Master Degree / Yüksek Lisans Tezleri

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

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COAR Access Rights: search.filters.coarAccessRights.open accessSubject: search.filters.subject.Heat exchangers

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Now showing 1 - 6 of 6
  • Master Thesis
    The Development of Forming Simulation Methodology of a Plate Type Heat Exchanger
    (01. Izmir Institute of Technology, 2023) Şimşek, İbrahim; Taşdemirci, Alper
    In this study, the production process of plate type heat exchangers was developed as a simulation methodology. Within the scope of the study, first, the parameters in the production process were determined. Then, mechanical characterization studies were planned with the AISI 316L stainless steel material used during production and the alternative AISI 304 stainless steel material, and the tests were completed with the support of the relevant stakeholders. The tests were determined according to the requirements of the simulation methodology. In this context, uniaxial tensile test, biaxial hydraulic bulge test and Split Hopkinson tensile tests were performed to obtain the necessary inputs for the mechanical characterization of the material and creating the material model. The material models established with the information obtained from the tests were validated with the modeling of the test setups in the numerical environment. The simulation methodology was developed in the LS-DYNA environment in the light of the process parameters obtained from the production and the data obtained from the mechanical characterization tests. The simulation model created with the developed methodology was verified because of comparison with the sample produced from AISI 316L stainless steel material taken from production. After the verified model was obtained, a simulation model was created with AISI 304 stainless steel. In addition, for the model formed with AISI 316L stainless steel, process parameters optimization study was carried out, and preliminary work activities related to reducing production times were carried out in numerical environment. After these modeling activities, the knowledge of the license plate was increased. In addition, effective plastic stress during the process, springback effect, residual stress values after springback, effective plastic strain, thickness distribution and thickness reduction values were obtained for the plate. By using the forming limit diagram of AISI 316L stainless steel, information about the final formability behavior was obtained.
  • Master Thesis
    Design Optimization of an Industrial Oven Heat Exchanger
    (01. Izmir Institute of Technology, 2021) Nergiz, Güven; Çetkin, Erdal
    The coating application of metals (especially in automotive and white goods sectors) is used in various fields to protect the metal against oxidation, corrosion, scratch, or high temperature to increase product lifetime. The most efficient technique in the coating application is powder coating where the powder is Epoxy-polyester. This process has three steps; surface pretreatment (washing), powder coating, and curing the coated metal. Metals may need to be dried and cured in ovens with 90°C and 200°C, respectively, for the required quality coating process. Burners are used as the heat source in the oven's heat exchangers. Due to high temperatures, the expanding heat exchanger is exposed to various thermal stresses. The stresses cause cracking and rupture problems. The regions where thermal stresses occur intensely are the surfaces with high-temperature differences. Various mass flow rates in the heat exchanger cause non-uniformity for how the energy to be transferred, thus non-uniform surface temperature distribution. In this study, a heat exchanger design provided by "ELECTRON – Sistem Teknik Makina" company has been studied. The mass flow rates in the heat transfer pipes (where the heat is mainly transferred) show deviations up to 75% from the ideal rate. With this study, deviations have been reduced to the level of ±10%. The results show that the maximum thermal stress on the heat exchanger was reduced by 24% with this improvement. In general, the uniform mass flow rates obtained in the heat transfer pipes provided a more homogeneous distribution of the surface temperatures, thus decreased thermal stresses.
  • Master Thesis
    Investigation of Microchannels Heat Exchangers for Condensers
    (01. Izmir Institute of Technology, 2021) Sevencan, Furkan Tuğberk; Çetkin, Erdal
    There are limited types of condenser types/designs in the market although there are many distinct heat exchangers available. One reason is related to the complexity of the phase-change mechanism and how it is affected by the geometric parameters of the heat exchanger. Technological requirements force the size of any component to become smaller and condensers are no exception for this trend. However, there is a limit for scaling down the current condensers, and their compactness cannot be decreased due to their serpentine design. The transition from serpentine designs to parallel microchannels is promising as the required coolant volume would decrease significantly for the same cooling due to enhanced heat exchange surface area. However, parallel channel designs are challenging to implement due to irregularities in pressure distribution which would yield phase change and condensation temperature significantly. In the present thesis, a microchannel heat exchanger was selected and the imperfections related to the pressure distribution irregularities were progressively developed numerically. Geometrical parameters were optimized to eliminate the flow maldistribution resulted from non-homogeneous pressure distribution in the condenser. The effects of header shape (from rectangular to tapered) on flow uniformity are not dramatic. Then, manifold channels were relocated with given protrusion depths which were optimized using an iterative approach. Relocating the channels enables the pressure uniformity. Finally, the condensation behavior of the design developed with the aim of enabling uniform flow resistance was documented. Under the given operational conditions, three different height channel design is 100% condensed R410a from the vapor phase into the liquid phase. A and B design were condensed the refrigerant fluid in a low Reynolds number meanwhile, C design was condensed in a high range of Reynold number. All in all, effects of maldistribution on flow regime were tried to be eliminated with new geometric design approaches and condensation effect in new geometries was able to be seen 100% at low flow rates.
  • 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.