PEM yakıt hücresi geometrilerinin ve çalışma parametrelerinin performansa etkilerinin sayısal incelenmesi
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Tarih
2024
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Kırıkkale Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu çalışmada değişen yakıt hücresi geometrilerinin ve çalışma koşullarının yakıt hücresi performansı üzerindeki etkileri incelenmiştir. Bu doğrultuda literatürde geleneksel tasarım olarak ifade edilen düzlemsel tasarıma sahip yakıt hücresine alternatif nitelikte olabilecek 5 farklı geometriye sahip yakıt hücresi tasarlanmıştır. Bu sayede yakıt hücresinin kullanım yeri ile çalışma ortamı dikkate alınarak performans açısından düzlemsel tasarıma alternatif olabilecek geometrilerin literatüre kazandırılması amaçlanmıştır. Tasarımı yapılan yakıt hücrelerinin performanslarının sağlıklı bir şekilde kıyaslanabilmesi için yakıt hücrelerinin her bir bileşeninin geometrik boyutları ile özellikleri eşdeğer olacak şekilde alınmıştır. Analizler hesaplamalı akışkanlar dinamiği programı ANSYS Fluent programının PEMFC modülü kullanılarak sayısal olarak yapılmıştır. Sayısal analizler dört farklı kısma ayrılarak yürütülmüştür. İlk kısımda tasarımı yapılan düzlemsel, silindirik, üçgen, dörtgen, beşgen ve altıgen yakıt hücrelerinin sabit sıcaklık, basınç ve stokiyometrik oranlarda gösterdiği performans ayrı ayrı incelenerek model geometri değişiminin yakıt hücresi performansı üzerindeki etkisi ortaya konulmuştur. İkinci kısımda yalnızca sıcaklık değeri değiştirilerek sıcaklık değişimlerinin yakıt hücreleri performansı üzerindeki etkisi incelenmiştir. Üçüncü kısımda; yalnızca basınç değeri değiştirilerek basıncın etkisi, dördüncü kısımda ise yalnızca stokiyometrik oran değiştirilerek stokiyometrik oranın tasarımı yapılan yakıt ? hücreleri performansı üzerindeki etkileri incelenmiştir. Her bir kısımda yakıt hücreleri için polarizasyon eğrileri elde edilmiştir. Bunun yanı sıra değişen çalışma koşulları altında farklı geometrilerdeki yakıt hücrelerinde gerçekleşen performans değişimleri ortaya konulmuştur. Böylece hangi model geometrisinin değişen çalışma koşullarında daha stabil performans gösterdiği bulunmuştur. Ayrıca sayısal analizler neticesinde elde edilen sıcaklık, hidrojen kütle kesri, oksijen kütle kesri ve su kütle kesri dağılımları da incelenerek yakıt hücrelerinde gerçekleşen performans değişimleri elde edilen dağılımlar ile birlikte yorumlanmıştır. Yürütülen çalışma neticesinde; belirli çalışma şartlarında en yüksek akım yoğunluğu değerine silindirik yakıt hücresinde, en yüksek güç değerine düzlemsel yakıt hücresinde, en düşük akım yoğunluğu ve güç değerine ise üçgen yakıt hücresinde ulaşılmıştır. Ayrıca sıcaklık değişimlerinin yakıt hücresi performansı üzerindeki etkisinin basınç ve stokiyometrik oranın etkisine kıyasla daha fazla olduğu, sıcaklık değerinin özellikle 363 K'in üzerine çıkmasıyla beraber yakıt hücreleri performanslarında %44-%51 oranında düşüşün meydana geldiği, basınç değerinin 1,4 atm, stokiyometrik oranın ise 1,5'in üzerine çıkmasıyla birlikte ise yakıt hücresi performans değerlerindeki değişimin oldukça sınırlı değerde kaldığı sonucu elde edilmiştir. Bununla birlikte değişen çalışma koşullarında en düzenli performans değişimi düzlemsel yakıt hücresinde, en düzensiz performans değişimi ise üçgen yakıt hücresinde elde edilmiştir. Sonuç itibarıyla yakıt hücresinin kullanılacağı cihazın geometrik yapısı ile yakıt hücresinin çalışacağı ortamın koşulları dikkate alındığında; silindirik, dörtgen, beşgen ve altıgen tasarımların düzlemsel tasarıma alternatif olarak kullanılabileceği sonucuna ulaşılmıştır. Anahtar Kelimeler: Hidrojen, PEM Yakıt Yakıt Hücresi, Yakıt Hücresi Tasarımı, Enerji, Performans Değişimi, Sayısal Analiz, ANSYS Fluent
In this study, the effect of varying fuel cell geometry and operating conditions on fuel cell performance was investigated. In this regard, PEM fuel cells with 5 different geomtries were designed as an alternative to the fuel cell with a planar design which is expressed as a conventional design in the literature. In this way, it was aimed to provide the literature with geometries that can be an alternative to planar desing in terms of performance by consedering the place of use of the fuel cell and the operating environment. In order to be able to compare the performances of the designed fuel cells in a reliable way, the geometrical dimensions of each component of the fuel cells and the properties of the components were taken the same. The analyses were performed numerically using the PEMFC module of the computational fluid dynamics programme ANSYS Fluent. Numerical analyses were carried out in 4 different sections. In the first part, the performance of the designed planar, cylindrical, triangular, quadrilateral, pentagonal and hexagonal fuel cells at constant temperature, pressure and stoichiometric ratios were analysed separately and the effect of model geometry variation on fuel cell performance was revealed. In the second part of the numerical analyses, only the temperature value was changed and the effect of temperature changes on fuel cell performance was investigated. In the third part of the analyses, the effect of the pressure was examined by changing the pressure value, and in the fourth part of the analyses, the effect of the stoichiometric ratio on the performance of the designed fuel cells was examined by changing the stoichiometric ratio. Polarisation curves were obtained for fuel cells in each section. In addition, the performance