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Engineered cementitious composites (ECCs) are special types of fibre-reinforced cementitious composites (FRCC) with higher strain capacity which can be achieved with low fibre volume as low as 2% and total elimination of coarse aggregates. Due to the outstanding performance of ECCs, they are suitable for various construction and repair applications. However, in order for ECCs to achieve their properties; a high amount of binder which is primarily composed of Portland cement (PC) is used alongside a special type of ultrafine silica sand (USS) which is different from the conventional natural fine aggregates. The production of PC is known to be detrimental to the environment due to its high carbon dioxide emissions coupled with the high consumption of natural resources. Thus, the high use of PC content in ECCs posed a sustainability threat. Similarly, the USS used in ECCs are not readily available everywhere and are expensive. The processing of the USS coupled with its transportation over long distances would also increase the cost and embodied carbon of ECCs. Hence, in order to promote more development and applications of ECCs for various applications; this dissertation aims to provide innovative ways to improve the sustainability of ECCs and their performances. This dissertation offers four solutions to improve the sustainability of ECCs which are (i) use of unconventional industrial by-products as partial replacement of PC (ii) total replacement of PC in ECCs with alternative sustainable binders (iii) replacement of USS in ECCs with recycled materials and (iv) the use of supplementary cementitious materials to replace a high volume of PC. The findings from this study revealed sustainable ECCs with acceptable mechanical and durability performance can be achieved with the use of alternative binders or replacement of the conventional USS used in ECC mixtures. The sustainability and cost assessment of the ECCs indicated that the incorporation of industrial by-products such as blast furnace slag (BFS) especially at higher content is beneficial to reducing the negative environmental impact and economic burden associated with ECCs compared to the conventional ECC. The sustainability index and cost index of the ECCs further showed that the use of BFS is more beneficial when the sustainability and cost of the ECCs are compared with the corresponding performance. Similarly, the use of recycled materials as an alternative to USS was found to result in a significant reduction in the embodied carbon and cost of ECCs. The use of recycled materials such as expanded glass (EG) as aggregates in ECCs was also found to improve the thermal insulation properties of ECCs making such ECC suitable for the production of building envelope elements.

II ABSTRACT Climate change is expected due to the increasing atmospheric concentrations of carbondioxide and other trace gasses, which lead to changes in the radioactive balance of the atmosphere. Such changes propagate further to those in temperature i and other climatic variables. Hydrologic systems and water resources are likely to be seriously impacted by global climate change. Such processes as surface runoff, precipitation, soil moisture, groundwater, water quality, and sea levels will be significantly exposed to effects of climate change. Eventually, these effects will have to be considered in water resources planning and management. The study presented stems from the above needs and addresses the problem of climate change-water resources interactions. It is intended here to investigate the possible effects of climate change on watershed scale hydrologic processes and water demand. Within this context, the current methods used in developed countries are applied to the case of the Gediz River Basin, and possible impacts of changes in climatic variables, i.e., precipitation and temperature, are investigated as they relate to runoff The results of the study should not considered as exact values to represent the effects of climate change. They are essentially `estimates` on `likely` effects of an expected climate change. However, the results also show that, if the prescribed climate change scenarios do occur in the future, they will have significant effects on the hydrology of the basin which, in turn, affects water demand for various water resources development plans. Accordingly, the study presented should be considered as an initial step towards assessment of climate change impacts and should be reaccomplished in future attempts towards any planning or management activity in the basin. ÖZET İklim değişikliği, atmosferdeki karbondioksit (CO2) ve diğer antropojen sera gazı konsantrasyonlarının giderek artması sonucu beklenmektedir. İklim değişikliğinin sonucunda beklenen en önemli olgu, sıcaklık, yağış, evapotranspirasyon, akış gibi temel iklimsel ve hidrolojik değişkenlerdeki muhtemel değişimlerdir. Bu etkilerin su kaynakları planlama ve yönetiminde değerlendirilmesi gerekmektedir. Sunulan çalışma, iklim değişikliğinin su kaynakları ile olan ilişkisini incelemektedir. Bu değişimlerden hidrolojik çevrimin ve su kaynaklarının gerek miktarı ve gerekse kalitesinin de etkilenmesi beklenmektedir. Dolayısıyla, küresel iklim değişikliğinin havza su dengesine ve su kaynaklarının planlama ve yönetimine de yansıması söz konusudur. Bu kapsamda sunulan çalışmada alt havza bazında sıcaklık ve yağış gibi iklim parametrelerinin, akıma olan etkileri incelenmiş ve duyarlılık analizi ile sonuçlar değerlendirilmiştir. 75

