Master Tezleri

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3D-printed multiprobe analysis system for solar fuel research; design, fabrication and testing
(Izmir Institute of Technology, 2016-12) Harmanlı, İpek; Karabudak, Engin; Ebil, Özgenç
Methods of generating electricity with unlimited, clean and cheap energy from solar energy are tried to be investigated and developed in practical and theoretical academic fields. Especially, photocatalytic water splitting (PWS) systems have been identified as the main method in this study as well as in many studies due to the advantages provided by production of solar fuels from water. In this research, a study was carried out on the alternatives of the both used experimental set-up and used photocatalytic material for PWS systems. A study has been carried out on both the used experimental setup and the used photocatalytic material alternatives in PWS systems. As an alternative experimental setup that allows small volume analysis for PWS by Unisense gas microsensors, a mini photoreactor was designed using 3-D drawing and printing techniques and its usability was tested for PWS applications. Moreover, some characterization results for the electronic band structure and the band gap of the lead (II) trioxovanadate (V) chloride [PbVO3Cl] crystal, which was discovered by Eanes and co-workers in 2007 at IZTECH, was introduced in this study by not only theoretical (DFT approximations; LDA, GGA and HSE06) but also experimental (XRD, Diffuse Reflectance Method- Tauc Plot, Raman Spectroscopy, Four Probe) methods. Also, its estimated theoretical price and its potential for future application in tandem solar fuel device as a photoanode in combination with Si photocathode was calculated and discussed. The results showed that the designed mini photoreactor system is an open to development apparatus that is suitable for PWS, besides, PbVO3Cl has an "indirect transition" band structure and a band energy of ~ 2.2 eV. Although it did not give an effective result in PWS applications done by the designed mini photoreactor, it can be said that it is a semiconductor which is worth studying and developing in detail for other researches in this field due to the compatibility of its band energy amount and optical properties for PWS.
An adaptive neuro-fuzzy approach for modeling the effects of water-in-diesel emulsion on diesel sprays
(Izmir Institute of Technology, 2016-09) Yavuz, Bekir Kağan; Rodriguez, Alvaro Diez; Saplıoğlu, Kemal
This thesis is prepared as an outcome of the Energy Engineering Master of Science program at Izmir Institute of Technology, IZTECH, in Turkey. The main purpose of this study is to analyse the effects of water content in diesel fuel spray behaviours using adaptive neuro-fuzzy inference system models (ANFIS) for compression ignition engines. The investigations are carried out using numerical models of ANFIS in MATLAB R2011a, generating simulations from training and test datasets based on recent experimental studies from the literature. The thesis primarily tests the use and the fitness of ANFIS models, modifying the neural network structure so that the simulations acceptably reach the experimental results accurately. Then secondarily, the simulation is used to investigate the effects of parameters originally not available in the related study. The investigation mainly focusses on water in diesel emulsions from pure diesel to an emulsion with 20% water content. Operational conditions such as chamber ambient pressure, injection pressure, chamber ambient temperature are also investigated to find their effects over spray penetration. It was found that the increase of water content in the diesel fuel did not have a relevant effect at very low and very high temperatures, however at medium-high temperatures it increased spray penetration. Furthermore, it was observed that the increase of chamber ambient pressure and chamber ambient temperature reduced the spray penetration as expected.
Adsorbent synthesis for the recovery of lithium water resources
(01. Izmir Institute of Technology, 2022-12) Kahvecioğlu, Anıl; Yüksel Özşen, Aslı
Lithium is a crucial mineral for the 21st century due to its utilization in a wide range of industries. Lithium demand will increase because of car battery developments and the necessity for power storage. Investigating alternative strategies for resource recovery is the only way to fulfill this unexpected rise properly and sustainably in demand. Adsorption has been discovered to have some technological advantages over other methods. It is considerably less expensive, lacks the chemical resistance present in membranes, lacks the significant electrical demand of electrochemical approaches, as well as the restricted selectivity and challenges in integration into commercial processes. Lithium manganese oxides, also known as lithium ion-sieves, are adsorbents for lithium extraction that have remarkably high selectivity, high adsorption capacity, minimal toxicity, good chemical stability and cheap cost. They are one of the most promising inorganic adsorbents. This research emphasized on the recovery of lithium from water resources through the use of lithium manganese oxide, which were synthesized in laboratory. They were transformed into spherical beads by adding chitosan, followed by crosslinking these beads with epichlorohydrin to increase their adsorption yield, stability, and reusability. Characterization techniques such as SEM, XRD and BET were applied on the adsorbents. Results shows that the adsorbents distributed uniformly, the adsorbent powder was mesoporous, and from the adsorption studies it was found that the adsorbent worked much better in alkaline conditions such as pH 12, optimum adsorbent dosage estimated as 4 g/L and the equilibrium time measured as 10 hours. From the desorption study approximately 95% of Li desorbed for the first cycle, after the second cycle the adsorbent efficiency started to decrease.
