Makine Mühendisliği Bölümü

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EXPERIMENTAL AND NUMERICAL ANALYSIS OF FLOW OVER A PICKUP TRUCK
(2021) İnce, İbrahim Timuçin; Mercan, Hatice; Onur, Nevzat
The drag forces and the overall drag coefficient of a typical pickup truck are investigated experimentally and the 3D numerical analysis is performed. A detailed 1/4-scale model is constructed and experiments are performed at Reynolds numbers around 2 × 106in the Ankara Wind Tunnel (ART). The experimental study is divided into two stages: in the first stage the pressure distribution along the symmetry axis is measured and in the second stage the drag forces and overall drag coefficient are measured at five different wind speeds. The measured data are compared with the 3D numerical simulation performed in FLUENT. The turbulence standard, realizable, and RNG k-∈ models, the standard and SST k-ω models, and finally the RSM are compared for three near-wall treatments: standard wall function, nonequilibrium wall function, and enhanced wall function. The comparison revealed that for lower velocities the best turbulence model-wall treatment couple is the realizable k-∈ model with Reynolds stress model with standard wall function, whereas for higher velocities the standard k-∈ turbulence model is observed to be more compatible with experimental data. The highest pressure value is measured in front of the pickup truck and the lowest pressure value is evaluated at the rim where the windshield and the roof meet. © 2021 Begell House Inc.. All rights reserved.
Citation - Scopus: 4
Fused Filament Fabrication in Cad Education: a Closed-Loop Approach
(Sage Publications inc, 2025) Totuk, Onat Halis; Selvi, Ozguen; Akar, Samet
Integrating low-cost fused filament fabrication 3D printing as a foundation for learning 3D modelling is explored. This method blends traditional computer aided design (CAD) instruction with additive manufacturing possibilities. Experimental results demonstrate increased comprehension speed and reduced learning time. This hands-on approach empowers students by enabling direct engagement with the modelling process. Analogous to reverse engineering, the strategy instructs engineering students from final product to model creation, closing the gap between theory and practice. Incorporating 3D printing bridges this divide, enhancing understanding, creativity and problem-solving. The study underscores technology's influence on learning strategies, aligning with the surge of 3D printing in education. Results link advanced design technology usage to improved student performance, with 3D-printed materials yielding 45% higher grades and 30% faster task completion. This study advocates curricular advancement for design-focused careers through enhanced technology integration and favourable 3D printing model reception.
Citation - WoS: 7
Citation - Scopus: 7
Development and Experimental Investigation of Electrochemical Drilling Method Using Rotary Tube Tool
(Gazi Univ, Fac Engineering Architecture, 2013) Ozerkan, H. Bekir; Çoğun, Can; Cogun, Can; Mekatronik Mühendisliği
In this study, a new hybrid electrochemical drilling (ECD) method, based on electrochemical machining in nonconventional machining processes, was developed. In the developed method, tube tool makes rotary motion together with inner through hole flushing. A small scale prototype ECD machine has been designed and manufactured to test the developed method. One of the important features of the new system is the regulation of tool feed rate using current feedback control. The Hadfield (manganese) steel, whose strain hardening behavior makes it very difficult to machine with conventional methods, and AISI 1040 steel, whose machinability is fairly good, were drilled using the prototype machine and results were compared. Workpiece material removal rate increased with the increasing machining voltage, tool rotational speed, electrolyte concentration and flushing pressure in both types of steels. Average radial overcut values increased with the rotational speed of the tool. The AISI 1040 steel hole geometries were regular than that of Hadfield steel. Experimental results showed that deep holes can be drilled successfully with the proposed hybrid ECD method.
Citation - WoS: 2
Citation - Scopus: 3
On the Stability of Inverse Dynamics Control of Flexible-Joint Parallel Manipulators in the Presence of Modeling Error and Disturbances
(Tubitak Scientific & Technological Research Council Turkey, 2019) Korkmaz, Ozan; Denizli, Mustafa Semih; Ider, Sitki Kemal
Inverse dynamics control is considered for flexible-joint parallel manipulators in order to obtain a good trajectory tracking performance in the case of modeling error and disturbances. It is known that, in the absence of modeling error and disturbance, inverse dynamics control leads to linear fourth-order error dynamics, which is asymptotically stable if the feedback gains are chosen to make the real part of the eigenvalues of the system negative. However, when there are modeling errors and disturbances, a linear time-varying error dynamics is obtained whose stability is not assured only by keeping the real parts of the frozen-time eigenvalues of the system negative. In this paper, the stability of such systems is investigated and it is proved that the linear time-varying system can be rendered stable by selecting the feedback gains such that the variation of the system becomes sufficiently slow. To illustrate the performance of the control method, deployment motion of a 3-(R) under bar PR planar parallel manipulator subject to impact is simulated. For the impact model, the impulse-momentum and the coefficient of restitution equations for the system are derived.
