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Due to the increasing energy demand and unit prices in all sectors, there is a growing trend towards renewable energy sources and an increase in energy efficiency efforts. One way to make energy more efficient is to increase the amount of heat transfer. One of the methods used to increase heat transfer is through extended (finned) heat transfer surfaces. In this study, the heat of the vapor phase propane (R290) in the compressor discharge line is utilized by passing through the finned tube inside the hot water tank The propane passing through the finned tube will cause the water in the tank to start heating. In situations where heat is needed in the system, heated water (defrosting, product heating, etc.) is used without consuming additional energy. The study examined the effect of changes in fin thickness, fin spacing according to different temperature differentials on heat transfer, as well as the impact of fin length and fin count. As a result of the study, an increase in fin thickness and fin spacing led to a decrease in the amount of heat transfer from the tube. It was observed that as fin thickness and fin spacing increased, the tube length extended, and the number of fins decreased. For water with a temperature difference of 45°C, calculations revealed that a tube with a fin thickness of 0.4 mm has a length of 16.98 cm and a fin count of 58. The use of finned tubes, in addition to shortening the tube length, also reduces the refrigerant charge amount. [ABSTRACT FROM AUTHOR]

It is known that nanoparticle additives have significant effects on increasing the thermal efficiency of thermal systems. The aim of this study is to examine the thermal performance of thermosiphon heat pipes (THP), one of the heat pipe types with the lowest manufacturing costs, by adding hybrid nanoparticles to the working fluid and to investigate the effects of hybrid nanoparticle addition. The effects of filling ratio and concentration on thermal performance were examined. It has been observed that the Al2O3+TiO2–H2O hybrid nanofluid can combine the high stability feature of one of the individual nanofluids with the high thermal conductivity feature of the other. It has been observed that the highest thermal efficiency in the hybrid nanofluid-filled system was achieved at 65% filling rate. Considering the combined effect of the two parameters by considering the filling rate together with the nanofluid concentration, it was seen that the condition where maximum performance was achieved was 65% filling rate and 0.5% nanofluid concentration. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bu çalışmada, periyodik dalgalı bir kanalda laminar pulsatif akışın hidrolik ve termal davranışları üzerindeki etkileri sayısal olarak analiz edilmiştir. Sayısal çözümler, sonlu hacim yaklaşımı ile analiz yapan FLUENT programı ile gerçekleştirilmiştir. Çalışmada, pulsatif genlik (A), Strouhal sayısı (St), Reynolds sayısı (Re) değiştirilmiş, diğer parametreler sabit tutulmuştur. Dalgalı kanalın alt ve üst yüzeyleri T=350K sıcaklığında korunmuştur. Sayısal sonuçlar, Nusselt sayısı (Nu), sürtünme faktörü (f) ve termo-hidrolik etkinlik (THE) açısından sürekli akış şartları ile karşılaştırılarak sunulmuştur. Pulsatif parametrelerin ve Reynolds sayısının kanal içindeki davranışını gözlemlemek için anlık akış ve sıcaklık dağılımları elde edilmiştir. Çalışma sonuçları, kanal içindeki akışın kanal geometrisinden, pulsatif parametrelerden ve Reynolds sayısından önemli derecede etkilendiğini göstermiştir. Artan Reynolds sayısı ve pulsatif parametreler ile hafif bir basınç düşüşü ile ısı transferinde kayda değer bir iyileşme sağlanmıştır.

In this study, the impact of geometric parameters of rectangular baffles with varying location angles and heights is investigated on the heat transfer and fluid flow characteristics of cross-triangular grooved channels. Computational methods are employed to explore these effects, utilizing the Ansys-Fluent program to solve the Navier-Stokes and energy equations, incorporating the k-e turbulence model for numerical simulations. The inlet temperature of the air, serving as the working fluid, is set at 293 K, while the wall surface temperature of the lower triangular grooved channel remains fixed at 373 K. Rectangular baffles are tested with angles of 30°, 60°, and 90°, and heights of 0.25H, 0.5H, and 0.75H, respectively. The numerical results show good agreement with a 3.53% deviation compared to existing empirical data in the literature. The obtained findings are presented in terms of mean Nusselt (Num) number, fluid temperature, and Performance Evaluation Criterion (PEC) number variations taking into consideration of pressure drop for each rectangular baffle angle and height. Additionally, contour distributions of temperature and velocity are evaluated for different Reynolds numbers (Re) and arrangements of rectangular baffles. It has been determined that the Nu number value increases by 197.56% at a 90° angle and 0.75H height, compared to the 0.25H baffle height at Re=6000. Furthermore, at Re=1000, the PEC number is 84.50% higher with a baffle height of 0.25H and a baffle angle of 30° compared to the condition with a 90° angle. [ABSTRACT FROM AUTHOR]