An analaytical approach to the urban outdoor lighting quality of residential areas in Izmir
(Izmir Institute of Technology, 2004) Çam, Rabia; Serim, Muharrem Erkal
The major aim of this study is to present a critical look on the existing outdoor lighting installations and put forward a comparative approach to assess the quality of outdoor lighting systems in the selected multi-family residential areas. This aim is based on a common assumption that the existing lighting system standards and installation arrangements are unsatisfactory. Upon considering the urban context, it can be stated that residential areas particularly are lack of well-illuminated public spaces. In this respect, this study aims to determine the common illumination problems that affect night-time outdoor space quality in residential areas and these factors behind this problems. The data and material necessary to carry out this study are obtained from literature survey and site survey. The collected data are evaluated through Cost Analysis and Analytical Hierarchy Process (AHP) used by Expert Choice Software. AHP has been used for the determination of priorities, evaluation of the outdoor lighting quality for the residential areas and selection of the best one in the selected residential areas that are MavisÌ§ehir, Oyak and Evka 3 in İzmir. Analysis indicated that the quality problems about outdoor illumination could be decreased through effective design and regular care and maintenance efforts. Key words: Lighting Quality, Illumination, Lighting, Outdoor Space Lighting, Light Pollution, Outdoor Space Quality, Analytical Hierarchy Process (AHP), Residential Area.
Analysis of a hydrogen fueled internal combustion engine
(Izmir Institute of Technology, 2005) Kahraman, Erol; Özerdem, Mehmet Barış
In the history of internal combustion engine development, hydrogen has been considered at several phases as a substitute to hydrocarbon-based fuels. Starting from the 70.s, there have been several attempts to convert engines for hydrogen operation.Together with the development in gas injector technology, it has become possible to control precisely the injection of hydrogen for safe operation. Since the fuel cell needs certain improvements before it is widely used in vehicles, the conventional internal combustion engine is to play an important role in the transition. This study examines the performance characteristics and emissions of a hydrogen fueled conventional spark sparkignition engine. Slight modifications are made for hydrogen feeding which do not change the basic characteristics of the original engine. Comparison is made between the gasoline and hydrogen operation and engine design changes are discussed. Certain remedies to overcome the backfire phenomena are attempted.
Analysis of geothermal circuit of Balçova-Narlıdere Geothermal District Heating System
(Izmir Institute of Technology, 2004) Bilal, Osman Yaşar; Toksoy, Macit
The aim of this study is to determine the performance of the Balçova . Narlıdere District Heating System and to reveal the critical points. During this study, with the help of Balçova Jeotermal Company.s database, Balçova . Narlıdere Geothermal District Heating System is simulated in Pipelab Geothermal District Heating System simulation program and the pressure and temperature distributions of the system are determined. In the light of these analyses, the critical points of the Balçova . Narlıdere Geothermal District Heating System are pointed out with the possible reasons and solution alternatives are discussed. Meanwhile, with the flow meters which are assembled to two apartment buildings chosen in the system, the amount of the fluid and the energy consumed by the users are observed. The observed values are compared with the calculated values according to the outdoor temperatures.
