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    Energy analysis of magnetite nanofluid flowing in newly designed sudden expansion tube retrofitted with dimpled fin
    (Pergamon-Elsevier Science Ltd, 2022) Guersoy, Emrehan; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Guerdal, Mehmet; Gedik, Engin; Arslan, Kamil; Kurt, Hueseyin
    Sudden expansion geometry plays an important role in the design of many engineering applications such as heat exchangers to avoid thermal stress on welded joints. While the heat transfer in these geometries is maximized at the reattachment points, it decreases to a minimum in the recirculation regions created by the fluid. To prevent this situation and improve the performance of the expansion tubes, nanofluid, and expanded surfaces can be used. For this purpose, forced convection of magnetite nanofluid flow in various expansion ratios has been investigated numerically in this study. Analyses have been performed on Reynolds ( Re ) numbers ranging from 100 to 2000, constant and uniform heat flux at 600 W/m(2), and volume concentrations (1.0 <=phi <= 2.0 vol.%). The result showed that while the Nu number increases with increasing Re number , the most efficient case is Dimpled Tube ( DT ) 9, and the highest value of performance evaluation criteria (PEC) has been obtained at phi= 2.0 vol.%. Compared with the water, the highest Nu number value has been obtained as 3.34% increased at Re = 20 0 0 and phi= 2.0 vol.%. When compared to the DT9 and Smooth Tube ( ST ) 1 where water was used as the working fluid at Re = 20 0 0 and phi= 2.0 vol.%, the PEC value increased by 8.66% and 110.31%, respectively. In addition, the bottom wall of the DT9 case performs higher convective heat transfer rate than the top wall.(c) 2022 Elsevier Ltd. All rights reserved.
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    Experimental and numerical study on ferrohydrodynamic and magneto-convection of Fe3O4/water ferrofluid in a sudden expansion tube with dimpled fins
    (Elsevier, 2024) Guersoy, Emrehan; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil; Dagdeviren, Abdullah
    Background: This study experimentally and numerically addresses magnetohydrodynamic forced convection including dimpled fins, Fe3O4/water ferrofluid, and DC magnetic field. In this research, focusing on the thermohydraulic performance improvement of a sudden expansion tube. It has been used different inlet diameters, dimple sizes, ferro nanoparticle concentrations, and magnetic field strengths to examine the heat transfer and fluid dynamics characteristics of the system. Methods: The study consists of two parts, i) experimental and ii) numerical. Steady-state, incompressible, Newtonian flow were considered but chemical reaction, viscous dissipation, buoyancy, and radiative heat transfer were neglected in this study. On the other hand, numerical solutions were carried out for single-phase method. This study was first compared with the studies in the literature on the flow in a sudden expansion tube without dimpled fins and the error rate was found to be less than 10%. In the analysis, dimpled fins with d=3, 5, and 7 mm at each P=15 mm (P/d=5.0, 3.0, and 2.14) have been used. As working fluid, Fe3O4/water ferrofluid with volume concentration of phi=1.0 % and 2.0% have been analyzed. Additionally, DC magnetic fields, which strength of Ha=0.1, 0.3, 0.5, 1.1, 3.2, and 5.3 (B =0.01, 0.03, 0.05, 0.1, 0.3, and 0.5T), have been applied on the sudden expansion tube surface as external force. Significant findings: Dimpled fins enhance the heat transfer by disrupting the boundary layer and forming secondary flows, while the ferrofluid increases the thermal conductivity and viscosity of the base fluid. Based on these explanations, dimpled fins increased the convective heat transfer rate at the rate of 96.0% compared with smooth tube. In addition, Fe3O4/water ferrofluid with phi=2.0 % performed the highest performance and performance evaluation criteria increased by 8.5%. The magnetic field also contributes to the heat transfer enhancement by inducing Lorentz force and mixing the flow. Excessive increasing of magnetic field strength adversely affected the system performance, and the highest performance evaluation criterion is acquired at Ha=3.2 by increasing 3.9%. Compared with smooth tube, compound effect of dimpled fins, Fe3O4/water ferrofluid, and magnetic field improved the average Nusselt number and performance evaluation criterion at the rate of 279.8 % and 207.9%, respectively.