Unsteady laminar confined and unconfined fluid flow and mixed (forced and free) convection heat transfer around equilateral triangular cylinders are investigated numerically. The computation model is a two-dimensional domain with blockage ratios of BR=0.5, 0.25, 0.2, 0.1, 0.05, and 0.0333, with the Reynolds numbers ranging from 100 to 200. The working fluid is water (Pr = 7). The effects of aiding and opposing thermal buoyancy are incorporated into the Navier-Stokes equations using the Boussinesq approximation. The Richardson number, which is a relative measure of free convection, is varied in the range -2 = Ri = 2. The governing equations are solved by using the Finite Volume Method with a second-order upwind scheme used for differencing of the convection terms, and the SIMPLE algorithm is used for the velocity-pressure coupling. A discussion of the effect of the blockage ratio on the mean drag, mean rms lift coefficients, the Strouhal number, and the mean Nusselt number is also presented. The iso-vorticity contours and dimensionless temperature field are generated to interpret and understand the underlying physical mechanisms. The results reveal that, in addition to the Richardson and Reynolds numbers, the blockage rate is effective in the vortex distribution in the channel. It has been determined that the vortices formed behind the cylinder spread to the channel with a decreasing blockage rate. Especially at high Reynolds numbers, both the drag coefficient and the mean Nusselt number are significantly affected by the blockage ratio. For Ri=0, the drag coefficients for BR=0.25 in comparison to the BR=0.05 case are about 9% and 29% larger for Re= 100 and 200, respectively. For BR<0.1, two-column vortex formation at the back of the cylinder gave way to single vortexes in the aiding thermal buoyancy condition (Ri=2) compared to Ri=0 and -2. Also, useful correlations for flow characteristics and heat transfer are derived using the computed data. [ABSTRACT FROM AUTHOR]

This study aims to investigate computationally the effect of the backward-facing step on the heat transfer from flush-mounted three electronic chips located downstream of the backward step. Heat transfer is compared for two different step heights and two distances of chips from backward facing step. Heat transfer is also compared with the case without backward facing steps. For this purpose, conservation, and Std. k-ω model equations considering two-dimensional, incompressible flow are solved by Computational Fluid Dynamics (CFD) method using ANSYS-Fluent software. Velocity, temperature and pressure distributions are obtained and compared for five different cases. Presence of backward-ward facing step decreases the heat transfer according to base case without backward-facing step, and high step height and short distance of chips from backward-facing step also increases this negative effect. When all chips' average Nusselt numbers are examined, the average Nusselt number decreases by 12,32%, 14,76%, 22,28%, and 22,69%, respectively in the 2nd, 3rd, 4th, and 5th geometries. So possible backward-facing step effect of other circuit elements during placement of electronic chips on circuit boards must be accounted in the thermal design of printed circuit boards. [ABSTRACT FROM AUTHOR]

