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    CFD Analysis Of Jet Flows Ejected From Different Nozzles
    (Oxford University Press [University Publisher], 2021) Kosa, Ergin; Ezgi, Cüneyt; Berkay, Çetin; Atmaca, Mustafa
    Nozzles are widely used to control the rate of flow, speed, direction, mass, shape and pressure of the stream in connection with many different engineering applications. This paper presents the performance predicted by a computational fluid dynamic (CFD) model, which are 3D models that utilize parametric analysis, realizable k-epsilon turbulence models and experimental measurement for a jet. Jet flows are ejected from three different slot nozzles: round-shaped nozzle, rectangular-shaped nozzle and 2D-contoured nozzle. In this numerical study, velocities of free jets have been predicted for different axial distances from the nozzle exit in the range of 0.2?z/B?12 when center velocity at the nozzle exit. CFD simulation results are compared to experimental results from literature. These results are consistent with the existing experiments.
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    Energy Recovery Analysis in A-Type Pressure Regulation and Measurement Stations in Istanbul, Esenyurt
    (Institute of Physics of the Polish Academy of Sciences, 2019) Atmaca, Mustafa; Uraltaş, Yunus; Onat, Ayhan; Ezgi, Cüneyt
    Converting energy sources into electrical energy is as important as gaining energy. After producing natural gas, which is one of the most common energy sources and classified as fossil fuel, it is sold by the natural gas and petrol companies to the world by compressing it in the compressor stations. Gas companies compress incoming gas which is lost in the pipeline into 35–75 bar equal to the loss rate and transfer it to the A-type pressure regulation measurement stations. In these stations, natural gas that enters with high pressure is reduced to 12–19 bar by throttle valve. This process happens using the Joule–Thomson effect. Hence, no energy is produced in this process. There is a big waste of producible electrical energy in this situation. In this work, turboexpander which is suitable for radial type variant flow has been considered to be used instead of throttle valve at the stations. In this work, A-type pressure regulation measurement station in Esenyurt yearly gas values, inlet and outlet gas pressure values, inlet and outlet temperature values were searched and gained electric energy value was searched in case of installing turboexpander to this station.
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    Modeling Study and Performance Investigation of a Thermoelectric Refrigerator
    (2021) Kosa, Ergin; Kepekçi, Haydar; Ezgi, Cüneyt
    Thermoelectric refrigerators are widely used in electronics, medical, and food industry application areas. A refrigeration effect can also be achieved without using any moving parts by merely passing a small current through a closed circuit made up of two dissimilar materials. This effect is called the Peltier effect, and a refrigerator that works on this principle is called a thermoelectric refrigerator. They consist of several thermoelectric legs sandwiched between two thermally conductive plates, one cold and one hot. Thermoelectric refrigerators presently cannot compete with the vapor-compression refrigeration system because of their low- coefficient of performance (COP). However, some applications have been preferred because of their small size, simplicity, quietness, and reliability. In this study, a thermoelectric cooler having a maximum cooling power of 50 W, having a dimension of 40mmx40mmx3.6 mm, is modeled in multi-physics software. Also, the performance of a thermoelectric refrigerator is investigated. It is computed the temperature difference between ceramics plates versus electric current and COP for a temperature difference between ceramics plates. The simulation results are compared with experimental data. The data obtained from the analyses have been compared with the experimental results and found to agree with each other. For the surface temperatures of 25 oC and 50 oC, the maximum coefficients of performance have been computed to be 1.091 and 1.445, respectively. In general, as the temperature of hot surfaces has increased for the same temperature differences, the COP of the thermoelectric cooler has increased.
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    Three-Dimensional Cfd Modeling Of Thermal Behavior Of A Disc Brake And Pad For An Automobile
    (Oxford University Press, 2020) Kosa, Ergin; Kepekci, Haydar; Ezgi, Cüneyt; Cihan, Ahmet
    The brake system of an automobile is composed of disc brake and pad which are co-working components in braking and accelerating. In the braking period, due to friction between the surface of the disc and pad, the thermal heat is generated. It should be avoided to reach elevated temperatures in disc and pad. It is focused on different disc materials that are gray cast iron and carbon ceramics, whereas pad is made up of a composite material. In this study, the CFD model of the brake system is analyzed to get a realistic approach in the amount of transferred heat. The amount of produced heat can be affected by some parameters such as velocity and friction coefficient. The results show that surface temperature for carbon-ceramic disc material can change between 290 and 650 K according to the friction coefficient and velocity in transient mode. Also, if the disc material gray cast iron is selected, it can change between 295 and 500 K. It is claimed that the amount of dissipated heat depends on the different heat transfer coefficient of gray cast iron and carbon ceramics.