An important limitation of polymer electrolyte fuel cell technology is the low mechanical strength and dimensional instability with changes of water content of proton exchange membranes (PEMs). A range of different approaches to more stable PEMs based on Nafion have been studied of which composite materials of Nafion with mechanically stronger polymers is one of the most promising directions. If successful, they will lead to thinner composite PEMs with enhanced fuel cell performance, life span, and cost-effectiveness. Developed in this thesis are electrospinning conditions for the fabrication of electrospun mats for potential application in PEMs. Polysulfone (PSU), poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride (PVDF) were tested as mechanically stronger but inert (minimal contribution to proton transport) polymers that can tolerate the fuel cell condition. PVDF-HFP generated defect free electrospun mats over a wide range of spinning conditions, while PSU required very specific conditions and no successful conditions were found for PVDF mostly due to over-wetting. These mats might function as mechanical support and could be tested as PEMs when filled with Nafion, but the complete filling of electrospun mats with Nafion has been proven difficult. Instead, the electrospinning of Nafion was tested to explore options of electrospinning mixed mats of two different polymers and co-electrospinning of core-sheath fibers. Two commercial Nafion solutions D520 and D2020 with 5 wt% and 20 wt% content of Nafion were electrospun together with polyethylene oxide of two different molecular weights as a carrier polymer. Mats of sufficient quality for PEM tests were obtained with solutions based on 20 wt% content of Nafion, a low flow rate of 0.2 mL/h, and the lower molecular weight polyethylene oxide as the carrier. Finally, coaxial electrospinning conditions for the formation of core-sheath fibers were developed for Nafion as sheath material and PVDF-HFP or PSU as the core material. Defect-free, core-sheath fibers were generated when the concentration of both solutions was high (20 wt%), the Nafion flow rate was about 0.2 mL/h for the sheath, and the core flow rate was below the flow rate of the sheath (0.1-0.15 mL/h for PVDF-HFP and 0.15 mL/h for PSU). Mats of these core-sheath fibers should provide good mechanical strength combined with much better compatibility with Nafion. A straightforward pore filling with Nafion solutions is expected and their investigation as PEMs in fuel cells is planned as future work.

The aggravating global problems of energy crisis, rising atmospheric greenhouse gas concentrations and accumulation of persistent waste have attracted the attention of scientists, policy-makers and global organisations to come up with effective and expeditious solutions to address these challenges. In this context, the development of sustainable technologies driven by renewable energy sources for the production of clean fuels and commodity chemicals from diverse waste feedstocks is an appealing approach towards creating a circular economy. Over the years, semiconductor photocatalysts based on TiO₂, CdS, carbon-nitrides (CNx) and carbon dots (CDs) have been widely used for the photocatalytic reforming (PC reforming) of pre-treated waste substrates to organic products, accompanied with clean hydrogen (H₂) generation. However, these conventional solar-driven processes suffer from major drawbacks such as low production rates, poor product selectivity, CO₂ release, challenging process and catalyst optimisation, and harsh waste pre-treatment conditions, which limit their commercial applicability. These challenges are tackled in this thesis with the introduction of new and efficient photoelectrochemical (PEC) and chemoenzymatic processes for reforming a diverse range of waste feedstocks to sustainable fuels. Solar-driven PEC reforming based on halide perovskite light-absorber is first developed as an attractive alternative to PC reforming. The PEC systems consist of a perovskite|Pt photocathode for clean H₂ production and a Cu-Pd alloy anode for reforming diverse waste streams, including pre-treated cellulosic biomass, polyethylene terephthalate (PET) plastics, and industrial by-product glycerol into industrially-relevant, value-added chemicals (gluconic acid, glycolic acid and glyceric acid) without any externally applied bias or voltage. Additionally, the single light-absorber PEC systems can also convert the airborne waste stream and greenhouse gas CO₂ to diverse products with the simultaneous reforming of PET plastics with no applied voltage. The perovskite-based photocathode