Master Degree / Yüksek Lisans Tezleri

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

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Publisher: search.filters.publisher.Izmir Institute of TechnologySubject: search.filters.subject.Heat exchangers

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  • Master Thesis
    An Investigation of Data-Based Fault Detection Methods in Petroleum Refineries
    (Izmir Institute of Technology, 2022) Yasmal, Aslı; Uzunlar, Erdal
    The petroleum refineries are complex systems vital for energy and production sectors. During production, these complex systems might experience various faults, including fluid leaks in unit operations. The detection of leaks is important for a reliable, safe, and efficient operation. Among the possible leak detection mechanisms, data-based leak detection methods are promising in terms of low investment cost, less human intervention, ability to detect small leaks in advance and direct integration capability to distributed control systems. The aim of this study is to investigate data-based leak detection methods in a heat exchanger in a petroleum refinery. To that end, possible leaking problems in petroleum refineries are assessed, multiple leak cases from a real heat exchanger in a petroleum refinery are determined, literature studies are searched for appropriate data-based leak detection methods, applicability of a set of data-based leak detection methods is studied with a literature benchmark data set, and the real cases of heat exchanger leaks are studied with the determined leak detection methods. Data sets for multiple leak cases of a heat exchanger are obtained from a TUPRAS refinery. The benchmark data set is obtained from Tennessee Eastman Process (TEP). Discrete Wavelet Transform (DWT), Auto Encoder (AE), and Exponentially Weighted Moving Average (EWMA) are selected as the data-based leak detection methods. The selected data-based methods are first studied with TEP data set, and good fault detection capability is observed. Then, the real leak cases are studied. All three data-based methods are found successful in detecting the actual leak cases. For some of the cases, leaks are detected with data-based methods in advance of the operation engineers noticing the leak.
  • Master Thesis
    Experimental Investigation of a Combi Boiler Heat Exchanger
    (Izmir Institute of Technology, 2018) Kara, Mehmet; Çetin, Erdal
    The combi boilers are divided into two types, condensing and conventional, in terms of waste gas heat recovery. In conventional types, the condensation occurrence is undesirable, and over time it causes corrosion in the main heat exchangers, which decrease the efficiency and the lifetime. Although life tests are performed to check if the condensation has occurred or not over time, these tests take a long time and require the high cost. In this thesis, it is aimed to find a heat transfer correlation and use the calculation method instead of life tests. Two different topics were investigated on three appliances with different design parameters in order to find out in which conditions the condensation on the heat exchangers has occurred. As the first topic, influences of the fresh air amount in combustion equations, on condensation was tested in conventional appliances of Type B and C. As the second subject, the effects of the exchanger design parameters on the condensation were tested by using copper finned and stainless steel finned heat exchangers. For this study, mapping tests were carried out in the laboratories of Bosch Thermotechnology in Manisa and the measurement results of CO2 percentages and temperature distributions of the combustion over the exchanger were used. Using mapping test data, different condensation temperatures were calculated for three appliances depending on the fresh air amount and exchanger design parameters. These variables are able to be used in the heat transfer correlation to make improvements on the condensation point without making life tests.
  • Master Thesis
    Design and Mechanical Behaviour of Brazed Plate Heat Exchangers
    (Izmir Institute of Technology, 2018) Gürler, Yiğit; Artem, Hatice Seçil
    In recent years, the developments in clean, renewable and efficient energy policies have been enabled to design new and innovative heat exchangers. The plate heat exchangers have crucial importance among these innovative products due to compact size and thermally efficient behaviour. There are many studies dealing with the thermo-fluidic behaviour of brazed plate heat exchangers. However, since the usage of these products often includes relatively high pressure and toxic fluids, the examination of structural stability of these products is cruical from the point of scientific perspective view. There are very few studies of plate heat exchangers regarding to mechanical aspects. Accordingly, in this thesis it is intended to investigate structural behaviour of brazed plate heat exchangers by numerical methods. For this purpose, the material properties of brazing interface of plate heat exchangers have been determined by experimental methods. The tensile and stress based fatigue experiments are carried out and the material models have been obtained. The validation of material model which is used in numerical analysis has been carried out by explicit method using maximum displacement as a boundary condition. The mechanical behaviour of chevron type brazed plate heat exchangers has been investigated by considering effect of chevron angle under different pressure conditions. The results have been obtained numerically in two stages; static structural analysis results and fatigue analysis. The numerical results show that the chevron angle has a significant effect on the formation of brazing points of plate heat exchangers. The dimensions of brazing points directly affects the overall structural behaviour of plate heat exchanger. It is observed that the single brazing point surface area and homogeneous distribution of brazing points on the plates are more critical than the total surface area. Finally, it is thought that the developed numerical methodology will lead to the structural design of brazed plate heat exchangers before the production of protoype molding and experimental testing. Eventually, it will be advantageous in terms of mold costs and time spent for experimental testing.
  • Master Thesis
    Numerical Analysis of Finned Downhole Heat Exchangers: a Parametric Study
    (Izmir Institute of Technology, 2002) Alpay, Selda; İlken, Zafer
    This study investigates the performance of an U-type Downhole Heat Exchanger (DHE) with a new pipe arrangement, where circular fins are fitted around the legs of the DHE.In the present work the heat transfer performance of optimized DHE with circular fins is investigated and compared with that of optimized with bare type DHE. This study numerically models a well with a DHE to determine the heat flow that can be extracted by the DHE. A DHE program is written in BASIC language to investigate the heat transfer rate both for bare and finned type DHEs. In order to verify the accuracy of this program comparisons are made with an experimental work for bare type DHEs. Also a computational fluid dynamics program, FLUENT, is used to study fluid and heat flow processes in the well and DHE systems. The results of the FLUENT program are also used to compare the DHE program. The simulations carried out also enable us to determine the influence of the design parameters of the finned type DHEs. Some examples of optimized geometries are finally shown and discussed.