amount result in EG reduction. The amount of EG reduction by using nanofluid becomes 21% and 27% at the highest loading.Item MIXED CONVECTION IN A VERTICALLY LAYERED FLUID-POROUS MEDIUM ENCLOSURE WITH TWO INNER ROTATING CYLINDERSIsmael, MA; Selimefendigil, F; Chamkha, AJIn this study, mixed convection in a vertically half partitioned cavity with two rotating adiabatic cylinders is numerically investigated. The horizontal walls are thermally insulated. The left vertical wall is kept isothermally at high temperature while the right vertical wall is kept isothermally at lower temperature. The Galerkin weighted residual finite element method is used to solve the governing equations. The numerical study is performed for various values of Rayleigh numbers (between 10(3) and 10(6)), angular rotational speed of the cylinders (between -5000 and 5000), Darcy numbers (between 10(-5) and 10(-2)), horizontal positions of the cylinder centers (between 0.4 and 0.6) and cylinder sizes (between 0.1 and 0.4). It is observed that angular velocity of the cylinders and cylinder sizes have a profound effect on the heat transfer enhancement along the hot vertical wall. The averaged heat transfer enhancements are 354.65% and 45.24% at a Rayleigh number of 10(6) compared to the case at a Rayleigh number of 10(3) for cylinder sizes of R = 0.1 and R = 0.4. Large variations in the local heat transfer are seen for various angular velocities of the cylinder, and cylinder rotation brings averaged heat transfer enhancement for sizes of R = 0.3 and R = 0.4. The averaged heat transfer enhances by 235.10% for a Darcy number of 10(-2) compared to a Darcy number of 10 5 using cylinder sizes of R = 0.1. The horizontal movement of the cylinder centers increases the averaged heat transfer by 34.08% for (D-1 = D-2 = 0.6) compared to configuration at (D-1 = D-2 = 0.4) for angular rotational speed of Omega = -5000.Item Mixed Convection of Pulsating Ferrofluid Flow Over a Backward-Facing StepSelimefendigil, F; Öztop, HF; Chamkha, AJIn this study, mixed convection of pulsating ferrofluid flow over a backward-facing step under the effect of a magnetic source is performed. Heat transfer and fluid flow characteristics for a range of flow parameters were identified in terms of streamlines, isotherms and local and averaged Nusselt number plots. Finite element method was used to solve the resulting governing equations. The effects of the Richardson number (0.05 <= Ri <= 50), strength of the magnetic dipole (0 <= gamma <= 6), horizontal and vertical locations of the magnetic dipole (H <= a <= 5H, -5H <= b <= -0.75H), amplitude and non-dimensional frequency of flow pulsation (0.25 <= A <= 1, 0.01 <= St <= 5) on the fluid flow and heat transfer enhancement were numerically investigated in detail. It was observed that the magnetic dipole parameters effect is different in pulsating flow compared to steady flow simulation results. The flow pulsation was found to enhance the average heat transfer which is about 17.5% in the absence of magnetic dipole source. When magnetic dipole source was used, up to 32% in the average heat transfer was obtained with flow pulsation. The primary recirculation zone behind the step is deteriorated by the presence of the magnetic source, and an addition vortex which is restricted to a very small region near the step is formed. The magnetic dipole source can be combined with flow pulsation to control the mixed convective flow over the backward-facing step.Item Impact of local elasticity and inner rotating circular cylinder on the magneto-hydrodynamics forced convection and entropy generation of nanofluid in a U-shaped vented cavitySelimefendigil, F; Öztop, HF; Sheikholeslami, MThis study analyzes the effects of a partial elastic wall and rotating circular cylinder on the convective heat transfer of carbon nanotube (CNT)-water nanofluid filled U-shaped cavity with entropy generation by considering inclined magnetic field effects. Numerical simulation is performed by using ALE with finite element method (FEM). Impacts of various important parameters such as Re number, Ha number, magnetic field orientation, elastic wall size and modulus, angular velocity, and horizontal position of the rotating cylinder on the forced convection are analyzed. When the values of Re number, strength of magnetic field (up to Ha number of 50), and orientation angle are increased, the average Nu value rises while the impact is opposite for higher elastic wall size and horizontal position of the cylinder above 0.4H. When the rotational cylinder effects are considered, enhancement up to 60%is obtained at the highest speed as compared to motionless cylinder case. The average Nu variation is in the range of 9%-10.45%at the highest value when varying the size and modulus