Prof. Dr. İsmail Hakkı Tavman danışmanlığındaki tezler
13 tez · Dokuz Eylül University
TFT LCD panellerde termal analiz ve numerik bir çalışma
According to television or in short TV?s worldwide market surveys and sales figures show that passing from CRT (Cathode ray tube ) televisions to LCD (Liquid Crystal Display) televisions has been swiftly increasing. Producing of CRT televisions is decreasing and comes to an end gradually. New television technology in the design of LCD TV has swiftly improved in recent years. TFT (Thin Film Transistor) panels used in LCD television are divided into two panels as CCFL (Cold Cathode Fluorescent Lamp) panel and LED (Light Diffuser diode) panel.This project aims to provide solutions for the 32inc LED panel thermal problems which are the reasons of increasing expenses, reducting of the life-time of the panel, worsening the quality of the image by using computer aided analysis programme and experimental tools.LED Panel?s normal working conditions of temperature characteristic will be determined with the help of computerized analysis program, the experimental studies and the resulting values of analysis program are compared between each other. Which parts of the panel affected by the temperature is determined by uncovering of the temperature distribution in the Panel. Improvement works will be made on available design by taking into consideration of the affected parts.With this project, LED panel which will be produced in VESTEL by making the analysis of the heat, heat-source problems that may occur will be to minimize at the design phase. This project which is wanted to be carried out within the scope of a master thesis between VESTEL Electronics Inc. and Dokuz Eylul University, Graduate School of Natural and Applied Sciences, Mechanical Engineering Department, Energy Program
Konutlarda enerji verimliliği ve derece gün bölgelerine göre farklı malzemelerde optimum yalıtım kalınlığının tespiti
Enerjinin pahalı olduğu ülkemizde enerji verimliliği, ön plana çıkmakta ve yasal düzenlemeler getirilmektedir. Enerji Verimliliği Kanunu ve buna bağlı olarak çıkarılan Binalarda Enerji Performans Yönetmeliği bu düzenlemelerden bazılarıdır. Binalarda Enerji Performans Yönetmeliği'nin amacı binalarda enerjinin verimli kullanılmasına ve çevrenin korunmasına ilişkin kuralları düzenlemektir. Dolayısıyla binalarda yalıtım uygulamaları söz konusu yönetmelikle zorunlu hale gelmektedir.Bu tezin amacı yalıtımın önemini vurgulamak ve ayrıca İzmir, İstanbul, Ankara ve Erzurum şehirlerinde seçtiğimiz örnek bina için farklı yalıtım malzemelerine göre optimum yalıtım kalınlıklarını ve enerji kazançlarını tespit etmektir. Optimum ısı yalıtım kalınlıklarını belirlemede TS 825 Isı Yalıtım Kuralları Standardı ile Ömür Maliyet Analizi yöntemleri kullanılmıştır. Yalıtım kalınlıklarının tespitinde İZODER (Isı Su Ses ve Yangın Yalıtımcıları Derneği) tarafından hazırlanan TS 825 Hesap programı kullanılmıştır. TS 825 standardında ülkemiz dört iklim bölgesine bölünmüş ve her bölge için ortalama sıcaklık değerleri belirlenmiştir. Bu çalışmada dört şehrin Devlet Meteroloji Genel Müdürlüğü'nden alınan 1975-2011 yılı ortalama dış sıcaklık değerlerine göre de hesaplamalar yapılmış alınan sonuçlar karşılaştırılmıştır. TS 825 standardı binanın yapısına ve çevre koşullarına göre ısı kaybını belirleyerek enerji ihtiyacını yıllık olarak hesaplayan bir metottur. Isı yalıtım kalınlıkları standardın izin verdiği ısı kaybı değerlerine göre belirlenir. Ömür Maliyet Analizi yönteminde ise ısı yalıtım kalınlıkları yakıt ve malzeme maliyetlerine göre belirli bir ömür süresi için hesaplanır. Bu iki yöntem ile yapılan hesapların sonuçları tablolarda ve grafiklerde gösterilmiştir.
