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Öğe Cooling of Heated Blocks with Triangular Guide Protrusions Simulating Printed Circuit Boards(Mdpi, 2022) Beyazoglu, Ebubekir; Yuce, Bahadir Erman; Ates, Murat; Yalindag, Rumeysa; Sokmen, Kemal Furkan; Pulat, ErhanThere is no study that investigates triangular guide protrusions including their systematical geometrical changes together with the effects of channel height in the open literature in the context of the authors' knowledge. Moreover, the number of laminar studies is less than turbulent studies, whereas low velocity or natural convection cases are still important, especially for small devices in small PCB passages. The objective of this study is to investigate numerically the effects of triangular guide protrusions for the enhancement of heat transfer from the blocks' simulated electronic components in laminar flow conditions. Two-dimensional, incompressible, steady, and laminar flow analysis was performed to predict fluid flow and heat transfer characteristics for three heated blocks in a PCB (printed circuit board) passage with triangular guide protrusions mounted on the upper wall. The Galerkin finite element method of weighted residuals was used to discretize conservation equations. The effects of the channel expansion ratio and inlet velocity were investigated for five geometrical cases. If the size of the protrusions is increased, the existence of protrusions starts to affect the flow patterns on the lower wall. The size of the last protrusion controls the flow structure downstream of the last block. On the upper wall, after the last protrusion, a recirculation is formed and the length of the recirculation increases with an increasing Re number. Moreover, the reattachment length of recirculation after the last block increases with an increasing Reynolds number for a fixed expansion ratio. Expansion ratio and inflow conditions caused by blocks and protrusions have a great influence on the formation of secondary recirculation in addition to the Reynolds number. Heat transfer increases with increasing sizes of upper triangular protrusions. Maximum overall heat transfer enhancement is provided as 47.7% with the geometry of the maximum sized protrusions for the channel height of 3 h. In the case of 4 h, the maximum overall heat transfer enhancement is 24.21%. These enhancements in heat transfer that can be encountered in PCB cooling applications may help the PCB cooling designers.Öğe Design and optimization of the hydrokinetic turbine blades using statistical approaches(Pergamon-Elsevier Science Ltd, 2026) Kale, Fatih Mehmet; Yilmaz, Naz; Bademlioglu, Ali Husnu; Sokmen, Kemal Furkan; Shi, WeichaoIn this study, the design and optimization of Horizontal Axis Hydrokinetic Turbine (HAHT) blades were carried out using statistical approaches. Taguchi and ANOVA analyses were employed as the statistical methods. Initially, experimental and detailed computational analyses were conducted to predict the hydrodynamic performance of a HAHT. Subsequently, Taguchi and ANOVA analyses were performed to investigate the effects of design parameters such as thickness ratio (t/c), pitch angle (phi) and twist angle (theta) on the hydrodynamic performance of HAHT blades for different r/R blade sections 0.4, 0.6 and 0.8, and the optimal design parameters were identified. The study aims to investigate the effect of the design parameters, which are the most important in HAHT designs, on the power coefficient (CP) and to obtain the maximum CP for the existing HAHT as a result of changes proposed by the Taguchi and ANOVA optimization method. For the optimal HAHT geometry, the CP increase is observed between 2 % and 6 % at different TSR values. As a result of the analyses, the maximum CP was obtained as 0.4499 for the optimal design parameters. Additionally, it was concluded that the pitch angle was the most influential parameter on CP. Overall, the optimized blade provided a maximum 6 % increase in CP at TSR 5 compared to the initial design, and the pitch angle affected more than 96 % of this improvement compared to other parameters.Öğe Experimental and numerical investigations of hydrodynamic performance for horizontal-axis hydrokinetic turbines(Univ Zagreb Fac Mechanical Engineering & Naval Architecture, 2025) Kale, Fatih Mehmet; Yilmaz, Naz; Sokmen, Kemal Furkan; Shi, WeichaoThis paper presents both experimental and numerical investigations of the hydrodynamic performance of Horizontal-axis Hydrokinetic Turbines (HAHTs) using experimental methods and Computational Fluid Dynamics (CFD) approaches, respectively. The innovative aspect of this study lies in the consistency of the results, achieved by aligning the method used in the CFD analyses for Hydrokinetic Turbines (HKTs) and airfoil profiles with experimental data. For this purpose, 2-D CFD analyses were first conducted with blade section geometries (Eppler 395 and S1210), which are commonly used in HKT designs. The aerodynamic characteristics (CL and CL/CD) of these blade sections were computed and compared with the experiments. Subsequently, a three-dimensional (3-D) turbine geometry, featuring three different pitch angles (PAs), was simulated using CFD, and the results were compared with experimental data obtained under the same operating conditions in the Emerson Cavitation Tunnel (ECT) at Newcastle University. The comparisons showed good agreement while the maximum relative error was calculated less than 10 % for the power coefficient (CP) of the turbine with a PA of 0 degrees. For the other PA (8 degrees), the maximum relative error was 11 % for CP and 14 % for the thrust coefficient (CT). The CFD investigations of HKTs revealed that the Detached Eddy Simulation (DES) model has less relative errors compared to the other turbulence models at the same Tip Speed Ratio (TSR) values, while the Sliding Mesh (SM) method describing rotation gives more consistent and closer results to the experiments, with the investigation of y+ point of view.