of the elastic wall. Flexible wall effects on the average Nu number variation becomes more pronounced when the angular rotational velocity is highest at the clockwise rotation and for the highest Re number. The average Nu number enhancements are 13%-14%at the highest Ha number. The entropy generation rates with varying Ha number, rotational velocity, and location of the cylinder are different for the left and right parts of the domains while impacts of elastic wall properties on the entropy generation rate are slight.Item Effects of different fin parameters on temperature and efficiency for cooling of photovoltaic panels under natural convectionBayrak, F; Oztop, HF; Selimefendigil, FThe photovoltaic panels are one of the most efficient energy systems that generate electricity by absorbing the solar radiation. Nevertheless, when the sun's rays are converted to electricity, a high amount of waste heat is generated. Therefore, the efficiency of photovoltaic (PV) panels needs to be studied to minimize the amount of waste heat. There is a non-linear relationship between the temperature, the current and the voltage values produced by the PV panels. In the present study, the performance of 75 W PV panels with polycrystalline cell structure under Elazig, Turkey climatic conditions were experimentally investigated. The system performances such as temperature, power and efficiencies were analyzed by applying different fin parameters (length, sequences) to PV panels. The aluminum fins were applied with 10 different configurations as given by A1-A10. The cell temperatures, output powers, power loss ratios and energy-exergy efficiencies were calculated based on measurements of the experimental study. It was observed that the temperature did not distributed homogeneously on the PV panel. In terms of the efficiency, the fins are designed as staggered array and the 7 cm x 20 cm dimensions showed the best results. The highest energy and exergy efficiencies values of the finned panels (A5) were calculated as 11.55%, and 10.91%, respectively.Item Thermo-hydraulic performance and entropy generation of biologically synthesized silver/water-ethylene glycol nano-fluid flow inside a rifled tube using two-phase mixture modelShahsavar, A; Jafari, M; Askari, IB; Selimefendigil, FIn this paper, the two-phase mixture model is used to determine the influence of the number of ribs on the first-law and second-law performance features of the laminar forced convection flow of a biologically prepared silver/water-ethylene glycol nano-fluid (NF) in a rifled tube. The influence of the Reynolds number (Re), nanoparticle concentrations (phi) on the outcomes are also evaluated. Two parameters of Performance Evaluation Criterion (PEC) and Figure of Merit (FOM) are defined to analyze the merit of using rifled tube and NF over the plain tube and water-ethylene glycol mixture (50:50 by volume) for the same Re and phi. The results showed that the increase in the number of ribs is desirable from the first-law viewpoint and undesirable from the second-law viewpoint. It was found that for all the examined cases, the hydrothermal performance of the rifled tube is always better than the plain tube, and boosting the Re and decreasing the phi leads to an increase in FOM. Moreover, it was observed that the PEC for the six-head and eight-head rifled tubes is always greater than unity and for the two-head rifled tube is always less than unity.Item MHD mixed convection of nanofluid in a three-dimensional vented cavity with surface corrugation and inner rotating cylinderSelimefendigil, F; Chamkha, AJPurpose This study aims to numerically examine mixed convection of CuO-water nanofluid in a three-dimensional (3D) vented cavity with inlet and outlet ports under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above. Design/methodology/approach The bottom surface is corrugated with a rectangular wave shape, and the rotating cylinder surface and cavity bottom surface were kept at constant hot temperatures while the cold fluid enters the inlet port with uniform velocity. The complicated interaction between the forced convection and buoyancy-driven convection coupled with corrugated and rotating surfaces in 3D configuration with magnetic field, which covers a wide range of thermal engineering applications, are numerically simulated with finite element method. Effects of various pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 1,000), angular rotational speed of the cylinder (between -30 and 30), solid nanoparticle volume fraction (between 0 and 0.04), corrugation height (between 0 and 0.18H) and number (between 1 and 20) on the convective heat transfer performance are numerically analyzed. Findings It was observed that the magnetic field suppresses the recirculation