Master Degree / Yüksek Lisans Tezleri
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Master Thesis Nükleer Enerji Yoluyla Yüksek Buhar Elektrolizinden Hidrojen Üretiminin Yaşam Döngüsü Değerlendirmesi(2025) Yapıcı, Tolunay; Çetkin, Erdalİklim değişikliğiyle mücadele, enerji sistemlerinde köklü bir dönüşümü gerektiriyor ve temiz enerji taşıyıcıları üzerine yapılan araştırmalara önem veriyor. Hidrojen, hem enerji taşıyıcısı hem de endüstriyel süreçlerde fosil yakıtların yerini alabilecek kritik bir hammadde olarak ortaya çıkmıştır. Hidrojen üretiminin çevresel performansı, öncelikle üretim yöntemiyle ilişkili karbon ayak izine bağlıdır. Nükleer enerji destekli Hidrojen üretiminin çevresel performansı, öncelikle üretim yöntemiyle ilişkili karbon ayak izine bağlıdır. Nükleer enerji destekli yüksek sıcaklıkta buhar elektrolizi (YSBE), büyük ölçekli, sürekli ve düşük karbonlu hidrojen üretimi için önemli bir potansiyel sunmaktadır. Bu çalışma, Türkiye'nin ilk nükleer tesisi olan Akkuyu Nükleer Güç Santrali'nde (NGS) YSBE yoluyla hidrojen üretiminin çevresel etkilerini Yaşam Döngüsü Değerlendirmesi (YDD) metodolojisini kullanarak değerlendirmektedir. Akkuyu'ya özgü farklı elektrolizör verimliliği senaryoları (%35, %40, %45, %47 ve %50) analiz edilerek, Küresel Isınma Potansiyeli (KIP), Asitlenme Potansiyeli (AP), Ötrofikasyon Potansiyeli (ÖP) ve Abiyotik Tükenme Potansiyeli (ATP) dahil olmak üzere çeşitli kategorilerdeki çevresel etkiler nicelendirilmiştir. Değerlendirmede, sadece hidrojen üretim ünitesinin girdileri ve çıktıları dikkate alınarak, kapıdan kapıya sistem sınırı kullanılmıştır. Sonuçlar, elektrolizör verimliliğindeki artışla birlikte çevresel etkilerin önemli ölçüde azaldığını göstermiştir. Ayrıca, Akkuyu NGS'nin hidrojen üretim kapasitesi çeşitli operasyonel senaryolar altında değerlendirilerek, Türkiye'nin enerji güvenliği ve karbonsuzlaşma hedeflerine potansiyel katkısı vurgulanmıştır. Akkuyu'ya özgü modelleme ve ayrıntılı verimlilik senaryoları sunan bu çalışma, son dönemdeki araştırmalardaki önemli bir boşluğu doldurmakta ve gelecekteki araştırma ve politika yapımına temel bir referans sunmaktadır.Master Thesis Development of a Dishwasher Drying System That Utilizes Wastewater Thermal Energy and Experimental Investigation of Its Performance(01. Izmir Institute of Technology, 2024) Dalbudak, Uğur Doğan Can; Çetkin, ErdalEv tipi Bulaşık makineleri, girdi olarak elektrik ve suyu kullanarak yıkama işlemi yapan ve hane halkının konforunu arttıran ev aletlerindendir. Bir yıkama çevriminde kullanılan elektriğin 70% ile 90% değişen kısmı suyu ısıtmak için kullanılır. Yıkama sonucunda oluşan 45°C-60°C sıcaklık aralığında olabilen atık su, kullanılmadan gidere boşaltılır. Bu tezde, atık suyun ısıl enerjisinden faydalanmak amacıyla termal enerji deposu (TED) geliştirilmiştir. TED üzerine, atık su ile ısıl etkileşimde olacak şekilde ek bir hava kanalı eklenmiştir. Bu kanala bağlı fan yardımıyla dış ortamdan 23°C sıcaklık ve 55% bağıl neme sahip hava kanaldan geçerken atık su enerjisi ile ısınıp yıkama kabinine gönderilmektedir. Sıcaklığı artan havanın nem taşıma kapasitesi artmakla beraber kabine göre bağıl nemi de düşük seviyelerde olduğu için kurutma performansını iyileştirmesi sağlanmıştır. TED ile ısıl etkileşimde bulunan hava kanalında kanat yapısına bağlı olarak ısı geçişini arttırmak için kanal içerisinde 5 farklı tipte kanat yapısı tasarlanarak hesaplamalı akışkanlar dinamiği ile analizi yapılmıştır. İlk olarak kanat yapılarının akış direncini ne yönde etkiledikleri araştırılarak hava çıkış debileri karşılaştırılmıştır. Sonrasında ise, kurutma evresinindeki başlangıç koşulları ile zamana bağlı çözüm yapılarak, kanatların ısı geçişi üzerine etkileri değerlendirilmiştir. En verimli sonucu veren kanal boyu uzanan kanat tasarımı ile prototip üretilmiştir. Kurutma performansı deneyleri prototip TED ile bulaşık makinesi EN 60436 standardına göre yapılmıştır. Çıkan sonuca göre B enerji sınıfı (0.595 kWh/çevrim) olan bir Bulaşık makinesine geliştirilen TED sistemi entegre edildiğinde, A sınıfına (0.544 kWh/çevrim) ulaşılmıştır.Master Thesis Experimental Investigation of a Photovoltaic Thermal System With Phase Change Material(01. Izmir Institute of Technology, 2024) Karakaya, Özlem; Çetkin, ErdalÇevre dostu enerji kaynakları arasında güneş enerjisi en yaygın kullanılanlardan biridir. Fotovoltaik sistemler, güneş ışığını elektrik enerjisine dönüştürerek bu enerji kaynağını kullanmanın temel yolunu oluşturur. Ancak, PV sistemlerin verimliliği, sıcaklık artışlarıyla azalır. Bu çalışma, PV panellerin performansını artırmak için faz değiştiren malzemeler ve su soğutmalı fotovoltaik termal sistemlerin entegrasyonunu araştırmaktadır. Çalışma iki aşamadan oluşmaktadır ve her iki deney de Antalya'da gerçekleştirilmiştir. İlk aşamada, erime noktaları 25°C ve 35°C olan faz değiştiren malzemelerle entegre edilmiş PV panellerin performansı, standart PV panellerle