Sürdürülebilir Kalkınma Amaçları

• 3

• MakaleYalnız künye2019/r/gumushane/11829
  Performance evaluation of ejector with different secondary flow directions and geometric properties for solid oxide fuel cell applications

  Genc, Omer; Timurkutluk, Bora; Toros, Serkan

  The mixing chamber length, secondary flow tube inclination angle, diffuser length and diverging angle as well as the direction of secondary flow on the ejector performance are numerically studied. The numerical results of 2560 different design points including the all combinations of the selected parameters indicate that the selected ejector geometric parameters have a great impact on the ejector performance. Within the parameter ranges considered, the best performance based on steam to carbon ratio and the entrainment is obtained from the ejector having a mixing chamber length of 30 mm, secondary flow tube inclination angle of 45°, diffuser length of 90 mm and diffuser diverging angle of 5°, regardless of the secondary flow direction. On the other hand, the parallel flow ejector, where the anode exhaust line flow direction is designed to be parallel to the primary flow direction, is found to exhibit slightly higher steam to carbon ratio and entrainment ratio compared to those of the counter flow ejector. Furthermore, it is seen that the parallel flow ejector can offer wider ranges of the ejector geometric parameters considered for a high performance whereas relatively rigid geometric parameters need to be selected for designing a counter flow ejector.

  • 
  İncele
• MakaleYalnız künye2018/r/gumushane/18386
  Numerical investigation and experimental verification of proton electrolyte membraned (pem) electrolyser

  Genç, Ömer; Kallioğlu, Mehmet Ali

  In this study, the physical and the electrochemical phenomena occurred within the proton exchange membrane (PEM) electrolysis cell and the effects of some operating parameters such as cell voltage, current density on the cell performance were investigated numerically and experimentally. The equations which characterize flow, mass transfer, conservation of charge and electrochemical reactions were solved by using COMSOL Multiphysics commercial software. In the experimental setup, the Membrane Electrode Group (MEG) which has 50 cm2 active area, porous titanium at anode and carbon paper as gas diffusion layer at cathode are used. The numerical results compared with measured experimental data. It is sound that while the model satisfactorily agrees with experimental data at low current densities, it deviates at high current densities mainly because of isothermal assumption employed. The numerical results have shown that the oxygen and hydrogen concentrations increase along the channel. Also the hydrogen production starts at 1.48 V and it increase as the current density increase. However, the voltage efficiencies of PEM electrolyser for numerical and experimental study were found as 0.809 and 0.871, respectively.

  İncele
• MakaleYalnız künye2018/r/gumushane/13074
  Geometric optimization of an ejector for a 4 kW SOFC system with anode off-gas recycle

  Genc, Omer; Toros, Serkan; Timurkutluk, Bora

  One of the important energy saving tools used in solid oxide fuel cell (SOFC) system is the anode off-gas recycling (AGR) via an ejector which allows the recirculation of the unused fuels in the anode exhaust gas including hot steam which is essential for the elimination of the carbon deposition and the initiation of the reactions in the reformer. In an ejector system developed for the SOFCs, the steam to carbon ratio (STCR) and entrainment ratio are the crucial parameters for the determination of the ejector performance. These parameters can be engineered by modifying the geometric dimensions and operation conditions. This study focuses on the determination of the maximum STCR value and entrainment ratio via numerical geometric analyses for a micro combined heat and power (μ-CHP) system based on 4 kW SOFC, utilizing methane. A detailed numerical procedure for designing an ejector is provided and the ejector performance is investigated for different critical dimensions (throat diameter, nozzle exit angle and nozzle position etc.). The results show that the nozzle position and the nozzle exit angle significantly affect STCR and the entrainment ratio. When the nozzle position increases and nozzle exit angle decreases, the entrainment ratio and STCR is found to increase. The entrainment ratio and STCR are determined as around 7.3 and 2.7, respectively for a specific design created in the study.

  • 
  İncele
• MakaleYalnız künye2017/r/gumushane/15169
  Determination of optimum ejector operating pressures for anodic recirculation in SOFC systems

  Genc, Omer; Toros, Serkan; Timurkutluk, Bora

  In this study, a numerical analysis of an ejector for micro combined heat and power system based on 18 kW Solid Oxide Fuel Cell (SOFC) using methane as fuel is presented. An ejector design, which reflects the real system conditions in the view of the flow characteristics, is provided and the ejector performance is numerically investigated for various methane pressure to exhaust pressure ratios and methane inlet temperatures. The results show that the fuel inlet temperature and the pressure ratio of the methane to exhaust significantly affect the steam to carbon ratio (STCR) and entrainment ratio. The higher pressure ratio and methane temperature allow a high entrainment ratio and STCR, but as pressure ratio and methane temperature increase, STCR and entrainment ratio remain unchanged after a specific value. 1140 different scenarios related with the inlet and outlet pressures of the ejector and methane temperature are created to determine the optimum operating conditions. The simulations show that the optimum methane inlet pressure is 7 bar and exhaust pressure is 1.159 bar for the ejector geometry of the interest. The entrainment ratio and STCR are determined as 2.05 and 0.92, respectively at this optimum scenario.

  • 
  İncele