zone obtained in the lower part of the inlet port and enhances the average heat transfer rate, which is 10.77 per cent for water and 6.86 per cent for nanofluid at the highest strength. Due to the thermal and electrical conductivity enhancement of nanofluid, there is 5 per cent discrepancy in the Nusselt number augmentation with the nanoadditive inclusion in the absence and presence of magnetic field. The average heat transfer rate of the corrugated surface enhances by about 9.5 per cent for counter-clockwise rotation at angular rotational speed of 30 rad/s as compared to motionless cylinder case. Convective heat transfer characteristics are influenced by introducing the corrugation waves. As compared to number of waves, the height of the corrugation has a slight effect on the heat transfer variation. When the number of rectangular waves increases from N = 1 to N = 20, approximately 59 per cent of the average heat transfer reduction is achieved. Originality/value In this study, mixed convection of CuO-water nanofluid in a 3D vented cavity with inlet and outlet ports is numerically examined under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. To the best of authors knowledge such a study has never been performed. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above.Item Nanoliquid Jet Impingement Heat Transfer for a Phase Change Material Embedded Radial Heating SystemSelimefendigil, F; Öztop, HFNanoliquid impingement heat transfer with a phase change material (PCM) installed radial system is considered. The study is performed by using the finite element method for various values of Reynolds numbers (100 <= Re <= 300), height of PCM (0.25H <= h(pcm) <= 0.75H), and plate spacing (0.15H <= h(s) <= 0.40H). Different configurations using water, nanoliquid, and nanoliquid + PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM, while best performance is achieved with nanoliquid and PCM-installed configuration. At Re = 100 and Re = 300, heat transfer improvements of 26% and 25.5% are achieved with the nanoliquid+ PCM system as compared to water without PCM. The height of the PCM layer also influences the heat transfer dynamic behavior, while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM heights while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation.Item Effects of flexible fins on melting process in a phase change material filled circular cavityAkbal, Ö; Selimefendigil, F; Öztop, HFIn this study, melting process in a phase change material (PCM) filled annular closed space by using flexible fins is analyzed. Cases with different number of flexible fins and without fin are compared in terms of phase change dynamics while two-way fluid structure interaction analysis is used. Temperature differences of 30 degrees C and 60 degrees C are considered between the walls of the circular enclosure while flexible fin numbers are varied between 0 and 10. It is observed that the melting is significantly accelerated by using the elastic fins. Due to the deflection of the elastic fins, melt process dynamics is influenced by varying fin number and its elastic modulus. Further reduction in the full phase transition occurs when the temperature difference is increased. As compared to un-finned case at temperature difference of 30 degrees C by using 10 flexible fins at Delta T = 60 degrees C, there is 87 % reduction in the complete phase transition time. The ANFIS (Adaptive Neuro-Fuzzy Interface System) based modeling approach is used for phase transition dynamics in circular enclosure equipped with flexible fins.Item Optimization assisted divide-combine approach to model cooling of a PV module equipped with TEG by using a trapezoidal shaped hybrid nano-enhanced cooling channel and performance estimation with generalized neural networksSelimefendigil, F; Oztop, HFInnovative cooling strategies and efficient thermal management techniques are needed to increase the efficiency of photovoltaic (PV) modules. In the current work, a novel cooling channel method and computational approach is utilized for thermal management of PV module combined with thermoelectric generator (TEG) unit. The method uses an optimization assisted divide-combine computational approach while a trapezoidal wavy cooling channel is utilized. Hybrid nanofluid is used in the cooling channel. Simulations for cooling channel and PV-TEG unit are conducted by using finite element method while COBYLA algorithm is considered for optimization of trapezoidal wavy channel. It is shown that the corrugation amplitude has the largest effect on a trapezoidal wavy channel's cooling effectiveness, while the inclination angle has the least effect. The range of average Nu improvements by adjusting the trapezoidal wavy channel's amplitude, wave number, and