A case study on the Balçova-Narlidere geothermal district heating system
Turkey is among the first five countries in abundance of geothermal resources around the world so geothermal energy is an important renewable energy resource in Turkey.In this study, following a general information concerning geothermal energy, it is specified in tables that the direct and indirect utilization of the geothermal resorces in Turkey and its established capacities at the present day are given. Direct utilization of geothermal energy focuses on district heating system and is implemented in 21 geothermal field. The biggest and the most important of all is that of the one in the Balçova-Narlıdere geothermal field. Concerning the Balçova-Narlidere district heating system, the general evaluation of the geothermal field, its historical development, geothermal wells, the total residence capacity, an evaluation of the system, price comparison with the other fuels, and the environmental factors are all discussed.Finally, the Narlıdere district heating system stage-3 project in Balçova-Narlıdere geothermal field is presented under the headings of geothermal loop, city loop and building loop. Each building situated in stage-3 is specified one by one and the total peak field and the total peak load are deducted and 3D design of the heating system is worked on.
Bir termik santralın enerji ve verim analizi
Bu çalışmada Yatağan Termik Santralinin termodinamiğin birinci ve ikinci yasa yönünden verim analizi yapılmıştır. Enerji santralinin verim analizi yapılırken farklı çevre koşulları ile yükler incelenmiş ve dikkate alınmıştır. Performans parametreleri ve değişimleri incelenmiştir. Çalışmada sistemi oluşturan her ünitedeki faydalı güç, tersinir güç ve tersinmezlik miktarları tespit edilmiş ve sistemin genel verimleri hesaplanmıştır. İncelenen Termik Santral için yapılan ekserji analiz sonuçları santralın verimi hakkında daha kesin yorum yapılmasına olanak vermektedir. Bu çalışma ile enerji santralının enerji ve verim analizi incelenmiş ve önemi dile getirilmiştir.Anahtar sözcükler: Çevrim, gaz türbini, enerji analizi
A study on thermal conductivity of polymer nanocomposites
In this work, graphite powder (400 nm) which has high thermal conductivity was mixed with HDPE in the Brabender Plasticorder mixer in certain conditions. Nanocomposites containing (2, 3, 4, 5, 6, 7, 10, 16 percent) volume fractions of graphite were fabricated. Thermal conductivity of high-density polyethylene (HDPE)-graphite nanocomposites is investigated experimentally and the results are compared with the theoretical models. A Hot-disk method is used to measure the thermal conductivity of nanocomposites consisting (2, 3, 4, 5, 6, 7, 10, 16 percent) volume fractions of high-density polyethylene (HDPE) matrix filled with graphite. Up to 6 percent volume of graphite, Russell model predict the thermal conductivity best.Also the surface morphology of the polymer nanocomposites was searched by scanning electron microscopy (SEM) in different magnifications and it can be said that graphite particles dispersed almost homogenously in polymer matrix.
Investigation of thermophysical properties of nanofluids
Nanofluids are liquid suspensions of particles with at least one of their dimensions smaller than 100 nanometer (nm). Nanofluid technology becomes a new challenge for the heat transfer fluid since it has been reported that the thermal conductivity of nanofluid is anomalously enhanced at a very low volume fraction of nanoparticles.In this study, a new application of a hot wire sensor for measurement of thermal conductivity of (nano)fluids, based on a hot wire thermal probe with ac excitation and 3 omega lock-in detection, were presented. Due to modulated heat flow in cylindrical geometry with a radius comparable to the thermal diffusion length, the necessary sample quantity is kept very low, typically 25 microliter. The thermal conductivities of de-ionized water based TiO2, SiO2, Al2O3 nanofluids and ethylene glycol based Al2O3 nanofluids were measured and their dependence of particle volume fraction and temperature were investigated. Our results show that thermal conductivity values are inside the limits of (moderately lower than) Hamilton-Crosser model. Our experiments at different temperatures show that relative thermal conductivity of nanofluids is not related with the temperature of the fluid.For industrial applications of nanofluids, one should also know the viscosity characteristics, since for heat transfer applications pump costs are important. We investigated the temperature dependent viscosity of nanofluids for different particle concentrations by a Sine-wave Vibro Viscometer. Viscosity of our nanofluids increase dramatically with the increase in particle concentration, Einstein model is found to be unable to predict this increase.
