The effect on the heat transfer of laminarnanofluid flow over the elliptic tube bundle

Bu çalışmada, sabit duvar sıcaklığına sahip eliptik boru demeti üzerinden geçen CuOsu nanoakışkanın laminer akışının ısı transferine ve sürtünme faktörüne etkileri sayısal olarak incelenmiştir. Çalışmada, farklı kesit alanına sahip eliptik borular kademeli olarak yerleştirilmiş ve analizler iki boyutlu olarak gerçekleştirilmiştir. Kullanılan eşitlikler, sonlu hacimler metodu ile SIMPLE algoritması kullanılarak çözülmüştür. Sayısal incelemelerde, nanoakışkan tipi ve partikül hacim oranı (j) sabit tutulmuş, eliptik kanalın en/boy oranı (AR) ve Reynolds sayısı (Re) değiştirilerek incelemeler gerçekleştirilmiştir. Bu parametrelerin ısı transferi karakteristiği ve sürtünme faktörü üzerindeki etkileri taban akışkan ile de karşılaştırılmıştır. Boru demeti üzerinden nanoakışkanların laminer akışında anlık hız ve sıcaklık dağılımları elde edilmiştir. Sayısal sonuçlar, ısı transferindeki iyileşmenin eliptik kanal kesitinden ve Reynolds sayısından oldukça etkilendiğini göstermiştir. Nanoakışkan kullanımı ile ısı transferinin de arttığı, ancak bu artışın sürtünme faktöründe de bir miktar artışa sebep olduğu gözlemlenmiştir. En yüksek ısı transferi performansı, AR=1,0 ve Re=1000’de yaklaşık olarak %15 olarak elde edilmiştir. Çalışma sonucunda boru demetleri üzerinden nanoakışkanların laminer akışı için en iyi termo-hidrolik performansı sağlayan parametreler belirlenmiştir. En iyi termohidrolik performans Re=1000 için AR=0,5’te yaklaşık olarak %12 olarak elde edilmiştir.In this study, the effect of the laminar flow of CuO-water nanofluids through the elliptical tube bundle with constant wall temperature on the heat transfer and friction factor are investigated numerically. In the study, elliptical tubes with different cross-sectional area are placed staggered and the analyses are carried out for two dimensions. The governing equations are solved by using SIMPLE algorithm with finite volume method (FVM). In the studies, the nanofluid type and particle volume fraction (j) are kept constant, Reynolds number (Re) and aspect ratio of the elliptic channel (AR) are changed. The effects on the friction factor and the heat transfer characteristics of these parameters are also compared with the base fluid. In the laminar flow of the nanofluids over the tube bundle, instantaneous velocity and temperature distributions are obtained. Numerical results have shown that the improvement in heat transfer is highly affected by the elliptic channel cross-section and Reynolds number. It has been observed that the heat transfer increases with the use of nanofluid, but this increase also causes slightly increase in friction factor. The highest heat transfer performance is obtained as approximately 15% at AR=1,0 and Re=1000. As a result of the study, the parameters providing the best thermo-hydraulic performance for the laminar flow of the nanofluids on the tube bundles are determined. The best thermo-hydraulic performance is obtained as approximately 12% fort Re=1000 at AR=0,5

Investigation of heat transfer performance using an oscillating vertical flat plate

In this study, the heat transfer performance of an oscillating vertical flat plate is experimentally and numerically investigated. Rayleigh number (Ra), Womersley number (Wo), and dimensionless oscillation amplitude (Ao) are changed, and the effects of these parameters on heat transfer performance are analysed. The numerical simulations are performed using a finite volume method-based computational fluid dynamics procedure, and the numerical results are validated by comparisons with the experiments. To explain the heat transfer mechanism, the instantaneous velocity and temperature profiles on the plate surface are obtained. It has been observed that the periodic oscillations continuously renewed the velocity and thermal boundary layer, increased the convection effects, and improved the heat transfer. Consequently, the heat transfer performance was significantly affected by the oscillation parameters and increased as both Wo and Ao increased for all tested Rayleigh numbers (Ra). The maximum heat transfer improvement achieved was about 45% at a high amplitude (Ao = 1.4) and frequency (Wo = 146) at Rayleigh number (Ra = 1.17 × 107). The results are presented as a function of dimensionless numbers. Copyright