karşılaştırılmıştır. Sonuçlar, faz değiştiren malzeme entegrasyonunun termal yönetimi iyileştirdiğini ve elektriksel verimliliği artırdığını göstermektedir. PV-PCM35 sistemi, yüksek sıcaklık koşullarında panel sıcaklığını 21.3°C oranında düşürerek, ortalama %2.16 ve maksimum %3.72 oranında verimlilik artışı sağlamıştır. İkinci aşamada, faz değiştiren malzeme ile entegre edilmiş su soğutmalı bir PV/T sistemin performansı, geleneksel PV sistemlerle karşılaştırılmıştır. Bulgular, PV/T-PCM sisteminin elektriksel verimlilikte önemli iyileştirmeler sağladığını ortaya koymaktadır. Su soğutma mekanizması, ısıyı etkili bir şekilde dağıtarak panel sıcaklıklarının düşük kalmasını sağlamış ve verimliliği artırmıştır. PV/T-PCM sistemi, maksimum elektriksel verimlilikte %3.79 ve termal verimlilikte %62.74 artış göstermiştir. Bu sonuçlar, PV/T-PCM sistemlerinin özellikle Antalya gibi yüksek sıcaklıklara sahip bölgelerde daha verimli enerji üretme potansiyeline sahip olduğunu göstermektedir.Master Thesis Investigation of Semi-Empirical Battery Aging Models of Electric Vehicles(2023) Yarımca, Gülşah; Çetkin, ErdalBatteries have been the focus of attention due to their numerous advantages in distinct applications such as recently on Electric Vehicles A limiting factor for adaptation by industry is related to the aging of batteries over time. Characteristics of battery aging vary depending on many factors such as battery type, electrochemical reactions and operation conditions. Aging could be considered in two sections according to its type: calendaring and cycling. This thesis presents a review of empirical and semi-empirical modelling techniques and studies of aging. It focuses on the trends observed across different studies for two types of aging and highlights the limitations and challenges of various models. It introduces three different models for semi-empirical modelling based on Arrhenius Law from the literature for calendar aging, which cover all three important factors for calendar aging: temperature, stage of charge, and time. Moreover, four more models are developed based on these three factors and the Arrhenius law to contribute to the literature. To examine the usability and compatibility of these models, we selected five different experimental sets based on different chemistries and operating conditions from the literature. We also added calendar aging experiments carried out within the scope of our HORIZON-Helios European Project and examined a total of six experimental sets. The Helios Project dataset is split into 70% training data and 30% prediction data to measure the ability to predict future capacity loss. For this purpose, linear regression and genetic algorithm methods were used to determine the parameters of each semi-experimental model by minimizing the mean square error value between the prediction results and experimental capacity data. As a result, it was seen that the numerical solution obtained using the genetic algorithm gave better results than the analytical solution obtained by linear regression. The objective of this thesis is to present comprehensive and accurate models by examining the compatibility of models proposed in the literature models developed in our research with experimental sets. 7 Semi-Empirical Models (SEM), based on a fixed set of defined parameters, have obtained satisfactory estimates of calendar obsolescence for given storage conditions. SEM-3 and 7 were able to predict capacity loss with low errors. In particular, SEM-3 had the lowest RMSE in most experimental sets. While model errors are generally close to each other, Redondo-Iglesias et. al model and Model 7 have lower errors, similar to SEM-3. When all data sets are examined, it is seen that the lowest and highest RMSE values in the model predictions are 0.036 and 3.91, respectively.Master Thesis Investigation of Windshield Defogging and Defrosting Designs To Decrease Energy Consumption in Vehicles(01. Izmir Institute of Technology, 2023) Ediz, Fatih; Çetkin, ErdalFogging and icing of windshields are general problems that affect driving safety and energy consumption. The aim of this study is to improve the truck windshield defogging system and reduce energy consumption. Firstly, we investigated the effects of vent position and width relative to the glass. In the first stage, we performed analysis on the truck xz plane (2D). We preferred this method to quickly see the effect of vent changes. In the second stage, we applied the modification parameters to the 3D duct model. In both studies, we determined that the independent variables had a statistically significant effect on the dependent variable and determined the parameters with the highest desirability value by using the Analysis of Variance method. Secondly, we added various separators to the duct model. We investigated the total mass flow rate coming to the driver's side with total pressure drop. In this thesis, we used the Eulerian Wall