The analysis of historical / cultural pattern development and conservation plans of Antalya Kaleiçi
(Izmir Institute of Technology, 2006) Süer, Ayşe; Seğmen, Ülker
Historical places are the physical conformation of differential relations and interactions which develop in the course of time at space. In this context; it is not sufficient for an efficient conservation plan to introduce only current urban structure in the preparation phase of the conservation plans.In this study, the urban development and transformation of historical city center of Antalya Kaleiçi has been analyzed in terms of its cultural periods, and the reflection of this historical urban structure to conservation plan decisions has been examined.The basic principle of this study is the analysis of urban pattern. In the process of the urban pattern analysis, the urban structure of Kaleiçi settlement is formed by investigating the urban structure features of each historical period and by taking into account the historical and geographical features of the Kaleiçi settlement as well.Two different urban patterns have been scrutinized in order to bring up the relationship between present and past in terms of urban structure. Consequently, it is stated that the effects of past could be observed in the development of current urban structure.As a result of the investigation of conservation plan decisions, it is found out that the historical urban structure had not been taken into account adequately when giving conservation plan decisions. Furthermore, another important absence of conservation plans, the interrelatedness of the archeological area and monumental buildings within whole urban structure, are introduced in this work.In conclusion, it is stated by setting forth the reasons that the examination of the historical urban structure as a whole necessitates not only handling urban structure in the physical sense but also investigating the urban structure in terms of historical and cultural integrity.In this study, additionally, a methodological approach for the analysis of historical urban structures has been introduced as a model for further conservation plans.
Analysis of two-axis sun tracking system
(Izmir Institute of Technology, 2003) Armakan, Elvan; Yardımoğlu, Bülent
In this study, a two-axis sun tracking system with an open loop computer control is analyzed. For this purpose, a gyroscope-like prototype with two degrees of freedom is designed. In order to control the prototype and track the sun all along the day, computer software based on astronomical equations is developed. Beside the software, an electronic circuit ensuring communication layer in between computer and the prototype is designed and manufactured.Software determining the sun position precisely and controlling the prototype is developed utilizing a Visual Basic compiler on a Pentium IV 1600 MHz computer. Input-output signals in between the computer and the electronic circuit is managed through the parallel port (LPT) of the computer. Control of the prototype motors are performed by amplifying the sun position-related computer signals on the electronic circuitry.Critical components of three-dimensional system model created in Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE) software are analyzed from statical aspect. In addition, mathematical model of the system and its stability analysis is generated in Matlab/Simulink software.Last, a fixed-type photovoltaic cell and a two-axis sun tracking photovoltaic cell satisfying a particular tracking sensitivity are theoretically analyzed and compared. A two-axis sun tracking system working to fulfill a specific tracking sensitivity is theoretically seen to provide about 40 % higher energy gain when compared to a fixed system under extraterrestrial solar radiation.
Anti-reflective and optical transparent coatings for thin film solar cells and glasses
(Izmir Institute of Technology, 2020-07) Kamolov, Shukrullo; Özyüzer, Lütfi
Antireflective coatings in some implementation necessary for the decreasing surface reflection, but in some applications also for increasing transmittance. Incident radiation on the surface of the optical material is divided into transmitted, reflected, scattered, and absorbed proportions, and the proportion of current energy that deployed among them is defined by RI (refraction indices). Solar panels made from crystalline or polycrystalline silicon, but another type of solar panel is a thin-film solar panel. Thin-film technology has several advantages, such as low material consumption, which leads to cost savings to production, the ability to absorb diffused solar radiation, a relatively high efficiency (up to 20%), long service life (efficiency decreases by 10-15% of the initial efficiency). For all types of photovoltaic devices, energy loss is an important issue. Single-layer and two-layer antireflection coatings with a low refractive index, coated and uncoated (SiO2) thin-film with the sol-gel method were prepared and compared in terms of performance and continuity. The photocatalytic performance of (SiO2) thin films in 1, 2, 3, 4, 5 and 24 hours was defined with methylene blue dye solution (20 mL) under UV source and was illuminated by it. The I-V characteristics curve of solar cells for small and large area was learned and increasing efficiency was observed. Adhesion tests in this study was applied by tape tests on substrates of glass. As a result, the field tests of small and large area glasses coated solar panels were realized, the low reflectance and high efficiency were obtained.