Citation - WoS: 3
Citation - Scopus: 5
Optimization of Vortex Promoter Parameters To Enhance Heat Transfer Rate in Electronic Equipment
(Asme, 2020) Ayli, Ece; Bayer, Ozgur
In this paper, optimization of the location and the geometry of a vortex promoter located above in a finned surface in a channel with eight heat sources is investigated for a Reynolds number of 12,500 < Re < 27,700. Heat transfer rates and the corresponding Nusselt number distributions are studied both experimentally and numerically using different vortex promoter geometries (square, circular, and triangular) in different locations to illustrate the effect of vortex promoter on the fluid flow. Optimization study considered a range of following parameters: blockage ratio of 0.30<(y/C) < 0.45 and interpromoter distance ratio of 0.2277 <(x/L) < 0.3416. Results show that fins over which rectangular and circular promoters are integrated perform better in enhancing the heat transfer. According to the numerical and experimental results, higher blockage ratios cause significantly higher heat transfer coefficients. According to the observations, as the interpromoter distances increase, shedding gains strength, and more turbulence is created. All vortex promoters enhance heat transfer resulting in lower temperature values on the finned surface for different (y/C) and (x/L) values and Reynolds numbers. The use of promoters enhances the heat transfer, and the decrease in the maximum temperature values is recorded on the finned surface changing between 15% and 27%. The biggest decrease in maximum surface temperature value is 500 K-364 K and observed in circular promoter case with (y/C) = 0.43, (x/L) = 0.3416, and Reynolds numbers of 22,200.
Citation - WoS: 5
Citation - Scopus: 6
Prediction of the Heat Transfer Performance of Twisted Tape Inserts by Using Artificial Neural Networks
(Korean Soc Mechanical Engineers, 2022) Kocak, Eyup; Ayli, Ece
A numerical study is undertaken to investigate the effect of twisted tape inserts on heat transfer. Twisted tapes with various aspect ratios and single, double, and triple inserts are placed inside a tube for Reynolds numbers ranging from 8000 to 12000. Numerical results show that the tube with a twisted tape and different numbers of tape is more effective than the smooth tube in terms of thermo-hydraulic performance. The highest heat transfer is achieved with the triple insert, with the highest turning number and an increment of 15 %. Then, an artificial neural network (ANN) model with a three-layer feedforward neural network is adopted to obtain the Nusselt number on the basis of four inputs for a heated tube with a twisted insert. Several configurations of the neural network are examined to optimize the number of neurons and to identify the most appropriate training algorithm. Finally, the best model is determined with one hidden layer and thirteen neurons in the layer. Bayesian regulation is chosen as the training algorithm. With the optimized algorithm, excellent precision for measuring the output is provided, with R2 = 0.97043. In addition, the optimized ANN architecture is applied to similar studies in the literature to predict the heat transfer performance of twisted tapes. The developed ANN architecture can predict the heat transfer enhancement performance of similar problems with R2 values higher than 0.93.
Citation - WoS: 17
Citation - Scopus: 20
Experimental Investigation of Flow and Heat Transfer in Rectangular Cross-Sectioned Duct With Baffles Mounted on the Bottom Surface With Different Inclination Angles
(Springer, 2014) Onur, Nevzat; Arslan, Kamil
In this study, steady-state forced convection heat transfer and pressure drop characteristics in a horizontal rectangular cross-sectioned duct, baffles mounted on the bottom surface with different inclination angles were investigated experimentally in the Reynolds number range from 1 x 10(3) to 1 x 10(4). The study was performed under turbulent flow conditions. Effects of different baffle inclination angles on flow and heat transfer were studied. Results are also presented in terms of thermal enhancement factor. It is observed that increasing in baffle inclination angle enhances the heat transfer and causes an increase in pressure drop in the duct.