Film (EWF) Model to model the defogging phenomenon on windshields. In the EWF model, the wall film is treated as a separate fluid phase, and the conservation equations for mass, momentum, and energy are solved separately for each fluid phase. As a result, we applied the obtained data to the current design. Windshield defogging performance has improved in the optimization model. The average film thickness in region A decreased by 8.2% compared to the current model, while the average film thickness in region B decreased by 48.1%.Master Thesis Numerical Investigation of Y-Shaped and Csc Micromixers(01. Izmir Institute of Technology, 2022) Samancıoğlu, Umut Ege; Çetkin, Erdal; Çetkin, ErdalMicromixers are one of the key parts in microfluidic devices. Therefore, passive micromixers have become a popular research topic. In this thesis, parametric optimization of a Y-shaped micromixer with mixing chamber is documented. Design parameters are; alpha () for the angle between the two inlet angles, beta () for the angle between the z axis and one of the inlet channels and theta () for the angle between the other inlet channel, z-eccentricity (zecc) is the distance between the centerline of an inlet channel and origin of the mixing chamber along z-axis, x-eccentricity (xecc) is the distance between the intersection point of the two inlets and the origin of the mixing chamber along x-axis, ratio of the inlet and outlet channel length (L1/L2), ratio of the inlet and outlet channel diameter (D1/D2), ratio of the inlet channel length and diameter (L2/D2) and ratio of mixing chamber volume to the total volume(Vsp). = 180o - 240o range and zecc= 20m corresponds to the optimal range. Effect of each parameter on the system is discussed and the best performing 3 mixer designs are further investigated. The optimized design yields 88.16% mixing efficiency with 9244.4 Pa pressure drop when Reynolds number is 81. Furthermore, performance of this design is compared with a reference design. The comparison shows that optimized design decreases the pressure drop more than 50% for all Reynolds numbers while having a higher mixing efficiency (up to 35%) with low Reynolds numbers (0.054-3).Master Thesis Numerical and Experimental Investigation of an Electric Vehicle Battery Module Thermal Management System(Izmir Institute of Technology, 2022) Gediksiz, Çağlar; Çetkin, ErdalToday, electric vehicles play an essential role in preventing pollution from fossil sources. Therefore, it is vital to develop battery technology in electric vehicles. The biggest problem experienced is the thermal runaways, which is a phenomenon that may cause burning and explosions following the decrease in battery capacities. The thermal runaway problem can be solved by using the thermal management system to keep the temperature range under control. In this study, a 6.7 kWh battery pack was produced. Battery pack operation consists of two parts, mechanical and thermal. In the mechanical part, battery pack assembly and drop tests, one of the mechanical tests, were carried out. At the end of the battery pack assembly, voltage measurements were made, and the accuracy of the assembly was demonstrated. Besides, a numerical and experimental study supported drop tests. As a result of this study, the battery case did not show permanent deformation (2.529x 108 N/m2) as suggested in the numerical experiments (1.263x 108 N/m2). Discharge characteristics and battery module model were discussed in the thermal management part. The information in the literature confirmed the discharge characteristic. The gap between the battery cells reached its most efficient value at 8 mm. In the developed battery module, thermal management was attempted using a heat plate and a cooling pipe. According to the numerical results, the battery module reaches 311.37K at 10C discharge. In the experimental process, the battery pack was charged with 15 amps and discharged with 30 amps. Moreover, the temperature values reached a maximum of 31 degrees. In the experiment on electric vehicles, a maximum discharge level of 255 A was observed. In this experiment, the battery pack reached a maximum of 36 degrees.Master Thesis Numerical Investigation of Various Heat Transfer Mechanisms on Thermal Management of a Lithium-Ion Battery Pack(Izmir Institute of Technology, 2022) Şahin, Resul Çağtay; Çetkin, ErdalLithium-ion battery packs are preferred in Electrical and Hybrid Vehicles (EVs and HEVs) due to their efficient and stable energy storage characteristics. Battery Thermal Management Systems (BTMS) have vital importance in EVs and HEVs to keep the batteries in desired temperature range to maximize performance and lifetime. Air cooling is a well-known method with the advantages of being simple and light but main concern for air cooling is effectiveness and pressure drops due to low heat capacity and thermal conductivity of air. This work compared various cooling designs for