enables the integration of different CO₂ reduction catalysts such as a molecular cobalt porphyrin, a Cu-In alloy and formate dehydrogenase enzyme, which produce CO, syngas and formate, respectively. The versatile PEC systems, which can be assembled in either a ‘two-compartment’ or standalone ‘artificial leaf’ configurations achieve 60‒90% oxidation product selectivity (with no over-oxidation) and >100 µmol cm‾² h‾¹ product formation rates, corresponding to 10²‒10⁴ times higher activity than conventional PC reforming systems. In addition to developing PEC platforms, this thesis also explores avenues for circumventing the harsh alkaline pre-treatment strategies (pH >13, 60‒80 ºC) adopted for photoreforming waste substrates. For this purpose, a chemoenzymatic pathway is introduced whereby PET and polycaprolactone plastics were deconstructed using functional enzymes under benign conditions (pH 6‒8, 37‒65 ºC), followed by PC reforming using Pt loaded TiO₂ (TiO₂|Pt) or Ni₂P loaded carbon-nitride (CNx|Ni₂P) photocatalysts. The chemoenzymatic reforming process demonstrates versatility in upcycling polyester films and nanoplastics for H₂ production at high yields reaching ∼10³‒10⁴ µmol gsub‾¹ and activities at >500 µmol gcat‾¹ h‾¹. The utilisation of enzyme pre-treated plastics also allowed the coupling of plastic reforming with photocatalytic CO₂-to-syngas conversion using a phosphonated cobalt bis(terpyridine) co-catalyst immobilised on TiO₂ (TiO₂|CotpyP). Finally, moving beyond solar-driven systems, a bio-electrocatalytic flow process is demonstrated for the conversion of microbe pre-treated food waste to ethylene (an important feedstock in the chemical industry) on graphitic carbon electrodes via succinic acid as the central intermediate. In conclusion, with its focus on improving efficiencies, achieving selective product formation, building versatile platforms, diversifying substrate and product scope, and reducing carbon footprint and economic strain, this thesis aims to bring sustainable waste-to-fuel technologies a step closer to commercial implementation.

Ammonia has been responsible for feeding population growth in the 20th century through synthetic fertilizer, and is poised to become the preferred energy storage medium for a society powered by renewable electricity in the 21st century. However, conventional brown ammonia production through the Haber-Bosch process is optimized for utilization of centralized and steady energy supply from fossil-fuels. When shifting to distributed and intermittent energy supply through wind and solar energy, a re-optimization is required for a low-capital and flexible green ammonia production processes. This thesis re-designs and Haber-Bosch process by targeting the integration of reaction and separation in a single process vessel at low pressures, thereby achieving the simplification and down-scaling of the high pressure recycle loop of the Haber-Bosch process. Materials are developed for this purpose, the feasibility of integration is demonstrated, and mathematical modeling is utilized for assessing the application of the single-vessel process to a range of renewable energy sources in comparison to competing ammonia production processes. Herein, a catalyst with low-temperature (< 350°C) and high-conversion (i.e. near equilibrium) activity is developed using ruthenium nanoparticles as the active metal supported on ceria and promoted with cesium to mitigate hydrogen and ammonia inhibition, respectively. This catalyst is compared to commercial iron-based catalyst from the perspective of the final application. Concurrently, a high-temperature (> 300°C) manganese chloride absorbent is developed that resists decomposition and is stable when supported on silica. These catalyst and absorbent are integrated in a layered reactor configuration to demonstrate the feasibility of the integrated process by exceeding single-pass reaction equilibrium. Mathematical modelling of ammonia production processes illustrates that at small-scales (< 1 t day-1) the single-vessel process is optimal compared to the Haber-Bosch process due to its modular design. In addition, it can achieve simpler ramping because the Haber-Bosch process is constrained by heat-integration in the recycle loop and the potential for runaway reaction. For final application, the pairing of ammonia production processes with examples of intermittent solar and wind sources demonstrates that the flexibility of the production process is essential when considering non-ideal sources of energy with a long-term (e.g. seasonal) oscillations. Flexible ammonia production also expands the economic usage of ammonia as an energy storage vector from the seasonal to the weekly time-scale, with advantage compared to batteries or hydrogen. The work of this thesis provides a framework for advancing the electrification of the chemical industry given the novel constrains of intermittent and distributed renewable energy. A systems level approach is applied from the ground up, starting from material design and progressing to optimized process design and application.

