Browsing by Author "Omeroglu, Gokhan"

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Experimental and Numerical Study on Effects of New-Generation Finned Heat Exchanger on Thermal Performance of Thermoelectric Cooling Systems
(Begell House Inc, 2024) Muratcobanoglu, Burak; Mandev, Emre; Omeroglu, Gokhan; Akpinar, Fatih; Oz, Erkan; Afshari, Faraz
In this study, an attempt has been made to increase the efficiency of the thermoelectric refrigerator by designinig a newgeneration finned heat exchanger. Surface extension, which is one of the most applied passive heat transfer enhancement techniques, was applied for this finned heat exchanger. In this application, the heat absorbed from the cooling room is transferred to the external environment more effectively. In addition, by using an external thermoelectric element (which is installed with the secondary heat exchanger), the heat exchanger cools down faster and the heat is transferred to the environment more quickly. The manufactured cooling system was tested experimentally under different working conditions, including natural and forced convection. The effects of air velocity and applied voltage to the external TE module on thermal performance were examined. Additionally, the external finned heat exchanger has been simulated and heat transfer characteristics have been evaluated using computational fluid dynamics. The lowest and highest COP values have been obtained as 0.003 and 0.011, respectively, when the external TE module has been passive. By providing 12 V for the external TE module, the lowest and highest COP values have been observed as 0.0031 and 0.0042, respectively. In addition, the importance of surface extension applications for the efficient operation of thermoelectric elements has been emphasized.
Experimental Investigation of Heat Transfer and Pressure Drop Characteristics of Ferrofluids in the Presence of Magnetic Field and Laminar Flow Conditions
(Begell House Inc, 2024) Muratcobanoglu, Burak; Mandeev, Emre; Omeroglu, Gokhan; Manay, Eyuephan
In this study, the heat transfer performance with forced convection of two different water-based nanofluids was investigated by applying an alternating magnetic field in a minichannel. CoFe2O4-water and MnFe2O4-water nanofluids have been prepared at 0.5 vol.% and tested. The tests were carried out in a minichannel under laminar flow conditions in the Reynolds numbers range of 300-1700. Nusselt numbers of each fluid used in the experiments were calculated and compared. At the Reynolds number of 1500, the CoFe2O4-water nanofluid exhibited an increase of 12% compared to pure water, while the MnFe2O4-water nanofluid showed an increase of 4%. The Nusselt number increased in both nanofluids by applying the magnetic field to nanofluids. The highest Nusselt number obtained was 9.35 for the CoFe2O4-water nanofluid in the presence of magnetic field. While this increase was more pronounced at low Reynolds numbers, a lower rate of increase was obtained at high Reynolds numbers. In addition, the use of nanofluids significantly increased the pressure drop compared to the base fluid. While an almost 100% increase in the pressure drop was observed for the CoFe2O4-water nanofluid compared to pure water, the 65% increase for the MnFe2O4-water nanofluid was maximum. At the highest Reynolds numbers, the maximum pressure drops were determined as 3.4 kPa for the CoFe2O4-water nanofluid and 3 kPa for the MnFe2O4-water nanofluid. It was also detected that the friction factor for CoFe2O4-water and MnFe2O4-water nanofluids was 80% and 40% higher, respectively, than for the base fluid.
Experimental Research of Dynamic Instabilities in the Presence of Coiled Wire Inserts on Two-Phase Flow
(Hindawi Ltd, 2013) Omeroglu, Gokhan; Comakli, Omer; Karagoz, Sendogan; Sahin, Bayram
The aim of this study is to experimentally investigate the effect of the coiled wire insertions on dynamic instabilities and to compare the results with the smooth tube for forced convection boiling. The experiments were conducted in a circular tube, and water was used as the working fluid. Two different pitch ratios (H/D = 2.77 and 5.55) of coiled wire with circular cross-sections were utilised. The constant heat flux boundary condition was applied to the outer side of the test tube, and the constant exit restriction was used at the tube outlet. The mass flow rate changed from 110 to 20 g/s in order to obtain a detailed idea about the density wave and pressure drop oscillations, and the range of the inlet temperature was 15-35 degrees C. The changes in pressure drop, inlet temperature, amplitude, and the period with mass flow rate are presented. For each configuration, it is seen that density wave and pressure drop oscillations occur at all inlet temperatures. Analyses show that the decrease in the mass flow rate and inlet temperature causes the amplitude and the period of the density wave and the pressure drop oscillations to decrease separately.
Investigation of Heat Transfer Properties of CuZnFe2O4-Water and NiZnFe4O4-Water Nanofluids Under Magnetic Field Effect
(Springer, 2024) Muratcobanoglu, Burak; Omeroglu, Gokhan; Manay, Eyuphan; Dumlu, Ahmet; Ayten, Kagan Koray
The aim of the present study is to investigate the heat transfer characteristics of CuZnFe2O4-water and NiZnFe4O4-water nanofluids since there is no study in the literature examining the thermal performances and thermophysical properties of the mentioned nanofluids under an external magnetic field. Experiments were conducted utilizing nanofluids with volume concentrations of 0.5% and 1.0% in a mini-channel, maintaining consistent heat flux boundary conditions over a Reynolds number range of 300-1300. Three magnetic field intensities (22 mT, 30 mT, and 38 mT) were applied using two electromagnets arranged perpendicular to the flow direction. The results demonstrate significant improvements in the Nusselt number with the use of nanofluids, particularly when subjected to an external magnetic field, indicating enhanced heat transfer. The impact of the magnetic field on heat transport is pronounced at low Reynolds numbers and with nanofluids containing a high concentration of nanoparticles. Moreover, the intensity of the magnetic field exerts a notable positive influence. Maximum enhancements in the Nusselt number were observed for both nanofluids at a volume concentration of 1.0%, Reynolds number of 300, and a magnetic field intensity of 38 mT. Interestingly, the CuZnFe2O4-water nanofluid exhibits greater responsiveness to the magnetic field compared to the NiZnFe4O4-water nanofluid. Relative to the case without a magnetic field, the NiZnFe4O4-water nanofluid showed a maximum Nusselt number increase rate of 24.62%, while the CuZnFe2O4-water nanofluid demonstrated a higher increase rate of 39.34%.