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Combined effects of magnetic and electrical field on the hydrodynamic and thermophysical parameters of magnetoviscous fluid flow
(Pergamon-Elsevier Science Ltd, 2015) Selimli, Selcuk; Recebli, Ziyaddin; Arcaklioglu, Erol
Combine effect of externally applied magnetic and electrical field on the hydrodynamic and thermophysical properties of incompressible steady state magnetoviscous flow of liquid lithium in an enclosure was examined for applied magnetic field values are B = 0 T to 0.15 T and electrical field values are E=0 V/m to +/-9e-6V/m. According to the results, increase of magnetic and electrical field decreases the flow velocity but also increases the shear stress, temperature, heat flux and Nusselt number. Application and increase of electrical field in the positive direction increases the influence of magnetic field on the hydrodynamic and thermophysical properties of flow domain. As for that increase of applied electrical field in the negative direction decreased the effect of magnetic field. (C) 2015 Elsevier Ltd. All rights reserved.
Değişken fiziksel özellikli akışkan ile ısı taşınımına manyetik alanın etkisinin sayısal olarak incelenmesi
(2008) Recebli, Ziyaddin; Atık, Kemal; Sekmen, Perihan
Manyetik alanın etkisiyle akışkanların hızlarının değiştiği bilinmektedir, Yapılan bazı çalışmalarda sıcaklıkla fiziksel özelliklerin değişmediği kabul edilerek manyetik alanın ısı taşınımına etkisi araştırılmıştır. Sıcaklığın etkisiyle akışkanların fiziksel özellikleri değişeceği için bu çalışmada sıcaklıkla fiziksel özellikleri değişen akışkan ile ısı taşınımına manyetik alanın etkisi incelenmiştir. Çözümde akışkana etkiyen elektromanyetik kuvveti içeren momentum, süreklilik ve enerji denklemleri kullanılmıştır. Silindirik koordinat sisteminde yazılan denklem sistemi sayısal metotlardan sonlu farklar yöntemiyle çözülerek manyetik alanın şiddetine ve akışkanın diğer fiziksel özelliklerine bağlı olarak eksenel ve radyal yönlerdeki sıcaklıklar ile Nusselt sayıları hesaplanmıştır.Çözüm sonuçlarına göre; akış yönüne dik olarak yerleştirilen manyetik alanın şiddeti artırıldığında soğutulan akışkan için hız ve sıcaklıklarda azalmalar olduğu görülmüştür. Daha önceki çalışmalarda tespit edildiği gibi Reynolds sayısının artışıyla Nusselt sayısının arttığı, manyetik alan etkisinin artmasıyla da Nusselt sayısının azaldığı bu çalışmada da gözlemlenmiştir. Elde edilen teorik sonuçlar, daha önce tarafımızdan, sabit fiziksel özellikli akışkanla yapılan benzeri çalışmanın sonuçları ile karşılaştırıldığında uyum içinde olduğu görülmüştür.
Electrical field effect on three-dimensional magnetohydrodynamic pipe flow: a CFD study
(Inderscience Enterprises Ltd, 2016) Recebli, Ziyaddin; Gedik, Engin; Selimli, Selcuk
Steady, laminar three-dimensional (3D) magnetohydrodynamic (MHD) flow of an electrically conducting fluid in a circular pipe under the both magnetic and electrical field are studied. External magnetic and electrical fields are applied perpendicular to the flow direction and each other while the fluid motion is subjected to constant pressure gradient along axial-direction in the present paper. Fluent 14.0, the finite element software based on the finite volume approach was used to calculate the 3D fluid dynamics and electromagnetic field partial differential equations iteratively. The originality of this work is that, in addition to magnetic field; the effect of electrical field on MHD flows is being examined with help of user defined function (UDF) code. The magnetic field leads to decrease in the velocity of flow, whereas the electrical field applied with magnetic field acted to increase and decrease the velocity of flow depending on the direction of applied external electrical field. The obtained results were depicted graphically and discussed.