Computational fluid dynamics application for determining flow characteristics of valves
The valves used in different fields of industry are the most indispensable elements of the flow control. The expectations of the users differ from one another according to the aim of the usage like having a longer lifeline, supporting a more sensitive flow control and having a minimum resistance to flow if necessary; that?s why, the engineers improve the existing valves and look for new models.Nowadays, computers are the greatest helpers of engineers. Computer support in the analysis of difficult problems like solving flow problems is a big facility. After drawing a valve in three dimensional with computers, the working conditions of valves can be analyzed using finite element method and computational fluid dynamics codes. The results of the changes in the geometry can be observed without producing a prototype via this analysis.In this study, the flow characteristic curves of the ball and butterfly types of valves, which are widely used in industry, are analyzed by ANSYS CFX and the results are compared with the catalogue data of the valve producing firms.
Air to air heat exchanger performance
Proper ventilation is obligatory in buildings where humans spend 70% of their life. Humidity, pollutant particles, smoke and harmful gases lower indoor air quality and cause sicknesses. To create an adequate air inside, dirty indoor air shall be exhausted and fresh air shall be taken from outdoors. To obtain controlled ventilation, buildings HVAC systems are designed by using mechanical ventilation. Mechanical ventilation is done with the help of an exhaust air fan, supply air fan and proper ventilation.Exhausted indoor air is conditioned air, for summer it is cooled and in winter it is heated to design temperatures. To transfer heat between exhaust air and supply air, air to air heat exchangers (heat recovery exchangers) are used in modern ventilation systems. By the help of air to air heat exchangers, fresh air from outdoors is pre-heated or pre-cooled by the help of exhausted air thus decreases the energy used to condition indoor air.Air to air heat exchangers are rated according to their efficiency which varies according to indoor and outdoor air temperatures. The same heat exchanger shall be evaluated according to the climate in which it is going to be installed.In this research, a sample heat recovery ventilator has been examined according to its energy savings. Outdoor air temperatures received from Devlet Meteoroloji Enstitusu has been evaluated by means of average values and hourly values. Energy savings in heating and cooling seasons are considered in different climates including warm, cold and extremely cold climates.
Fiber takviyeli polimer kompozitler mekanik performansinda arayüzeylerin etkisi
In this study, structure of ?-GPS (?-glycidoxypropyltrimethoxysilane) on glass surfaces after fiber surface treatments was analyzed and effects of the treatments on mechanical properties of glass fiber/epoxy composites were investigated. Fiber surface treatments were used to create the beneficial interface between the fiber and the matrix. Glass fibers were treated using wet chemical and plasma polymerization processes to improve the interfacial adhesion between fiber and matrix.The structure of ?-GPS on glass surfaces after wet chemical and plasma polymerization processes and the interaction between glass surface and ?-GPS were examined using Fourier Transform Infrared Spectroscopy (FT-IR), contact angle measurement device and Scanning Electron Microscopy (SEM). The influence of plasma power and exposure time on the properties of thin films prepared by plasma polymerization of ?-GPS on the glass surfaces was also investigated by X-ray Photo-electron Spectroscopy (XPS). XPS analyses were utilized to reveal the presence of functional groups in the films. Morphologies of the films on the glass surfaces were observed by Atomic Force Microscopy (AFM) and SEM.The effects of fiber surface treatments on mechanical properties of glass fiber/epoxy composites were investigated. Mechanical properties of the composites were investigated by tensile tests, flexural tests and short beam shear tests. The fracture surfaces of the composites were observed with SEM. Mechanical properties of the composites were improved by wet chemical and plasma polymerization studies.Keywords: Glass fiber, Plasma polymerization, Silane treatment, Interface, Interfacial adhesion, Interlaminar shear strength
Kombine çevrimli enerji santralinin verim analizi
In this study, efficiency analysis of combined cycle power plant which is working inÇiğli for industrial zone for first and second laws of thermodynamics is realized.While analyzing of efficiency of combined power plant different environmentalconditions and loads are observed and considered. The variations of the performanceparameters and their magnitudes are studied. The useful power, reversible power andirreversibility are obtained for each component which constitutes the plant, andoverall efficiencies of the plant are calculated. The results show the exergy analysesfor a steam cycle system predict the plant efficiency more precisely. In addition tothis, with this study, the efficiency of combined cycle power plant for second law ofthermodynamic is showed and gives the attention on it.
