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Öğe Effects of Twisting Ratio, Diagonal Length, and Pitch Ratio of Hexagonal Pin Fins on Thermo-hydraulic Performance of Heat Sink(Toronto Metropolitan University, 2023) Gürdal, M.; Tekir, M.; Algbourie, N.I.; Pazarlioglu, H.K.; Arslan, K.While the effect of the twisting ratio on a heat sink was investigated for the first part of the study, the diagonal length and pitch ratio were observed for following step. The parametric studies were applied under turbulent regime (2658? Re?7138) to monitor thermo-hydraulic performance of novel proposed design. The edge length of the pin fins (Lef) was varied regarding their diagonal length (5? Lef ? 6) while the pitch ratio (P/e) and twisting ratio were varied in the range of 0.75? P/e?1.0 and 50?TR? 200 respectively. By using the turbulent model SST k-? with low-Re correction model on ANSYS Fluent, the computational study has been carried out to discretize RANS equations. Average Nusselt number (Nu) and average Darcy friction factor (f) which define the thermo-hydraulic performance of system were elucidated in detail. As a result, the best thermo-hydraulic performance was achieved as 1.55 by using the lowest twisting ratio (TR=200), pitch ratio (p/e=0.75) and the highest diagonal length (Lef=6) and at Re=2658. © 2023, Toronto Metropolitan University. All rights reserved.Öğe Hydrothermal behavior of hybrid magnetite nanofluid flowing in a pipe under bi-directional magnetic field with different wave types(Elsevier Ltd, 2022) Tekir, M.; Gedik, E.; Arslan, K.; Kadir, Pazarlioglu, H.; Aksu, B.; Taskesen, E.This experiment setup has been developed to elucidate the effect of different wave types (sinusoidal, triangle, square) of bi-directional magnetic field on hydrothermal characteristics of hybrid magnetite nanofluid flowing through a tube. The bi-directional magnetic field is not a novel method among active methods of heat transfer enhancements, yet the effects of different wave types have not been researched so far. In this study, the effects of different wave types of alternating magnetic fields with various frequencies (f) (2, 5, and 15 Hz) on flow and heat transfer characteristics of Fe3O4-Cu/Water hybrid magnetic nanofluid flow have been investigated experimentally. The major findings have been discussed for different combinations of hybrid magnetite nanofluid, types of waves, values of Reynolds number (Re), and f. The hydrothermal characteristics and their effects on usability in the industry with high efficiency have been established in terms of average Nusselt number (Nu), average friction factor (f), and Performance Evaluation Criteria (PEC). It is concluded that the use of triangle wave type with f = 15 Hz with 2% Fe3O4/water shows the highest enhancement in f by 500% compared to distilled water (DW) at Re = 994 while the use of square wave type with f = 5 Hz using the same Re and nanofluid presents the highest increase in Nu by 15.3% compared with DW. Above all, the triangular wave type is determined as an optimum wave type for f = 15 Hz while the sinus and square wave types are realized as optimum ones for f = 5 Hz. © 2022 Elsevier LtdÖğe IMPACT OF TWISTED DUCTS WITH DIFFERENT TWIST RATIOS ON HEAT TRANSFER AND FLUID CHARACTERISTICS OF NIO/WATER NANOFLUID FLOW UNDER MAGNETIC FIELD EFFECT(Begell House Inc., 2022) Pazarlioglu, H.K.; Gürdal, M.; Tekir, M.; Arslan, K.; Gedik, E.Laminar forced convection of NiO/water nanofluid in a twisted square duct has been investigated numerically under the effect of an external magnetic field (B = 0 G, 450 G, and 550 G) in the Reynolds number range of 500 ? Re ? 2000. Four different twist ratios (D/L = 0.0, 1.0, 1.5, and 2.0) of the square duct have also been examined. The nanoparticle volume fractions (NPVF) of NiO/water nanofluid have been selected between 0.6 vol.% and 2.5 vol.%. The effects of the magnitude of the magnetic field (MF), twist ratio, Reynolds number, and nanoparticle volume fraction on thermohydraulic performance have been examined by using the homogeneous model in the numerical analyses. The results of the numerical computations have been reported with average Nusselt number Nu, pressure loss, average Darcy friction factor f, and performance evaluation criterion (PEC). The highest heat transfer increment by 20% has been achieved at D/L = 2.0 with the highest nanoparticle volume fraction, namely, 2.5 vol.% NiO/water nanofluid, compared to the case of distilled water (DW) flowing in a plain duct (PD). In addition, it was determined that the magnetic field effect increases the convective heat transfer in the twisted duct with D/L = 2.0 up to 35% compared to the cases in the absence of a magnetic field at D/L = 2.0. Among all cases, the highest PEC has been obtained with 2.5 vol.% NiO/water nanofluid flowing in the twisted duct with the twist ratio D/L = 2.0. © 2022 by Begell House, Inc.Öğe A NUMERICAL INVESTIGATION ON THE THERMO-HYDRAULIC PERFORMANCE OF DIMPLED FIN CONFIGURATIONS IN A RECTANGULAR CHANNEL(Begell House, Inc, 2022) Pazarlioglu, H. K.; Gurdal, M.; Tekir, M.; Altunay, F. M.; Arslan, K.The main purpose of the study is to observe the effect of dimple fin diameter and arrangement on thermohydraulic performance under a turbulent flow regime. In this context, it was investigated numerically for convective heat transfer and flow characteristics of air flowing in a rectangular channel with different dimple configurations. The present study has conducted the analyses for fully developed flow under uniform and constant heat flux conditions of 800 W/m(2). The simulations have been carried out with Reynolds numbers ranging from 15000 to 25000. As a result, Among the 5 cases, the highest heat transfer and friction coefficient was obtained for the rectangular channel with a dimple fin diameter of 2 mm. On the other hand, Nusselt number and friction coefficient values are compatible with the literature. The highest performance evaluation criteria value was obtained at Re=15000 and for case 5. After all, it was observed that the forced convection heat transfer ratio increased with dimple diameter and Reynolds number.
