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Öğe CFD ANALYSIS OF LAMINAR FORCED CONVECTIVE HEAT TRANSFER FOR TiO2/WATER NANOFLUID IN A SEMI-CIRCULAR CROSS-SECTIONED MICRO-CHANNEL(Yildiz Technical Univ, 2019) Kaya, H.; Ekiciler, R.; Arslan, K.In this study, forced convection flow and heat transfer characteristics of TiO2/water nanofluid flow with different nanoparticle volume fractions (1.0%, 2.0%, 3.0% and 4.0%) in semi - circular cross - sectioned micro - channel was numerically investigated. The three - dimensional study was conducted under steady state laminar flow condition where Reynolds number changing from 100 to 1000. CFD model has been generated by using ANSYS FLUENT 15.0 software based on finite volume method. The flow was under hydrodynamically and thermally developing flow condition. Uniform surface heat flux boundary condition was applied at the bottom surface of the micro - channel. The average and local Nusselt number and Darcy friction factor values were obtained using numerical results. Also, the effects of using nanofluid on local values of Nusselt number and Darcy friction factor were investigated. Numerical results indicate that the increasing of nanoparticle volume fraction of nanofluid, the average Nusselt number increases; however, there is no significant variation in average Darcy friction factor.Öğe A cfd investigation of al 2 o 3 /water flow in a duct having backward-facing step(2019) Ekıcıler, R.; Aydeniz, E.; Arslan, K.Al 2 O 3 /water forced convection nanofluid flow was numerically studied in a duct with backward-facingstep. Nanoparticle volume fraction was changed between 1%-5%. Diameter of nanoparticle was constant (d p =40nm). The Reynolds number was increased from 100 to 500. The step and total height of the duct were 4.8 mmand 9.6 mm, respectively. The bottom wall, which was positioned after the step, was heated with 2000 W/m 2 andthe rest of the walls were adiabatic. Nusselt number, velocity profiles and friction factor were investigated indetail. It was obtained that Nusselt number increases with increasing nanoparticle volume fraction and Reynoldsnumber.Öğe A CFD INVESTIGATION OF Al2O3/WATER FLOW IN A DUCT HAVING BACKWARD-FACING STEP(Yildiz Technical Univ, 2019) Ekiciler, R.; Aydeniz, E.; Arslan, K.Al2O3/water forced convection nanofluid flow was numerically studied in a duct with backward-facing step. Nanoparticle volume fraction was changed between 1%-5%. Diameter of nanoparticle was constant (d(p)=40 nm). The Reynolds number was increased from 100 to 500. The step and total height of the duct were 4.8 mm and 9.6 mm, respectively. The bottom wall, which was positioned after the step, was heated with 2000 W/m(2) and the rest of the walls were adiabatic. Nusselt number, velocity profiles and friction factor were investigated in detail. It was obtained that Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number.Öğe A CFD investigation of Al2O3water flow in a duct having backward facing step(Yildiz Technical University, 2019) Ekiciler, R.; Aydeniz, E.; Arslan, K.Al2O3water forced convection nanofluid flow was numerically studied in a duct with backward facing step. Nanoparticle volume fraction was changed between 5%. Diameter of nanoparticle was constant (dp=40 nm). The Reynolds number was increased from 100 to 500. The step and total height of the duct were 4.8 mm and 9.6 mm, respectively. The bottom wall, which was positioned after the step, was heated with 2000 W/m2 and the rest of the walls were adiabatic. Nusselt number, velocity profiles and friction factor were investigated in detail. It was obtained that Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number. © 2019 Yildiz Technical University.Öğe Comparison of different turbulent models in turbulent-forced convective flow and heat transfer inside rectangular cross-sectioned duct heating at the bottom wall(Springer International Publishing, 2014) Arslan, K.; Onur, N.In this study, steady-state turbulent-forced flow and heat transfer in a horizontal smooth rectangular cross-sectioned duct was numerically investigated. The study was carried out in the turbulent flow region where Reynolds number ranges from 1 × 104 to 5 × 104. The flow was developing both hydrodynamically and thermally. The bottom surface of the duct was assumed to be under constant surface temperature. A commercial CFD program Ansys Fluent 12.1 with different turbulent models was used to carry out the numerical study. Different turbulence models (k–? Standard, k–? Realizable, k–? RNG, k–? Standard and k–? SST) were used. Based on the present numerical solutions, new engineering correlations were presented for the heat transfer and friction coefficients. The numerical results for different turbulence models were compared with each other and the experimental data available in the literature. It was observed that k–? turbulence models represented the turbulent flow condition very well for the present study. © Springer International Publishing Switzerland 2014.