Citation - WoS: 12
Citation - Scopus: 16
Fast Fluorometric Enumeration of E. Coli Using Passive Chip
(Elsevier, 2019) Cogun, Ferah; Yildirim, Ender; Boyaci, Ismail Haklu; Cetin, Demet; Ertas, Nusret; Kasap, Esin Nagihan; Dogan, Uzeyir
In this report, a passive microfluidic chip design was developed for fast and sensitive fluorometric determination of Escherichia coli (E. coli) based on sandwich immunoassay. Initially, magnetic nanoparticles (MNPs) and chitosan modified mercaptopropionic acid capped cadmium telluride (CdTe) quantum dots (QDs) were functionalized with E.coli specific antibody to form a sandwich immunoassay with the E. coli. The magnetic separation and preconcentration of the E.coli from the sample solution was performed in the vial. Conjugation of QDs to the magnetically captured E. coli and washing were performed using a passive type of microchip. The microfluidic chip consists of four microchambers connected to each other by microchannels which act as capillary valves. Signal measurement was performed at the last chamber by using a hand-held spectrofluorometer equipped with a fiber optic reflection probe. The selectivity of the method was tested with Enterobacter aerogenes (E. aerogenes) and Salmonella enteritidis (S. enteritidis), it was observed that these bacteria have no interference effect on E.coli determination. The calibration curve was found to be linear in the range of 10(1)-10(5) cfu/mL with a correlation coefficient higher than 0.99. The limit of detection was calculated as 5 cfu/mL. The method was successfully applied to spiked tap and lake water samples. The results suggest that the developed method is applicable for on-site E. coli detection and offers several advantages such as large dynamic range, high sensitivity, high selectivity and short analysis time.
Citation - WoS: 1
Citation - Scopus: 1
Analyses of Plate Perforation for Various Penetrator-Target Plate Combinations
(Korean Soc Mechanical Engineers, 2022) Akyurek, Turgut
In this study, kinetics and kinematics of perforation process for various penetrator-target plate combinations is analyzed, a methodology in a flow chart format to decide on failure mode, and for each failure mode, an appropriate combined analytical model that requires only common test data is proposed. The proposed methodology and analytical models that are recommended for the related failure mode are assessed by using a huge amount of test data from the literature. The penetrator-target plate configurations cover the penetrators with ogive, conical, hemi-spherical and blunt noses, at different plate thicknesses, and plate thickness to penetrator diameter ratios, made of different metallic materials. Analyzed failure modes include ductile hole enlargement, plugging, dishing, and petal forming. Assessment is done for impact velocities ranging between 215-863 m/s. The estimations based on the proposed flow chart and recommended failure models are in good agreement with the related test data and numerical analysis results.
Kinematic Analyses of Metallic Plate Perforation by Penetrators With Various Nose Geometries
(defence Scientific information Documentation Centre, 2022) Akyurek, T.
This study analyses kinematics of a metallic plate perforation by a penetrator with truncated ogive nose geometry to find solutions also to blunt, conical, ogive, and hemi-spherical nosed penetrators. Plugging, ductile hole enlargement, dishing, and petal forming failure modes are used in the analyses. Acceleration throughout perforation is calculated by using the related failure mode, analytical model, and the target-penetrator interaction geometry. Depending on the failure model; back lip and front lip formation during ductile hole enlargement, plug formation during plugging, and deflection of target plate during dishing is also analysed. Analyses are based on projectile???s equation of motion, momentum and energy equations, and projectile-target plate interactions. The analyses results for selected cases, with the impact velocity range 215-863 m/s, are compared with the test data. The residual velocity estimation for a strike velocity is close to the related test data with an error of 0.3-2.2 %, except for conical nosed penetrators at impact velocities approaching the ballistic limit velocity.
Citation - WoS: 8
Citation - Scopus: 8
Supervised Learning Method for Prediction of Heat Transfer Characteristics of Nanofluids
(Korean Soc Mechanical Engineers, 2023) Kocak, Eyup; Ayli, Ece
This study focuses on the alication and investigation of the predictive ability of artificial intelligence in the numerical modelling of nanofluid flows. Numerical and experimental methods are powerful tools from an accuracy point of view, but they are also time- and cost-consuming methods. Therefore, using soft-computing techniques can improve such CFD drawbacks by patterning the CFD data. After obtaining the aropriate ANN and ANFIS architecture using the CFD data, many new data can be created without requiring numerical and experimental methods. In the scope of this research, the FCM-ANFIS and ANN methods are used to predict the thermal behaviour of the turbulent flow in a heated pipe with several nanoparticles. A parametric CFD study is carried out for water-TiO2, water-CuO, and water-SiO2 nanofluid through a pipe. The Reynolds number is varied between 7000 and 15000, and the nanofluid concentration is varied between 0.25 % and 4 %. The effects of using nanofluid on local values of Nusselt number and shear stress distribution were investigated. Numerical results indicate that with the increasing nanoparticle volume fraction of nanofluid, the average Nusselt number increases, but the required pumping power also increases. The obtained soft computing results demonstrate that the FCM clustering ANFIS has given better results both in training and testing when it is compared to the ANN architecture with an R-2 of 0.9983. Regarding this, the FCM-ANFIS is an excellent candidate for calculating the Nusselt number in heat transfer problems.