ESTIMATING WIND ENERGY POTENTIAL WITH PREDICTING BURR LSM PARAMETERS: A DIFFERENT APPROACH
(Yildiz Technical Univ, 2018) Kose, Bayram; Duz, Murat; Guneser, M. Tahir; Recebli, Ziyaddin
Estimating wind energy potential and wind speed frequency are important for planning wind energy conversion plants. Probability distribution functions are utilized to model wind speed distributions. In this study, an estimation was model designed by using the least squares method to predict the wind speed density with the Burr distribution, which has not been studied before. To confirm this model, the annual data of eight different weather stations were analysed, and the results were compared with the Weibull distribution model, which is the most popular one in the literature. For predicting the parameters of both models least square method and maximum likely methods were used. Regarding the comparison results, the performance of designed estimation model (Burr LSM) is higher than the Weibull distribution models, especially for the locations with higher average wind speeds. The results show that the Burr LSM is better than the others for seven of eight weather stations in terms of the power density.
EVALUATION THE EFFECTS OF USED REFRIGERANTS R134a AND R600a IN COOLING SYSTEMS ON THE SYSTEM PERFORMANCE
(Yildiz Technical Univ, 2014) Selimli, Selcuk; Recebli, Ziyaddin; Gorken, Mehmet
Known as R134a refrigerant is in the class of refrigerants as uneconomic and having global warming potential. In the scope of study, determination the effect of R600a refrigerant which is known more environment friendly and economic alternative of R134a refrigerant on the cooling performance of the cooling machine was aimed. In this reason, effect of R134a and R600a refrigerants on the cooling performance of the cooling machine was experimentally studied. Experimentation setup was established with 70x70x50 cm dimensions cooling room and cooling unit. 100 gr refrigerant filled experimentation setup was operated at 28 degrees C and 35 degrees C ambient temperature in a period of time and according to the taken measurements cooling systems COP value was compared. As a result, using R600a refrigerant instead of R134a refrigerant, the cooling machine average COP value was increased 4%. This case demonstrates that R600a using cooling machine performs higher performance than R134a using cooling machine. Also, it was seen that a using coolant R134a cooled the space faster than a using coolant R600a in cooling machine.
Experimental Observation of Effect of Heat Pump on Vacuum Tube Solar Collector Performance
(Gazi Univ, 2013) Selimli, Selcuk; Recebli, Ziyaddin; Aydin, Alper
In this study, combine operation of air source heat pump and vacuum tube solar collector system was experimentally observed. Contribution of heat pump system on solar collector system performance was determined. Solar collector experimentation setup was constructed with 30 It water storage tank and 4 items vacuum tube. Heat pump condenser which is in the form of pipe coil was placed into the water storage tank. System evaporator is fan assisted aluminium fin and 2400 W capacities. Heat pump compressor is 745 W power. Temperature was controlled by 303-363 K range thermostat. During the experimentations solar radiation intensity, heating time and temperature of water was recorded. Experimentations were repeated for three different operation conditions. In the first day, solar collector and heat pump system, the second day, only solar collector and on the third day, only heat pump system was operated and experimentation was completed. It is determined that, the system efficiency was enhanced about 5% according to the evaluations.
IMPACT OF ELECTRICAL AND MAGNETIC FIELD ON COOLING PROCESS OF LIQUID METAL DUCT MAGNETOHYDRODYNAMIC FLOW
(Vinca Inst Nuclear Sci, 2018) Selimli, Selcuk; Recebli, Ziyaddin
Cooling period of liquid metal while flowing under imposed magnetic and electrical field was studied for laminar steady flow condition. Computational analyses were done by ANSYS Fluent software MHD module. For applied each constant value of magnetic field induction (B = 0 T, B = 0.05 T, B = 1 T), the electrical field intensity was applied positively as E+ (1e-4, 1e-5) V/m and negatively as E-(-1e-4, -1e-5) V/m. Increase of the E+ field intensity decreased the local temperature (increased cooling rate) but also increased the heat flux and Nusselt number. Also, decrease of E- in the opposite direction increased the temperature but also decreased the heat flux and Nusselt number. It could be signified that by the application of magnetic field or together with electrical field, the heat transfer could be improved or attenuated.