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 ENERGY, ENTROPY, AND EXERGY ANALYSES OF SUDDEN EXPANSION TUBE WITH CONVEX SURFACE USING FERROFLUID(Begell House Inc., 2024) Gürsoy, E.; Gürdal, M.; Gedik, E.; Arslan, K.Energy, entropy, and exergy analyses have been examined in sudden expansion tube (SET), which used in many thermal applications such as heat exchangers, micro-scale industry application, with both smooth (ST) and convex fin (CFT) surfaces. For the purpose of enhancing the thermal and hydraulic efficiency a ternary approach in which SET, and nanofluid, and convex fin have been employed together. Numerical parametric analyses have been carried out under steady-state, fully developed flow, and constant heat flux conditions with laminar, transitional and turbulent flow regimes (500?Re?10000) using Finite Volume Method (FVM). Two different working fluids as water and ferrofluid (Fe3O4/water) with ?=2.0% volume fraction have used. According to numerical results, the highest increment in the average Nusselt number (Nu) was caused by ferrofluid oc-curred in the laminar flow regime, approximately 7.0%, and its effect on the Darcy friction factor (f) was approximately 4.0%. On the other hand, the average Nu increased nearly twofold under the effect of convex fins at the transitional flow regime. Convex fins severely affected the f, causing an in-crement of nearly 260% in the turbulent flow regime. In the irreversibility analysis, convex fins performed the lowest dimensionless total entropy generation reducing up to 46.0% and increased the second-law efficiency up to 14.0% at Re=2000. Furthermore, the results of first-law efficiency, exergy outlet, exergy loss, and pumping power were investigated in detail and entropy generation results were supported with contours. © 2024, Begell House Inc. All rights reserved.Öğe ENTROPY GENERATION ANALYSIS OF FORCED CONVECTION FLOW IN A SEMICIRCULAR MICROCHANNEL WITH TiO2/WATER NANOFLUID(Begell House Inc, 2019) Kaya, H.; Ekiciler, R.; Arslan, K.In this study, entropy generation caused by heat transfer and friction of forced convection flow in a semicircular cross-sectioned microchannel with TiO2/water nanofluid was numerically analyzed. The volume concentrations of the nanofluid were taken 1.0%, 2.0%, 3.0%, and 4.0%. Local and total entropy generation due to the heat transfer and friction were calculated for the microchannel. A three-dimensional analysis was simulated under steady-state laminar flow conditions with Reynolds number varying from 100 to 1000. The results of the simulation were obtained using the CFD code. The flow was considered as hydrodynamically fully developed under thermally developing conditions. A uniform heat flux boundary condition was applied at the bottom surface of the microchannel. According to the results of the numerical study, the effect of the nanofluid volume concentration and fluid velocity on entropy generation was evaluated. The findings show that the total and friction values of entropy generation increase with increasing flow velocity, while heat transfer entropy generation values decrease since nanofluids improve the heat transfer capability. Also, the results indicate that an increase in the volume concentration of the nanofluid causes friction entropy generation enhancement while heat transfer entropy generation decreases in all cases.