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    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, Engin
    The 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.
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    Evaluation of nanoparticle shape factor on a laminar forced convective heat transfer characteristics of various nanofluids flow in a tube using single-phase numerical model
    (Taylor & Francis Inc, 2024) Tastan, Gizem; Gursoy, Emrehan; Alakour, Abdullah; Gedik, Engin
    Nanotechnology is advantageous in improving thermophysical properties and enhancing heat transfer rate compared with conventional fluids due to their superior thermophysical properties. These properties vary with many parameters such as concentration and shape. In this study, the effect of nanoparticles shape is numerically explored on heat transfer performance under a laminar flow regime (Re=500 and 2000) through the smooth tube. Heat transfer enhancement capability of the nanoparticle shapes with targeted reference to average Nusselt number, average Darcy friction factor, pumping power, and performance evaluation criterion have been investigated. Three types of nanofluids (Fe3O4/water, Al2O3/water, and GO/water) with various nanoparticle shapes (brick, cylindrical, platelet, and spherical) and different nanoparticle volume fractions (phi=1.0, 2.0, 3.0, and 4.0%) have been used as heat transfer fluid in analyzes. Numerical results show that heat transfer performance was greatly influenced by changing nanoparticle shapes. The highest average Nusselt number was obtained for GO/water nanofluid with platelet nanoparticle shape and phi=4.0%. Compared to water, Fe3O4/water, and Al2O3/water, the average Nusselt number in GO/water increased by 64.34%, 54.02%, and 43.41%, respectively. The highest performance evaluaton criterionwas obtained for the GO-water nanofluid with platelet nanoparticle shape at Re=2000. On the other hand, it is found that the Fe3O4/water nanofluid with platelets nanoparticle shape causes the highest pumping power compared with other analyzed nanofluids.
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    The first and second law analyses of thermodynamics for CoFe2O4/H2O flow in a sudden expansion tube inserted elliptical dimpled fins
    (Pergamon-Elsevier Science Ltd, 2023) Pazarlioglu, Hayati Kadir; Gursoy, Emrehan; Gurdal, Mehmet; Tekir, Mutlu; Gedik, Engin; Arslan, Kamil; Taskesen, Edip
    In this paper, thermo-hydraulic performance and entropy generation of the sudden expansion tube with elliptical dimpled fins (DFs) at different directions was computationally performed at different Reynolds (Re) numbers ranging between 100 & LE;Re & LE;2000 using cobalt ferrite/H2O (CoFe2O4/H2O) nanofluid (NF) (0.0 & LE;& phi;& LE; 2.0). The novelty of this study is to investigate the effect of the elliptical DF and its arrays in the sudden expansion tube in terms of thermodynamics laws (energy and entropy generations). While the sudden expansion ratio (D2/D1) is 2.5, elliptical dimple width (a) and height (b) show variations between 4 and 8 mm. In addition, the distances among elliptical DFs (P) are taken as P = 10, 15, and 20 mm while the diameter (D1) and length (L1) of the inlet tube are D1=8 mm and L1=375 mm. The diameter (D2) and length (L2) of the tube with the sudden expanding and elliptical DFs are D2=20 mm and L2=1125 mm, respectively. The study comprehensively exhibits results of the thermo-hydraulic performance and entropy generation based on numerical data. The results demonstrated that the highest heat transfer rate is recorded by the case of DT3, and DT3 enhances the convective heat transfer rate by 221%, and increases the pressure drop by 17.38% at Re=2000 compared to smooth tube (ST). It was observed that as the Re increases, the performance evaluation criteria (PEC) gradually increases too, and the highest PEC has been obtained for DT3 as 2.11 at Re=2000. The entropy generation (EnG) was also evaluated in terms of both geometric designs and volumetric concentrations. Moreover, the best total EnG was found around 17% for DT3 at the Re=1000 and & phi;=2.0% compared to ST using H2O. Consequence of the applied analyses, the use of elliptic DFs in a sudden expansion tube enhances the convective heat transfer rate and decreases total EnG.
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    An innovative approach of alternating magnetic field diversified with different wave types and magnet positions for ferrofluid flow in dimpled tube
    (Elsevier, 2023) Gurdal, Mehmet; Gursoy, Emrehan; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Gedik, Engin
    The purpose of the present experimental study is to investigate the forced magneto-convection of the Fe3O4/H2O ferrofluid flowing along smooth and dimpled tubes implemented with alternating magnetic field (B = 0.16 T and f = 5 Hz). All experiments were carried out for the working fluids pure water and ferrofluid with 1.0% volume fraction in the laminar flow regime (1131 & LE; Re & LE; 2102). Also, an original perspective of this study is to use of changing magnetic field wave types (Sinus, Triangle, and Square) and positions at different axial distances (x/D = 20, x/D = 40, and x/D = 60). Findings shed light on that the highest convective heat transfer ratio was realized at x/D = 20 location and square wave type for all cases. The average Nusselt number of the dimpled tube subjected to square wave type applied at x/D = 20 is increased by 58.13% compared to smooth tube without magnetic field and using H2O as working fluid. Moreover, when the friction factor was compared for the same conditions, the increment rate has been seen by 85.73%. Although Nusselt number is reached to its highest level using square wave type, the highest Performance Evaluation Criteria is detected around 1.45 using dimpled tube subjected to alternating magnetic field with triangle wave type applied at x/D = 20 for Re = 1131.