Copyright of Duzce University Journal of Science & Technology is the property of Duzce University Journal of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, heat transfer characteristics of helical heat exchangers were investigated under steady state conditions. In the experiments, the inlet temperature of the cold water into the heat exchanger was set as 20 °C and the hot water temperature was set as 50 °C. The flow rates of cold water were set as 2 - 3 - 4 and 5 l/min. The outlet temperature of the cold water from the heat exchanger was measured and the inside Nu number was calculated. For numerical study a three dimensional model of the heat exchanger was designed. Numerical analysis was carried out to determine the thermal properties and velocity contours in the heat exchanger using a computational fluid dynamics software program package (Fluent 18.2). The inside Nu number and the outlet temperature of the water from the heat exchanger were compared with the data recorded in the experimental study. The computational fluid dynamics results were obtained to be in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Advances in Engineering & Pure Sciences is the property of Marmara University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study represents Computational Fluid Dynamics (CFD) analyses to improve the heat transfer on the two sides of a thermoelectric generator (TEG) by utilizing heat sinks to recover the waste heat of hot air. In this respect, the temperature difference between the hot and cold sides of the TEG, the heat transfer rate on the hot and cold sides and the pressure drop between the inlet and outlet of the hot and cold air are investigated for varying hot air inlet temperature and Re number in terms of improving the heat transfer and accordingly the output power of the TEG. According to the numerical results, the maximum temperature difference between the hot and cold sides of the TEG concerning hot air inlet temperature of 600 °C and Re number of 16800 is specified as 418.9 °C and 478.1 °C, respectively. In terms of heat transfer, maximum heat transfer rate on the hot side for hot air inlet temperature of 600 °C and Re number of 16800 is specified as 180.4 W and 205.1 W, respectively, while the maximum heat transfer rate on the cold side is specified as 168.0 W and 192.6 W. The maximum pressure drop occurs as 304.4 Pa for the Re number of 16800. As a result, increasing hot air inlet temperature and Re number yields an increase in the temperature difference, the heat transfer rate on the hot side, and the heat transfer rate on the cold side. Besides, pressure drop increases with increasing Re number. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Güneş destekli hava ısıtıcıların çok yaygın kullanım ile birlikte ısı transferi verimlerinin düşük olduğu bilinmektedir. Bu konuda çeşitli çalışmalar yürütülmektedir. Yapılan bu çalışmada yutucu plaka üzerine kare kesit yapay pürüzlülük oluşturularak tasarlanan bir güneş destekli hava ısıtıcısının sayısal analizi yapılmıştır. Kütle, momentum ve enerji korunumu denklemlerinin sayısal simülasyonu, yaygın kullanılan hesaplamalı akışkanlar dinamiği yazılımı olan ANSYS Fluent ile sonlu hacimler metodunu kullanarak türbülanslı, zorlanmış konveksiyon ısı transferine maruz kalan tam gelişmiş akış için 2-boyutlu olarak yapılmıştır. Yutucu plaka üzerine 1000 W.m-2 sabit ısı akısı uygulanarak 4 farklı Reynolds sayısında (4000, 8000, 12000 ve 16000) ve 3 farklı pürüzlülük oranında (5,33, 10,67 ve 16,00) akış oluşturulmuştur. Reynolds sayısına bağlı olarak Nusselt sayısı, sürtünme faktörü değişimi ve akışkan çıkış sıcaklığı irdelenmiştir. Ayrıca, Reynolds sayısının ve pürüzlülük oranının ısı arttırma oranına etkisi incelenmiştir. Maksimum ısı arttırma oranı (Re=800 ve P/e=16’de) 1,20 olarak hesaplanmıştır. Yutucu plaka üzerinde yapay pürüzlülükler oluşturularak laminer alt tabakada türbülans sağlanması ile ısı transferinin arttırıldığı görülmüştür. Akışkan giriş ve çıkış sıcaklık farkı 4 K civarında bulunmuştur.

The brake system is the most significant active safety system that converts the vehicle's mechanical energy into heat energy based on the braking pair's friction. The transfer of heat in the brake pair during braking occurs by conduction, convection, and radiation. In disc brakes, which are widely used today, the effect of the heat transfer coefficient, which continually changes with the disc's angular velocity on the cooling of the braking pairs is important. The change in heat convection coefficient can be calculated with a numerical approach. In this study, on disc temperature effect of heat convection coefficient and angular velocity has been examined with the finite element method using the experimental data in the SAE J2522 Comprehensive Brake Efficiency Test Standard, fading test procedure. Disc brake design has been designed in the SOLIDWORKS program, and analysis has been carried out using ANSYS 2020 R2 in steady-state thermal analysis. It has been determined that the cooling amounts at the initial of braking are higher than the cooling amounts at the end of braking, and the effect of cooling by convection in the reduction of the temperature difference at the end of braking compared to the initial state is between 91.22% and 91.74%. [ABSTRACT FROM AUTHOR]

In this study, the heat transfer from two different model surfaces (roof and crown) and flow structure in the channels with the cross flow-impinging jet flow were numerically analyzed by using water, 0.02% GO (Graphene Oxide)-Water and 2% Diamond-Water nanofluids. The numerical study was carried out steady and three dimensional using the Ansys-Fluent program with k-ε turbulence model. A fin with 90o angle was added on the upper channel surface from the impinging jet inlet at distinct distances. A constant heat flux of 1000 W/m² was applied to the model surfaces. The channel heights are fixed and the Re range of the fluids is 5000-15000. The numerical results obtained from the study were compared with the results of the experimental studies in the literature and it was seen that the results were compatible and acceptable. The results of the study were comparatively examined for water and nanofluids as the mean Nu and surface temperature variations for each model in the channels without fins and at different fin distances. Also, velocity and temperature contour distributions of the combined jet Diamond-Water nanofluid flow were visualized. However, performance coefficient (C) and mean Nu (Num) and, surface temperature values (Tm) were evaluated for all three patterned surfaces in the channels. Num increases for GO-Water nanofluid at Re=15000 and fin distance of 2D are 47.53% and 57.42% compared to the case of using finless and water fluid for the roof and crown model surfaces, respectively. [ABSTRACT FROM AUTHOR]

