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Öğe Bir Otobüs Modeli Etrafındaki Akış Yapısının CFD Yöntemi İle İncelenmesi ve Sürükleme Kuvvetinin Pasif Akış Kontrol Yöntemi İle İyileştirilmesi(2018) Bayındırlı, Cihan; Çelik, Mehmet; Demiralp, MehmetBu çalışmada, 1/64 ölçekli bir otobüs modelinin aerodinamik direnç katsayısı hesaplamalı akışkanlar dinamiği (CFD) yöntemi ile tespit edilmiştir. Akış analizleri x yönünde 15 m/s, 20 m/s, 25 m/s ve 30 m/s serbest akış hızlarında 173000-346000 Reynolds sayısı aralığında gerçekleştirilmiştir. Akış analizleri Fluent® programında yapılmıştır. Otobüs modelinin aerodinamik direnç katsayısı ortalama 0.657 olarak tespit edilmiş, toplam direncin basınç ve sürtünme kaynaklı dağılımı belirlenmiştir. Model otobüs üzerinde basınç kaynaklı direnç oluşturan bölgeler akış görüntülemeleri ile tespit edilmiştir. Akış yapısını iyileştirilmek ve basınç kaynaklı direnci azaltmak için üçgen kesitli akış kontrol elemanı geliştirilmiştir. Akış kontrol elemanı 15 mm çapında eşkenar üçgen şeklinde olup model otobüsün ön tampon üzerine konumlandırılmıştır. Model 1 otobüsün aerodinamik direnç katsayısı 0.623 olarak tespit edilmiştir. Bu pasif akış kontrol yöntemi ile aerodinamik direnç katsayısında ortalama % 5.27 iyileşme sağlanmıştır. Elde edilen bu iyileşmenin yüksek taşıt hızlarında yakıt tüketimine etkisi yaklaşık %3’tür. Bu orandaki bir aerodinamik iyileşmenin bir otobüste yıllık yakıt tüketimine etkisi değerlendirilmiştir.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 Metal-hidrit yataklarda hidrojen şarj/deşarj işlemine etki eden proses parametrelerinin incelenmesi(2008) Kaplan, Yüksel; Bayrak, Mustafa; Demiralp, Mehmet[Abstract Not Available]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 Investigation of Flow Characteristic Around A Bus Model by CFD Method and Improvement of Drag Force by Passive Flow Control Method(Gazi Univ, 2018) Bayindirli, Cihan; Celik, Mehmet; Demiralp, MehmetIn this study, aerodynamic drag coefficient of 1/64 scaled bus model was determined by the Computational Fluid Dynamics (CFD) method. Flow analyzes were performed at 15 m/s, 20 m/s, 25 m/s ye 30 m/s in x direction, between the range of 173000-346000 Reynolds numbers. Flow analysis was made in Fluent (R) program. The aerodynamic drag coefficient (CD) of the bus model was determined as 0.657 on average, the distribution of total drag was determined as pressure-friction based. After the flow visualization, the areas are detected where forms aerodynamic drag on the model bus. A triangular section flow control element has been developed to improve the flow structure and decrease the pressure based drag. The flow control element is an equilateral triangle with a diameter of 15 mm and positioned on the front bumper of the model bus. The aerodynamic drag coefficient of model 1 bus was determined as 0.623. With this passive flow control method, the aerodynamic drag coefficient improved by %5.27. The effect of this improvement on fuel consumption is about 3 % at the high vehicle speed. The effect of this aerodynamic improvement on the annual fuel consumption of a bus has been evaluated.
