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    Öğe
    Investigations of flow structures and performances of heat transfer in semi-circular grooved ducts by applying field synergy principal analysis: An experimental and numerical study
    (Pergamon-Elsevier Science Ltd, 2023) Tokgoz, Nehir; Erdinc, Mehmet Tahir; Kaska, Onder; Sahin, Besir
    The present study aimed at investigating the flow structure and heat transfer mechanism through the corrugated channel experimentally and numerically. Particle imaging velocimetry (PIV), which can give detailed information about the wake and shear flow regions, was used for the experiments. The experimental and numerical works were performed considering Reynolds numbers in the range of 6 x 103 <= Re <= 12 x 103 and 3 x 103 <= Re <= 2 x 104, respectively. In the numerical part, aspect ratios (R/hp) of examined grooves have been chosen as 0.1, 0.2, and 0.3, and for the experiment, only one aspect ratio was chosen which was 0.3. The experimental studies were conducted regarding different Reynolds numbers as well as the distributions of instantaneous and timeaveraged velocity contours, Turbulence Kinetic Energy, Reynolds shear stress, and vorticity. The standard SST k-omega turbulent method was employed for the case of numerical study to predict the thermal performance (eta) along with Nusselt numbers (Nu) the friction factors (f) and local field synergy angles (alpha, beta) were calculated. As a result, the Nusselt number (Nu) values of the corrugated channels were higher than the parallel plate, and the increment in the Nusselt number initially increased and later decreased with Reynolds numbers for all aspect ratios considered.
  • Küçük Resim
    Öğe
    Numerical Investigation of Magnetohydrodynamic Forced Convection and Entropy Production of Ferrofluid Around a Confined Cylinder Using Wire Magnetic Sources
    (Springer, 2022) Tumse, Sergen; Zontul, Hakan; Hamzah, Hudhaifa; Sahin, Besir
    The current study numerically explored the hydrothermal flow and entropy generation properties of ferrofluid (water and Fe3O4) on a cylindrical body in the rectangular channel subjected to the non-uniform magnetic field going through current carrying wires. The effect of various parameters, such as ferrofluid volume fraction, phi the strength of the non-uniform magnetic field, Ha, and Reynolds number, Re, on the flow characteristics, and forced convection heat transfer, is investigated using finite-volume-based Ansys Fluent 20. Obtained results demonstrate that the applied magnetic field shortens the length of recirculating wake downstream of the cylinder at Re = 25 and makes unsteady flow with alternate vortex shedding as time-independent steady flow for Hartmann numbers greater than Ha >= 6 at Re = 100. At Re = 50, the total drag coefficient, C-D, gets higher by almost 20% when Ha increases from Ha = 0 to Ha = 6 and subsequently grows by 61% at Ha = 10. The findings show that the average Nusselt number, Nu(avg), demonstrates monotonic behavior with the Ha and it augments when the strength of the non-uniform magnetic field increases. The Nu(avg) improvement is in the vicinity of 11.71% at Ha = 10 and 23.26% at Ha = 18 for Re = 25. The maximum value of entropy generation reduces, S-L, when the non-uniform magnetic field is applied. Moreover, increasing the Hartmann number, Ha influences the high levels region of entropy production by relatively extending this zone towards the downstream of the channel and covering more area around the cylinder. According to the outcomes of numerical simulation, there is an increase in Nu(avg) with 3.98% and 3.88% for Ha = 2 and 18, respectively, when the ferrofluid volume fraction rises from phi = 0% to phi = 4% at Re = 25. Finally, the optimum thermal performance criterion, xi, is obtained at Re = 150 for Ha = 0 and phi = 4%.