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Öğe Effect of magnetic field locations on thermo-magnetic convection performance of Fe3O4/H2O ferrofluid flowing in a novel dimpled tube: An experimental study(Pergamon-Elsevier Science Ltd, 2023) Gursoy, Emrehan; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Tekir, Mutlu; Arslan, Kamil; Gedik, EnginThe aim of this study is to examine the hydrothermal behavior of Fe3O4 Ferrofluid flowing under the effect of uniform magnetic field (0 T <= B <= 0.3 T). In addition, magnetic field locations were changed for each experiment to observe effect of the magnetic field locations (x/D = 20, 40, 60) on the hydrothermal behavior of the proposed system. Fe3O4 Ferrofluid was prepared in phi = 1.0% volume concentration in water and flows under the laminar regime (1131 <= Re <= 2102). Comparisons of the hydrothermal behavior of the novel proposed parameters were performed according to combinations of the different magnetic field locations and magnitudes. It is concluded that the highest Nusselt number was obtained using B = 0.3 T for the magnetic field location of x/D = 20 for both in smooth and dimpled tubes. Compared to B = 0 T, the Nusselt number enhancement was detected by 64.03% for smooth tube for the magnetic field location of x/D = 20 for B = 0.3 T whereas Nusselt number wasaugmented by 45.40% for dimpled tube for the same input parameters. Furthermore, no considerable changes in friction factor was determined under magnetic field effect when the application of magnetic field locations was changed. As a result of these findings, the highest increase in Performance Evaluation Criteria belonging dimpled tube was calculated by 33.54% at Re = 2102 for B = 0.16 T for the magnetic field location of x/D = 20. As a general conclusion, this study can shed light on investigating ferrofluids behavior under magnetic field applied in var-iable magnetic field locations.Öğe Effects of sinusoidal turbulator in cylindrical channel on heat transfer and flow characteristics(Maejo Univ, 2020) Altun, Aziz Hakan; Gurdal, Mehmet; Berber, AdnanEffects of heat transfer and flow characteristics on Reynolds numbers of different sinusoidal turbulators placed separately from a pipe in the turbulent flow were investigated experimentally. The experiments were carried out under forced flow and constant heat flow conditions. The elements, which drew a sine curve used as a turbulator, were positioned axially to the channel centre. The experiments were repeated for 3 width values of sinusoidal turbulators that correspond to 3D/4, D/2 and D/4 (D = inner diameter of test pipe). The experiments showed that although there were increases in the rate of heat transfer with the turbulator, they caused considerable pressure drop. As a result, as the width of the turbulator increased, the heat transfer ratio (the Nusselt number) and coefficient of friction increased. Increase in Nusselt number was about 39-86% at D/4 width, 70-119% at D/2 width and 72-170% at 3D/4 width. It was observed that the coefficient of friction was significantly affected by the width of the sinusoidal turbulator, being about 0.02 in the case of straight pipe, 0.184 - 0.242 at D/4 width, 0.345 - 0.415 at D/2 width, and 0.416 - 0.451 at 3D/4 width. In addition, increasing coefficient of friction increased pressure drop and power required for pumping.Öğe Experimental study on the heat transfer enhancement in a rectangular channel with curved winglets(Taylor & Francis Inc, 2022) Berber, Adnan; Gurdal, Mehmet; Yetimoglu, MuhammedEffects of the curved winglet vortex generator inserts (CWVGs) on the forced convection heat transfer, friction factor, and performance evaluation criteria (PEC) interior flow were experimentally examined in this work. The CWVGs manufactured in CNC from aluminum 6061 material were used as the expanded finned surface with different attack angles (alpha) of 0 degrees, 30 degrees, and 60 degrees. In the study, air was used as the fluid. The experiments were realized in the Reynolds number ranging from 6000 to 20000. The results showed that the CWVG insert in a rectangular channel ensured significantly higher Nusselt number than that of the channel without the insert through friction factor that was also increased. The Nusselt number and friction factor increased with the increase in the attack angle (alpha) of CWVG insert. The heat transfer enhancement by the CWVGs with attack angle of 0 degrees, 30 degrees, and 60 degrees ensured higher than that of the plain tube in the range of 217.39-291.30%, 260.86-465.21%, and 278.26-476.08%, respectively. The friction factors in the inner rectangular channel produced by the CWVGs with attack angle of 0 degrees, 30 degrees and 60 degrees, were about 8.93-10.33, 10.66-14.16, and 14.96-19.13 times above the plain tube, respectively. The performance evaluation criteria (PEC) for CWVGs with attack angle of 0 degrees, 30 degrees, and 60 degrees were in the range of 1.22-1.78, 1.28-1.86, and 1.32-1.89, respectively.Öğe Prediction of heat transfer in a circular tube with aluminum and Cr-Ni alloy pins using artificial neural network(Taylor & Francis Inc, 2021) Berber, Adnan; Gurdal, Mehmet; Bagirsakci, KazimThis work aims to estimate the experimental heat transfer coefficients of a circular channel using artificial neural network. The experiments are carried out at a forced turbulent flow regime of 10,000 < Re <50,000. The obtained experimental Nusselt numbers are compared using the ANN (Artificial Neural Network). In the developed ANN structure are showed mean square error (MSE), average relative deviation (ARD %), and correlation coefficient (R-2) in modeling of overall experimental datasets of Nusselt number. As a result, it is observed that the heat transfer correlation predicted by ANN are sufficiently consistent with the experimental results.