In this study, heat transfer from trapezoidal and crown patterned surfaces and performance analysis were investigated numerically by using water and 0.02% volumetric concentration GO (Graphene Oxide)-Water nanofluid in channels without fin and different fin distances (N = D and 2D) and 60o angle with combined jet flow. Numerical analysis was carried out steady and in three dimensions with the k-ε turbulence model Ansys-Fluent program. The outcomes of the work were matched with the Nu outcomes of the experimental work in the literature and they were discovered to be compatible. At N = 2D and Re = 15000, the average Num numbers of the nanofluid on all three trapezoidal and crown-patterned surfaces were found to be 18.35% and 24.09% higher than the without fin and water fluid, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research aimed to find the process of value adding for glass wool waste from the glass wool composite board used in the vehicle industry. The waste was reprocessed to be an insulator and to determine the suitable conditions for hot-press forming to create new materials having high thermal resistant properties. Firstly, the properties of the original board; the thermal resistances (R) and the noise absorption coefficients (NRC), were measured and were found averages of 0.9055 m2K/W and 0.3955, respectively. The reprocessing conditions were varied by 2 levels; high and low, of 5 control factors; density, thickness, pressure, temperature, and surface roughness. Three repeating processes for each condition were performed. The Design of Experiment (DoE) was the full factorials; 25 experiments, by using the Analysis of Variance (ANOVA) to find main and interaction factors relating to the properties. From the ANOVA results with the α level of significance at 0.05, it was found that the main factors responding to the high values of the thermal resistance were the thickness and density. This resulted in the suitable conditions for the hot-press process of both the new smooth and rough pads with a density of 96 kg/m3 and a thickness of 25 mm. The R values of the new insulators were in between 0.88 - 0.98 m2K/W and, additionally, the high NRC values were also provided in between 0.46 - 0.49. These findings could be applied for wall designing, wall decorations and heat shields for indoor rooms and different types of buildings. [ABSTRACT FROM AUTHOR]

Physics-informed neural networks (PINNs) have drawn attention in recent years in engineering problems due to their effectiveness and ability to tackle problems without generating complex meshes. PINNs use automatic differentiation to evaluate differential operators in conservation laws and hence do not need a discretization scheme. Using this ability, PINNs satisfy governing laws of physics in the loss function without any training data. In this work, we solve various incompressible thermal convection problems, and compare the results with numerical or analytical results. To evaluate the accuracy of the model we solve a channel problem with an analytical solution. The model is highly dependent on the weights of individual loss terms. Increasing the weight of boundary condition loss improves the accuracy if the flow inside the domain is not complicated. To assess the performance of different type of networks and ability to capture the Neumann boundary conditions, we solve a thermal convection problem in a closed enclosure in which the flow occurs due to the temperature gradients on the boundaries. The simple fully connected network performs well in thermal convection problems, and we do not need a Fourier mapping in the network since there is no multiscale behavior. Lastly, we consider steady and unsteady partially blocked channel problems resembling industrial applications to power electronics and show that the method can be applied to transient problems as well. [ABSTRACT FROM AUTHOR]

In this study, the effect of triangular concave ramp (UIBR) on film cooling efficiency (FSE) and flow characteristics in film cooling was numerically investigated. In order to protect the jet stream from the effect of the main stream, the UIBR is placed on the surface where the jet hole meets the surface and the main stream comes from. In order to determine the most suitable design parameters of the UIBR, three different inclination angles (ar) of 10°, 25° and 45°, three different dimensionless ramp heights (h/d) as 0.15, 0.30 and 0.50 examined. However, calculations were performed at blowing ratios (M) of 0.30, 0.60, 0.85 and 1.25. In order to accurately determine the physical properties of the film cooling in accordance with the real operating conditions, air was used for the main flow and CO2 was used for the fluid injected to the surface in the calculations. Accordingly, the jet stream to main stream density ratio (YO) is 1.50. CO2 was injected into the surface through a circular jet hole with an angle of aj=35° with the surface and a diameter of d=4 mm. Numerical studies were carried out using Ansys FLUENT developed for Computational Fluid Dynamics (CFD) and the Transition k-kl-ω turbulence model. The results are compared to a conventional flat surface without ramp. According to the numerical results, increasing the ramp height and decreasing the ramp angle significantly increased the FSE. As a result, the highest increase in area-averaged FSE compared to conventional film cooling was obtained as 305.44% in the ramp design with h/d=0.50 and ar=10°. [ABSTRACT FROM AUTHOR]