Citation - WoS: 4
Citation - Scopus: 4
Critical Decision Making for Rehabilitation of Hydroelectric Power Plants
(Taylor & Francis inc, 2023) Westerman, Jerry; Celebioglu, Kutay; Ayli, Ece; Ulucak, Oguzhan; Aradag, Selin
Due to their diminishing performance, reliability, and maintenance requirements, there has been a rise in the demand for the restoration and renovation of old hydroelectric power facilities in recent decades. Prior to initiating a rehabilitation program, it is crucial to establish a comprehensive understanding of the power plant's current state. Failure to do so may result in unnecessary expenses with minimal or no improvements. This article presents a systematic rehabilitation methodology specifically tailored for Francis turbines, encompassing a methodological approach for condition assessment, performance testing, and evaluation of rehabilitation potential using site measurements and CFD analysis, and a comprehensive decision-making process. To evaluate the off-design performance of the turbines, a series of simulations are conducted for 40 different flow rate and head combinations, generating a hill chart for comprehensive evaluation. Various parameters that significantly impact the critical decision-making process are thoroughly investigated. The validity of the reverse engineering-based CFD methodology is verified, demonstrating a minor difference of 0.41% and 0.40% in efficiency and power, respectively, between the RE runner and actual runner CFD results. The optimal efficiency point is determined at a flow rate of 35.035 m(3)/s, achieving an efficiency of 94.07%, while the design point exhibits an efficiency of 93.27% with a flow rate of 38.6 m(3)/s. Cavitation is observed in the turbine runner, occupying 27% of the blade suction area at 110% loading. The developed rehabilitation methodology equips decision-makers with essential information to prioritize key issues and determine whether a full-scale or component-based rehabilitation program is necessary. By following this systematic approach, hydroelectric power plants can efficiently address the challenges associated with aging Francis turbines and optimize their rehabilitation efforts.
Modeling and Optimization of a Peano-Hasel Actuator Peristaltic Pump
(Natl inst Science Communication-niscair, 2023) Mistikoglu, Selcuk; Totuk, Onat Halis
Peano-Hasel (hydraulically amplified self-healing electrostatic) pumps are crucial devices with unique mechanisms and versatile applications. They simulate muscle contractions to move fluids or materials through tubes. The Peano-Hasel method, a specific design, achieves flow by compressing a segmented tube externally. Exploring the design aspects of Peano-Hasel pumps can lead to advancements in optimizing their performance, efficiency, reliability, and control systems. This paper presents a novel method of peristaltic pumping on soft pipes using Peano-HASEL actuators. In the study, a design evaluation of an external ring-type pump over a PDMS (Polydimethylsiloxane -commonly referred to as silicone) tube containing Newtonian fluids is made, and a novel multi-pouch ring shape design is proposed. Our method utilizes a peripheral and compact design that allows for more efficient sinusoidal pumping action. The close proximity of the rings in the longitudinal direction enhances the effectiveness of the pumping process. The actuator is analytically modeled and optimized for maximum areal contraction and flow rate using a differential evolution algorithm. A MATLAB Simulink Simscape model is generated, and the system is simulated. As a result, an optimal solution for the number of pouches was found to be eight, considering ring geometry and applicability. It was also seen from the simulation that a sinusoidal squeezing scheme of a ring-type pump creates the desired action. Based on the analytical model presented, it has been demonstrated that the optimal flow rate is achieved when there are eight pouches, and they are fully circular after being energized.