ABSTRACT THE ENERGY ANALYSIS AND THE MULTIVARIABLE ENERGY OPTIMIZATION OF A YANKEE HOOD DRYER Toppare, Akın Salih M.S., Department of Chemical Engineering Supervisor: Prof. Dr. Güniz Gürüz Januray 2002, 116 Pages The Yankee Hood dryer is the crucial section of the paper machine due to the high consumption of energy. As a consequence of continuously increasing energy costs, determination of the proper conditions is essential to operate the tissue machine in the most efficient and economic means while ensuring paper quality. The objective of this study is to evaluate the performance of the Paper Machine 3 (PM3) in `İpekkağıt` tissue factory, in order to achieve the desired mproduction rate while keeping the drying parameters within the limits at the minimum energy cost. The steady state rate of heat transfer to the wet sheet is analyzed considering the two-way mechanism, from steam through the cast iron shell and from heated air. The critical drying parameters are air supply velocity, wet and dry hood temperatures and steam flow rate. The approach to this problem is to use the steady state analytical model developed for PM2 and, to solve the material and energy balances for each system defined previously [1]. Data for the machine parameters are taken from the plant. Balance equations are solved with the available data for the unknown parameters and for the determination of drying parameters. Three heat exchangers together with the Yankee hood dryer were also included in the analysis of the overall system. In sequence these are used to heat process water, for ceiling heating and to heat the make-up air stream respectively. The overall energy usage efficiency of the dryer was calculated as 38% and the corresponding values were obtained as 41, 49 and 50% by the inclusion of heat exchanger into the system boundary. For the optimization studies, energy consumption is related to the drying parameters. The total energy consumption consist of steam, electricity and natural gas; which are expressed as functions of steam flow rate and the air temperature of wet and dry hoods. A computer program using the Simplex Method is used to evaluate the optimum values of each drying parameter and hence the consumption ivvalues. A typical set of results with the optimized values for 1 hour production of tissue paper 1 has shown the consumption of 1759 kW of natural gas, 1242 kW of steam and 575 kW of electricity. Based on the cost values $ 26, $ 34.8 and $ 34.3 were obtained respectively. The optimized values of wet and dry hood temperatures and the steam flow rate (486°K, 416°K and 1 1430 kg/h) are close to the values taken from the factory (497°K, 425°K and 13200 kg/h) for a maximum production Keywords: Yankee Hood Dryer, Paper Drying, Energy Consumption, Linear Optimization, Simplex Method. öz YANKEE HOOD KURUTUCUSUNUN ENERJİ ANALİZİ VE ÇOK DEĞİŞKENLİ ENERJİ OPTİMİZASYONU Toppare, Akın Salih Yüksek Lisans, Kimya Mühendisliği Bölümü Tez Yöneticisi: Prof. Dr. Güniz Gürüz Ocak 2002, 116 Sayfa Yankee Hood kurutucusu yüksek enerji tüketimi nedeniyle kağıt makinasının en önemli kısmıdır: Sürekli artan enerji Batları sonunda, istenilen kağıt özelliklerinin sağlanması ile birlikte, kağıt makinasının verimli ve ekonomik çalışması çok önemlidir. Bu çalışmanın amacı İpekkağit Sânayi ve Ticaret A.Ş. fabrikasında bulanan 3 numaralı kurutucunun istenilen üretim hızında çalışabilmesi amacıyla viperformansının incelenmesidir. Bu amacı sağlarken kurutma limitleri içerisinde mümkün olan en düşük enerji maliyetin sağlanması hedeflenmiştir. Islak kağıt üzerine yatışkın durumdaki ısı transferi buhardan ve ısıtılmış havadan olmak üzere iki yönlü olarak analiz edilmiştir. Kritik kurutma parametreleri olarak hava-hızı, yaş ve kuru kısımdaki haubelerin sıcaklığı ve buhar debisi belirlenmiştir. Kurutma makinası 2 için geliştirilmiş olan yatışkın durum analitik model 3 numaralı kurutucu için adapte edilmiş ve kurulmuş olan kütle ve enerji denkliklerinin çözülmüştür [1]. Analizler için gerekli veriler