Dikili'de jeotermal bölgesel ısıtma sisteminin araştırılması
Jeotermal bölgesel ısıtma sistemlerinin kurulumu için ciddi yatırımlar gerekmektedir. Bunedenle kurulum ve isletme süresince yasanabilecek sorunlar ve maliyetler çok iyi analizedilmelidir. Sistem dizaynı ve maliyetler konusunda farklı analiz yöntemleri mevcuttur. Buarastırmada, Dikili jeotermal ısıtma sistemi (DJIS), ekonomik hız, Pipelab simülasyonprogramı ve optimum çap yöntemleriyle analiz edilmektedir. Bu analizlerde, Dikili bölgesi üçkapalı devre olarak incelenmektedir. Bunlar; sale, Barıskent ve Danıstay hatlarıdır.Ekonomik hız yönteminde, ekonomik hız çizelgelerinden yararlanarak, DJIS'nin boruçapları dizayn edilmektedir. Kapalı devrelerin her biri için, gerekli kütlesel debi hesaplanarak,kritik devre analizi yapılmaktadır. Sonuç olarak gerekli kütlesel debi ve yerel kayıplar, salehattı (DN 300); 230,7 kg/s ve 966,193 kPa, Barıskent; 63,5 kg/s ve 388,93 kPa ve Danıstayhattı; 167,4 kg/s ve 415,874 kPa hesaplanmaktadır. Pipelab simülasyon programındaDJIS'nin debi, hız ve basınç kaybı analizi diyagramlarla yapılmaktadır. Problemli hatlarbelirlenip, çözümler önerilmektedir. Bu analiz sonucunda: Birlik Kooperatif'in içinde,dagıtım hattına en son baglanan blokta bir basınç dengesizligi, Danıstay ana dagıtım hattındaise hız dengesizlikleri görülmekte ve çözüm önerileri sunulmaktadır. DJIS içinden, dösenmisolan sale hattı seçilerek, bu hat üzerinde optimum çap yöntemi uygulanmaktadır. En düsüktoplam maliyet (K), DN 300 için 761 629,36 YTL/yıl hesaplanmaktadır.
Polimer kompozitlerin termal özellikleri ve mekanik anizotropisi
The primary purpose of the study is to investigate the anisotropic behavior of different non-crimp stitched fabric (NCF) reinforced polyester and epoxy composites. Composite laminates were manufactured by vacuum infusion of resin into the fabric. Tensile and three-point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this study an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear tests was discussed. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the stability and/or the instability of matrix-fiber interfaces. Infrared spectrum of composites were obtained by Fourier transform infrared spectroscopy (FT-IR). Thermal investigations on six selected type composites have been made. They differ with regard to the type of the resin matrix that have been reinforced with the different type of fiber. Changes in the specific heat capacity of composites have been determined by differential scanning calorimetry. Thermal conductivity measurements in through the thickness direction of composites were performed using a differential scanning calorimeter (DSC). Measurements were carried out over a wide range of temperatures. The thermal stability of composites in air atmosphere has been followed over a wide range of temperatures using thermogravimetric (TGA) and differential thermal analysis (DTA).
Efficiency and energy losses for combi boilers
In this thesis study, the potential for efficiency improvement methods for gas-fired combi boilers are investigated. Efficiency and energy losses are experimentally determined, while the performance of a gas-fired combi boiler is evaluated using energy and exergy analysis. This thesis consists of mainly five chapters. In the first chapter, main description and contribution of the gas-fired combi boilers for domestic and commercial in the overall energy balance worldwide are given. The second chapter includes a classification of the combi boilers according to different categories, while main components of room sealed flue combi boiler are briefly explained. In the following chapter, efficiency measurement techniques based on the related standards, detailed combustion equations, exergy analysis and energy loss sources are examined. A brief description of condensing boilers and the state of the technological improvement for these boilers are also presented. The fourth chapter contains experimental studies on efficiency and energy losses, which have been performed at the laboratories of Bosch Heating Systems Research and Development department, in Manisa. In the last chapter; the test results obtained are assessed, while main topics of the thesis are given briefly. Average energy and exergy efficiency values for the combi boilers studied are found to be 91 and 13.6 of percentage, respectively.