battery modules based on the surface temperature of batteries and the parasitic power consumption. Modules were built with COMSOL Multiphysics 5.5, and their accuracy was validated by experiments. Each module involves an equal number of batteries whose thermal characteristics were simulated by the electrochemical-thermal battery model, the P3D multiscale model. As a result, the maximum temperature was reduced by 5% (1.8°C) for inline alignment with baffles and 7.2% (2.8°C) for staggered modules, and the temperature gradient was reduced by 40% (1.7°C) for inline and 35% (1.5°C) for staggered alignments. While fan power consumption of inline alignment with triangle baffles (0.98W) was 3.5 times higher than the base design (0.27W), it was 0.23W for staggered design. Moreover, the cooling performance of different winglet parameters was compared and documented.Master Thesis Numerical and Experimental Investigations of an Air-Cooled Battery Thermal Management System(01. Izmir Institute of Technology, 2021) Göçmen, Sinan; Çetkin, ErdalElectric vehicles play an integral role in eliminating pollution related to transportation, especially if electricity is generated via renewable sources. However, storing electricity onboard requires many battery cells. If the temperature of the cells is not strictly regulated, their capacity decreases in time, and they may burn or explode due to thermal runaway. Battery thermal management systems emerged for safe operations by keeping the battery cell temperatures under limit values. However, the current solutions do not yield uniform temperature distribution for all the cells in a pack. Here, we document that constant temperature distribution can be achieved with uniform coolant distribution to the channels located between batteries. To this end, we performed both numerical and experimental investigations. The design process of the developed battery pack begins with a design used in current packs. Later, how the shape of the distributor channel affects flow uniformity is documented. Then, the design complexity was increased to satisfy the flow uniformity condition, which is essential for temperature uniformity. The design was altered based on a constructal design methodology with an iterative exhaustive search approach. The uncovered constructal design yields a uniform coolant distribution with a maximum of 0.81% flow rate deviation along channels. The developed design is palpable and easy to manufacture relative to the tapered manifold designs. The results also document that the peak temperature difference between the cells decreases from a maximum of 12 K to 0.4 K. Additionally, the developed design was simulated by using Newman, Tiedeman, Gu, and Kim (NTGK) electrochemical battery model, which provides more realistic results due to its heat generation approach in a battery cell. The electrochemical model was simulated with fluid and heat flow simultaneously at the battery pack level. The accuracy of numerical studies is validated by experimental work. The results show that the peak temperature can be kept under the desired operational temperature with a minimum deviation in the temperature difference.Master Thesis Design Optimization of an Industrial Oven Heat Exchanger(01. Izmir Institute of Technology, 2021) Nergiz, Güven; Çetkin, ErdalThe coating application of metals (especially in automotive and white goods sectors) is used in various fields to protect the metal against oxidation, corrosion, scratch, or high temperature to increase product lifetime. The most efficient technique in the coating application is powder coating where the powder is Epoxy-polyester. This process has three steps; surface pretreatment (washing), powder coating, and curing the coated metal. Metals may need to be dried and cured in ovens with 90°C and 200°C, respectively, for the required quality coating process. Burners are used as the heat source in the oven's heat exchangers. Due to high temperatures, the expanding heat exchanger is exposed to various thermal stresses. The stresses cause cracking and rupture problems. The regions where thermal stresses occur intensely are the surfaces with high-temperature differences. Various mass flow rates in the heat exchanger cause non-uniformity for how the energy to be transferred, thus non-uniform surface temperature distribution. In this study, a heat exchanger design provided by "ELECTRON – Sistem Teknik Makina" company has been studied. The mass flow rates in the heat transfer pipes (where the heat is mainly transferred) show deviations up to 75% from the ideal rate. With this study, deviations have been reduced to the level of ±10%. The results show that the maximum thermal stress on the heat exchanger was reduced by 24% with this improvement. In general, the uniform mass flow rates obtained in the heat transfer pipes provided a more homogeneous distribution of the surface temperatures, thus decreased thermal stresses.