Düşey düz bir levhanın periyodik salınımlarının ısı transferine etkisi

Bu çalışmada, düşey düz bir levhanın periyodik salınımlarının ısı transferi üzerindeki etkisi deneysel ve sayısal olarak incelenmiştir. Deney sistemi, içinde deneysel modelin hareket ettiği şeffaf bir muhafazayı, modelin salınım hareketini üreten volan-motor sistemini, güç kaynağını, veri toplama sistemini ve bilgisayarı içerir. Deneysel model, üzerine termoelemanlar yerleştirilmiş iki bakır levha ve levhalar arasına yerleştirilmiş Kapton ısıtıcılardan oluşur. Çalışmada, levhanın yüzeyine uygulanan ısı akısı (q″), Womersley sayısı (Wo) ve boyutsuz salınım genliği (Ao) değiştirilmiş ve bu parametrelerin ısı transferi üzerindeki etkisi analiz edilmiştir. Ayrıca, çalışma deneysel verilere dayalı kontrol hacim tabanlı bir HAD çözücüsü kullanılarak sayısal olarak çözülmüştür. Sayısal sonuçlar, deneysel sonuçlarla karşılaştırılmıştır. Salınım genliği ve frekansının ısı transferine etkisini göstermek için levha yüzeyinde anlık hız ve sıcaklık görüntüleri elde edilmiştir. Sayısal ve deneysel sonuçlar, ısı transferinin salınım parametrelerinden önemli derecede etkilendiğini ve salınım genliği ve frekansının artması ile arttığını göstermiştir.In this study, effects on heat transfer of periodic oscillation of a vertical flat plate are experimentally and numerically investigated. The experimental setup includes a transparent enclosure hosting a moving experimental model, flywheel-motor assembly generating the oscillating movement of the model, power supply, data logger and personal computer. The experimental model comprises two copper plates with attached thermocouples and Kapton heaters placed between the plates. In the study, heat flux applied to surface of the plates (q″), the Womersley number (Wo) and dimensionless oscillation amplitude (Ao) are varied and the effect of these parameters on the heat transfer is analysed. Furthermore, the study is numerically solved using a control-volume based CFD solver based on experimental data. The numerical results are compared with the experimental results. Instantaneous velocity and temperature profiles of the plate are obtained to explain the heat transfer mechanism. The numerical and experimental results are shown heat transfer is significantly affected by oscillation parameters and the heat transfer increases with the increase in both oscillation amplitude and frequency

Effect on heat transfer of periodic oscillations of a vertical flat plate

Bu çalışmada, düşey düz bir levhanın periyodik salınımlarının ısı transferi üzerindeki etkisi deneysel ve sayısal olarak incelenmiştir. Deney sistemi, içinde deneysel modelin hareket ettiği şeffaf bir muhafazayı, modelin salınım hareketini üreten volan-motor sistemini, güç kaynağını, veri toplama sistemini ve bilgisayarı içerir. Deneysel model, üzerine termoelemanlar yerleştirilmiş iki bakır levha ve levhalar arasına yerleştirilmiş Kapton ısıtıcılardan oluşur. Çalışmada, levhanın yüzeyine uygulanan ısı akısı (q″), Womersley sayısı (Wo) ve boyutsuz salınım genliği (Ao) değiştirilmiş ve bu parametrelerin ısı transferi üzerindeki etkisi analiz edilmiştir. Ayrıca, çalışma deneysel verilere dayalı kontrol hacim tabanlı bir HAD çözücüsü kullanılarak sayısal olarak çözülmüştür. Sayısal sonuçlar, deneysel sonuçlarla karşılaştırılmıştır. Salınım genliği ve frekansının ısı transferine etkisini göstermek için levha yüzeyinde anlık hız ve sıcaklık görüntüleri elde edilmiştir. Sayısal ve deneysel sonuçlar, ısı transferinin salınım parametrelerinden önemli derecede etkilendiğini ve salınım genliği ve frekansının artması ile arttığını göstermiştir.In this study, effects on heat transfer of periodic oscillation of a vertical flat plate are experimentally and numerically investigated. The experimental setup includes a transparent enclosure hosting a moving experimental model, flywheel-motor assembly generating the oscillating movement of the model, power supply, data logger and personal computer. The experimental model comprises two copper plates with attached thermocouples and Kapton heaters placed between the plates. In the study, heat flux applied to surface of the plates (q″), the Womersley number (Wo) and dimensionless oscillation amplitude (Ao) are varied and the effect of these parameters on the heat transfer is analysed. Furthermore, the study is numerically solved using a control-volume based CFD solver based on experimental data. The numerical results are compared with the experimental results. Instantaneous velocity and temperature profiles of the plate are obtained to explain the heat transfer mechanism. The numerical and experimental results are shown heat transfer is significantly affected by oscillation parameters and the heat transfer increases with the increase in both oscillation amplitude and frequency

