Person: KARAGÖZ, İRFAN
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KARAGÖZ
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İRFAN
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Publication Numerical investigation of heat and flow characteristics in a laminar flow past two tandem cylinders(Vinca Inst Nuclear Sci, 2021-01-01) Aydın, Neslihan; Özalp, Alper; Karagöz, İrfan; AYDIN, NESLİHAN; ÖZALP, ABDURRAHMAN ALPER; KARAGÖZ, İRFAN; 0000-0002-7442-2746; AAB-9388-2020; AAB-9496-2022Heat and flow characteristics were investigated numerically for a laminar stream past two tandem circular cylinders placed in a channel. The blockage ratios (beta = D/H) were chosen to be 0.6, 0.7, and 0.8, respectively, and the gap between the cylinders was varied proportionally to the cylinder diameter as g = 0.2D, 0.7D, 1.5D, and 4D at a low Reynolds number (Re = 40). The effects of the blockage ratio, as well as the gap between two cylinders on heat and flow features were examined in detail. Shear stresses, dimensionless static pressure, heat transfer coefficient, and separation points from the cylinders were determined from the velocity and temperature fields in the flow domain. The results showed that the separation angle decreases with both the blockage ratio and the gap size on the downstream cylinder, whereas heat transfer increases with both the blockage ratio and the gap size on the upstream cylinder.Publication Response of a proton exchange membrane fuel cell to step changes in mass flow rates(Wiley-v C H, 2021-06-20) Küpeli, Seda; Çelik, Erman; Karagöz, Irfan; Karagöz, Irfan; KARAGÖZ, İRFAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0002-7442-2746; JCN-7685-2023; AAB-9388-2020Transient regime effects are particularly important in fuel cells designed for vehicles. Three-dimensional modeling of a proton exchange membrane fuel cell with a serpentine channel is presented, and the response of the fuel cell to a step-change in the mass flow rates is analyzed by using the computational fluid dynamics techniques. After a validation study of the mathematical and numerical model, step increases of 20% in mass flow rates are applied to the inlet boundary conditions, and time dependent power and current density responses of the fuel cell are analyzed. Polarization curves are generated for the assessment of the fuel cell performance, and their variations in time are presented. The results show that current and power densities increase with time at low cell voltage values due to concentration losses; however, increases in power and current are negligible at high voltages.Publication Effects of separation space diameter on the performance of a novel reverse flow cyclone(Taylor, 2019-10-13) Sakin, Ali; Karagöz, İrfan; Avcı, Atakan; KARAGÖZ, İRFAN; AVCI, ATAKAN; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0002-7442-2746; AAB-9388-2020A numerical study was carried out to investigate the effect of separation space diameter on the performance of a novel reverse flow tangential inlet cyclone design by using the Eulerian-Lagrangian approach. The design of this cyclone is based on the idea of increasing vortex length and decreasing pressure drop compared with traditional cyclones. This novel cyclone differs from the traditional cyclones with separation space and vortex limiter instead of the conical part. A qualitative numerical study was performed to analyze the effect of separation space diameter on the cyclone performance at different flow rates by evaluating velocity profile, pressure drop, fractional and overall efficiencies. The results show that the collection efficiency of smaller particles increases while pressure drop decreases significantly with the increase in separation space diameter for D-1/D < 0.5.Publication Investigation of the effects of intermediate reservoirs and intermediate feedings applications on the performance of proton exchange membrane fuel cells(Elsevier, 2023-02-09) Çelik, Erman; Karagöz, İrfan; KARAGÖZ, İRFAN; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0002-7442-2746; AAB-9388-2020This study presents the design principles and details of a new flow field based on the shape and reflex similarity of the circulatory systems of living things. This design has intermediate reservoirs that collect and distribute the flow channels and also allow for intermediate feedings. This design is applied to a proton exchange membrane fuel cell, and its performance is tested and compared with a conventional serpentine type of flow channel. The novel fuel cell with intermediate reservoirs reaches a current density of 0.171 A/cm2 at 0.406 V and displays a power density 10 % higher than the serpentine flow field. Moreover, eleven cases involving symmetrical and asymmetrical feeding arrangements are also examined. The case of 70 %, 20 % and 10 % symmetrical feeding at the main and intermediate inlets shows the highest performance by providing a 38 % higher power density compared to the serpentine flow field.