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Öğe 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, HueseyinSudden 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.Öğe 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, EnginThe 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.Öğe Numerical energy and entropy analyses of a tube with wavy tape insert including CoFe2O4/water nanofluid under laminar regime(Elsevier Science Inc, 2024) Yildirim, Furkan; Guerdal, MehmetThe primary objective of this investigation is to assess the impact of vortex generator geometry and nanofluid on thermohydraulic and irreversibility characteristics within a laminar flow regime. The study introduces an original CoFe 2 O 4/ H 2 O (1 % vol.) nanofluid and employs a wave tape insert to induce forced convection in a tube, accompanied by first and second-law thermodynamic analysis. The novelty of this research lies in the numerical exploration of heat transfer and flow profiles for a nanofluid in a tube, varying the wave rate (y = 4-5-6). The investigation considers the laminar model and single-phase approach in all analyses under constant heat flux (q = 2000 W/m 2 ). The study observed that the nanofluid flowing in the tube with a wave ratio of 4, 5, and 6 resulted in an average enhancement in the Nusselt number of 93.25 %, 86.26 %, and 80.06 %, respectively. The optimal performance evaluation criterion (PEC) for water flowing in the tube with a wave ratio of 6 at Re = 500 exhibited an increase of 11.0 %, whereas the CoFe 2 O 4 /H 2 O flow showed a 9.14 % increment in the average PEC along the Reynolds number. Moreover, the total entropy generation values for water flowing in tubes with wave ratios of 5, 6, and 4 exhibited increases of 101.88 %, 94.66 %, and 51.34 %, respectively, in comparison to the smooth tube.Öğe 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, KamilThe 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.Öğe Thermal performance of Fe3O4/water nanofluid flow in a newly designed dimpled tube under the influence of non-uniform magnetic field(Elsevier France-Editions Scientifiques Medicales Elsevier, 2022) Altunay, Fethi Murat; Pazarliog, Hayati Kadir; Guerdal, Mehmet; Tekir, Mutlu; Arslan, Kamil; Gedik, EnginThe effects of alternating and constant magnetic fields on heat transfer characteristics of nanofluid flow in a dimpled tube have not been investigated either numerically or experimentally. In this context, the hydrothermal performance of Fe3O4/water (1.0 vol%) ferronanofluid flow in the dimpled tube (P/d = 3.75 and 11.25) has been examined under laminar flow regime (1131 <= Re <= 2102) in this experimental study. While the magnitudes of magnetic fields are 0.16 T, the alternating magnetic field is utilized with square wave type at frequencies of 1, 2, 5 Hz. It is concluded that the dimpled tube causes up to 78.4% increase in Nusselt number compared to the smooth tube, while up to 118.9% increase in Darcy friction factor. The constant magnetic field enhances the Nusselt number up to 4.04% compared to the absence of a magnetic field using ferronanofluid as a working fluid. Higher frequencies of the alternating magnetic field results in higher thermal performance. Alternating magnetic field effect with f = 5 Hz offers 37.3% Nusselt number enhancement compared to the constant magnetic field effect in all tube geometries. It was also seen that P/d = 11.25 gives the highest Performance Evaluation Criteria while the magnetic field effect decreases it in all tube geometries.