An Investigation into the Effects of Box Geometries on the Thermal Performance of Solar Cookers
(Taylor & Francis Inc, 2008) Kurt, Huseyin; Deniz, Emrah; Recebli, Ziyaddin
The effect of box geometry, such as cylindrical and rectangular, on the performance of solar cookers has not been investigated. In this study, two different model box type solar cookers, which are in rectangular and cylindrical geometries, were constructed using the same material and were tested to investigate the effects of box geometries on the cooker performance. The experimental studies were conducted under the same operating conditions. The obtained results from the experiments were used to calculate the thermal efficiency and specific and characteristic boiling times. These parameters of the cookers were determined for 0.5, 1, and 1.5 kg of fresh water. It is observed that the cylindrical model has higher temperatures than the rectangular model under the same operating conditions. The thermal efficiency increased from 12.7 to 36.98% for cylindrical and 9.85 to 28.25% for rectangular model, when the quantity of water was increased from 0.5 to 1.5 kg; similarly, the characteristic boiling time was decreased from 39.56 to 14.35 for the cylindrical and 43.74 to 15.77 (min m-2 kg-1) for the rectangular model, respectively. The cylindrical model provided high thermal performance, which is indicated by high thermal efficiency and low characteristic boiling time, in comparison with the rectangular model.
Isı pompasının vakum tüplü güneş kollektör performansına etkisinin deneysel incelenmesi
(2013) Selımlı, Selçuk; Recebli, Ziyaddin; Aydın, Alper
Bu çalışmada, hava kaynaklı ısı pompası ve vakum tüplü güneş kolektörü sisteminin kombine çalışması deneysel olarak incelenmiştir. Güneş kollektör sistemi performansına ısı pompası çevriminin katkısı belirlenmiştir. Deney düzeneği güneş kollektör sistemi 30 litrelik su deposu ve 4 adet vakum tüpü ile oluşturulmuştur. Kollektör deposuna serpantin şeklinde, ısıpompası kondenseri (yoğuşturucu) yerleştirilmiştir. Sistem evaporatörü olarak 2400 W gücünde alüminyum kanatçıklı fan destekli evaporatör kullanılmıştır. Isı pompası kompresörü 745 W gücündedir. 303-363 K aralığında çalışan termostat ile sıcaklık kontrolü sağlanmıştır. Deneyler esnasında güneş ışınım şiddeti, ısınma süresi ve su sıcaklık değerleri ölçülerek kaydedilmiştir. Deneyler üç farklı çalışma durumu için tekrarlanmıştır. Birinci gün ısı pompası ve güneş kollektör sistemi, ikinci gün sadece güneş kollektör sistemi ve üçüncü gün ise sadece ısı pompası sistemi çalıştırışarak deneyler tamamlanmıştır. Yapılan değerlendirmeler neticesinde sistem veriminde %5 artış olduğu belirlenmiştir.
