Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

Browse

Filters

2018 - 20204

Settings

Access Right: Open AccessAuthor: search.filters.author.Toprak, Kasım

Search Results

Now showing 1 - 4 of 4
  • Master Thesis
    Numerical and Experimental Investigation of Thermal Performance of Graphene Reinforced Aluminium
    (01. Izmir Institute of Technology, 2020) Yılmaz, Ahmet Berk; Toprak, Kasım; Kandemir, Sinan
    Graphene is a material with superior properties such as high thermal conductivity and mechanical strength. These exceptional properties make graphene a good candidate for being used as a reinforcement agent in other materials. Aluminium is a widely used material in industry for thermal applications for being cheap, lightweight and having high thermal conductivity. In the literature, there are many examples of graphene reinforced aluminium production. Also, the effects of graphene on thermal conductivity and mechanical properties of aluminium are also investigated experimentally. However, there are limited molecular dynamics studies for graphene-aluminium composites. In this work, aluminium, graphene and graphene coated aluminium are modeled and simulated with non-equilibrium molecular dynamics method. Length, width, height, temperature dependence of thermal conductivity of these models are investigated. In addition, effects of graphene layer number, defect size and defect locations are also reported. Additionally, an experimental setup is designed and produced for a comparative study. Thermal performances of aluminium alloy and graphene nanoplatelet reinforced aluminium are investigated with a convection heat transfer test.
  • Master Thesis
    Thermal Performance of Graphene Coating on Copper
    (Izmir Institute of Technology, 2019) Ersavaş, Gizem; Toprak, Kasım; Çelebi, Cem; Toprak, Kasım; Çelebi, Cem
    Over heat is always a problem for electronic devices because the locally generated heat cannot be transferred appropriately to the corresponding heat sink fast enough. This situation leads to affect materials’ structures, mechanical properties and conductivities badly. In order to avoid this problem, high thermal conductivity materials are used to dissipate the heat quickly. Thanks to the development of technology, the size of the electronic devices is reduced day by day. This also shrinks the size of the interconnect components. So this situation leads to researchers to investigate nano-sized interconnect components and copper, which is a widely used material, is one of them. Copper is one of the preferred metals for electronic devices because of high thermal conductivity, easy processability, and high use in daily life and industry. For example, copper components, which is used in electronic, are getting so thin and must carry so much current. And that causes to increase friction. Thus heat is occurred. Consequently, cooling problems have arisen. And if the material’s cooling problem won’t be solved then the material can be damaged. It is thought that to overcome this problem, coating with a high thermal conductivity material such as graphene, the thermal conductivity can be improved. In this study, thermal performance of graphene-coated copper were investigated numerically and experimentally. This study consist of two main sections. The first part, MD simulation code was created using C++ programming language to investigate thermal conductivity of copper, different number of graphene layers and these graphene layers were coated on copper in different length, width, height and temperature. In the second part, the thermal performance of pure copper, annealed copper, a layer of graphene-coated copper, and multilayer graphene-coated copper was studied by the experimental setup at three different temperatures and volume flow rates.
  • Master Thesis
    Theoretical Performance Optimization of Solar Absorption Chiller Coupled To Underground Cooling Tower
    (Izmir Institute of Technology, 2018) Ouedraogo, Kiswendsida Elias; Toprak, Kasım; Özkol, Ünver
    The study aims to enhance the thermal/economic performance of a solar powered absorption heat pump used for the cooling/heating of a shopping center in Izmir. MATLAB and TRNSYS are used to simulate the system. First, borehole thermal energy storage is added to the system to store the heat rejected by the chiller condenser in summer for later use in winter. Secondly, cooling water out of a condenser is partially stored during an 8:00-16:00 working time, and cooled from 16:00 to 8:00 to take advantage of the lower ambient temperature at night. Lastly, chilled water storage is added to the system to level the cooling load. The study revealed that the borehole efficiency is 37%. Also, it enhanced the solar fraction in winter by 40% and increased the system cooling load to heat input ratio by 110%. The second study showed that operating a cooling tower at night can reduce cooling water temperature by 5°C. In the last study, producing chilled water 24h/day reduced the required cooling capacity of the chiller to 34% of its current capacity of 1020kW, thus increasing the capacity factor from 41% to 96%. A brief economic analysis showed that the levelized cost of cooling/heating is 0.034$/kWh and 0.049$/kWh for the system with chilled water storage and the system without chilled water storage respectively. This represented a cost reduction of 29%.
  • Master Thesis
    Investigation of the Rotor Speed Impact on the Efficiency of Rotary Heat Recovery Ventilation Devices
    (Izmir Institute of Technology, 2018) Dilşen, Mustafa; Toprak, Kasım; Toksoy, Macit
    In this study, the thermal efficiency of the rotary (regenerative) heat exchanger has been experimentally investigated in a heat recovery mechanical ventilation device. Beside impact of the same variable on pressure drop of the heat exchanger has been researched. Experiments have been carried out in a laboratory which belongs to a company manufactures heat recovery ventilation devices. The rotor has been tested within a commercial ventilation device rather than being tested alone in order to realize the actual conditions. Test results have also been compared with mathematical model results calculated with respect to the equations according to the literature research. NTU (number of transfer units) method has been used to calculate the thermal efficiency by using the various relevant equations which had been previously proposed by various researchers. The efficiency equation, which had a good agreement with the experimental results, has been determined by evaluating this comparison as a conclusion. Keywords and Phrases: heat transfer, heat recovery, energy recovery, ventilation, mechanical ventilation, regenerative heat exchanger, rotary heat exchanger (rotary wheel), thermal efficiency, thermal effectiveness, pressure drop.