changes in fuel cells of different geometries under varying operating conditions were revealed. In this way, it was found which model geometry shows more stable performance under varying operating conditions. In addition, the temperature, hydrogen mass fraction, oxygen mass fraction, water mass fraction distributions obtained as a result of numerical analyses were also examined and the performance changes in fuel cells were interpreted together with the obtained distributions. As a result of the study, the highest current density value was obtained in the cylindrical fuel cell, the highest power value was obtained in the planar fuel cell, and the lowest current density and power value was obtained in the triangular fuel cell under specific operating conditions. In addition, it was concluded that the effect of temperature changes on fuel cell performance was greater than the effect of pressure and stoichiometric ratio, especially with the increase of temperature value above 363 K, fuel cell performances decreased by 44%-51%, while the change in fuel cell performance values was very limited with the increase of pressure value above 1.4 atm and stoichiometric ratio above 1.5. On the other hand, under varying operating conditions, the most steady performance change was obtained in the planar fuel cell and the most irregular performance change was obtained in the triangular fuel cell. As a result, it was concluded that cylindrical, quadrilateral, pentagonal and hexagonal designs can be used as an alternative to planar design, considering the geometric structure of the device in which the fuel cell will be used and the conditions of the environment in which the fuel cell will operate. Keyboards: Hydrogen, PEM Fuel Cell, Fuel Cell Desing, Energy, Change in Performance, Numerical Analysis, ANSYS Fluent
In this study, the effect of varying fuel cell geometry and operating conditions on fuel cell performance was investigated. In this regard, PEM fuel cells with 5 different geomtries were designed as an alternative to the fuel cell with a planar design which is expressed as a conventional design in the literature. In this way, it was aimed to provide the literature with geometries that can be an alternative to planar desing in terms of performance by consedering the place of use of the fuel cell and the operating environment. In order to be able to compare the performances of the designed fuel cells in a reliable way, the geometrical dimensions of each component of the fuel cells and the properties of the components were taken the same. The analyses were performed numerically using the PEMFC module of the computational fluid dynamics programme ANSYS Fluent. Numerical analyses were carried out in 4 different sections. In the first part, the performance of the designed planar, cylindrical, triangular, quadrilateral, pentagonal and hexagonal fuel cells at constant temperature, pressure and stoichiometric ratios were analysed separately and the effect of model geometry variation on fuel cell performance was revealed. In the second part of the numerical analyses, only the temperature value was changed and the effect of temperature changes on fuel cell performance was investigated. In the third part of the analyses, the effect of the pressure was examined by changing the pressure value, and in the fourth part of the analyses, the effect of the stoichiometric ratio on the performance of the designed fuel cells was examined by changing the stoichiometric ratio. Polarisation curves were obtained for fuel cells in each section. In addition, the performance changes in fuel cells of different geometries under varying operating conditions were revealed. In this way, it was found which model geometry shows more stable performance under varying operating conditions. In addition, the temperature, hydrogen mass fraction, oxygen mass fraction, water mass fraction distributions obtained as a result of numerical analyses were also examined and the performance changes in fuel cells were interpreted together with the obtained distributions. As a result of the study, the highest current density value was obtained in the cylindrical fuel cell, the highest power value was obtained in the planar fuel cell, and the lowest current density and power value was obtained in the triangular fuel cell under specific operating conditions. In addition, it was concluded that the effect of temperature changes on fuel cell performance was greater than the effect of pressure and stoichiometric ratio, especially with the increase of temperature value above 363 K, fuel cell performances decreased by 44%-51%, while the change in fuel cell performance values was very limited with the increase of pressure value above 1.4 atm and stoichiometric ratio above 1.5. On the other hand, under varying operating conditions, the most steady performance change was obtained in the planar fuel cell and the most irregular performance change was obtained in the triangular fuel cell. As a result, it was concluded that cylindrical, quadrilateral, pentagonal and hexagonal designs can be used as an alternative to planar design, considering the geometric structure of the device in which the fuel cell will be used and the conditions of the environment in which the fuel cell will operate. Keyboards: Hydrogen, PEM Fuel Cell, Fuel Cell Desing, Energy, Change in Performance, Numerical Analysis, ANSYS Fluent
Açıklama
Fen Bilimleri Enstitüsü, Makine Mühendisliği Ana Bilim Dalı
Anahtar Kelimeler
Enerji, Energy, Makine Mühendisliği