MHD numerical analyses of hydrodynamically developing laminar liquid lithium duct flow
(Pergamon-Elsevier Science Ltd, 2015) Selimli, Selcuk; Recebli, Ziyaddin; Arcaklioglu, Erol
Magnetic effects on steady state laminar liquid lithium duct flow were studied at hydrodynamically developing flow region. Studied duct model was constructed with dimensions are (15.7 x 5 x 150 mm). Model side walls were estimated conductive and top-bottom walls were defined insulated. Magnetic field applied with values are as B = 0 T, B = 0.05 T, B = 0.1 T and B = 0.15 T. Magnetic field effect was maximized by normally applying it on the flow stream. Hydrodynamic parameters are velocity, pressure, viscosity and density were numerically studied by ANSYS Fluent software MHD module. It is concluded that increase of magnetic field increased the local pressure but also decreased local velocity, density and dynamic viscosity. Obtained results compared with studies in literature and supported. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Mr (manyeto-reolojij) akışkanın akış hareketlerine manyetik ve elektrik alan etkisinin teorik ve deneysel olarark incelenmesi
(2012) Kurt, Hüseyin; Recebli, Ziyaddin; Gedık, Engin; Yaltırık, Hüseyin; Ergün, Alper
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A NUMERICAL INVESTIGATION OF EFFECT OF MAGNETIC FIELD ON HEAT CONVECTION WITH VARIABLE PHYSICAL PROPERTIES
(Pamukkale Univ, 2008) Recebli, Ziyaddin; Atik, Kemal; Sekmen, Perihan
In some studies, the effect of magnetic field on heat convection has been investigated given that physical properties are constant regardless of temperature. The effect of magnetic field on heat convection and fluids whose physical properties change by temperature has been investigated in this study as physical properties of fluids change by the effect of temperature. Momentum, continuity and energy equations including electromagnetic force affecting the fluid were used in the solution. Temperatures at axial and radial directions and Nusselt numbers were calculated depending on magnetic field intensity and other physical properties of fluid by solving the equation system written in cylindrical coordinates system by means of one of the numerical methods which is finite difference method. According to results, velocity and temperature of the cooled fluid decreased following an increase in the intensity of magnetic field placed vertically to flow direction. As determined in the previous one, this study also indicated that the increase in Reynolds number increases Nusselt number, and increasing the effect of magnetic field decreases Nusselt number. The theoretical results of the present study are in conformity with the results of our previous one.
Performance analysis of open cycle gas turbines
(John Wiley & Sons Ltd, 2009) Kurt, Hueseyin; Recebli, Ziyaddin; Gedik, Engin
In this study, the performance of ideal open cycle gas turbine system was examined based on its thermodynamic analysis. The effects of some parameters, such as compressor inlet temperature (CIT), pressure ratio (PR) and the turbine inlet temperature (TIT), on the performance parameters of open cycle gas turbine were discussed. The turbine net power output, the thermal efficiency and the fuel consumption of the turbine were taken as the performance parameters. The values of these parameters were calculated using some basic cycle equations and variables values of thermodynamic properties. Other variables such as lower heating value, combustion efficiency and isentropic efficiencies of compressor and turbine were assumed to be constant. The result showed that the net power output and the thermal efficiency increased by a decrease in the CIT and increase in the TIT and PR values. If it is aimed to have a high net power output and the thermal efficiency for the turbine, the CIT should be chosen as low as possible and the TIT should be chosen as high as possible. Copyright (C) 2008 John Wiley & Sons, Ltd.
SOLAR VACUUM TUBE INTEGRATED SEAWATER DISTILLATION - AN EXPERIMENTAL STUDY
(Univ Nis, 2016) Selimli, Selcuk; Recebli, Ziyaddin; Ulker, Semra
The subject of this study is the seawater distillation process enhancement through integration of the solar vacuum tube into the system. Positive effects on the rate of distillated freshwater achieved by means of the enhanced system have been investigated experimentally. Experiments were done in the Turkish city of Samsun in the Black Sea region. A distillation pond setup having the volume of 0.015m(3) and a water surface area of 0.24m(2) was constructed. The distillation pond is covered with a condensation glass and also equipped with a 0.15m solar vacuum tube that is inclined at an angle of 30 degrees to the ground, a feed water tank connected with a ball cock, and distillated fresh water tank. Experimental results have shown that the rate of distilled fresh water was enhanced for about 62.5% by integrating the solar vacuum tube and the natural distillation pond. Isolation of the condensation glass not only prevents the light transmission to the pond but also heat loss from the pond; hence the rate of the distillated fresh water is increased for about 137.5% due to the natural distillation.
