Browsing by Subject "Adaptive network based fuzzy inference system"

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    Magnetic field effects on the forced convection of CuO-water nanofluid flow in a channel with circular cylinders and thermal predictions using ANFIS
    (Elsevier Ltd, 2018) Selimefendigil F.; Öztop H.F.
    Numerical simulation of forced convection of CuO-water nanofluid over circular cylinders within a channel was conducted under the influence of a uniform magnetic field by using the finite element method. In the channel, four circular cylinders which are arranged in a two by two matrix configuration are used and they are kept at constant temperature. Effects of various pertinent parameters of the configuration such as the Reynolds number (between 100 and 1000), Hartmann number (between 0 and 10), solid particle volume fraction (between 0 and 0.04) and horizontal distance between the circular cylinder centers (between 0.5 and 8 times of the channel height) on the fluid flow and convective heat transfer were analyzed. The potential use of magnetic field in the reduction of the wake region behind the circular cylinder and augmentation of the heat transfer in the presence of nanoparticle inclusion to the base fluid was examined. It was observed that the established secondary peaks of local Nusselt number along the hot surface for moderate and higher values of Reynolds number reduces with Hartmann number and disappears at the highest value of Hartmann number. When the Hartmann number is increased from Ha = 0 to Ha = 10, 23% of the average heat transfer enhancement is achieved for cylinder which is located in the first row and second column (some distance far away from the wake of the first column cylinder). The average Nusselt number was found to augment by about 17–20 % at the highest and lowest values of Reynolds number and Hartmann numbers for circular cylinders which are placed at (first row first column) and (first row second column). Highly accurate and fast predictions of the average Nusselt number for the circular cylinders are obtained with Adaptive-Network-Based Fuzzy Inference System (ANFIS) modeling. © 2018 Elsevier Ltd
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    Corrugated conductive partition effects on MHD free convection of CNT-water nanofluid in a cavity
    (Elsevier Ltd, 2019) Selimefendigil F.; Öztop H.F.
    In the present study, free convection in a cavity with a corrugated partition which have different fluids on different parts of the partition was numerically examined. In one of the domains carbon nanotube (CNT)-water nanofluid with an inclined uniform magnetic field is considered. A triangular wave form of conductive corrugated partition is used. The numerical simulation was performed with Galerkin weighted residual finite element method. Various values of pertinent parameters of current thermal configuration such as Rayleigh number (between 104 and 106), Hartmann number (between 0 and 50), magnetic inclination angle (between 0° and 90°), solid particle volume fraction (between 0 and 0.03), number of triangular waves (between 1 and 40), height of triangular waves (between 0.01H and 0.2H) and thermal conductivity ratio (between 0.1 and 100) and their influence on the hydro-thermal behavior were examined. It was observed that significant enhancements in the Nusselt number is obtained with CNTs. The average heat transfer decreases for higher values of Hartmann number but slightly varies as the value of magnetic inclination angle changes. As the number and height of the triangular waves increase, the average heat transfer reduce which are 32% and 27% for the highest values of number and height of triangular waves both for water and nanofluid. For forecasting the average heat transfer coefficient of the current thermal system, a novel method based on Proper Orthogonal Decomposition (POD) and Adaptive-Network-Based Fuzzy Inference System (ANFIS) is used which yields highly accurate results that are computationally inexpensive. © 2018 Elsevier Ltd
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    Thermoelectric generation from vented cavities with a rotating conic object and highly conductive CNT nanofluids for renewable energy systems
    (Elsevier Ltd, 2021) Selimefendigil F.; Öztop H.F.
    In the present work, thermoelectric power generation from cavities with ventilation ports is considered by using a rotating conic object and carbon-nanotube particles in the base fluid. Effects of different pertinent parameters such as Reynolds numbers of hot and cold fluid streams (between 200 and 1000), rotational Reynolds number of the conic object (between −400 and 400), size (between 0.05H and 0.25H) and horizontal location (between 0.2H and 0.6H) of the object and nanoparticle volume fractions of nanoparticles (between 0 and 0.02) on fluid flow, interface temperature and generated thermoelectric output power characteristics were studied. It was observed that exit port location of the hot cavity, fluid stream Reynolds number and rotational Reynolds number of the object have significant impacts on the fluid flow, interface temperatures and output power. When lowest and highest fluid stream Reynolds number is compared, 43.75% variations in the output power is obtained. The clockwise rotation of the conic object results in higher thermoelectric power generations as compared to a stationary cone while up to 49.20% increments of the power is attained at the highest rotational speed. The size of the rotating object is influential on the power generation while its horizontal location has slight effects. When nanofluid at the highest solid volume fraction configuration is compared with pure water case, 20% increment in the thermoelectric power is obtained. A predictive model for power estimations with adaptive network-based fuzzy inference system is proposed for input parameters of hot and cold fluid stream Reynolds number and rotational Reynolds number of the conic object which delivers accurate and fast prediction results. © 2021 Elsevier Ltd