fabrikadan alınmıştır. Bilinmeyen parametreler, bilinen verilerle denkliklerin çözülmesi yoluyla bulunmuştur. Yankee silindiri ve haubelerden oluşan kurutma sisteminin analiz sınırları, varolan ısı değiştiricilerinin eklenmesi ile genişletilmiştir. Isı değiştiricileri sırasıyla geri dönüşüm havası, kullanma suyu ve çatının ısıtılması amacıyla kullanılmaktadırlar. Isı değiştiriciler olmadan ısıl verimlilik %38 iken sırayla eşanjörlerin katılmasıyla bu rakam %4T, %49 ve %50 ye ulaşmıştır. Optimizasyon çalışmaları için kullanılan enerji miktarı kurutma parametrelerine bağlanmıştır. Harcanan toplam enerji buhar, elektrik ve doğal gaz şeklinde üç ana kaynaktan oluşup, miktarlar sırası ile buhar debisi ve yaş ve kuru haube sıcaklıklarına bağlanmıştır: Simplex metodunu kullanan bir bilgisayar programı ile hesaplamalar yapılmıştır. Bir saat baz alınarak yapılan bir ürün çalışmasında 1759 kW doğal gaz, 1242 k W buhar ve 575 kW elektrik harcaması viibulunmuştur. Maliyet olarak bu rakamlar sırasıyla 26$, 34.8$ ve 34.3$ tutarındadır. Optimize edilmiş olan yaş ve kuru haube sıcaklıkları ve buhar debisi (486°K, 416°K and 1 1430 kg/s), fabrikadan en verimli üretim değeri olarak alınan değerlere oldukça yakındır (497° K, 425 °K ve 13200 kg/s). Anahtar Kelimeler: Yankee Hood Kurutucusu, Kağıt Kurutma, Enerji Sarfiyatı, Lineer Optimizasyon, Simplex Metodu. vııı 116

oz HAFİF PETROLLERİN YANMA MEKANİZMALARINA MATRİSİN VE BASINCIN ETKİLERİNİN ISISAL ANALİZ TEKNİKLERİYLE İNCELENMESİ KESKİN, Cengizhan Yüksek Lisans, Petrol ve Doğal Gaz Mühendisliği Bölümü Tez Yöneticisi: Prof. Dr. Mustafa V. KÖK Nisan 2001, 115 Sayfa Yerinde yanma birçok kimyasal ve fiziksel oluşum içeren karmaşık bir işlemdir. Bu işlemin verimliliğini artırmak için, petrolün yanmasını etkileyen faktörler daha fazla bilgi edinmek gereklidir. Bu çalışma, matrisin ve basıncın hafif petrollerin yanmasına olan etkileri üzerine odaklanmıştır. Bu çalışmanın temel amaçlan, reaksiyon parametrelerinin, petrollerin API gravite farklarının yanmaya olan etkilerinin, matrisdeki ve parçacık boyutundaki değişikliklerin reaksiyon parametrelerine olan etkilerinin ve basınçdaki değişimin reaksiyon kinetiğine ve parametrelerine olan etkilerinin belirlenmesidir. Bu çalışmada, 10 °C/dak. ısıtma hızında ve yaklaşık 50 mg ağırlığındaki numuneler kullanılarak 16 termogravimetri/türevsel termogravimetri ve 56 yüksek basınçlı türevsel taramalı kalorimetre deneyleri yapıldı. Deneylerde kullanılan numuneler petrol-kireçtaşı ve petrol-kumtaşı karışımlarından oluşmaktadır.Termogravimetri ve türevsel termogravimetri deneylerinden elde edilen verilerin kinetik analizi, Arrhenius kinetik teorisine dayanan Arrhenius ve Coats- Redfern kinetik analiz modelleriyle yapıldı. Yüksek basınçlı türevsel taramalı kalorimetre deneylerinden elde edilen veriler ise Roger-Morris kinetik modeli kullanılarak analiz edilmiştir. Tüm bu modellerden yararlanılarak reaksiyonların aktivasyon enerjileri, katsayıları ve Arrhenius sabitleri hesaplanmıştır. Analizlerin sonucunda, petrolün API gravitesi arttıkça, petrol + kireçtaşı karışımlarının düşük ve yüksek sıcaklıkdaki oxidasyon bölgelerinde aktivasyon enerjisinin düştüğü görüldü. Petrol + kumtaşı numunelerinde parçacık boyutundaki değişim sonucunda herhangi bir kesin sonuç elde edilemedi. Yüksek basınçlı türevsel taramalı kalorimetre deneylerinin birçoğunun sonucunda, basınç arttıkça reaksiyon sıcaklıkları ve aktivasyon enerjileri azaldı ama toplam kalorilik değerler arttı. Yine bu deneylerde parçacık boyutu küçüldükçe, aktivasyon enerjileri azaldığı buna karşın toplam kalorifik değerlerin arttığı gözlendi. Anahtar Kelimeler: Isısal Analiz, Termogravimetri, Türevsel Termogravimetrik Analiz, Türevsel Taramalı Kalorimetre, Yanma, Kinetik Analiz, Aktivasyon Enerjisi VI ABSTRACT EFFECTS OF MATRIX AND PRESSURE ON LIGHT CRUDE OIL COMBUSTION BY THERMAL ANALYSIS TECHNIQUES KESKİN, Cengizhan M.Sc, Department of Petroleum and Natural Gas Engineering Supervisor: Prof. Dr. Mustafa V. KÖK April 2001, 115 Pages In-situ combustion is a complex process involving many chemical and physical changes. In order to improve its efficiency it is necessary to have more knowledge of the factors influencing the process. This study focused on the effects of matrix and pressure on light crude oil combustion. Main objectives of the study are to determine; the parameters of the reactions, the effects of API gravity differences of crude oils on combustion, effects of changes in sand type and mesh size on reaction parameters and effects of changes in pressure on both reaction kinetics and parameters. A total of 16 TG/DTG and 56 HPDSC experiments were performed with a sample size of approximately 50 mg, at heating rate of 10 °C/min. Samples used in the experiments were composed of crude oil-limestone and crude oil- sandstone mixtures. IllArrhenius and Coats and Redfern methods, both based on Arrhenius kinetic theory, were used for the kinetic analysis of the data generated by the TG/DTG experiments. On the other hand, Roger and Morris method was used to analyse the data obtained from HPDSC experiments. Using these methods, activation energies, reaction orders and Arrhenius constants of the reactions were calculated. From the results of the analysis, it is concluded that as the API gravity of the crude oil increased, activation energies for both LTO and HTO regions of crude oil + limestone samples decreased, but no exact results were reached for the crude oil + sandstone samples from the changes in mesh size. In most of the HPDSC experiments, as the pressure increased, reaction temperatures and activation energies decreased but the total heating values increased and as the mesh size increased, activation energies decreased but the total heating values increased. Key Words: Thermal Analysis, Thermogravimetry, Differential Thermal Analysis, Differential Scanning Calorimetry, Combustion, Kinetic Analysis, Activation Energy IV 115

A prevalência de fontes de energia renovável nas redes elétricas tem crescido exponencialmente nos últimos anos. No entanto, esta transição também apresenta novos desafios para o planeamento das redes devido à natureza intermitente e imprevisível da produção de energia renovável. Para lidar com estes desafios, este estudo introduz uma metodologia estocástica que permite que as redes façam investimentos informados em novas linhas e sistemas de armazenamento de energia. Focando numa rede de 180 barramentos em Portugal, a pesquisa utiliza uma abordagem estocástica de duas etapas que considera o impacto sazonal e a alta penetração de fontes de energia renovável. Fatores como a localização e o tipo de linhas de energia, e o tamanho e a disposição dos sistemas de armazenamento de energia são considerados. A incerteza na produção eólica e solar, bem como nos dados de carga, é destacada na pesquisa, variando de acordo com as estações do ano e os períodos diários. Ao incorporar a incerteza e ao utilizar análise de risco condicional, o modelo fornece uma compreensão abrangente da dinâmica da rede. Os resultados demonstram o interesse económico da abordagem proposta, mesmo em eventos extremos, com reduções potenciais de custos de até 34%. Além disso, o modelo visa minimizar os valores de CO2 e considera a remuneração dos geradores distribuídos, que muitas vezes é negligenciada no planeamento da rede. O estudo incorpora 42 parques eólicos, 33 parques fotovoltaicos, três geradores de biomassa, uma subestação e sistemas de armazenamento de energia existentes. Ele garante uma remuneração justa para os participantes, enquanto minimiza os custos de planeamento, emissões de carbono e investimentos. O modelo proposto considera os impactos das estações do ano, incerteza e emissões de CO2, fornecendo insights para o planeamento de redes em distribuição de energia renovável. Esta pesquisa oferece uma estrutura abrangente para um futuro mais limpo e sustentável, combinando incertezas, armazenamento, remuneração de recursos distribuídos, análise de risco condicional e emissões de carbono.