Theoretical analyses of immiscible MHD pipe flow
(Pergamon-Elsevier Science Ltd, 2015) Recebli, Ziyaddin; Selimli, Selcuk; Ozkaymak, Mehmet
In this study, effect of normally applied magnetic field on immiscible fluid flow hydrodynamic flow characteristic has been analytically investigated. Flow case modelled for two different flow patterns. The first one is low electrically conductive fluid (gasoline) inner core and higher one (salty water) outer flow regional pattern and the second one is high electrically conductive fluid inner core and lower one is outer regional flow case in a vertical circular pipe. Flow models have been modelled in differential form theoretical equations and solved with Laplace Transform method. Solved equation systems presented the dependent statement of the local flow velocity and flow rates to the magnetic field induction, pipe radius and pressure gradient. It is estimated that high electrically conductive fluid was directly affected by the magnetic forces which is created by the magnetic field, and also low electrically conductive fluid was indirectly affected from the magnetic field because of the interfacial tension between the fluids. As a result, overall velocity of the flow domain was reduced more by the magnetic forces in the event of low conductive fluid inner core and high conductive fluid outer regional flow case. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Thermal performance parameters estimation of hot box type solar cooker by using artificial neural network
(Elsevier France-Editions Scientifiques Medicales Elsevier, 2008) Kurt, Hueseyin; Atik, Kemal; Ozkaymak, Mehmet; Recebli, Ziyaddin
Work to date has shown that Artificial Neural Network (ANN) has not been used for predicting thermal performance parameters of a solar cooker. The objective of this study is to predict thermal performance parameters such as absorber plate, enclosure air and pot water temperatures of the experimentally investigated box type solar cooker by using the ANN. Data set is obtained from the box type solar cooker which was tested under various experimental conditions. A feed-forward neural network based on back propagation algorithm was developed to predict the thermal performance of solar cooker with and without reflector. Mathematical formulations derived from the ANN model are presented for each predicting temperatures. The experimental data set consists of 126 values. These were divided into two groups, of which the 96 values were used for training/learning of the network and the rest of the data (30 values) for testing/validation of the network performance. The performance of the ANN predictions was evaluated by comparing the prediction results with the experimental results. The results showed a good regression analysis with the correlation coefficients in the range of 0.9950-0.9987 and mean relative errors (MREs) in the range of 3.92516-7.040% for the test data set. The regression coefficients indicated that the ANN model can successfully be used for the prediction of the thermal performance parameters of a box type solar cooker with a high degree of accuracy. (c) 2007 Elsevier Masson SAS. All rights reserved.
Three dimensional numerical analysis of magnetic field effect on Convective heat transfer during the MHD steady state laminar flow of liquid lithium in a cylindrical pipe
(Pergamon-Elsevier Science Ltd, 2013) Recebli, Ziyaddin; Selimli, Selcuk; Gedik, Engin
In this study, effect of perpendicularly applied magnetic field on steady state laminar liquid lithium flow in a horizontal circular pipe was theoretically analysed with 3D computer base programme. Convective heat transfer behaviour has been examined. Liquid lithium flow was observed for two different conditions as cooling and heating with constant wall temperature. Analyse was proceeded for thermal fully developed but hydro-dynamically transient region of flow. Calculation was carried out with ANSYS Fluent software. As a result, by the increase of magnetic field induction, the local flow velocity was decreased, but the Nusselt number, skin friction coefficient and pressure was increased for the heating and cooling conditions of liquid lithium through the pipe length. Additionally, while the liquid lithium was heating the fluid temperature was decreased and also while the liquid lithium was cooling the fluid temperature was increased by the increase of magnetic field induction through the pipe length. Increase of magnetic field induction enhanced the convective heat transfer and so, indirectly improved the cooling and heating of liquid lithium. (C) 2013 Elsevier Ltd. All rights reserved.