Assesment of genes that play role in phenolic compound degradation in olive orchard microbiome
(Izmir Institute of Technology, 2019-10) Acar, Ertuğrul; Soyer Dönmez, Ferda
The olive tree (Olea Europea L.) is one of the most important fruit trees in Mediterranean countries. Its products, olive oil and table olives, are important components of the Mediterranean diet and widely consumed all around the World. Olives and virgin oil provide a rich source for phenolic compounds. The plant phenolics are secondary metabolites, and possesses several common biological and chemical properties. In this study, microorganisms were collected from soil, olive leaves, fruits, and Olive fruit fly larva and Olive mill wastewater (OMWW). They were characterized by 16S rRNA analysis. The microorganisms that were tolerant to phenolic compounds were selected in order to seek which genes were associated with the phenolic compound degradation. The genes related to the degradation of the selected organisms were identified by Sanger Sequencing and the level of phenol-degrading gene expression were aimed to be compared by using qPCR and Droplet Digital PCR (ddPCR). Microorganisms which degrade phenolic compounds can be harnessed for the purpose of bioremediation. However, the number of defined phenolic compound degrading microorganisms is still low in the literature. For this reason, many different microorganisms were used at the same time for bioremediation. Investigation of olive orchard microorganisms and phenolic-degrading genes might benefit bioremediation in the future. In this study, 8 different bacterial strains were identified and characterized from olive orchards. After that, their phenol hydroxylase and catechol 1,2 dioxygenase genes tried to be sequenced with primers designed by using of reference strains in NCBI database.
Atmospheric effects on short term wind power forecasting
(01. Izmir Institute of Technology, 2021-07) Kalay, Yüksel; Bingöl, Ferhat; 01. Izmir Institute of Technology
Wind power all over the world are being popularizing unlike decrease in conventional sources due to environmental issues. However, power acquired from wind is not stable during day and night, which means that intermittent due to nature of the source. Forecasting in wind power plant is very challenging compared to forecasting of production of conventional power plant. Although there are many robust and site-specific models in order to forecast wind power accurately, decrease of deviation in wind power forecasting by using statistical, physical and hybrid models is still open to new approaches. In this study, four different forecast models based numerical weather prediction (NWP) models for three different wind farms which have different atmospheric conditions are examined to improve wind farm-based power forecasting. For this purpose, wind power forecasting of the providers was categorized based on atmospheric effects, which are site temperature and turbulence. Results have been compared with real time power production from wind turbine supervisory control and data acquisition (SCADA) system. Afterwards, new method based on selecting best provider for specific condition was developed by considering atmospheric effects on power forecasting. It should be noted that the method is an engineering approach, not a new forecast model. In many cases, newly developed method has succeeded to outperform in comparison to results belonging to forecast providers. Hourly and daily wind power forecasting that have significant role in electricity market has been improved for selected wind farms by the help of an engineering approach used in this study. Same method is also implementable to another wind farm if required inputs exist.
Biodiesel production from safflower using heterogeneous cao based catalysts
(Izmir Institute of Technology, 2012) Yalman, Emir; Şeker, Erol
In this study, the activities of heterogeneous mixed oxide catalyst; calcium oxide on alumina was investigated in the transesterification of canola and safflower vegetable oils to produce biodiesel, i.e. methyl esters. The primary goal of this study is to understand the effect of calcination temperature and calcium oxide (CaO) loading on the conversion activity of calcium oxide on alumina in the transesterification of canola and safflower vegetable oils. The mixed oxide catalyst was prepared by a modified single step sol-gel method. Calcium oxide was chosen because of its well known basic property. This study shows that calcium oxide on alumina catalysts having high CaO dispersion, calcined at high temperature, gave high biodiesel yields even under the reaction conditions, such as low reaction temperature, 50 Â°C, 9 of methanol/Oil molar ratio, 6 wt. % of catalyst/oil, and also short biodiesel reaction time, such as 4 â€“ 10 minutes in the transesterification of safflower and canola oils. Also, it was observed that 70% CaO/Al2O3 catalyst when calcined at 700 Â°C was the most active catalyst among all the catalysts prepared in this study. Moreover, the reusability of CaO/Al2O3 demonstrated that ~20 â€“ 250 ppm of Ca was lost during the reaction and the amount of Ca cation leaching depended on the reaction time, CaO loading and the calcination temperature. Also, it was found that Ca cation loss occurred during the reaction did not hinder the activity of the catalysts, which was found by the reusing the catalysts for couple times. Besides, when the biodiesel yield was higher than 70%, the system was influenced by external mass transfer limitation.
