Yazar "Kaplan Y." seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A mathematical model for hydrogen evolution in an electrochemical cell and experimental validation(2006) Mat M.D.; Kaplan Y.; Ibrahimoglu B.; Veziroglu N.; Alibeyli R.; Kuliyev S.Electrochemical reaction is largely employed in various industrial areas such as hydrogen production, chlorate process, electroplating, metal purification etc. Most of these processes often take place with gas evaluation on the electrodes. Presence of gas phase in the liquid phase makes the problem two-phase flow which is much knowledge available from heat transfer and fluid mechanics studies. The motivation of this study is to investigate hydrogen release in an electrolysis processes from two-phase flow point of view and investigate effect of gas release on the electrolysis process. Hydrogen evolution, flow field and current density distribution in an electrochemical cell are investigated with a two-phase flow model. The mathematical model involves solutions of transport equations for the variables of each phase with allowance for inter phase transfer of mass and momentum. An experimental set-up is established to collect data to validate and improve the mathematical model. Void fraction is determined from measurement of resistivity changes in the system due to the presence of bubbles. A good agreement is obtained between numerical results and experimental data. Copyright © (2006) by AFHYPAC.Öğe Application of a bubble-induced turbulence model to subcooled boiling in a vertical pipe(ASME, Fairfield, NJ, United States, 1999) Mat M.D.; Kaplan Y.; Ilegbusi O.J.Subcooled boiling of water in a vertical pipe is numerically investigated. The mathematical model involves solution of transport equations for vapor and liquid phase separately. Turbulence model considers the turbulence production and dissipation by the motion of the bubbles. The radial and axial void fractions, temperature and velocity profiles in the pipe are calculated. The estimated results are compared to experimental data available in the literature. It is found that while present study satisfactorily agrees with experimental data in the literature, it improves the prediction at lower void fractions.Öğe Application of an internal variable model to the mushy zone in alloy solidification(2001) Mat M.D.; Aydemir G.; Kaplan Y.In this study, the solidification of a generic binary alloy in a two-dimensional cavity is numerically investigated. The mushy region that is formed during solidification is considered a non-Newtonian fluid, then a critical solid fraction and a porous medium thereafter. An internal variable which represents the agglomeration and disagglomeration of grains is used in the model. The solidification problem is also solved using a porous model, which is employed generally in the literature and the results are compared with those obtained with the new model. The new model is found to predict an irregular interface morphology between the mushy region and the liquid region.Öğe Effects of lamination conditions on the performance of anode-supported solid oxide fuel cells(Electrochemical Society Inc., 2015) Timurkutluk B.; Timurkutluk C.; Ciflik Y.; Korkmaz H.; Kaplan Y.Solid oxide fuel cells (SOFCs) operate at high temperatures and produce electricity and heat energy from fuels in an electrochemical way. Membrane electrode assembly (MEA) composed of a dense electrolyte coated with two porous electrodes on each side is generally constructed on the electrolyte. However, high operation temperatures are required to obtain acceptable performance values due to high electrolyte resistance as a result of the use of thick electrolyte layer as a mechanical support for MEA. Alternatively, the cells can be fabricated as anode-supported where the anode is responsible for supporting the cell mechanically. By doing so, the operation temperature can be lowered due to reduced electrolyte thickness. In this study, the effects of isostatic press parameters i.e. temperature and pressure for NiO/YSZ anode support on the anode-supported cell performance and the microstructure of the anode support are investigated. The experimental results reveal that the cell performance is strongly influenced by the pressing parameters. In this aspect, the optimum pressing temperature and pressure are found to be 50°C and 40 MPa, respectively. © The Electrochemical Society.Öğe Heat and mass transfer of hydrogen storage in metal-hydrogen Reactors(2006) Kaplan Y.; Mat M.D.; Ibrahimoglu B.; Veziroglu N.; Alibeyli R.; Kuliyev S.Hydrogen energy is the best alternative to fossil fuels due to its high calorific value and being environmentally friendly. Hydrogen also produces more energy per unit weight than any other fuel. However, storage problem of hydrogen prevents its wide usage and commercialization. Hydrogen absorption in two LaNi5-H2 reactors is experimentally and theoretically investigated. In the experimental program, two tanks are filled with LaNi5 alloy and hydrogen is charged with a constant pressure. The temperature changes in the tanks are measured at several locations and recorded in a computer. Hydriding process is identified from measured temperature histories. An experimental set up is designed to study main characteristics of hydriding process and effect of bed geometry and heat transfer on the hydriding process. Hydriding process is characterized by exothermic reaction between LaNi5 and H2 and rapid temperature increase due the heat release. Hydriding time mainly depend on the successful heat removal from the bed. A bed geometry which provides more heat transfer area significantly reduces hydriding time In the theoretical program, a two dimensional mathematical model, which considers complex heat and mass transfer and fluid flow is developed and numerically solved. The governing equations are numerically solved and calculated results are compared with experimental data. It is found that mathematical model adequately captures the main physics of the hydriding process and can be employed for a better hydride bed design to reduce hydriding time. A reasonable agreement between the numerical results and experimental data is obtained. Copyright © (2006) by AFHYPAC.Öğe Influence of sintering support design on the properties of NiO-YSZ anode support micro-tubes(Elsevier Ltd, 2018) Timurkutluk B.; Timurkutluk C.; Toros S.; Kaplan Y.The effects of the sintering support design on the microstructural and mechanical properties of NiO/YSZ anode support micro-tubes are investigated in this study. For this purpose, a number of micro-tubes of the same geometrical properties are fabricated via extrusion method from the same extrusion paste. The micro-tubes are then sintered at the same temperature on sintering plates with different C- and V-type sintering channels designed. The micro-tubes after sintering are found to have similar geometric properties. However, the microstructural investigations and three point bending tests indicate that the microstructural properties of the micro-tubes are strongly influenced by the sintering plate design. As a result, the flexural strength of the micro-tubes are found to be different. Among the cases considered, the micro-tubes of V2 (half of the micro-tube is initially in the V-type channel) and V4 (whole micro-tube is initially in the V-type channel) design provide relatively fine microstructure and thus relatively higher flexural strength values at a reliability of 80%. The flexural strengths of these micro-tubes are also found to be more consistent. © 2017 Elsevier Ltd and Techna Group S.r.l.Öğe Investigation of thermal aspects of hydrogen storage in a LaNi5-H2 reactor(2006) Kaplan Y.; Ilbas M.; Mat M.D.; Demiralp M.; Veziroglu T.N.In this work, hydrogen absorption in a LaNi5-H2 reactor is investigated experimentally and numerically. Experimental measurements were carried out on a cylindrical metal-hydride reactor filled with LaNi5 alloy. During the experiments hydrogen was charged at a constant pressure. The performance of the reactor during hydriding process was obtained at different fluid temperatures and hydriding process was identified from measured temperature histories. The temperature changes in the reactor were measured at several locations and recorded in a computer. The numerical simulation of the reactor was also performed. A two-dimensional mathematical model has been established and solved numerically by the method of finite volume for the simulation. The numerical results are compared with the measured data to validate the mathematical model. The predicted results are in good agreement with the experimental measurements. Copyright © 2005 John Wiley & Sons, Ltd.