In this study, the changes in heat transfer, friction factor and efficiency values caused by the rotation effect given to the fluid by rotating the cylindrical tube at various speeds was investigated experimentally. The experiments were carried out by rotating the cylindrical tube at different revolutions and the Reynolds number between 500 and 1800 values. As a result of the experiments, it was observed that the Nusselt number, friction factor and efficiency values increased with the increase in rotational speed. In addition, the effects of the increase in the rotational speed of the pipe on the fluid were observed with the flow observation experiments performed in laminar flow. From these images; It has been observed that linear flow, which has laminar flow characteristics, gains turbulent flow characteristics with the increase in rotational speed. The results obtained were found to be in agreement with the literature. [ABSTRACT FROM AUTHOR]

In this study, heat transfer performance with single and cascade air jets over the plane surface heat sink was numerically investigated with Ansys-Fluent software. Numerical analyses was carried out using the time-independent k-ε turbulence model. The effects of ten different Reynolds numbers (4000≤Re≤40000) and single and cascade nozzle numbers on the heat transfer were investigated. Analyzes were carried out at a distance of 40 mm between the nozzle and the heat sink. The air, on the other hand, was sent to the control volume at a temperature of 293.15 K at velocities corresponding to the determined Reynolds numbers. In the study, temperature contours showing the temperature distribution on the heat sink and streamline images in which turbulence formation is observed on the heat sink surface are presented. As a result, cooling performance increased with increasing Reynolds number in both nozzle types. It was determined that while the single nozzle showed a better cooling performance than the cascade nozzle up to approximately 38000 Reynolds number, better heat transfer was obtained with the cascade nozzle after 38000 Reynolds number. The Nusselt number showed an increase of 60% at the lowest Reynolds number in the single nozzle compared to the cascade nozzle, and 15% in the cascade nozzle at the highest Reynolds number compared to the single nozzle. It has been observed that the numerical results obtained are compatible with the experimental studies conducted with single and cascade air jets separately in the literature. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bu çalışmada sıcak bir plakanın çarpan jet akışla soğutulmasının ısı transferi ve akış karakteristikleri hesaplamalı akışkanlar dinamiği yöntemi ile sayısal olarak incelenmiştir. Sıcak plakanın aynı yükseklikteki düz, zikzak, yamuk ve dikdörtgen kesitli geometrileri için ikili nozul sistemi kullanılarak türbülanslı çarpan jet akış ile soğutulması durumunda ısı transferi ve hidrolik performanslar karşılaştırılmıştır. Hesaplamalarda çalışma akışkanı olarak hava kullanılmış olup, taşınımla gerçekleşen ısı transferi performansının analizi için ortalama ve yerel Nusselt (Nu) sayılarının dağılımı elde edilmiştir. Hidrolik performans için pompalama gücü değerleri karşılaştırılmıştır. Türbülanslı çarpan jet akış için k-ε türbülans – duvar yakın modelinin kullanılmıştır. Elde edilen sonuçlara göre, yamuk kesitli plakanın en yüksek ısıl performansa sahip olduğu ve taşınımla gerçekleşen ısı transfer hızı aynı şartlarda düz plakadan yaklaşık %52,2 daha yüksek olduğu belirlenmiştir. Termo-hidrolik performans açısından Nusselt sayısı/Pompalama Gücü oranı hesaplanmış ve en düşük performansın basınç farkının en yüksek olmasından dolayı dikdörtgen kesit için oluştuğu gözlemlenmiştir. Bununla birlikte yerel Nusselt sayılarının dağılımına bakıldığında, nozulların çarptığı noktalarda en yüksek değerleri alıp çıkış kısımlarına doğru azaldığı belirlenmiştir. Çarpan jetler kullanılarak soğutma işlemi yapılan sıcak plaka yüzey kesit şeklinin taşınımla gerçekleşen ısı transferini önemli ölçüde arttırdığı görülmüştür.