Carbon dioxide hydrogenation on alumina supported ruthenium catalysts
(Izmir Institute of Technology, 2019-07) Hamza, Gökmen Oğuzcan; Şeker, Erol
In this study the effect of basicity of catalyst is investigated using different metal oxide supported Nickel and Ruthenium catalyst. The basic strength of catalysts was orchestrated with using different types of metals and different composition of supports. In this study Al2O3-CaO, Al2O3-MgO, Al2O3-BaO supports were used with nickel and ruthenium catalyst, which synthesized with sol-gel method. Different mass ratios of supports were used such as; 100%, 70%/30%, %50/50%, 20%/80% respectively. For all metal oxides Nickel loadings are 1 %, 5% and Ruthenium loading is 0.5%. Calcination temperature was 500 0C with 6 hours. All catalysts were used in methanation reaction with conditions varies between 300-600 0C, inlet ratio of CO2/H2 1/4 to 1/6 and GSHV 5000h-1/10000h-1. The products were analyzed using GC and catalysts were analyzed using XRD NH3-TPD and BET. Nickel load selected as 1%, magnesium supported catalysts' the main crystallites were aluminum oxide and magnesium oxide for 30%,50%,80; respectively. Calcium supported catalyst had had alumina and calcium oxide crystallites for 30%,50% respectively. Barium supported catalysts had had alumina and barium mix oxide crystallites for 30%,50% respectively. For 5% Nickel loaded 70-30% alumina magnesia mix oxide catalyst magnesia and alumina crystallites are found. Aluminum magnesium mix oxide catalysts had higher basicity than aluminum barium mix oxide catalysts for 1% nickel catalysts. Ruthenium based magnesium alumina mix oxide catalyst had higher basicity than nickel-based magnesium alumina catalysts. Ruthenium catalysts had higher total performance towards both of the reverse water gas shift reaction and carbon dioxide methanation than nickel-based catalysts.
Catalytic pyrolysis of virgin and waste polyolefins
(01. Izmir Institute of Technology, 2023-06) Çalık, Fatma Defne; Yıldız, Günay; Şeker, Erol
The fact that increasing plastic production and the mismanaged waste released to the environment put the ecosystem at risk. One of the most promising recycling methods developed within this framework has been pyrolysis. In this thesis, a model feedstock mi (No: 119N302). Thermal (batch and continuous) and catalytic pyrolysis (in-situ and ex-situ) techniques were applied to the polyolefins. Silica-alumina-based solid acid catalysts were produced with the simple sol-gel method to compete with commercial ZSM-5 (30) and ZSM-5 (50). Catalyst-to-plastic ratios between 1/100 and 1/1000 were used for in-situ, and 200 h-1 and 500 h-1 WHSVs were used for ex-situ mode. 57 wt.% pyrolysis oil was produced from the thermal pyrolysis of the virgin PO mixture in the batch system. In the ex-situ catalytic pyrolysis experiments by 500 h-1 WHSV and by ZSM-5, silica-alumina, and ZSM-5 supported silica-alumina, 36 wt.%, 56.6% wt.% and 45.2 wt.% liquid, and by 200 h-1 WHSV, 29.9 wt.%, 54.1 wt.%, and 57.9 wt.% pyrolysis oils were collected, respectively. The most successful test in terms of product composition was ES2 with 82.9% gasoline (8.8% BTEX), and 16.7% diesel-range hydrocarbons. The motivation was investigating whether it was suitable to produce liquid hydrocarbons, in the range of C5-C20, as a feedstock in the petrochemical industry. As a result, it has been proven that energy recovery was possible and sustainable by plastics recycling instead of using fossil fuels.
