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Öğe 2D-axisymmetrical modeling and experimental study of hydrogen absorption in copper coated metal hydride(Pergamon-Elsevier Science Ltd, 2023) Atalmis, Gamze; Toros, Serkan; Timurkutluk, Bora; Kaplan, YukselThe storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi5. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Development of ceramic fiber reinforced glass ceramic sealants for microtubular solid oxide fuel cells(Elsevier Sci Ltd, 2022) Timurkutluk, Cigdem; Toruntay, Furkan; Onbilgin, Sezer; Atalmis, Gamze; Timurkutluk, BoraCeramic fibers in various forms with different fiber sizes are tested to improve the sealing performance of glass ceramic seals for micmtubular solid oxide fuel cell applications. In this regard, several sealing pastes are prepared by mixing each ceramic fibers type with glass ceramics at 1.25 wt %. Five layered micmtubular anode supported cells are also fabricated by extrusion and dip coating methods to evaluate the sealing performance of the composite sealants. The pastes are applied between the cells and gas manifolds made of Crofer22 APU. The electrochemical and sealing performances at an operating temperature of 800 degrees C under hydrogen are investigated after the glass forming process. Microstructures of the sealants are also examined by a scanning electron microscope. Experimental investigations reveal that the cells sealed by the pastes with ceramic bulk fiber and ceramic fiber rope gasket show acceptable open circuit potentials close to the theoretical one. These cells can be also pressurized up to around 150 kPa back pressure in the sealing performance tests. On the other hand, the pastes without any filler, with ceramic rope and with ceramic blanket exhibit poor sealing performance due to gas leakage originated from flowing of the main glass ceramic matrix from the joints. Therefore, ceramic bulk fiber and ceramic fiber rope gasket are found to behave as a stopper and can be used to prevent glass ceramics from flowing for microtubular solid oxide fuel cells or similar applications.Öğe Effect of expanded natural graphite addition and copper coating on reaction kinetics and hydrogen storage characteristics of metal hydride reactors(Pergamon-Elsevier Science Ltd, 2024) Atalmis, Gamze; Toros, Serkan; Timurkutluk, Bora; Kaplan, YukselExperimental and numerical studies are carried out to determine the effects of copper coating and/or ENG (expanded natural graphite) addition on the hydrogen storage performance of ground LaNi5. The amounts of copper coating and/or ENG addition are also investigated. The results reveal that the thermal conductivity of ground LaNi5 can be improved by up to similar to 6 and similar to 12 times with copper coating and ENG addition, respectively. This results in enhanced hydrogen absorption kinetics thereby significantly reduced hydrogen charging times, compared to those determined for LaNi5 without any addition. On the other hand, the amount of hydrogen stored shows a decreasing trend with increasing copper coating and ENG addition since the weight of storage material loaded to the reactor is kept the same. Nevertheless, the optimum copper and ENG contents are determined regarding the amount of stored hydrogen and the corresponding charging time. Similar H/M values are obtained with the optimized powders with additives compared to that of ground LaNi5. Based on these results, various new samples are also prepared by mixing the decided copper coated LaNi5 and ENG added LaNi5 powders and examined to optimize the composition of these blended powders.Öğe Experimental improvement of the performance of the open cathode-direct methanol fuel cell stack by magnetic field effect(Pergamon-Elsevier Science Ltd, 2024) Celik, Selahattin; Yagiz, Mikail; Atalmis, GamzeOpen Cathode Direct Methanol Fuel Cell (OC-DMFC) stack performance is achieved at different methanol temperatures (25, 40, 55 and 70 degrees C), methanol concentrations (0.5, 1, 2 and 4 M) and air flow rates (3.5, 4.8 and 6.4 m/s). Each parameter, whose performance was tested separately, was presented by making comparisons within itself. The effect of performance changes on peak power densities under relatively low electromagnetic fields (4.7, 12.4, 28 and 35 mT) was investigated by exposing the 10-cell OC-DMFC stack to a magnetic field with the help of ferritic magnets. Ferritic magnets placed on the OC-DMFC stack anode and cathode surfaces, It is designed to create an electromagnetic field. Thus, the magnetic field affected both surfaces. When the magnetic field was 35 mT, the OC-DMFC reached a power density of 17.5 mW cm(-2). When the DMFC stack is exposed to the magnetic field, its performance is increased by similar to 16%.