ABSTRACT MODELING OF MULTI-PHASE COMBUSTION PROCESSES JUDEH, Ramzi ( ŞAHÎN, Remzi) Ph.D., Department of Mechanical Engineering Supervisor: Prof. Dr. Hüseyin VURAL June 2001, 216 pages Most of the power plants active today employ turbulent combustion of fossil fuels to generate electricity in large scales. The modeling of such combustion systems is a challenging field of research since it involves complex phenomena such as turbulent particle dispersion, participating radiation and pollutants formation. The work of this thesis involves description of a steady-state computer model of swirling fired-type furnaces in which pulverized coal particles and natural gas stream are fed from two concentric ports (either together or separately) in cylindrical axisymmetric coordinate system. The gas phase is modeled in terms of Eulerian continuum conservation equations of mass, momentum, energy and species concentrations, for Favre-averaged quantities. The highly-coupled, non-linear set of elliptical partial differential equations that describe the system are solved by an iterative line-by-line technique after transferring it to a system of finite difference equations. Turbulence is considered by the standard linear k-e model. Gas-phase reactions are modeled assuming local instantaneous equilibrium and gaseous combustion is modeled with a probability 111density function of the mixture fraction. Radiation from gases, walls, particles, is handled by the discrete ordinates model, derived from flux considerations. The particle phase is modeled in a Lagrangian framework based on the `Particle- Source-In-Cell` (PSIC) technique, such that each `computational particle` contains many identical particles possessing the same size, velocity, temperature, etc. The Lagrangian ordinary differential equations of mass, momentum, and energy are solved for each computational particle to provide its trajectory, mass, velocity and temperature. Particles interact with the gas phase by exchanging mass, momentum and energy with it and displacing it. The particle equations are discretized by finite difference scheme after they have been cast in the same coordinate frame as the gas phase equations. Two-step coal devolatilization scheme is used along with a heterogeneous reaction scheme that allows for both diffusion and chemical reaction. In the result chapter of present thesis, firstly, the mathematical model is assessed against three sets of experimental data corresponding to turbulent confined jets cold flows. Secondly, the model is employed to perform calculations for an axisymmetric pilot-scale combustor for two cases: one natural gas-fired and one pulverized coal- fired. In these calculations the significant features of the flow field are illustrated with the velocity field, temperature field and gaseous species concentrations. Two sets of validation data are used for comparison and the computed results agree fairly well with the available experimental data. Finally, the code is used to simulate the case of simultaneous combustion of two fuels: Natural gas representing the gaseous fuels and pulverized coal representing the solid phase fuels. The effects of various combinations of the two fuels on the combustion process are investigated. Keywords: Combustion modeling, Multi-phase combustion, Gas phase combustion, Solid phase combustion, Pulverized coal combustion, Turbulence modeling, Radiative Heat transfer, Finite-difference, Coal devolatilization, Char combustion. IV öz ÇOK FAZLI YANMA OLAYLARININ MODELLENMESI JUDEH, Ramzi (ŞAHİN, Remzi) Doktora, Makina Mühendisliği Bölümü Tez Danışmanı: Prof. Dr. Hüseyin VURAL Haziran 2001, 216 sayfa Günümüzde faaliyette bulunan termik santralların büyük bir bölümü, elektrik üretmek için fosil kökenli yakıtların türbülanslı yanmasından faydalanmaktadır. Böyle bir yanma sistemim modellemek, içerdiği karmaşık olaylar türbülans, tanecik dağılımı, radyasyon ve kirletici madde oluşumu gibi, nedenlerle ilgi çekici bir araştırma konusudur. Bu tez, gaz ve/veye katı yakıta sahip yanma sistemini silindirik koordinatlarda, simüle eden, iki boyutlu, daimi