Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Natural Ventilation Design for Historic Libraries With Cfd (computational Fluid Dynamics) Simulation(Izmir Institute of Technology, 2019) Gülhan, Özcan; Gökçen Akkurt, Gülden; Erek, AytunçLibraries accumulate and protect written and printed works that make permanent knowledge and cultures have been accumulated throughout human history. Paper-based collections kept in libraries are the heritage of humanity. They are under risk of mechanical, biological and chemical degradation over the years caused by the fluctuations in temperature and relative humidity values and inability to control these values. The aim of the Thesis is to reduce degradation risks on paper-based collections in historic libraries by providing preventive conservation without damaging the structure of the building. The historic Necip Paşa Library which is home for 1147 manuscripts was chosen as a case study. In order to provide preventive conservation for manuscripts, firstly indoor microclimatic data were collected for one year and analyzed to observe the risks that may cause degradation types on manuscripts. Only chemical degradation risk was detected. Window controlled seven natural ventilation scenarios were developed to reduce the risk. Finally, ventilation scenarios were analyzed by Ansys Fluent 17.1. Computational Fluid Dynamics (CFD) modelling was used to observe the effect of natural ventilation scenarios on indoor relative humidity according to outdoor relative humidity and wind direction. Finally, k-? turbulence model was used in CFD analysis. Results shows that during the high chemical degradation risk period (May-October), outdoor air temperature and relative humidity are suitable only 7.53% of the total time which allows appropriate natural ventilation. As a conclusion, natural ventilation is not enough to decrease chemical degradation risk totally for the Library. Therefore, additional mechanical ventilation is required.Master Thesis Investigation of Oil Flow and Heat Transfer in Transformer Radiator(Izmir Institute of Technology, 2015) Kaymaz, Özben; Başaran, Tahsin; Erek, AytunçTransformer losses are produced by the current passing through resistance on the winding conductors. These losses are converted to heat energy as all electrical machines. Transformer life depends on the aging of cellulose-based insulation material in winding. Winding temperature must be kept below a certain temperature limit, because the excess heat in the windings directly accelerates the aging of insulation material. Oil-immersed transformers are cooled by using transformer oil. In this study, flow and heat transfer of transformer radiator filled with mineral oil, silicone oil and ester oil were investigated. Oil in radiator was modelled in 3D, thereby oil flow volume was created, heat transfer calculations were made with using different type transformer oils and investigation of flow behavior is studied. Temperature dependent density, thermal conductivity and viscosity values are obtained from oil suppliers. Transformer oil database was composed by using curve fitting methods in MathCAD Software to use in CFD (Computational Fluid Dynamics) analysis in Fluent software. Finally, the pressure differences were obtained for each oil type. According to the velocity versus pressure difference graph that was obtained from the results of this study, inertial resistance and viscous resistance could be described which are required in future studies to use porous medium approach. Number of elements and computation domain will be decreased by using porous medium approach, then complete transformer model could be analyzed. Additionally, thermal characteristics of transformer oils were obtained and compared in this study. Accordingly, natural ester oil had the best heat transfer and pressure drop.