Öğe Fabrication of glass ceramic sealants with ceramic fiber filler for solid oxide fuel cells(Elsevier Sci Ltd, 2022) Toruntay, Furkan; Atalmis, Gamze; Timurkutluk, Cigdem; Timurkutluk, BoraIn this study, ceramic fibers are used as a filler material for glass ceramic sealant in solid oxide fuel cells to improve the thermal cycle behavior. Beside the bare glass ceramic sealant for comparison, multilayered sealants with different ceramic fiber contents are fabricated to investigate the effect of ceramic fiber quantity also. The mechanical performances of the samples are measured via tensile tests by placing them between two metallic interconnector plates after the glass formation process as well as after 1, 5 and 10 thermal cycles. The results show that the mechanical strength in general tends to decrease with increasing the ceramic filler content, which can be attributed to poor adhesion due to reduced glass ceramic composition. On the other hand, thermal cycle behavior of the samples with ceramic fibers is found to be improved at some extend. This may be due to the behavior of ceramic filler network and relatively slow crystallization with increasing the amount of the filler as proven by microstructural observations. Especially for the sample including 4 ceramic fiber interlayers each having 0.030 g ceramic fibers, the mechanical strength shows an increasing trend with the number of thermal cycles.Öğe INVESTIGATION OF HYDROGEN KINETICS OF COPPER PELLETS WITH ENG ADDITIVES(International Association for Hydrogen Energy, IAHE, 2022) Atalmis, Gamze; Yelegen, Nebi; Demiralp, Mehmet; Kaplan, YukselIn this study, the hydrogen storage capabilities and thermal conductivity of the materials will be improved by applying both expanded natural graphite (ENG) addition and copper plating methods to the LaNi5 alloy. The optimized LaNi5-Cu alloy will be selected, ENG will be added at 1%, 5%, 10% and 20% ENG to this alloy and its application together with copper will be optimized. The obtained materials were characterized by XRD, SEM, BET and their thermal conductivity coefficients were measured with the Hot Disk Thermal Constants Analyzer device. In addition, the effect of storage materials with improved thermal conductivity on the hydrogen charging/discharging process in the metal hydride reactor will be experimentally investigated at the determined pressure. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.Öğe The effect of copper coated metal hydride at different ratios on the reaction kinetics(Pergamon-Elsevier Science Ltd, 2023) Atalmis, Gamze; Demiralp, Mehmet; Yelegen, Nebi; Kaplan, YukselIn this study, the process parameters that affect the improvement of hydrogen storage material properties were investigated. In order to accelerate the hydrogen charge/ discharge processes and to obtain the required hydrogen at the desired flow rates in a short time, the thermal conductivity of the storage materials has been improved, and density analyses have been made. The ideal grinding time has been determined for the LaNi5 material. Within the scope of the experimental studies, the thermal conductivity coefficients of LaNi5 coated with copper and LaNi5 ground for 5 h and coated with copper were increased by 500-750%, and the copper plating ratios were optimized. The materials obtained were characterized by XRD, SEM, and their density was measured with the Helium Pyknometer device and their thermal conductivity coefficients with the Hot Disk Thermal Constants Analyzer. In addition, the hydrogen storage of materials with increased thermal conductivity was investigated experimentally in the metal hydride reactor at the determined pressure. In the study, it was seen that the storage material coated with copper increases the heat transfer, reduces the hydrogen charging time in the metal hydride reactor, and increases the stable discharge time. & COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe The effect of expanded natural graphite added at different ratios of metal hydride on hydrogen storage amount and reaction kinetics(Pergamon-Elsevier Science Ltd, 2024) Atalmis, Gamze; Sattarkhanov, Kurshod; Demiralp, Mehmet; Kaplan, YukselIn this study, metal hydride pellets were formed to accelerate the hydrogen charge/ discharge processes. The heat transfer in hydrogen storage material was improved by employing Expanded natural graphite (ENG). The ideal grinding time for LaNi5 material was determined to be 5 h. In the study, LaNi5 alloy was mixed with ENG in 1%, 5%, 10%, and 20% proportions by weight. The amount of hydrogen stored in the reactor by each mixture at 10 bar pressure was measured depending on time. Within the scope of experimental studies, the thermal conductivity coefficient of LaNi5 materials containing 20% ENG by weight was increased by 1380%. Thus, hydrogen charge/discharge processes were accelerated. Storage materials were characterized by XRD and SEM. The thermal conductivity coefficients were measured with the Hot Disk Thermal Constants Analyzer device, and the densities were measured with the Helium Pycnometer device. LaNi5 was chosen as the storage material in the study. It was found that 1-5 wt% ENG addition increased the reaction kinetics without significantly reducing the hydrogen storage capacity in storage alloys. However, in alloys with higher ENG concentrations, the hydrogen storage capacity decreased. The reaction kinetics were increased in the range of 135-260%. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe The effect of powder and pellet forms of added metal hydride materials on reaction kinetics and storage(Pergamon-Elsevier Science Ltd, 2024) Atalmis, Gamze; Sattarkhanov, Kurshod; Kaplan, Ruveyda N.; Demiralp, Mehmet; Kaplan, YukselIn the present research, metal hydride pellets were synthesized to enhance the kinetics of hydrogen charge/ discharge processes. By incorporating ENG (expanded natural graphite) and copper additives, we observed improvements in the heat transfer coefficients and storage capacities of the hydrogen storage materials. The reactor is designed to contain 1000 g of storage material in the form of powder or 25 pellets each weighing 40 g. The influence of storage materials with enhanced thermal conductivity on the hydrogen charge/discharge process was experimentally studied in a metal hydride reactor under a pressure of 10 bar. The reactor was heated under vacuum (10-4-4 mmHg) to approximately 200 degrees C for 2 h in order to complete the activation process. Following the heating process, the reactor was allowed to cool to ambient temperature, after which the hydrogen was introduced to the reactor at 10 bar pressure for 50 min. The absorption and desorption procedure was reiterated up to 20 cycles, and recordings of data were taken at intervals of 5 cycles to monitor the variations between the cycles. After 10 charge/discharge cycles under pressure of 10 bar, the hydrogen stored in the reactor amounted to approximately 9.93 g in pellet form and 7.20 g in powder form.Öğe THE EXPERIMENTAL STUDIES ON ELECTROLYSER MODE OPERATION OF UNITIZED REGENERATIVE PEM FUEL CELL(International Association for Hydrogen Energy, IAHE, 2022) Yelegen, Nebi; Altuntop, Enis Selçuk; Atalmis, Gamze; Kaplan, YükselA unitized regenerative proton exchange membrane fuel cell (UR-PEMFC) is an electrochemical component that is capable of operating both as electrolyser and fuel cell mode. While UR-PEMFC produces hydrogen and oxygen by decomposing water in the electrolyser mode, it can also produce electricity and heat by using hydrogen as fuel in the fuel cell mode. A reversible system possesses several distinctive advantages for instance, high specific energy, pollution free, and most importantly, the decoupled energy storage capacity with rated power [1]. In this study, the performance of a unitized regenerative fuel cell and stack in electrolyser mode was investigated. The active areas of URFC are 100 cm2, and the stack has three cell, which has a 100 cm2 active area. The clamping pressure is optimized for cell and stack by using pressure film. Thus, the contact resistance was minimized, and optimum contact was achieved. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