Mixed convection heat transfer from a vertical flat plate subjected to periodic oscillations

In this study, effects on mixed convection heat transfer of oscillation parameters on a vertical flat plate surface subjected to constant heat flux are experimentally and numerically investigated. The experimental setup includes a hanger-pulley system installed above a transparent enclosure contain a moving experimental model, flywheel-motor assembly generating the oscillating movement of the experimental model, power supply, and datalogger. The experimental model comprises two copper plates with attached thermocouples and Kapton heaters placed between the plates. In the study, heat flux applied to surface of the plates (q”), the Womersley number (Wo) and dimensionless oscillation amplitude (Ao) are varied. The effects of these parameters on the heat transfer performance are analyzed. This study is numerically solved using a control-volume based Computational Fluid Dynamics solver based on experimental data. The numerical results are compared with the experimental results and open literature. Instantaneous velocity and temperature profiles on the plate are obtained to explain the heat transfer mechanism. According to the numerical and experimental results, heat transfer performance is significantly affected by oscillation parameters and heat flux applied to the plate surface. The mixed convection heat transfer increases with the increase in oscillation parameters for all tested heat fluxes. The obtained results are presented as a function of dimensionless numbers

Heat transfer enhancement iheat transfer enhancement in a channel with inclined baffles under pulsating flow: a cfd studyn a channel with inclıned baffles under pulsating flow: a cfd study

This study numerically investigated hydraulic and thermal performance in a channel with inclined baffles under pulsating flow conditions. The baffles were placed in a staggered arrangement. The governing equations were discretized with the finite volume method (FVM), and the pressure-velocity coupling was handled by the SIMPLE algorithm. The Strouhal number (St: 0.5, 1, 2, 3, and 4), pulsation amplitude (A: 0.2, 0.5, and 0.8), and Reynolds number (200 ≤ Re ≤ 1000) were changed. The top and bottom surfaces of the channel were kept at Tw = 350 K, and thermal improvement and friction factor were calculated for a pulsating cycle. The results were given in terms of thermal enhancement (η), relative friction factor (frel), and performance evaluation criteria (PEC). The flow and temperature contours were presented to determine the impacts of the pulsation frequency, the pulsation amplitude, and the Reynolds number. The results showed that the pulsation amplitude and the pulsation frequency contributed remarkably to thermal enhancement with increasing Reynolds numbers, while the heat transfer improved significantly depending on pulsation parameters together with a slight rise in friction factor. The highest thermal enhancement achieved was about 1.47 at Re = 1000, A = 0.8, and St = 4. The highest PEC obtained was approximately 1.12 at Re = 1000, A= 0.2, and St = 4. © 2023 Begell House Inc.. All rights reserved

Performance of Using Tag-based Feature Sets in Web Page Classification

As the Web is a large collection of data growing daily, an automatic Web page classification mechanism is needed to effectively reach to useful information. Majority of the Web pages are in the form of HTML documents, therefore the aim of this study is to explore the effect of HTML tags on classification process, and try to determine the most valuable HTML tags for feature extraction of the classification task. To achieve this goal, we employ 13 different datasets, and use 5 popular classifiers that are SVM, naïve bayes (NB), kNN, C4.5, and OneR. The statistical analysis shows that, the features extracted by using solely the anchor, <p> or <title> tags can be used as an alternative to the features extracted from the whole Web page. SVM is the best among the classifiers used in this study. Using the HTML tags for feature extraction improves classification accuracy

Heat transfer in a triangular wavy channel with cuo-water nanofluids under pulsating flow

WOS: 000460088000017In this paper; heat transfer and pressure drop characteristics of CuO-water nano-fluid flow in a isothermally heated triangular-wavy channel under pulsating inlet conditions are numerically investigated. A numerical simulation is conducted by solving the governing continuity, momentum, and energy equations for laminar flow using the finite volume approach. In the studies, the main parameters including the Reynolds number, pulsating amplitude and frequency, are changed while the nanoparticle volume fraction and the other parameters are kept constant for all cases. Numerical results are compared with the steady flow conditions, which showed that heat transfer performance significantly increases due to improve thermal conductivity and the use of nanoparticles in the pulsating flow conditions. The results indicate that there is a high potential for promoting the thermal performance enhancement by using nanoparticles under pulsating flow in wavy channels. It is found that the heat transfer enhancement increases with increasing pulsating amplitude and Reynolds number, and there is a slight increase in pressure drop. The obtained results are given as a function of dimensionless parameters