inclination are obtained as 36%-42%, 13.5%-15%, and 2.5%-3%. The average PV-cell temperature decreases by approximately 2.7oC to 3.4oC when the cooling channel is connected to the PV-TEG unit. It also decreases by approximately 1oC to 1.3oC when the wave number is changed. The optimum corrugation height (b/H) and inclination (0) for the best cooling performance are found as (b/H, 0)=(0.5, 36) when using 3 waves and (b/H, 0)=(0.5, 13.16) when using 11 waves. The PV-cell temperature drops with optimal channel configurations with wave numbers of 3 and 11 are obtained as 4.3oC and 6oC, respectively, in comparison to the reference cooling channel (flat channel employing only pure fluid). While the PV-TEG unit is coupled with parametric simulation of the cooling channel, generalized neural network models are used to successfully estimate the PV-cell temperature and TEG power. More complex channel assemblies and consideration of multiple PV-TEG combined units can be developed using the proposed optimization-assisted divide-combine methodology.Item Cooling of a Partially Elastic Isothermal Surface by Nanofluids Jet ImpingementSelimefendigil, F; Öztop, HFNumerical study of nanofluid jet impingement cooling of a partially elastic isothermal hot surface was conducted with finite element method. The impingement surface was made partially elastic, and the effects of Reynolds number (between 25 and 200), solid particle volume fraction (between 0.01 and 0.04), elastic modulus of isothermal hot surface (between 10 4 and 10 6), size of the flexible part (between 7.5 w and 25 w), and nanoparticle type (spherical, cylindrical, blade) on the fluid flow and heat transfer characteristics were analyzed. It was observed that average Nusselt number enhances for higher Reynolds number, higher values of elastic modulus of flexible wall, smaller size of elastic part, and higher nanoparticle solid volume fraction and for cylindrical shaped particles. It is possible to change the maximum Nusselt number by 50.58% and 33% by changing the elastic modulus of the hot wall and size of elastic part whereas average Nusselt number changes by only 9.33% and 6.21%. The discrepancy between various particle shapes is higher for higher particle volume fraction.Item Mixed convection of nanofluid filled cavity with oscillating lid under the influence of an inclined magnetic fieldSelimefendigil, F; Öztop, HFIn this study, mixed convection of an oscillating lid-driven cavity filled with nanofluid under the influence of an inclined uniform magnetic field was numerically investigated. The cavity is heated from below and cooled from above while side walls are assumed to be adiabatic. The top wall velocity varies sinusoidally while no-slip boundary conditions are imposed on the other walls of the cavity. The governing equations was solved by Galerkin weighted residual finite element formulation. The numerical investigation was performed for a range of parameters: Richardson number (10(-1) <= Ri <= 10(2)), Hartmann number (0 <= Ha <= 60), inclination angle of the magnetic field (0 <= gamma <= 90), non-dimensional frequency of the oscillating lid (0.001 <= St <= 1) and solid volume fraction of the nanoparticle (0 <= phi <= 0.04). It is observed that the flow and thermal patterns within the cavity are affected by the variation of these parameters. The heat transfer process becomes inefficient for high Strouhal number, high Hartmann number and high Richardson number. Maximum enhancement of averaged heat transfer and the damping of the convection within the cavity due to the Lorentz forces caused by magnetic field are attained for magnetic inclination angles of gamma = 90 degrees and gamma = 60 degrees. As the solid volume fraction of nanoparticles increases averaged heat transfer enhancement of 28.96% is obtained for volume fraction of phi = 0.04 compared to base fluid. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Item Effects of an adiabatic inclined fin on the mixed convection heat transfer in a square cavitySelimefendigil, F; Oztop, HFIn this study, a square cavity with two ventilation ports in the presence of an adiabatic fin placed on the bottom wall of the cavity is numerically analysed for the mixed convection case for a range of Richardson numbers (Ri = 0.1,1, 10, 30) and at Reynolds number of 300. The top and bottom walls of the cavity are kept at constant temperature while the verticals walls are assumed to be adiabatic. The effect of the fin height, inclination angle and Richardson number on the fluid flow and heat characteristics is numerically analysed. The results are presented in terms of streamlines, isotherm plots and averaged Nusselt number plots. It is observed that length and inclination angle of the fin significantly alter the streamlines