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Öğe CFD ANALYSIS OF LAMINAR FORCED CONVECTIVE HEAT TRANSFER FOR TiO2/WATER NANOFLUID IN A SEMI-CIRCULAR CROSS-SECTIONED MICRO-CHANNEL(Yildiz Technical Univ, 2019) Kaya, H.; Ekiciler, R.; Arslan, K.In this study, forced convection flow and heat transfer characteristics of TiO2/water nanofluid flow with different nanoparticle volume fractions (1.0%, 2.0%, 3.0% and 4.0%) in semi - circular cross - sectioned micro - channel was numerically investigated. The three - dimensional study was conducted under steady state laminar flow condition where Reynolds number changing from 100 to 1000. CFD model has been generated by using ANSYS FLUENT 15.0 software based on finite volume method. The flow was under hydrodynamically and thermally developing flow condition. Uniform surface heat flux boundary condition was applied at the bottom surface of the micro - channel. The average and local Nusselt number and Darcy friction factor values were obtained using numerical results. Also, the effects of using nanofluid on local values of Nusselt number and Darcy friction factor were investigated. Numerical results indicate that the increasing of nanoparticle volume fraction of nanofluid, the average Nusselt number increases; however, there is no significant variation in average Darcy friction factor.Öğe A CFD INVESTIGATION OF Al2O3/WATER FLOW IN A DUCT HAVING BACKWARD-FACING STEP(Yildiz Technical Univ, 2019) Ekiciler, R.; Aydeniz, E.; Arslan, K.Al2O3/water forced convection nanofluid flow was numerically studied in a duct with backward-facing step. Nanoparticle volume fraction was changed between 1%-5%. Diameter of nanoparticle was constant (d(p)=40 nm). The Reynolds number was increased from 100 to 500. The step and total height of the duct were 4.8 mm and 9.6 mm, respectively. The bottom wall, which was positioned after the step, was heated with 2000 W/m(2) and the rest of the walls were adiabatic. Nusselt number, velocity profiles and friction factor were investigated in detail. It was obtained that Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number.Öğe A CFD investigation of Al2O3water flow in a duct having backward facing step(Yildiz Technical University, 2019) Ekiciler, R.; Aydeniz, E.; Arslan, K.Al2O3water forced convection nanofluid flow was numerically studied in a duct with backward facing step. Nanoparticle volume fraction was changed between 5%. Diameter of nanoparticle was constant (dp=40 nm). The Reynolds number was increased from 100 to 500. The step and total height of the duct were 4.8 mm and 9.6 mm, respectively. The bottom wall, which was positioned after the step, was heated with 2000 W/m2 and the rest of the walls were adiabatic. Nusselt number, velocity profiles and friction factor were investigated in detail. It was obtained that Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number. © 2019 Yildiz Technical University.Öğe EFFECT OF THE NANOFLUID FLOW AND EXTENDED SURFACES ON AN ABRUPT EXPANSION TUBE REGARDING THERMODYNAMIC IRREVERSIBILITY(Begell House Inc., 2024) Pazarlioglu, H.K.; Ekiciler, R.Numerous scientists have examined circular dimpled surfaces, tubes, and other approaches for enhancing heat transfer. Moreover, the dimples’ angle of attack has a substantial effect on the tube’s flow and thermal features. This numerical study presents a novel approach to enhancing heat transfer rate in a tube subjected to constant heat flux by incorporating a surface dimpling strategy and evaluates three different tube layouts with elliptical dimpled fins for different working fluids such as DW and Al2O3/DW nanofluid (? = 0.5–1.0%) by using ANSYS Fluent v2020R2 under laminar flow conditions. Under identical circumstances, the thermal performances of proposed designs are compared to those of a smooth tube, and the influence of the elliptical dimpled fin angle of attack on these parameters is determined for different Reynolds numbers (1000 ? Re ? 2000). When comparing the Nusselt number of a tube with/without elliptical dimpled fins, it is found that EDT 1 performed better. Lower Reynolds numbers are shown to result in a greater friction factor. Besides, elliptical dimpled fins promote flow mixing within the tube and the establishment of a thermal boundary layer. At a 135° attack angle (EDT 1), the 1.0% Al2O3/DW nanofluid is found to be the best-performing nanofluid in the dimpled tube, improving Nu by up to 44.56%. Furthermore, ff presented an increase of 29.18% when comparing ST and EDT 1 flowing 1.0% Al2O3/DW at Re = 2000, while total S•gen is diminished by 37.75% in the same conditions. © 2024 by Begell House, Inc.