Copyright of Beykent Üniversitesi Fen ve Mühendislik Bilimleri Dergisi is the property of Beykent Universitesi Fen Bilimleri Enstitusu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sınırlandırılmış bir kanal içerisinde yer alan tek kare silindir (KS) üzerinden iki boyutlu laminer sürekli akış için blokaj (=B/H) oranının ısı transferi ve akış karakteristiklerine olan etkisi incelenmiştir. Çalışmada Reynolds sayısı Re=40 değerinde sabit tutulurken blokaj oranı =0.125-0.8 değerleri arasında değiştirilmiştir. Hesaplamalarda ANSYS CFX 14.0 kullanılmıştır. Blokaj oranı etkisinin KS yüzeyleri üzerindeki sürükleme katsayısı (Cd), sürtünme katsayısı (Cf), boyutsuz yeniden birleşme uzunluğu (Lr/B) ve ortalama Nusselt sayısı (Nu) üzerine olan etkileri incelenmiştir. Blokaj oranı arttıkça sürükleme katsayısı (Cd), sürtünme katsayısı (Cf) ve ortalama Nusselt sayısı (Nu) değerlerinin arttığı ancak boyutsuz yeniden birleşme uzunluğu (Lr/B) değerinin azaldığı bulunmuştur. Sürükleme katsayısı (Cd), sürtünme faktörü (Cf), boyutsuz yeniden birleşme uzunluğu (Lr/B) ve ortalama Nusselt sayısı değerlerinin blokaj oranına göre değişimini veren bağıntılar elde edilmiştir.

Çarpan jetler, günümüzde minyatürleşme ile ısı transfer alanının azaldığı ve dolayısıyla son derece yüksek ısı akılarına sahip elektronik bileşenlerin soğutulmasında büyük bir öneme sahiptir. Bu çalışmada ise bilgisayarlarda da kullanılan ve ısı üretim miktarı oldukça fazla olan mikroçiplerin soğutulmasının iyileştirilmesi incelenmiştir. Bu amaçla, üç tarafı kapalı ve bir tarafı açık kesiti dikdörtgen olan kanallar içerisindeki sur ve dikdörtgen şeklinde olmak üzere iki farklı desene sahip 1000 W/m2 sabit ısı akılı bakır plakalı yüzeylerin tek bir hava jeti akışı ile soğutulmasının sayısal araştırması yapılmıştır. Sayısal araştırma, zamandan bağımsız ve üç boyutlu olarak enerji ve Navier Stokes denklemlerinin k-ε türbülans modelli Ansys-Fluent bilgisayar programının uygulanmasıyla gerçekleştirilmiştir. Kesiti dikdörtgen olan kanalın üst ve alt yüzeyleri adyabatik iken sur ve dikdörtgen desenli yüzeylere sabit ısı akısı uygulanmıştır. Kullanılan jet akışkanı hava olup, kanala giriş sıcaklığı 300 K’dir. Çalışma için belirlenen Re sayısı aralığı 4000-10000 iken jet-plaka arası uzaklık (H/Dh) için değerlendirilen aralık ise 4-10’dur. Elde edilen sonuçlar, literatürde bulunan çalışmanın sayısal ve deneysel sonuçlarıyla karşılaştırılmış olup, birbirleriyle uyum içerisinde oldukları görülmüştür. Sonuçlar, sur ve dikdörtgen şeklindeki her bir desenli yüzey için ortalama Nu sayısı ve yüzey sıcaklığının değişimi olarak sunulmuştur. Farklı H/Dh oranları ve Re sayıları için kanal boyunca jet akışın sıcaklık, hız ve akım çizgisi konturu dağılımları sur ve dikdörtgen desenli yüzeyler için değerlendirilmiştir. Ayrıca, çalışmada her iki desenli geometride tüm yüzeyler için ortalama Nu sayısı, yüzey sıcaklığı ve jet akışın kanaldan çıkış sıcaklık değerleri analiz edilmiştir. Re=4000 ve H/Dh=4 için sur desenli yüzeylere göre dikdörtgen desenli yüzeylerde %31.45 daha yüksek ortalama Nu sayısı değeri elde edilmiştir.