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    The first and second law analyses of thermodynamics for a human living at Kastamonu and Karabük cities in Turkiye
    (Elsevier, 2024) Guerdal, Mehmet; Guersoy, Emrehan; Gedik, Engin
    The phenomenon of heat dissipation and exergy transfer during the respiratory process in the human body holds significant importance concerning thermal comfort and wellness. In this study, the effect of the environmental condition of the Kastamonu and Karab & uuml;k Provinces in the T & uuml;rkiye's West Blacksea region on human body thermoregulation behavior has been investigated for the last eight years (2015-2022). It has been found that the cumulative heat loss and entropy generation associated with human respiration are markedly influenced by seasonal and environmental fluctuations. Besides, it has been detailly examined that the effects of average air temperature, average relative humidity, and average atmospheric pressure used as meteorological data on energy loss, entropy generation, and exergy flow have been investigated. The results reveal that most heat loss originates from metabolism energy at the rate of 5.935 W/m(2). In addition, it was observed that heat exchange realized by passive systems such as convection and evaporation exhibited the maximum energy loss. Moreover, the results revealed that an increment in environmental temperature and relative humidity causes a decrement in convective heat loss. An evaluation of lowest heat loss and the highest exergy values was obtained specifically for & Idot;nebolu distriction (PZ-3). Accordingly, the minimum finding in heat loss, quantified as 1.9099 W/m(2), was observed in the month of August, while the zenith in exergy, reaching 0.2846 W/m(2), was likewise noted during the same temporal interval. Besides, the level of thermal comfort at each location is computed. According to the predicted mean vote (PMV) and Predicted Percentage Dissatisfied (PPD) indexes, it was concluded that the dissatisfaction of the atmospheric conditions in the provinces in four seasons is high on the human body.
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    Parametric analysis of different Al2O3 nanoparticle shapes and expansion angles for sudden expanded tube regarding the first law of thermodynamics
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2024) Guersoy, Emrehan; Pazarlioglu, Hayati Kadir; Guerdal, Mehmet; Gedik, Engin; Arslan, Kamil
    The thermo-hydraulic performance of Al2O3/H2O nanofluid with different nanoparticle shapes flowing in a sudden expansion tube with variable sudden expansion inclination angles and elliptical dimpled fins with different diameters were numerically investigated. Investigation of variable sudden expansion inclination angles, elliptic dimpled fins, and different nanoparticle shapes together reveals the novelty of this study. The main purpose of this study is to analyse the effect of nanofluid particle shapes, sudden expansion inclination angles, and elliptical dimpled fin on thermo-hydraulic performance for sudden expansion tube. The platelet, cylindrical, and blade nanoparticle shapes of Al2O3 nanoparticle (phi = 1.0 %) were separately mixed into base fluid to obtain working fluid. Numerical studies were carried out under laminar flow regime (500 <= Re <= 2000). Furthermore, the sudden expansion tube was assumed to have inclination angles with alpha = 30 degrees, 45 degrees, 60 degrees, and 90 degrees. The results presented that the highest Performance Evaluation Criterion is obtained for the case of DT6 using Al2O3/H2O with platelet nanoparticle shape at Re = 2000. Besides, the highest Nusselt number and Performance Evaluation Criterion were realized at the inclination angle of 45 degrees. The increment rate of Nusselt number and Performance Evaluation Criterion at alpha = 45 degrees were determined as 8.75 % and 10.52 % compared to alpha = 30 degrees, respectively. Moreover, elliptical dimpled fins with sized as a = 6 mm and b = 12 mm presented the highest thermo-hydraulic performance, and this condition showed an increment of 153.9 % compared to case of a = 2 mm and b = 4 mm.