Öğe Investigation of heat transfer types in an automobile fog lamp with computational fluid dynamic analysis(LLC Editorial of Journal "Light Technik" lights-nr@inbox.ru VNISI rooms 327334106 Prospect Mira Moscow 129626, 2016) Sokmen, Kemal Furkan; Yamankaradeniz, Nurettin; Coşkun, SalihThis study investigated the temperature distribution and heat transfer in an automobile fog lamp. First, a mesh independent solution was obtained. The results were compared with the literature and validated with test results. Measurements were taken from five different points by using thermocouple. Tests were applied for two hours at 24 oC. For thermal analysis, ANSYS CFX 12.1 was employed. Air flow inside the fog lamp was assumed as steady, incompressible, laminar and three-dimensional. Thermophysical property variations, buoyancy and radiation effects were taken into consideration. The radiation effect is an important heat transfer type to be considered in the temperature distribution on the lenses of automotive lighting systems. The radiation effect can have a negative influence on the lens due to the selection of unsuitable material. Despite the complexity of the bulb geometry and its non-isothermal surface conditions, general flow and heat transfer characteristics did not change. © 2016, LLC Editorial of Journal “Light Technik”. All rights reserved.Öğe Taguchi and CFD-based hydrodynamic performance investigations of diffuser-augmented hydrokinetic turbines(Pergamon-Elsevier Science Ltd, 2026) Kale, Fatih Mehmet; Yilmaz, Naz; Bademlioglu, Ali Husnu; Sokmen, Kemal Furkan; Shi, WeichaoIn recent years, interest in renewable energy technologies has been increasing as part of the effort to obtain clean energy. One of these technologies, Hydrokinetic Turbines (HKT), converts the kinetic energy of water flow into electricity. However, these turbines fail to reach the theoretically calculated power coefficient (CP). To overcome this issue, researchers are developing various diffuser designs to enhance efficiency. In this study, the effects of the parameters used in diffuser design (foil type, diffuser length, tip clearance, and angle of attack) on the CP were investigated using Taguchi analysis, and an optimum diffuser design was developed for the Horizontal Axis Hydrokinetic Turbine (HAHT) based on the obtained experimental results. For the validation study of HAHT and CP calculations of the Diffuser-Augmented Hydrokinetic Turbine (DAHT), the Computational Fluid Dynamics (CFD) method was employed. According to the results of the Taguchi analysis, it was determined that diffuser length is the most influential parameter on the CP. Additionally, it was found that the effect of tip clearance on CP is relatively limited compared to other parameters. For the optimum operating parameters, maximum CP value was calculated as 0.7006. Consequently, a 67 % increase in the CP of the existing HAHT was achieved.Öğe Thermal management and fin characteristic optimization of an electronic power supply utilizing Taguchi and ANOVA methods(Pergamon-Elsevier Science Ltd, 2024) Bademlioglu, Ali Husnu; Karatas, Osman Bedrettin; Sokmen, Kemal Furkan; Yuruklu, EmrahIn the rapidly advancing field of electronic power supplies, managing thermal performance is critical. This study focuses on optimizing fin geometries to enhance the thermal management of an amplifier used in car multimedia systems, utilizing Taguchi and ANOVA methods for both thermal and volumetric efficiencies. Analyses were conducted on the impact of five distinct fin parameters-fin gap, fin thickness, separated plate thickness, fin base thickness, and fin height-on the system's thermal behavior and the fin volume. Computational Fluid Dynamics (CFD) analyses were performed for 24 different configurations. These analyses showed significant potential for improvement in the original design, with optimizations leading to an 8.31% reduction in the amplifier temperature and a 51.91% reduction in the fin volume. The study identifies fin height as the most effective parameter on the amplifier temperature, with an effect rate of 57.26%, while fin base thickness showed the most significant effect on the fin volume, with an effect rate of 66.98%. These findings not only provide a basis for more efficient design but also offer predictive insights through formulated regression equations, thus reducing the dependency on extensive experimental setups.Öğe Thermal optimization of intercellular distance in lithium-ion batteries and numerical analysis of the original honeycomb metal integrated battery pack(Elsevier, 2022) Karatas, Osman Bedrettin; Sokmen, Kemal FurkanIn Lithium-ion batteries, it is necessary to keep the system temperature within an acceptable range to extend the working life. A thermal management system is also required to maintain temperature uniformity. In this study, first, the steady and transient thermal behavior of 18650 Lithium-ion batteries was investigated, and the results were validated. After this, a module design consisting of 14 battery cells was made and the distance intercellular in this module was optimized. A thermal analysis study of the battery pack was carried out for the most suitable layout. In the study, the differences among modules with cell connection distances of 20, 25, 30, 35 and 40 mm were compared in terms of heat transfer and mounting. To calculate heat transfer data, a Computational Fluid Dynamics based program, FLOEFD was used. According to the results obtained from the analyses, it was determined that the distances between cell centers should be 20 mm, or 25 mm in terms of heat transfer and mounting. Additionally, the design of a metal insert with a honeycomb shape inside the plastic enclosure of the module containing 14 battery cells was examined. It was found that the designed metal insert package had a significant effect on lowering the temperature of the batteries. While the open module maximum temperature was 41.89 degrees C, the module maximum temperature in the package dropped to 37.39 degrees C. In addition, effective results were obtained for equal aging. The cell temperature differences were found to be 0.24 degrees C, 0.17 degrees C, and 0.59 degrees C for Aluminum, Copper and Steel, respectively in metal integrated battery pack analyzes.