Catalytic surface coatings for household ovens
(Izmir Institute of Technology, 2016-07) İzer, Alaz; Şeker, Erol
The emission of harmful volatile compounds, such as aldehydes, and also carbon monoxide could occur during cooking processes at home or industry due to the combustion and cracking of spilled vegetable oil on the walls of an oven. It is known that the by-products generated during cooking could affect human health and environment if they are properly vented or removed. To eliminate the health and environmental problems related to oven emission, self-cleaning catalytic materials coated walls for ovens seem to be viable alternative to the toxic and time consuming chemical cleaning solutions. In this project, a sol-gel method and also the dip coating technique was used to produce a catalytic material coated aluminum plates. Specifically, the calcination time and the temperature were studied to better understand the relationship between the textural/chemical properties of the catalyst coated metal plates and their catalytic activities. The studied calcination temperatures were 450°C, 500°C and 550°C whereas the calcination time were 10 min, 30 min and 60 min for each type of catalyst. Aluminum oxide supported nickel and also aluminum oxide - manganese oxide supported nickel catalysts were prepared as the catalyst that were used in coating. The catalytic activities of the catalyst coated plates were determined using canola oil as a function of reaction time which were 1h at 170°C and 200°C. The results have been shown that the most convenient calcination conditions for the canola oil combustion were 500°C for 30 minutes by using aluminum oxide – manganese oxide supported nickel catalyst.
Characterizations of simple-direct modules
(01. Izmir Institute of Technology, 2020-12) Diril, Müge; Büyükaşık, Engin; Durğun, Yılmaz; 01. Izmir Institute of Technology
In this thesis, we study on simple-direct-injective and simple-direct-projective modules. We give a complete characterization of the aforementioned modules simple-direct-injective and simple-direct-projective modules over the ring of integers. The rings whose simple-direct-injective right modules are simple-direct-projective are fully characterized. These are exactly the left perfect right H-rings. The rings whose simple-direct-projective right modules are simple-direct-injective are right max-rings. For a commutative Noetherian ring, we prove that simple-direct-projective modules are simple-direct-injective if and only if simple-direct-injective modules are simple-direct-projective if and only if the ring is Artinian. In addition, Various closure properties and some classes of modules that are simple-direct-injective (resp. projective) are given.
Cogeneration sustainability study for the Izmir Institute of Technology
(Izmir Institute of Technology, 2017) Ahmad, Awais; Rodriguez, Alvaro Diez
In this study, feasibility of Cogeneration/Combined Cycle System will be evaluated for the Izmir Institute of Technology. Turkish Energy Policy lacks some key factors which need to be highlighted for achieving Energy targets. The first aim of this study is to compare the policies and implementation of combined cycle systems of Turkey with Europe and to analyze the steps carried out by European Countries to achieve sustainability. The main objective of this study includes the implementation of a combined cycle system based on the data collection from the authorities of the Institute to analyze the deficiencies of existing system and to propose a more efficient system for meeting the energy demand. Two systems were taken in consideration, a gas turbine and a reciprocating engine based combined cycle system, detailed energy analysis with emissions and cost analysis were presented to determine what case provides the best solution to meet the energy demand.
Compliant control of a teleoperated endoscope robot
(Izmir Institute of Technology, 2018-07) Işıtman, Oğulcan; Dede, Mehmet İsmet Can
With the development of the technology, robots are started to be used in many medical application including minimally invasive surgery to overcome disadvantages of conventional open surgery procedures. This thesis is a part of the research project called “Robot-assisted endoscope control that can be controlled by the surgical tools (NeuRobo- Scope)” for the minimally invasive endoscopic pituitary gland tumor surgery side. During the procedure, endoscope is handled by a robot which moves the endoscope in the human nasal cavity and the movement of the endoscope is constrained by soft tissues. Another operation scenario is the positioning of the endoscope by the surgeon backdriving the endoscope holder robot. In the scope of this thesis, two research problems are addressed which are controlling the interaction between (1) surgeon - robot and (2) robot - soft tissue. First, the interaction of the surgeon and the robot is studied. Effects of the compliant controller parameters are experimentally tested by using a single degree of freedom non-backdrivable experimental set-up. A task is defined to quantitatively compare the effect of the controller parameters on the performance in terms of the energy efficiency and the accuracy. The second research problem involves human nasal tissue modeling in order to design an accurate controller. To acquire data from the human cadaver, a new hand-held measurement device is designed. The external forces and moments and the soft tissue models are obtained in an ex-vivo experiment. After the soft tissue models are identified, a modified interaction control is proposed for the teleoperated endoscope holder robot. The defined surgery procedure is tested with the proposed interaction controller via single degree-of-freedom experimental set-up. Experiments of the proposed controllers were successful for the defined operation scenario and the results show that it is possible to realize the motion control of the surgical robots in a constrained environment.