rejim bir bilgisayar programının tanımlanmasından oluşmaktadır. Bu programda, sıvı yakıt ve kömür tanecikleri için Lagrange denklemleri, gaz fazı için ise Euler denklemleri kullanılmıştır. Moment, basınç ve entalpi için gaz fazı hareket denklemleri, bir dizi eliptik kısmi türevsel denklemlerle tanımlanır. Bu denklemler, sonlu fark denklemler sistemine aktarıldıktan sonra iterasyon tekniğiyle çözümlenirler. Türbülansın, standart doğrusal bir k-s modeli olarak düşünülür. Gaz fazı reaksiyonları, bölgesel anlık dengelerin var olduğu kabul edilerek modellenmektedir. Gazlardan, duvarlardan, ve parçacıklardan kaynaklanan radyasyon da uygun bir modelle incelenmektedir.Partikül fazı, parçacık gruplarının aldıkları ortalama yolu izleyen bir Lagranj sisteminde modellenmiştir. Kütle, moment ve enerji için yazılan Lagrange denklemleri, izlenen yol, kütle, hız ve sıcaklığı bulmak amacıyla hesaplanan herbir partikül için çözülür. Partiküller, gaz fazı ile kütle, moment, enerji değişerek ve yer değiştirerek birbirlerini etkilerler. Partikül denklemleri gaz fazı denklemleri ile aynı koordinat sistemine dönüştürüldükten sonra sonlu farklar yöntemi ile elde edilirler. İki basamaklı kömür buharlaşma şeması, hem difüzyon hem de kimyasal reaksiyona imkan veren bir heterojen reaksiyonla birlikte kullanılır Bu tezin sonuçlar bölümünde, ilk olarak, türbülanslı sınırlı soğuk jet akışlara karşılık gelen üç set deneysel veri yardımıyla matematiksel model oluşturuldu. îkinci olarak, bu model eksenel simetrik pilot ölçekli fırında iki durum için hesapların yapılmasında kullanıldı. Bu hesaplamalarda, akış alanının önemli özellikleri, hız alanı, sıcaklık alanı, ve gaz bileşenleri konsantrasyonu ile gösterildi. İki set karşılaştırma verisi yazılan programın doğrulanması için kullanıldı ve hesaplanan sonuçların mevcut deneysel veriye oldukça yalan olduğu görüldü. Sonuç olarak, program iki yakıtın eş zamanlı yanması durumunu simülasyon için kullanıldı: gaz yakıtları temsil eden doğal gaz ve katı yakıtları temsil eden toz haline getirilmiş kömür. İki yakıtın çeşitli bileşimlerinin yanma olayı üzerindeki etkileri araştırıldı. Anahtar Kelimeler: Yanma modellenmesi, çok fazlı yanma, gaz yanması, katı yanması, toz haline getirilmiş kömür yanması, türbülans modelleme, kömür buharlaşması, heterojen reaksiyon. VI 216

The deep-sea, defined as the area 200 m below the surface, is facing emerging chemical, physical and biological stressors. Currently, very little is known regarding deep-sea ecosystems both globally and in the Arctic. In this thesis I undertook a literature review on the current understanding of global deep-sea ecosystems through the use of stable isotopes. Specifically, I synthesized the available literature on spatial variation, energy pathways, depth, temporal variation, feeding behaviour, niche, trophic position and body size isotopic trends. This thesis then presents a case study examining the isotopic niche of five teleost and two decapod species within Arctic deep-sea food webs across the localized latitudinal gradient of Baffin Island. Spatial variation in isotopic niche was quantified using 13C and 15N for seven deep-sea species at three locations on Baffin Island, Nunavut to determine whether the “Latitudinal Niche Breadth Hypothesis” which states that niche breadth should increase with latitude holds true in the Arctic. Overall, isotopic patterns in global deep-sea ecosystem are variable; consistent trends are not observed across all taxa and habitats. It was concluded that niche breadth did not consistently increase with latitude in the eastern Canadian Arctic; localized conditions (e.g. sea ice, temperature) and individual condition (e.g. hepatosomatic index) may contribute more to a species’ niche than latitude. Overall, this thesis improves our understanding of deep-sea ecosystems globally, contributes baseline data for future monitoring, and by investigating multiple species and locations it will provide input on how climate change may impact Arctic food web diversity, energy dynamics and ecosystem structure to aid in sustainable fishery development.