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 INTERNATIONAL MOBILITY OF ACADEMICS: SCIENCE MAPPING THE EXISTING KNOWLEDGE BASE(Emerald Publishing, 2023) Polat, M.; Arslan, K.The worldwide interdependency of nations has been acknowledged throughout the globalization literature and by many national and international organizations, including higher education institutions (HEIs), which have become an essential tool to accelerate this process. Financial, cultural, and political motives have driven 21st century higher education (HE) toward a more international direction shaping HE policies and promoting the mobility of ideas and individuals across the world. Utilizing bibliometric and descriptive tools, the article aims to analyze the existing knowledge base on international mobility of academics (IMA) as a core component of internationalization. More specifically, the study examines 423 papers published between 1970 and 2021 in Scopus and Web of Science (WoS) databases to reveal the big picture of the knowledge base by identifying the volume, growth trajectory, geographical dispersion, the most influential authors, articles, journals as well as the intellectual structure and the topical foci in the field. The findings have produced four distinct schools of thought labeled as “Knowledge Transfer and Mobility Networks,” “Academic Mobility in IHE Process,” “Expatriate Studies,” and “Scientific Mobility.” Moreover, the co-occurrence keyword map has yielded several topical foci: “Internationalization and Expatriate Academics,” “Academic Mobility and Career Paths,” and “Knowledge Transfer, Migration, © 2024 by Mustafa Polat and Kürşat Arslan.Öğe Laminar Forced Convection and Entropy Generation of ZnO-Ethylene Glycol Nanofluid Flow through Square Microchannel with using Two-Phase Eulerian-Eulerian Model(Isfahan Univ Technology, 2019) Uysal, C.; Arslan, K.; Kurt, H.In this paper, convective heat transfer and entropy generation of ZnO-EG nanofluid flow through a square microchannel are numerically investigated. Flow is modelled by using Eulerian-Eulerian two phase flow model. Nanoparticle volume fraction of ZnO-EG nanofluid ranged between %1.0 and %4.0. As a result, it is found that the convective heat transfer coefficient of flow increased from 9718.15 W/m(2) K to 23010.79 W/m(2) K when 4.0% ZnO nanoparticle addition to pure EG at Re=100. Total entropy generation of ZnO-EG nanofluid decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. It is also observed that the Bejan number decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid.Öğe Laminar forced convection and entropy generation of ZnO-ethylene glycol nanofluid flow through square microchannel with using two-phase Eulerian-Eulerian model(Isfahan University of Technology, 2019) Uysal, C.; Arslan, K.; Kurt, H.In this paper, convective heat transfer and entropy generation of ZnO-EG nanofluid flow through a square microchannel are numerically investigated. Flow is modelled by using Eulerian-Eulerian two phase flow model. Nanoparticle volume fraction of ZnO-EG nanofluid ranged between %1.0 and %4.0. As a result, it is found that the convective heat transfer coefficient of flow increased from 9718.15 W/m2K to 23010.79 W/m2K when 4.0% ZnO nanoparticle addition to pure EG at Re = 100. Total entropy generation of ZnO-EG nanofluid decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. It is also observed that the Bejan number decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. © 2019 Isfahan University of Technology.Öğe Numerical analysis of effect of impinging jet on cooling of solar air heater with longitudinal fins(Begell House Inc., 2021) Pazarlioglu, H.K.; Ekiciler, R.; Arslan, K.In this study, the effect of impinging jet cooling on solar air heater with and without longitudinal fins has been numerically investigated. The absorber plate surface of the solar air heater is modeled as a constant heat flux condition. Numerical analyses have been conducted on turbulent flow conditions (10,000 ? Re ? 50,000). The jet flow velocity has been taken constant. The effect of fin height and mass flow rate of working fluid on the thermal efficiency of the solar air heater has been analyzed in detail. Variation of the convection heat transfer coefficient as a function of Reynolds number has also been determined for finned and unfinned conditions. Temperature and local Nusselt number distributions on the absorber plate have been defined as contour graphs. It is found that the Nusselt number and thermal efficiency enhance by adding impingement jets and increasing the Reynolds number. Also, it is obtained from numerical analyses that the convection heat transfer coefficient increases with increasing the fins height. Finally, it is revealed that using impinging jets and fins enhances the efficiency and convection heat transfer up to 23.35% and 15%, respectively. © 2021 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.