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    Investigation of magneto-convection characteristics in a sudden expanding channel with convex surface geometry under thermally developing flow conditions
    (Emerald Group Publishing Ltd, 2024) Gursoy, Emrehan; Pazarlioglu, Hayati Kadir; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil; Dagdeviren, Abdullah
    PurposeThe purpose of this study is to analyse the magnetic field effect on Fe3O4/H2O Ferrofluid flowing in a sudden expansion tube, which has specific behaviour in terms of rheology, with convex dimple fins. Because the investigation of flow separation is a prominent application in performance, the effect of magnetic field and convex dimple on the thermo-hydraulic performance of sudden expansion tube are examined, in detail.Design/methodology/approachDuring the solution of the boundary conditions of the sudden expansion tube, finite volume method was used. Analyses have been conducted considering the single-phase solution, steady-state, incompressible fluid and no-slip condition of the wall under forced convection conditions. In the analyses, it has been assumed that the flow was developing thermally and has been fully developed hydrodynamically.FindingsThe present study focuses on exploring the influence of the magnetic field, nanofluid concentration and convex dimple fins on the thermo-hydraulic performance of sudden expansion tube. The results indicate that the strength of the magnetic field, nanofluid concentration and convex dimple fins have a positive effect on the convective heat transfer in the system.Originality/valueThe authors conducted numerical studies, determining through a literature search that no one had yet investigated enhancing heat transfer on a sudden expansion tube using combinations of magnetic fields, nanofluids and convex dimple fins. The results of the numerical analyses provide valuable information about the improvement of heat transfer and system performance in electronic device cooling and heat exchangers.
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    Numerical simulation of sudden expansion tubes with Ag-MgO nanofluid and innovative fin structure: A thermo-fluidic analysis
    (Elsevier Science Inc, 2024) Pazarlioglu, Hayati Kadir; Gursoy, Emrehan; Gurdal, Mehmet; Said, Zafar; Arslan, Kamil; Gedik, Engin
    This study introduces an innovative approach to employing mono/hybrid nanofluids in tubes with sudden expansion, structured at various expansion angles and equipped with novel capsule -type dimpled fins. Pumping of hybrid nanofluids into sudden expansion tube combined with capsule -type dimpled fins and different expansion angles (ranging from 30 degrees to 90 degrees ) has not been investigated so far in terms of energy, exergy, and entropy analyses. Recognizing the attention currently devoted to the climate effect of a system exposed to high thermal loads, this study sheds light on the literature how a system preferred by engineers and professionals can be cooled down efficiently to increase the performance of the system. The objective is to analyze a detailed 3Estudy (energy, exergy, and entropy production) on water -based mono and hybrid nanofluids, exploring various volume fractions and combinations (including 2.0 % Ag, 2.0 % MgO, and blends of Ag-MgO). The study finds that a 45 degrees expansion angle, combined with capsule -type dimpled fins and 0.5 % Ag-1.5 % MgO nanofluid, offers the most efficient tube design, enhancing the average Nusselt number by 20.0 % . This configuration, also, reduces total entropy generation by approximately 23.0 % and shows exergy output by 26.0 % , though it does lead to a 26.0 % decrease in second law efficiency due to increased pumping power. Interestingly, the first law efficiency remains unchanged mainly across different nanofluid types. These findings provide valuable insights into optimizing heat transfer and fluid dynamics in engineering applications.
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    Performance improvement of air separation unit for an iron-steel industry using enhanced exergy analysis
    (Springer, 2024) Gursoy, Emrehan; Gedik, Engin; Georgiev, Aleksandar G.; Kecebas, Ali; Kurt, Huseyin
    In this study, the thermodynamic performance of a real operating three-stage turbo/centrifugal type main air compressor for the air separation unit in an iron-steel industry was evaluated using both conventional and enhanced exergy analyses. Furthermore, the interaction and the potential for improvement of system components at two different airflow rates, 210,000 Nm3 h-1 and 240,000 Nm3 h-1, were investigated under real operating conditions. The results indicated that the conventional exergy analysis of the system yields efficiency rates of approximately 21.3% and 25.0% for these airflow rates, respectively. It was found that implementing operating conditions proposed by the enhanced exergy analysis could increase the system's exergy efficiency to about 40.8% and 80.7%, respectively. The primary causes of exergy destruction in the compressor are generally attributed to frictions occurring in the impeller, diffuser, and volute, as well as shock waves and air circulation during the compression process. It was observed that system efficiency could potentially increase to 80.7% with improvements in compressors and pump. The study also determined that enhanced exergy analysis is beneficial for identifying losses in system components and is seen as a tool that complements conventional exergy analysis.