Computational fluid dynamics (CFD) analysis of latent heat storage in heat exchangers by using phase change materials (PCM)
(Izmir Institute of Technology, 2020-07) Demirkıran, İsmail Gürkan; Çetkin, Erdal; Rocha, Luiz Aberto Oliveira
The development of TES applications and materials takes the attention of many researchers, but the current literature rarely involves studies concerning medium temperature applications. This thesis compares available phase change materials (PCMs) for the medium temperature range. For this aim, Erythritol was defined as PCM in the numerical analyses. The effect of heat transfer fluid (HTF) tube position and shell shape on the melting time and sensible energy requirement for melting a phase change material (PCM) in a latent heat thermal energy storage (LHTES) application were investigated. Tube location and shell shape are essential due to the shape of the melted region, i.e., similar to the boundary layer. Results show that the S-curve of melting becomes steeper if the tubes are distributed such that the intersection of melted regions is delayed. Therefore, melted regions should be packed into a finite space which uncovers the shape of the shell that minimizes melting time and required sensible energy. Results show that, rectangular-shaped shell design where the tubes located near the bottom end decreases melting time and sensible energy from 67 minutes to 32 minutes and from 161.8 kJ/kg to 136.3 kJ/kg for %72.3 liquid fraction relative to the circular-shaped shell, respectively. In the four-tube cases, then the required melting time and sensible energy decrease 80% and 3.8% through the rectangular-shaped shell design for the PCM to melt completely, respectively. Overall, the results show that sensible energy storage and especially melting time can be decreased greatly by just varying the design.
A computational study on the structures and proton affinities of b3+ ions; peptide mass fragment product
(Izmir Institute of Technology, 2015-07) Boz, Seçkin; Elmacı Irmak, Nuran
Mass spectrometry is the tool of choice during most of the proteomics studies to get amino acid sequence. However, unambiguously identifying amino acid sequence from mass spectra is not easy and straight forward task. Deeper understanding is needed to support both existing knowledge and develop newer models on dissociation patterns of protonated peptides and it will help to improve efficiency of current algorithms used in peptide identification. In this study, the structures of b3+ ions and their neutral forms were investigated by using computational methods. First, potential energy surface of b ions are scanned using molecular dynamics simulations and conformer samples are collected. Then, in order to reduce number of conformers, principal coordinate analysis was applied to find and select different structures within the sample. Selected conformers were optimized using density functional theory calculations. Proton affinities of b ions are determined by the energy difference between most stable conformers of the positively charged and neutral peptide fragments. Different amino acids were used to understand the role of side chain of amino acids on both structures and proton affinities of b3+ ions; XA2+ where X=N, H, C, Y, D, L and F. The results showed that, b3+ ions prefer to have linear oxazolone structure. However, in their neutral states, cyclic structures are relatively far more stable than linear isomers. Histidine display different behavior than other amino acids. Side chain of histidine holds protons and forms stable structures. The energies of cyclic and linear isomers of Histidine containing b ions are close to each other. Histidine containing peptide fragments have larger proton affinity comparing to others. Difference of proton affinities between linear and cyclic conformers varies based on amino acid used. This difference is lower than 10kcal/mol in histidine, asparagine and aspartic acid containing peptide fragments. There is no dramatic position preference of the X-amino acid for the N- or C- terminals or middle position with the exception of Asn and Asp (unlike the center) and Histidine which likes to be at C-terminal.

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Browsing Master Tezleri by Department "Energy Systems Engineering"