Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Mechanical EngineeringSubject: search.filters.subject.Thermodynamics

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  • Master Thesis
    Thermodynamic Optimization of Downhole Heat Exchangers for Geothermal Power Generation
    (Izmir Institute of Technology, 2016) Parmanto, Slamet; Gökçen Akkurt, Gülden; Yıldırım, Nurdan; Gökçen Akkurt, Gülden; Yıldırım Özcan, Nurdan; 03.10. Department of Mechanical Engineering; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Geothermal reservoirs have various thermodynamic and physical properties. The heat extraction and power generation from the geothermal reservoirs depend on the reservoir properties. Downhole heat exchangers (DHEs) are designed to move the heat extraction process into the geothermal well. The working fluid is injected to the DHE which suspends in the geothermal well, heated by geothermal fluid and then returned to the surface through the inner pipe. DHEs have been used for heating purposes widely but there is no application for electricity generation. Because of the natural convection on the geothermal fluid side, convective heat transfer coefficient is low and simultaneously the heat extraction rate is low comparing with extracting geothermal fluid by downhole pumps. Therefore if the temperature is high but flowrate is low in a geothermal well, DHEs are good alternatives to harness the energy from that well. Considering the number of wells with abovementioned conditions in the World, there is a potential for electricity generation coupling geothermal power plants with DHEs. The main purpose of the Thesis is to develop a thermodynamic and economic evaluation model of DHEs for power generation and to examine the feasibility of the model. The thermodynamic model is developed by EES software and over 300 simulations have been conducted to identify the effects of the insulation, geothermal well conditions, geometry of DHE, mass flowrate and the type of working fluids to the performance of DHE system. The economic analyses are conducted to evaluate the thermodynamic results regarding the economic consideration such as Net Present Value (NPV), simple payback time and electricity production rate. The results show that the insulation on the inner pipe is desirable to prevent heat loss along DHEs. The best design of the DHE is a design with deeper the depth, larger the diameter of the inner pipe, and higher mass flowrate for a specific geothermal heat source. The best design for the case study resulted as a work output of 3152 kW with annual net revenue and payback time of $1.75 million and 2.24 years, respectively. Besides, the economic evaluation gives positive value for NPV which means investment in DHE for geothermal power generation is acceptable.
  • Master Thesis
    A Mathematical Model of the Human Thermal System
    (Izmir Institute of Technology, 2005) Yıldırım, Eda Didem; Özerdem, Barış; Özerdem, Mehmet Barış; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Mathematical model of the human thermal system, which has been greatly developed in recent years, has applications in many areas. It is used to evaluate the environmental conditions in buildings, in car industry, in textile industries, in the aerospace industry, in meteorology, in medicine, and in military applications. In these disciplines, the model can serve for research into human performance, thermal acceptability and temperature sensation, safety limits. Present study investigates the mathematical modeling of the passive part of the human thermal system. The Bio-Heat Equation is derived in order to solve the heat transfer phenomena in the tissue and with environment. It is assumed that the body is exposed to combination of the convection, evaporation and radiation which are taken into account as boundary conditions when solving the Bio-Heat Equation. Finite difference technique is used in order to find out the temperature distribution of human body. The derived equation by numerical method is solved by written software called Bio-Thermal. Bio-Thermal, is used to determine temperature distribution at succeeding time step of the viscera, lung, brain all tissue type of the torso, neck, head, leg, foot, arm, hand, and mean temperature of torso, neck, head, leg, foot, arm, hand. Additionally, for overall body, mean temperature of the bone tissue, muscle tissue, fat tissue, and skin tissue and mean temperature of the total body can be obtained by Bio-Thermal Software. Also, the software is to be capable of demonstrating the sectional view of the various body limbs and full human body. In order to verify the present study, predictions of the present system model are compared with the available experimental data and analytical solution and show good agreement is achieved.