Citation - WoS: 3
Citation - Scopus: 4
Performance Optimization of Finned Surfaces Based on the Experimental and Numerical Study
(Asme, 2023) Ayli, Ece; Kocak, Eyup; Turkoglu, Hasmet
This paper presents the findings of numerical and experimental investigations into the forced convection heat transfer from horizontal surfaces with straight rectangular fins at Reynolds numbers ranging from 23,600 to 150,000. A test setup was constructed to measure the heat transfer rate from a horizontal surface with a constant number of fins, fin width, and fin length under different flow conditions. Two-dimensional numerical analyses were performed to observe the heat transfer and flow behavior using a computer program developed based on the openfoam platform. The code developed was verified by comparing the numerical results with the experimental results. The effect of geometrical parameters on heat transfer coefficient and Nusselt number was investigated for different fin height and width ratios. Results showed that heat transfer can be increased by modifying the fin structure geometrical parameters. A correlation for Nusselt number was developed and presented for steady-state, turbulent flows over rectangular fin arrays, taking into account varying Prandtl number of fluids such as water liquid, water vapor, CO2, CH4, and air. The correlation developed predicts the Nusselt number with a relative root mean square error of 0.36%. This research provides valuable insights into the effects of varying Prandtl numbers on the efficiency of forced convection cooling and will help in the design and operation of cooling systems. This study is novel in its approach as it takes into account the effect of varying Prandtl numbers on the heat transfer coefficient and Nusselt number and provides a correlation for the same. It will serve as a valuable reference for engineers and designers while designing and operating cooling systems.
Citation - WoS: 4
Citation - Scopus: 7
Enhanced Gradient Crystal-Plasticity Study of Size Effects in a Β-Titanium Alloy
(Iop Publishing Ltd, 2017) Nowag, Kai; Roy, Anish; Ghisleni, Rudy; Michler, Johann; Silberschmidt, Vadim V.; Demiral, Murat
A calibrated model of enhanced strain-gradient crystal plasticity is proposed, which is shown to characterize adequate deformation behaviour of bcc single crystals of a beta-Ti alloy (Ti-15-3-3-3). In this model, in addition to strain gradients evolving in the course of deformation, incipient strain gradients, related to a component's surface-to-volume ratio, is accounted for. Predictive capabilities of the model in characterizing a size effect in an initial yield and a work-hardening rate in small-scale components is demonstrated. The characteristic length-scale, i.e. the component's dimensions below which the size effect is observed, was found to depend on densities of polar and statistical dislocations and interaction between them.
Citation - WoS: 3
Citation - Scopus: 3
A Comparative Study of Effects of Additive Particle Size and Content on Wetting Behavior and Brazing Performance of C/Sic Composite
(Springer, 2023) Esen, Ziya; Dericioglu, Arcan F.; Saltik, Simge
This study has focused on the influence of size and content of SiC particle incorporation on the wetting behavior of the Ticusil brazing filler alloy and on its brazing performance in C/SiC composite/Ti6Al4V alloy joints. The effect of the size and content of additive SiC particles on the variation of molten brazing filler alloy contact angle was recorded at various brazing time and temperatures. Moreover, the microstructural evolution and mechanical properties of the additive containing C/SiC composite/Ti6Al4V alloy joints produced by the brazing method were investigated. The contact angles in both brazing filler alloys containing nano- and micro-sized SiC particles exhibited a sudden decrease with time during isothermal holding as observed in as-received brazing filler alloys. As the quantity of the SiC particles increased in the brazing alloy, the recorded contact angle values including the final, stable contact angle increased, while the time for the drastic contact angle change also increased remarkably. Compared to as-received counterparts, the addition of 2 wt.% nano-sized SiC and 1 wt.% micro-sized SiC particles improved the shear strength of the joints by 35 and 8%, respectively. Although the recorded contact angle values were close to each other in brazing alloys containing SiC particles with different sizes (37 and 42 degrees for 1 wt.% micro-sized and 2 wt.% nano-sized additions), higher increment was achieved in the mechanical performance of the joints with nano-sized SiC additive due to more homogeneous reinforcement effect of the nanoparticles. The results indicated that the optimum brazing filler alloy contact angle for the highest shear strength is similar to 40 degrees for both nano- and micron-sized additive containing Ticusil filler alloy.
