Makina Mühendisliği Bölümü
https://hdl.handle.net/11655/86
2024-03-29T12:41:33ZDesign of a Rotary Union For Coolant Transfer to Radar System
https://hdl.handle.net/11655/34348
Design of a Rotary Union For Coolant Transfer to Radar System
Vural, Yiğit
In this thesis, a rotary joint for cooling fluid transfer to the radar system is developed. The design and analysis to meet the specified technical requirements were verified by tests. In dynamic sealing tests, the sealing, friction, and life performances of PTFE-based seals with ENP and HVOF coatings under different temperature and pressure conditions were investigated. It has been shown that the coating on the AISI4140QT steel rotor using WC/Co/Cr 86/10/4 powder by HVOF method can provide sealing without abrasion in long-term use.
2023-01-01T00:00:00ZInvestigation of Transition Flow Over S809 Airfoil Using Infrared Thermography and Numerical Methods
https://hdl.handle.net/11655/34346
Investigation of Transition Flow Over S809 Airfoil Using Infrared Thermography and Numerical Methods
Aykut, Necla Ecenaz
This thesis presents the results of an experimental and numerical study that investigates the detection of boundary layer transitional flow using infrared thermography and Computational Fluid Dynamics analysis.
The experimental part of this thesis involves wind tunnel experiments conducted in METUWIND large-scale multi-purpose wind tunnel. S809 laminar airfoil was used as a test object and experiments were conducted in the boundary layer test section (TS2) of METUWIND. Experiments were performed for different Reynolds numbers at 0° angle of attack and different angles of attack at a Reynolds number of 5×10^5. Thus, separate effects of Reynolds number and angle of attack on the variation of the separation, transition onset, and reattachment points on the chordwise position of the airfoil were examined. In addition, the effect transition strip was observed experimentally using a vortex generator.
In the numerical part of the thesis, CFD simulations of the experimental cases were carried out. Effects of different turbulence transition models (k-ω-γ transition model, transition k-kl-ω model and transition SST model) were examined and implemented to the cases of the thesis using a commercial software. Afterwards, transition models were compared among themselves and with the standard k-ε turbulence model to highlight the difference.
The experimental process and results were compared and discussed with the results of numerical methods. The chordwise positions of the separation, transition, and reattachment points were successfully determined using the IR thermography method and CFD analyses, and the results were consistent. As the Reynolds number changes within the range of 5×10^5, 6×10^5 and 7×10^5 for 0° angle of attack, the chordwise position of the transition onset point did not show significant variations because of the low variation of the Reynolds number. As the angle of attach changes within the range of 0°, 3°, 6° and 9° for 5×10^5 Reynolds number, the chordwise position of the transition onset point approached the leading edge of the airfoil.
2023-06-01T00:00:00ZThermal Behavior and Performance of Lithium-ion Batteries at Low Temperatures
https://hdl.handle.net/11655/34320
Thermal Behavior and Performance of Lithium-ion Batteries at Low Temperatures
Tekin, Altay
In this thesis, the performance and thermal behavior of a commercial lithium-ion battery were investigated experimentally at low temperatures. Identical batteries are subjected to 0.5C and 1.0C charge-discharge at three different temperature settings (25°C, 4°C and -20°C). Furthermore, an in-house 1-D electrochemical-3-D thermal coupled model was utilized to simulate the low temperature conditions along with the charge-discharge tests. Experiments conducted with a battery test system show that as the temperature decreases, the available capacity of the lithium-ion batteries decreases, and heat generation inside the battery increases. The model is able to predict battery voltage and surface temperature at room temperature. However, as the operating temperature gets lower, the discrepancy between the model and the experimental data begins to increase. At low temperatures, the electrochemical properties of the lithium-ion batteries change drastically. To capture the effects of varying temperature dependent parameters, a sensitivity analysis was performed comparing the 1C experimental discharge data at -20°C with the model predictions. The sensitivity analysis indicates that decreasing temperature has negative effect especially on the electrolyte transport properties. It is demonstrated that while changing the electrolyte diffusion coefficient, electrolyte transport number, SEI film resistance, and the specific heat capacity of the battery have the largest impact on the battery voltage and temperature predicted by the model, electrode diffusion coefficient, electrolyte ionic conduction coefficient, and reaction rate constants have less impact. Results also show that the temperature dependent characterization of the model parameters is crucial for more accurate predictions.
2023-01-01T00:00:00ZDesign and Manufacturing of A Dryer Using Waste Heat From A Household Refrigerator
https://hdl.handle.net/11655/34313
Design and Manufacturing of A Dryer Using Waste Heat From A Household Refrigerator
Karacaoğlu, Şahin Murat
In this thesis, the dual use of a heat pump is examined in order to avoid waste of energy and reduce the equipment, volume, and cost used for both cooling food and drying clothes. Energy efficiency in household appliances is very important due to the increasing impact of environmental pollution on natural life, the difficulty of accessing natural resources, and international standards. At the same time, living space saving and program duration are important for user comfort. In this context, the system is designed production-oriented, the concept design calculations were carried out. Then, the performance and efficiency of the system is calculated by applying a series of tests at different configuration and subcomponent positions. The design is drawn via Solidworks 3D design software. Conservation of mass and performance analysis is performed for the designed system. The designed system is dried 320 grams of wetness in 960 grams of wet laundry in 3 hours and 38 minutes and also is increased the the cooling performance of the refrigerator. In addition, with the energy savings achieved in clothes drying process, the cost of the clothes dryer chamber is amortised after 4 years, 11 months and 5 days of use. The biggest advantage of the design is to reduce the energy consumption of the clothes dryer chamber thanks to the usage of waste heat that is drawn from the refrigerator part of the heat pump cycle. On the other hand, the main disadvantage is that the refrigerator and clothes dryer chambers have to be physically nearby, which may require radical changes in the interior architecture design of the houses. However, this disadvantage can be eliminated by new generation house designs that prioritize economic and environmental efficiency, or by designing the compartments where cooling and heating are required (for example, an ice room and clothes drying room can be designed side by side) in the service sector applications such as hotels that require profitability and efficiency. In addition, it can be a solution that transferring cold and hot flows that are taken from the heat pump to the related remote departments despite the losses.
2023-01-01T00:00:00Z