Çarpan jetler, günümüzde minyatürleşme ile ısı transfer alanının azaldığı ve dolayısıyla son derece yüksek ısı akılarına sahip elektronik bileşenlerin soğutulmasında büyük bir öneme sahiptir. Bu çalışmada ise bilgisayarlarda da kullanılan ve ısı üretim miktarı oldukça fazla olan mikroçiplerin soğutulmasının iyileştirilmesi incelenmiştir. Bu amaçla, üç tarafı kapalı ve bir tarafı açık kesiti dikdörtgen olan kanallar içerisindeki sur ve dikdörtgen şeklinde olmak üzere iki farklı desene sahip 1000 W/m2 sabit ısı akılı bakır plakalı yüzeylerin tek bir hava jeti akışı ile soğutulmasının sayısal araştırması yapılmıştır. Sayısal araştırma, zamandan bağımsız ve üç boyutlu olarak enerji ve Navier Stokes denklemlerinin k-ε türbülans modelli Ansys-Fluent bilgisayar programının uygulanmasıyla gerçekleştirilmiştir. Kesiti dikdörtgen olan kanalın üst ve alt yüzeyleri adyabatik iken sur ve dikdörtgen desenli yüzeylere sabit ısı akısı uygulanmıştır. Kullanılan jet akışkanı hava olup, kanala giriş sıcaklığı 300 K’dir. Çalışma için belirlenen Re sayısı aralığı 4000-10000 iken jet-plaka arası uzaklık (H/Dh) için değerlendirilen aralık ise 4-10’dur. Elde edilen sonuçlar, literatürde bulunan çalışmanın sayısal ve deneysel sonuçlarıyla karşılaştırılmış olup, birbirleriyle uyum içerisinde oldukları görülmüştür. Sonuçlar, sur ve dikdörtgen şeklindeki her bir desenli yüzey için ortalama Nu sayısı ve yüzey sıcaklığının değişimi olarak sunulmuştur. Farklı H/Dh oranları ve Re sayıları için kanal boyunca jet akışın sıcaklık, hız ve akım çizgisi konturu dağılımları sur ve dikdörtgen desenli yüzeyler için değerlendirilmiştir. Ayrıca, çalışmada her iki desenli geometride tüm yüzeyler için ortalama Nu sayısı, yüzey sıcaklığı ve jet akışın kanaldan çıkış sıcaklık değerleri analiz edilmiştir. Re=4000 ve H/Dh=4 için sur desenli yüzeylere göre dikdörtgen desenli yüzeylerde %31.45 daha yüksek ortalama Nu sayısı değeri elde edilmiştir.

We present a GPU-accelerated method for large scale, coupled incompressible fluid flow and heat transfer problems. A high-order, nodal discontinuous Galerkin method is utilized to discretize governing equations on unstructured triangular meshes. A semi-implicit scheme with explicit treatment of the advective terms and implicit treatment of the split Stokes operators are used for time discretization. The pressure system is solved with a conjugate gradient method together with a fully GPU-accelerated multigrid preconditioner. The code is built on scalable libParanumal solver which is a library of high-performance kernels for high-order discretizations. Performance portability is achieved by using the open concurrent compute abstraction, OCCA. A set of numerical experiments including free and mixed convection problems indicate that our approach experimentally reaches design order of accuracy. [ABSTRACT FROM AUTHOR]

In this study heat extraction ratio of a solar pond was investigated numerically by using the Discrete Ordinates Method (DOM) with the direct solver PARDISO by using nested dissection multithreaded preordering algorithm, and the findings without exchanger were compared with experimental data to validate simulation accuracy of numerical approaches in the Mediterranean climatic condition. The solar pond was modeled with the same dimension as a previous experimental system and a heat exchanger was placed in the heat storage zone and simulation to take out the hot water at a certain flow was performed with the commercial software COMSOL. The solar position was defined for Adana and ambient data was obtained by processing the ASHRAE Weather Data Viewer 5.0. As a result, the maximum and minimum heat extraction ratio (HER) is calculated as 13.39 % in July and 2.96 % in September for a flow rate of 0.007 kg/s; 24.27 % in June, and 3.23 % in September for a flow rate of 0.014 kg/s, respectively. [ABSTRACT FROM AUTHOR]

