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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 Effects of Twisting Ratio, Diagonal Length, and Pitch Ratio of Hexagonal Pin Fins on Thermo-hydraulic Performance of Heat Sink(Toronto Metropolitan University, 2023) Gürdal, M.; Tekir, M.; Algbourie, N.I.; Pazarlioglu, H.K.; Arslan, K.While the effect of the twisting ratio on a heat sink was investigated for the first part of the study, the diagonal length and pitch ratio were observed for following step. The parametric studies were applied under turbulent regime (2658? Re?7138) to monitor thermo-hydraulic performance of novel proposed design. The edge length of the pin fins (Lef) was varied regarding their diagonal length (5? Lef ? 6) while the pitch ratio (P/e) and twisting ratio were varied in the range of 0.75? P/e?1.0 and 50?TR? 200 respectively. By using the turbulent model SST k-? with low-Re correction model on ANSYS Fluent, the computational study has been carried out to discretize RANS equations. Average Nusselt number (Nu) and average Darcy friction factor (f) which define the thermo-hydraulic performance of system were elucidated in detail. As a result, the best thermo-hydraulic performance was achieved as 1.55 by using the lowest twisting ratio (TR=200), pitch ratio (p/e=0.75) and the highest diagonal length (Lef=6) and at Re=2658. © 2023, Toronto Metropolitan University. All rights reserved.Öğe IMPACT OF TWISTED DUCTS WITH DIFFERENT TWIST RATIOS ON HEAT TRANSFER AND FLUID CHARACTERISTICS OF NIO/WATER NANOFLUID FLOW UNDER MAGNETIC FIELD EFFECT(Begell House Inc., 2022) Pazarlioglu, H.K.; Gürdal, M.; Tekir, M.; Arslan, K.; Gedik, E.Laminar forced convection of NiO/water nanofluid in a twisted square duct has been investigated numerically under the effect of an external magnetic field (B = 0 G, 450 G, and 550 G) in the Reynolds number range of 500 ? Re ? 2000. Four different twist ratios (D/L = 0.0, 1.0, 1.5, and 2.0) of the square duct have also been examined. The nanoparticle volume fractions (NPVF) of NiO/water nanofluid have been selected between 0.6 vol.% and 2.5 vol.%. The effects of the magnitude of the magnetic field (MF), twist ratio, Reynolds number, and nanoparticle volume fraction on thermohydraulic performance have been examined by using the homogeneous model in the numerical analyses. The results of the numerical computations have been reported with average Nusselt number Nu, pressure loss, average Darcy friction factor f, and performance evaluation criterion (PEC). The highest heat transfer increment by 20% has been achieved at D/L = 2.0 with the highest nanoparticle volume fraction, namely, 2.5 vol.% NiO/water nanofluid, compared to the case of distilled water (DW) flowing in a plain duct (PD). In addition, it was determined that the magnetic field effect increases the convective heat transfer in the twisted duct with D/L = 2.0 up to 35% compared to the cases in the absence of a magnetic field at D/L = 2.0. Among all cases, the highest PEC has been obtained with 2.5 vol.% NiO/water nanofluid flowing in the twisted duct with the twist ratio D/L = 2.0. © 2022 by Begell House, Inc.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.