and isotherms and hence the thermal performance of the system. For the best performance at different fin lengths, optimum inclination angle changes.Item Natural convection in a flexible sided triangular cavity with internal heat generation under the effect of inclined magnetic fieldSelimefendigil, F; Öztop, HEIn this numerical study, magnetohydrodynamics natural convection in a flexible sided triangular cavity with internal heat generation is investigated. The inclined wall of the cavity is cooled and flexible while the left vertical wall is partially heated. Galerkin weighted residual finite element method is used to solve the governing equations. The effects of pertinent parameters such as external Rayleigh number (between 10(4) and 10(6)), internal Rayleigh number (between 10(4) and 10(7)), elastic modulus of flexible wall (between 500 and 10(5)), Hartmann number (between 0 and 40) and inclination angle of the magnetic field (between 0 degrees and 90 degrees) on the fluid flow and heat transfer characteristics were numerically investigated. It was observed local and averaged Nusselt number enhance with external Rayleigh number but in the vicinity of the upper location of the heater local heat transfer deteriorates due to the inclined wall deformation with increasing external Rayleigh number. Heat transfer reduces with internal Rayleigh number and Hartmann number. Averaged heat transfer decreases 13.25% when internal Rayleigh number is increased from 10(4) to 10(7) and decreases 40.56% when Hartmann number is increased from 0 to 10. The reduction in the convection with magnetic field is effective for higher values of external Rayleigh numbers and averaged heat transfer increases with magnetic field inclination angle. (C) 2016 Elsevier B.V. All rights reserved.Item Effects of Combined Utilization of Active Cooler/Heater and Blade-Shaped Nanoparticles in Base Fluid for Performance Improvement of Thermoelectric Generator Mounted in Between Vented CavitiesSelimefendigil, F; Oztop, HFA wide range of technical applications, including solar power, waste heat recovery, electronics thermal management, and heat exchangers, employ thermoelectric generators. They can be mounted in between channels / cavities where hot and cold fluid streams exist. In this study, two novel methods of enhancing the power generation from thermoelectric generator device mounted in between vented cavities are proposed by combined utilization of active heater/cooler rectangular blocks and blade-shaped nanoparticles in base fluid. Finite element method investigation is conducted numerically for a range of hot and cold stream Reynolds numbers (250-1000), non-dimensional hot and cold block sizes (0.01-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-$$\end{document}0.4), and heating/cooling increments (0-10), with nanoparticle loading limited to 0.03. Higher values of Reynolds number results in a rise in thermoelectric generator power. When comparing the cases of lowest and highest Reynolds number combinations, a 219%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} increase in power is achieved. The thermoelectric generator power will rise by around 27.5%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} when the object size reaches its maximum. However, for moderate object sizes, up to 31.6%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} reduction in power generation can be realized. Greater temperature differences result in a linearly rising power generation, with an achievable power increase of up to 22%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document}. When nanoparticle loading in the base fluid for both cavities is raised to its maximum value, the resultant power increases by around 30%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30\%$$\end{document}. Thermoelectric generator power rises by 67.8%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} when an active heater/cooler with nanofluid is used in vented cavities, as opposed to the reference scenario of employing no object and only water. The thermoelectric generator device's hot and cold interface temperatures are accurately estimated using the artificial neural network based method. The estimated temperature can be used as boundary condition for the solution of the governing equations in the thermoelectric generator device domain which will decrease the computational cost when dealing with very complex channel configurations.Item A computational analysis on convective heat transfer for impinging slot nanojets onto a moving hot bodyCosanay, H; Oztop, HF; Selimefendigil, FPurpose The purpose of this study is to perform computational analysis on the steady flow and heat transfer due to a slot nanojet impingement onto a heated moving body. The