Öğe The effect of volume fraction of Sio2 nanoparticle on flow and heat transfer characteristics in a duct with corrugated backward-facing step(Serbian Society of Heat Transfer Engineers, 2018) Ekiciler, R.; Aydeniz, E.; Arslan, A.K.In this paper, flow and heat transfer characteristics of SiO2-water nanofluid flow over a corrugated backward-facing step are numerically investigated. The nu-merical study is performed by solving governing equations (continuity, momen-tum, and energy) with finite volume method. The duct inlet and step heights are 4.8 mm. The expansion ratio is 2. The upstream wall, Lu, and downstream wall, Ld, lengths are 48 cm and 96 cm, respectively. The downstream wall of the duct is subjected to a constant and uniform heat flux of 2000 W/m2. The ranges of the volume fraction of nanoparticles and Reynolds number are 0%-3.0% and 135-240, respectively. The effects of the volume fraction of nanoparticles on the average Nusselt number, average Darcy friction factor, and velocity distribution are investigated under laminar forced convective nanofluid flow condition. It is revealed that the nanoparticle volume fraction substantially influences the heat transfer and flow characteristics. The volume fraction of 3.0% shows the highest heat transfer performance. © 2018 Society of Thermal Engineers of Serbia.Öğe ENTROPY GENERATION ANALYSIS OF FORCED CONVECTION FLOW IN A SEMICIRCULAR MICROCHANNEL WITH TiO2/WATER NANOFLUID(Begell House Inc, 2019) Kaya, H.; Ekiciler, R.; Arslan, K.In this study, entropy generation caused by heat transfer and friction of forced convection flow in a semicircular cross-sectioned microchannel with TiO2/water nanofluid was numerically analyzed. The volume concentrations of the nanofluid were taken 1.0%, 2.0%, 3.0%, and 4.0%. Local and total entropy generation due to the heat transfer and friction were calculated for the microchannel. A three-dimensional analysis was simulated under steady-state laminar flow conditions with Reynolds number varying from 100 to 1000. The results of the simulation were obtained using the CFD code. The flow was considered as hydrodynamically fully developed under thermally developing conditions. A uniform heat flux boundary condition was applied at the bottom surface of the microchannel. According to the results of the numerical study, the effect of the nanofluid volume concentration and fluid velocity on entropy generation was evaluated. The findings show that the total and friction values of entropy generation increase with increasing flow velocity, while heat transfer entropy generation values decrease since nanofluids improve the heat transfer capability. Also, the results indicate that an increase in the volume concentration of the nanofluid causes friction entropy generation enhancement while heat transfer entropy generation decreases in all cases.Öğe Numerical analysis of effect of impinging jet on cooling of solar air heater with longitudinal fins(Begell House Inc., 2021) Pazarlioglu, H.K.; Ekiciler, R.; Arslan, K.In this study, the effect of impinging jet cooling on solar air heater with and without longitudinal fins has been numerically investigated. The absorber plate surface of the solar air heater is modeled as a constant heat flux condition. Numerical analyses have been conducted on turbulent flow conditions (10,000 ? Re ? 50,000). The jet flow velocity has been taken constant. The effect of fin height and mass flow rate of working fluid on the thermal efficiency of the solar air heater has been analyzed in detail. Variation of the convection heat transfer coefficient as a function of Reynolds number has also been determined for finned and unfinned conditions. Temperature and local Nusselt number distributions on the absorber plate have been defined as contour graphs. It is found that the Nusselt number and thermal efficiency enhance by adding impingement jets and increasing the Reynolds number. Also, it is obtained from numerical analyses that the convection heat transfer coefficient increases with increasing the fins height. Finally, it is revealed that using impinging jets and fins enhances the efficiency and convection heat transfer up to 23.35% and 15%, respectively. © 2021 by Begell House, Inc.