Two-dimensional CFD simulation of magnetorheological fluid between two fixed parallel plates applied external magnetic field
(Pergamon-Elsevier Science Ltd, 2012) Gedik, Engin; Kurt, Huseyin; Recebli, Ziyaddin; Balan, Corneliu
This paper presents a two-dimensional Computational Fluid Dynamics (CFDs) simulation for the steady, laminar flow of an incompressible magnetorheological (MR) fluid between two fixed parallel plates in the presence of a uniform magnetic field. The purpose of this study is to develop a numerical tool that is able to simulate MR fluids flow in valve mode and determine B-0, applied magnetic field effect on flow velocities and pressure distributions. A uniform transverse external magnetic field is applied perpendicular to the flow direction. The equations governing the steady flow of an incompressible MR fluid are implemented in the commercial code Ansys 14.0 Fluent which is a flexible CFD code based on finite volume approach. The governing differential equations describing the flow between parallel plates under magnetic field are solved numerically by using Fluent MHD module based on solving the magnetic induction equation method. The external applied magnetic field, B-0, takes values between 0 and 1.5 T with 0.5 T step size, was applied to determine B-0 effects on fluid flow. The numerical solutions for velocity and pressure distributions were obtained for different magnetic fields. It was observed that increase in B-0 leads to decrease flow velocity. Results, obtained from numerical study was plotted graphically and disgusted in the present paper. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
Üç fazlı karışımların yerçekimsiz ortamda ve homojen karışım şartlarında yatay silindirik borudaki akışının teorik incelenmesi
(2007) Recebli, Ziyaddin
Bu çalışmada sıvı-sıvı–katı üç fazlı karışımın yatay silindirik boru içerisinden akışı incelenmiştir. Kararlı akışı ifade eden diferansiyel denklem sisteminin D’Alambert yöntemi ile analitik olarak çözümünden karışım fazlarının yerel hızları için ifadeler elde edilmiştir. Bu karışımın kararsız akışı sonlu farklar yöntemi kullanılarak sayısal yöntem ile de çözülmüştür. Kararlı akışın gelişim sürecini görmek için fazların yerel hızlarının zamana bağlı grafikleri çizilmiştir. Kararlı akışın analitik ve sayısal çözüm sonuçları farklı yarıçaplar için yerel hız grafikleri çizdirilerek karşılaştırılmıştır. Her iki çözümden elde edilen hız profillerinin uyum içerisinde oldukları saptanmıştır.
Unsteady flow of two-phase fluid in circular pipes under applied external magnetic and electrical fields
(Elsevier France-Editions Scientifiques Medicales Elsevier, 2012) Gedik, Engin; Kurt, Huseyin; Recebli, Ziyaddin; Kecebas, Ali
The unsteady viscous incompressible and electrically conducting of two-phase fluid flow in circular pipes with external magnetic and electrical field is considered in this present study. Effects of both uniform transverse external magnetic and electrical fields applied perpendicular to the fluid and each other on the two-phase (solid/liquid) unsteady flow is investigated numerically. While iron powders are being used as the first phase of two-phase fluid, pure water was used as the second phase. The system of the derived governing equations, which are based on the Navier-Stokes equations including Maxwell equations, are solved numerically by using Pdex4 function on the Matlab for both phases. The originality of this study is that, in addition to magnetic field, the effect of electrical field on two-phase unsteady fluids is being examined. The magnetic field which is applied on flow decreases the velocity of both phases, whereas the electrical field applied along with magnetic field acted to increase and decrease the velocity values depending on the direction of electrical field. Electrical field alone did not display any impact on two-phase flow. On the other hand, analytical and numerical results are compared and favorable agreements have been obtained. Crown Copyright (C) 2011 Published by Elsevier Masson SAS. All rights reserved.

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