The cooling of hot surfaces through drawing heat by means of fins attached to the surface is widely used technique in many systems. The fins increase the heat transfer surface area, thereby improving the heat transfer. In this study, the velocity and temperature distributions of the working fluid, air, flowing at constant temperature and constant Reynolds numbers over the hexagonal fins, placed in a rectangular duct, having the same surface area and same arrangement but facing at different angles to the flow plane; 0°, 15° and 30°, were analyzed numerically. Computational fluid dynamics (CFD) analysis was carried out with Ansys Fluent. The results were obtained for pressure drop, temperature and velocity distributions at all angles (0°, 15° and 30°). As a result of the analyses performed, 15° facing angle was concluded to be the best by the virtue of the fact that the heat transfer coefficient was improved by the renewal of the boundary layer and by the turbulence occurred between the fins. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Research & Development (IJERAD) is the property of International Journal of Engineering Research & Development and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Computer Aided Engineering is an effective tool utilized to drive an exhaust manifold design by early assessment within the engine program development phase. However, in the end, for exhaust manifold design verification, various tests must be performed in engine dynamometer cells under severe operating conditions. The test running durations are up to 2500 hours for the heavy-duty (HD) exhaust manifold. Therefore, the validation tests are expensive and time-consuming. Alternative ways are sought to replace these expensive tests for cost reduction purposes and more efficient dynamometer cells. Thus, the custom test rig is designed and built. This system contains the burner system supplying hot gas at a similar temperature and mass flow ranges with the engine. The drawback of the burner system is, it runs in steady-state mode, so very challenging to replicate the engine's pulsating flow effect exactly. Therefore, with the coupling of Star-CCM+ and Modefrontier, the CAE study is carried out to assess the feasibility of obtaining similar manifold skin temperature distribution in the burner test cell with engine conditions. It is aimed to determine the correct valve opening positions regulating the mass flow rate through the runners. This innovative methodology reduces the trialand-error count in the experiment phase. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Research & Development (IJERAD) is the property of International Journal of Engineering Research & Development and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Artificial neural network (ANN) is a modelling of the human brain. The aim of this study is to estimate the heat distribution with ANN around different cylinders. Within the scope of the study, square and circular cylinders were discussed. In this study, the temperature analysis of the cylinders was carried out with a program written in Fortran, not using a package program whose exact background is unknown. The results obtained from a writing code are more reliable. The study is discussed in two dimensions. The 3 most commonly used algorithms (Levenberg - Marguardt (LM), Pola-Ribiere Conjugate Gradient (CGP) and Scaled Conjugate Gradient (SCG)) were used to train with ANN. Cylinder type, x-coordinate and y-coordinate were the input variables; and temperature was the output variable. The most suitable algorithm was found to be LM-18 algorithm. The proximity of artificial neural networks and real values was evaluated statistically. These were R², CoV and RMSE. R², CoV and RMSE values in the training phase of Levenberg - Marguardt -18 neuron were determined to be 0.9939, 0.0044, 0.0107 while their values in the test phase were 0.9850, 0.0043 and 0.0190 respectively. The fact that the R² value is so close to 1 is an indication that ANN is working very well. [ABSTRACT FROM AUTHOR]

Bu çalışmada, içerisine dairesel halkalar yerleştirilmiş olan bir boruda laminer pulsatif akış giriş şartlarında nanoakışkanların ısı transferi ve sürtünme faktörüne etkileri sayısal olarak incelenmiştir. Çalışmalarda korunum denklemleri, FLUENT ANSYS 15.0 paket programı kullanılarak, tariflenen sınır şartlar için sonlu hacim metodu (SHM) ile ayrıklaştırılmış ve SIMPLE algoritması kullanılarak çözülmüştür. İlk olarak farklı Reynolds sayılarında ve değişen partikül hacim oranlarındaki farklı nanoakışkan tiplerinin sürekli akış şartlarında ısı transferine etkileri analiz edilmiştir. Daha sonra en iyi ısı transferi sağlayan bu nanoakışkan parametreleri sabit tutularak nanoakışkanların pulsatif akışının ısı transferine etkileri araştırılmıştır. Farklı pulsatif parametreler için ortalama Nusselt sayısı ve ortalama sürtünme faktörü hesaplanmıştır. Sayısal sonuçlar sürekli akış durumunda Reynolds sayısının ve partikül hacim oranının artması ile ısı transferinin iyileştiğini göstermiştir. Ayrıca nanoakışkanların pulsatif akışı durumunda pulsatif parametrelerin artması ile sürtünme faktöründe bir miktar artış ile birlikte ısı transferinde iyileşme sağlandığı gözlemlenmiştir. Elde edilen sonuçlar, içerisinde dairesel halkalar bulunan bir boruda nanoakışkanların pulsatif akışının ısı transferi iyileşmesinde önemli bir potansiyele sahip olduğunu göstermiştir.