Citation - WoS: 8
Citation - Scopus: 9
Analysis of Heat Transfer Enhancement of Passive Methods in Tubes With Machine Learning
(Sage Publications Ltd, 2024) Ayli, Ece; Turkoglu, Hasmet; Yapici, Ekin Ozgirgin
This study investigates the efficacy of machine learning techniques and correlation methods for predicting heat transfer performance in a dimpled tube under varying flow conditions, including the presence of nanoparticles. A comprehensive numerical analysis involving 120 cases was conducted to obtain Nusselt numbers and friction factors, considering different dimple depths and velocities for both pure water and water-Al2O3 nanofluid at 1%, 2%, and 3% volume concentrations. Utilizing the data acquired from the numerical simulations, a correlation equation, SVM ANN architectures were developed. The predictive capabilities of the statistical approach, ANN, and SVM models for Nusselt number distribution and friction factor were meticulously assessed through mean average percentage error (MAPE) and correlation coefficients (R2). The research findings reveal that machine learning techniques offer a highly effective approach for accurately predicting heat transfer performance in a dimpled tube, with results closely aligned with Computational Fluid Dynamics (CFD) simulations. Particularly noteworthy is the superior performance of the ANN model, demonstrating the most precise predictions with an error rate of 2.54% and an impressive R2 value of 0.9978 for Nusselt number prediction. In comparison, the regression model achieved an average error rate of 6.14% with an R2 value of 0.8623, and the SVM model yielded an RMSE value of 2.984% with an R2 value of 0.9154 for Nusselt number prediction. These outcomes underscore the ANN model's ability to effectively capture complex patterns within the data, resulting in highly accurate predictions. In conclusion, this research showcases the promising potential of machine learning techniques in accurately forecasting heat transfer performance in dimpled tubes. The developed ANN model exhibits notable superiority in predicting Nusselt numbers, making it a valuable tool for enhancing thermal system analyses and engineering design optimization.
Citation - WoS: 31
Citation - Scopus: 37
Void Growth in High Strength Aluminium Alloy Single Crystals: a Cpfem Based Study
(Iop Publishing Ltd, 2017) Siddiq, M. Amir; Demiral, Murat; Asim, Umair
High strength aluminium alloys that are produced through forming and joining processes are widely used in aerospace components. The ductile failure in these metals occurs due to the evolution and accumulation of microscopic defects, such as microvoids and shear bands. The present work investigates the underlying physical mechanisms during ductile failure by performing a rigorous, fully-validated, three-dimensional crystal plasticity, finite element study with aluminium alloy single crystals. Representative volume element (RVE) based simulations of single crystalline aluminium alloys (AA-5xxx) with different void geometries and orientations have been performed. Both local and nonlocal crystal plasticity constitutive models have been implemented in a finite element framework and are used to seek new insights into the interrelationships among void growth, initial porosity, initial void size, plastic anisotropy, and local/nonlocal size effects.
Citation - WoS: 5
Citation - Scopus: 5
Analysis and Testing of a Contraction-And Micromixer for Micromilled Microfluidics
(Springer Heidelberg, 2017) Yildirim, Ender
In this paper, numerical analysis and experimental investigation of a micromixer, which was specifically designed for microfluidic devices fabricated by micromilling, is presented. The mixer is composed of series of contractions and expansions in zigzag arrangement along a mixing channel. Mixers, fabricated by micromilling on polymethylmethacrylate (PMMA), were tested with %0.1 Ponceau 4R red food dye solution and distilled water. According to experiment results, over 70% mixing efficiency could be obtained for the flows with Reynolds number (Re) greater than 40. It was also numerically shown that by increasing the number of successive contractions and expansions, it could be possible to achieve over 80% mixing efficiency when Re = 55 for the species with diffusion coefficient of 5 x 10(-9) m(2)/s. Although the micromixer was specifically designed for micromilling, it is expected that the mixer can be useful in any microfluidic device fabricated by any other technique.
Experimental and Numerical Investigation of Transition To Turbulent Flow and Heat Transfer Inside a Horizontal Smooth Rectangular Duct Under Uniform Bottom Surface Temperature
(Springer, 2013) Onur, Nevzat; Arslan, Kamil
In this study, steady-state turbulent forced flow and heat transfer in a horizontal smooth rectangular duct both experimentally and numerically investigated. The study was carried out in the transition to turbulence region where Reynolds numbers range from 2,323 to 9,899. Flow is hydrodynamically and thermally developing (simultaneously developing flow) under uniform bottom surface temperature condition. A commercial CFD program Ansys Fluent 12.1 with different turbulent models was used to carry out the numerical study. Based on the present experimental data and three-dimensional numerical solutions, new engineering correlations were presented for the heat transfer and friction coefficients in the form of and , respectively. The results have shown that as the Reynolds number increases heat transfer coefficient increases but Darcy friction factor decreases. It is seen that there is a good agreement between the present experimental and numerical results. Examination of heat and mass transfer in rectangular cross-sectioned duct for different duct aspect ratio (alpha) was also carried out in this study. Average Nusselt number and average Darcy friction factor were expressed with graphics and correlations for different duct aspect ratios.

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