Person: SAKA, KENAN
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SAKA
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KENAN
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Publication Performance assessment and solution procedure for series flow double-effect absorption refrigeration systems under critical operating constraints(Springer Heidelberg, 2019-06-01) Yılmaz, İbrahim Halil; Kaska, Önder; Saka, Kenan; SAKA, KENAN; Kaynaklı, Ömer; KAYNAKLI, ÖMER; 0000-0001-7840-9162; 0000-0002-2296-894X; AAH-5303-2021; AAX-2458-2020In this study, the effects of critical operational constraints on the operational domain of a double-effect lithium bromide/water absorption refrigeration system and its performance were investigated. These constraints were determined as the equivalence state of concentrations, the thermal unbalance between the system components of high-pressure condenser and low-pressure generator, freezing and crystallization risk of lithium bromide/water solution. For the system analysis, a simulation program was developed, and its detailed solution procedure was presented. The program outputs were initially validated with the literature. Subsequently, parametric studies were conducted for broad ranges of the component temperatures. The results demonstrate that the considered constraints were essential for acceptable design and the operational control of double-effect absorption refrigeration systems. The simulations will help to figure out under which operating conditions a double-effect absorption refrigeration system functions effectively and what kind of control strategies are essentially required to increase the coefficient of performance. Based on the operation scenario of fixed high-pressure generator temperature, the proposed system can enhance the coefficient of performance up to 31% and 84% as compared to its counterparts which function under the variable high-pressure generator temperature and the pinch point temperature difference (5K between the high-pressure condenser and the low-pressure generator), respectively.Publication Analysis and modeling of a membrane electrode assembly in a proton exchange membrane fuel cell(Amer Inst Physics, 2020-07-01) Orhan, Mehmet F.; Kahraman, Huseyin; Saka, Kenan; SAKA, KENAN; Bursa Uludağ Üniversitesi/Yenişehir İbrahim Orhan Meslek Yüksekokulu.; 0000-0002-2296-894X; AAH-5303-2021In this study, a membrane electrode assembly of a proton exchange membrane fuel cell is modeled. Using the analytical model, a computational analysis has been conducted along with an extensive parametric study. Variation of ohmic losses, water content, and voltage drops from anode to cathode side of the membrane electrode assembly with many design/operation parameters such as thickness, temperature, pressure, and local/total humidity and conductivity, diffusivity, and resistivity have been evaluated at various current densities. Also, effect of molar concentration of hydrogen on hydrogen diffusive flux due to pressure change between the anode and cathode at different membrane thicknesses has been presented. Furthermore, variation of water uptake and concentration with the ratio of water and hydrogen fluxes, the current density, and membrane dry density have been studied along with their interrelation. It is observed that as the membrane thickness increases, its resistivity increases as well, causing higher ohmic losses. On the other hand, the water content increases with the thickness until a maximum point and then starts to decrease. Therefore, the membrane thickness should be optimized carefully to have desirable humidity levels with minimum crossover and losses.Publication Analysis of stack operating conditions for a polymer electrolyte membrane fuel cell(Pergamon-elsevier Science Ltd, 2022-08-07) Orhan, Mehmet Fatih; Saka, Kenan; SAKA, KENAN; Bursa Uludağ Üniversitesi/Yenişehir Meslek Yüksekokulu.; Bursa Uludağ Üniversitesi/Mühendislik-Mimarlık Fakültesi.; 0000-0002-2296-894X; AAH-5303-2021A polymer electrolyte membrane fuel cell is investigated in this study to assess its efficiency. In this regard, various operating conditions such as cell temperature, pressure, reactant/product flow rates and humidity affects are investigated analytically, and their interrelationships are discussed. The stack water management, mass transport phenomenon, ionic and electrical conductivity are also evaluated. The results are experimentally verified using a polymer electrolyte membrane fuel cell with an active surface area of 100 centimeters square. The membrane electrode assembly consists of Nafion (R) HP membrane. Also, AvCarb EP40 gas diffusion layers with 200 mu m thicknesses are used. Results confirm that the overall stack efficiency can increase remarkably with the optimization of its operating parameters. The highest efficiencies are achieved around 100% humidity ratio of reactants at both cathode and anode. While high operating pressures improves individual cell efficiency, there are contradictory concerns at the stack level such as parasitic loads, losses, leakages and manufacturing costs.Publication Design and optimization of fuel cells: A case study on polymer electrolyte membrane fuel cell power systems for portable applications(Wiley-Hindawi, 2022-07-21) Orhan, Mehmet Fatih; Saka, Kenan; Yousuf, Mohammad; SAKA, KENAN; Bursa Uludağ Üniversitesi/Yenişehir İbrahim Orhan Meslek Yüksekokulu.; AAH-5303-2021Fuel cells are energy conversion devices that directly convert chemical energy of fuels such as hydrogen to useful work with negligible environmental impact and high efficiency. This study deals with thermodynamic analysis and modeling of polymer electrolyte membrane fuel cell (PEMFC) power systems for portable applications. In this regard, a case study of powering a computer with a PEMFC is presented. Also, an inclusive evaluation of various parameters such as voltage polarization, overall system efficiency, power output, and heat generation is reported. In addition, a parametric study is conducted to study the effect of many design and operation parameters on the overall efficiency. Results show the direct influence of current density and temperature values on optimization of the design parameters in PEMFCs.Publication Design and analysis of gas diffusion layers in a proton exchange membrane fuel cell(Mdpi, 2023-01-01) Orhan, Mehmet Fatih; Hamada, Ahmed T.; Saka, Kenan; SAKA, KENAN; Bursa Uludağ Üniversitesi/Yenişehir Meslek Yüksekokulu.; 0000-0002-2296-894X; AAH-5303-2021; AAI-6045-2021A proton exchange membrane fuel cell is an energy convertor that produces environmentally friendly electrical energy by oxidation of hydrogen, with water and heat being byproducts. This study investigates the gas diffusion layer (GDL) of the membrane electrode assembly (MEA) in proton exchange membrane fuel cells (PEMFCs). In this regard, the key design concerns and restraints of the GDL have been assessed, accompanied by an inclusive evaluation of the presently existing models. In addition, the common materials used for the GDL have been explored, evaluating their properties. Moreover, a case study of step-by-step modeling for an optimal GDL has been presented. An experimental test has been carried out on a single cell under various compressions. Lastly, a parametric study has been performed considering many design parameters, such as porosity, permeability, geometrical sizes, and compression of the GDL to improve the overall efficiency of the fuel cell. The results are presented in this paper in order to help ongoing efforts to improve the efficiency of PEMFCs and facilitate their development further.