object is moving at constant speed and nanoparticle is included in the heat transfer fluid. The unsteady flow effects and interactions of multiple impinging jets are also considered. Design/methodology/approach The finite volume method was used as the solver in the numerical simulation. The movement of the hot body in the channel is also considered. Influence of various pertinent parameters such as Reynolds number, jet to target surface spacing and solid nanoparticle volume fraction on the convective heat transfer characteristics are numerically studied in the transient regime. Findings It is found that the flow field and heat transfer becomes very complicated due to the interaction of multiple impinging jets with the movement of the hot body in the channel. Higher heat transfer rates are achieved with higher values of Reynolds number while the inclusion of nanoparticles resulted in a small impact on flow friction. The middle jet was found to play an important role in the heat transfer behavior while jet and moving body temperatures become equal after t = 80. Originality/value Even though some studies exist for the application of jet impingement heat transfer for a moving plate, the configuration with a solid moving hot body on a moving belt under the impacts of unsteady flow effects and interactions of multiple impinging jets have never been considered. The results of the present study will be helpful in the design and optimization of various systems related to convective drying of products, metal processing industry, thermal management in electronic cooling and many other systems.Item Analysis of hybrid nanofluid and surface corrugation in the laminar convective flow through an encapsulated PCM filled vertical cylinder and POD-based modelingSelimefendigil, F; Öztop, HFIn the present work, performance assessment of a PCM filled three dimensional vertical cylinder is con-ducted under the combined effects of surface corrugation and presence of binary nanoparticles in the heat transfer fluid. The numerical simulation is performed by using finite element method with varying values of Reynolds number (100 <= Re <= 750 ), number (1 <= N <= 8) and height (H/10 <= h <= H/2 ) of rect-angular type corrugation form and volume fraction of particles (0 <= phi <= 0.02) in unsteady configuration. Thermal transport features are enhanced while charging time is reduced for higher values of Reynolds number, solid volume fraction of the binary mixture in the heat transfer fluid. Complete charging time is reduced by 57 % with increase of Reynolds number from 100 to 750 while it is reduced by 23 % when nanofluid at the highest solid volume fraction is used instead of water. However, the corrugation param-eters have reverse effects on the charging process. A computational framework for reconstruction of heat transfer fluid and PCM temperatures for the unsteady parametric configuration in the computational do-main is offered by utilizing proper orthogonal decomposition (POD) technique with 25 modes for heat transfer fluid and 75 modes for PCM. (C) 2021 Elsevier Ltd. All rights reserved.Item Mixed convection and entropy generation of nanofluid flow in a vented cavity under the influence of inclined magnetic fieldSelimefendigil, F; Oztop, HFIn this study, mixed convection and entropy generation in a vented cavity with inlet and outlet ports are examined under the effects of an inclined magnetic field. Galerkin weighted finite element method was used for the solution of the governing equations. The numerical simulations are performed for various values of Reynolds numbers (between 100 and 500), Hartmann number (between 0 and 50) and solid particle volume fractions of CuO nanoparticles (between 0 and 4%). Different walls and domains of the computational model are considered for the heat transfer and entropy generation analysis. It was observed that at low Reynolds number number, magnetic field has the potential to enhance the heat transfer at the highest strength while the effect of magnetic field is to reduce the convection at higher Reynolds number. The contributions of different hot walls to the overall heat transfer change considerably with the change of Hartmann number while the effect of magnetic inclination angle is marginal. Inclusion of nanoparticle results in heat transfer enhancement in the absence and presence of magnetic field and the amount of enhancement is 25-27% at the highest value of solid nanoparticle volume fraction. Different parts of the cavity contribute differently to the overall entropy generation when Hartmann number varies while the overall entropy generation first decreases and then increases when the value of Hartmann number increases. The addition of nanoparticles increases the overall entropy generation rate.