Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2019/r/gumushane/15122
  Natural convection in an enclosure with a pair of discrete heat sources

  Saglam, Mehmet; Sarper, Bugra; Aydin, Orhan

  An experimental and numerical study is carried out to investigate natural convection cooling characteristics of discrete heat sources in a rectangular enclosure. One of the sidewalls of the enclosure is heated by a pair of identical discrete heat sources, whereas the other sidewall is maintained at a constant temperature. The effect of the heat dissipation ratio of the heat sources on buoyancy-induced flow and heat transfer characteristics is investigated. Experimental studies are performed for a constant value of the modified Rayleigh number (Ra = 7.7 × 105) and three different values of the heat dissipation ratio (rh = q1 = q2 = 0.5, 1 and 2), whereas numerical studies cover the range of 104to 5 × 106 for the modified Rayleigh number and different values of the heat dissipation ratios between 0.25 and 2. In the experimental study, qualitative flow visualization studies are carried out as well as temperature measurements. In the numerical study, a commercial computational fluid dynamics code in ANSYS Fluent is used. The variations of the surface temperatures, the hot spot temperature, and the mean Nusselt number with the modified Rayleigh number and the heat dissipation ratio are obtained. Results are presented in terms of streamlines, isotherms, and heat lines.

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• MakaleYalnız künye2018/r/gumushane/15328
  Experimental and numerical investigation of natural convection in a discretely heated vertical channel: Effect of the blockage ratio of the heat sources

  Sarper, Bugra; Saglam, Mehmet; Aydin, Orhan

  This study deals with the buoyancy induced flow and heat transfer in a parallel plate channel with a heat source array, which simulates an electronic package. The heat source array consists of four discrete protruding heat sources made of copper. The focus of this study is concentrated on the effect of heat source blockage ratio (br) on recirculating flow and cooling performance of the system. Studies are conducted both for flush mounted or protruding heat source cases. Four different values of the blockage ratio of the protruding heat sources (br = 0.125, 0.25, 0.375 and 0.5) are considered. The range of the modified Grashof number covers the values between 9.6 × 105 and 1.53 × 107. In the experiments, flow visualization and temperature measurements are conducted. Numerical studies are performed via ANSYS Fluent software. From the experimental results and numerical studies, it is found that buoyancy induced flow and cooling performance is significantly affected by the blockage ratio of the heat source array.

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• MakaleYalnız künye2018/r/gumushane/13340
  Natural convection in a parallel-plate vertical channel with discrete heating by two flush-mounted heaters: effect of the clearance between the heaters

  Sarper, Bugra; Saglam, Mehmet; Aydin, Orhan; Avci, Mete

  In this study, natural convection in a vertical channel is studied experimentally and numerically. One of the channel walls is heated discretely by two flush-mounted heaters while the other is insulated. The effects of the clearance between the heaters on heat transfer and hot spot temperature while total length of the heaters keeps constant are investigated. Four different settlements of two discrete heaters are comparatively examined. Air is used as the working fluid. The range of the modified Grashof number covers the values between 9.6 × 105 and 1.53 × 10.7 Surface to surface radiation is taken into account. Flow visualizations and temperature measurements are performed in the experimental study. Numerical computations are performed using the commercial CFD code ANSYS FLUENT. The results are represented as the variations of surface temperature, hot spot temperature and Nusselt number with the modified Grashof number and the clearance between the heaters as well as velocity and temperature variations of the fluid.

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• MakaleYalnız künye2018/r/gumushane/11850
  Constructal Placement of Discrete Heat Sources with Different Lengths in Vertical Ducts under Natural and Mixed Convection

  Sarper, Bugra; Saglam, Mehmet; Aydin, Orhan

  In this study, convective heat transfer in a discretely heated parallel-plate vertical channel which simulates an IC package is investigated experimentally and numerically. Both natural and mixed convection cases are considered. The primary focus of the study is on determining optimum relative lengths of the heat sources in order to reduce the hot spot temperature and to maximize heat transfer from the sources to air. Various values of the length ratio and the modified Grashof number (for the natural convection case)/the Richardson number (for the mixed convection case) are examined. Conductive and radiative heat transfer is included in the analysis while air is used as the working fluid. Surface temperatures of the heat sources and the channel walls are measured in the experimental study. The numerical studies are performed using a commercial CFD code, ANSYS FLUENT. The variations of surface temperature, hot spot temperature, Nusselt number, and global conductance of the system are obtained for varying values of the working parameters. From the experimental studies, it is showed that the use of identical heat sources reduces the overall cooling performance both in natural and mixed convection. However, relatively decreasing heat sources lengths provides better cooling performance.

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  İncele
• MakaleAçık Erişim2018/r/gumushane/11338
  Natural convection in an enclosure with a discretely heated sidewall: Heatlines and flow visualization

  Saglam, M.; Sarper, B.; Aydin, O.

  Natural convection inside a rectangular enclosure is investigated experimentally and numerically. One of the sidewalls is heated discretely by two flush-mounted heat sources. The other sidewall is kept at a constant temperature, while the horizontal walls are unheated. Heat dissipation rates of the heat sources are equal to each other. The aspect ratio of the enclosure (AR) is 2 and the working fluid is air (Pr=0.71). The study is focused on the validation of the two and three dimensional computations under real test conditions against experiments for various modified Rayleigh number values. Experimental study is performed for various modified Rayleigh numbers in the range of 7.7×105 and 3.1×106 while numerical part covers the values between 104 and 5×106. Temperature measurements and flow visualization studies are performed in the experimental work, and streamlines, isotherms and heatlines are presented in the numerical part of the study. From the experimental and numerical studies, it is shown that two dimensional computations reflects the general characteristics of the problem, conduction and radiation heat transfer are not negligible, surface temperatures increase with the modified Rayleigh number and heatline approach is an important tool to analyze convective heat transfer.

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• Yüksek Lisans TeziAçık Erişim2013/r/gumushane/20602
  Üçgen kesitli kapalı ortamda engel kullanımının doğal taşınıma etkisinin sayısal olarak incelenmesi

  Buğra Sarper

  Bu çalışmada, düşey adyabatik yüzeyine engel yerleştirilen üçgen kapalı ortamdaki doğal taşınım sayısal olarak incelenmiştir. Üçgen kapalı ortamın yatay eksenle yaptığı eğimin (=0º-315º), engel uzunluğunun (l*=0.125-0.375), engel genişliğinin (w*=0.025-0.125), düşey yüzey üzerindeki engel pozisyonunun (h*=0.1-0.7) ve engel ile havanın ısı iletim katsayısı oranlarının (kr=0.1-10 ve engel adyabatik) doğal taşınıma etkileri, 1000 ile 1000000 Rayleigh sayısı aralığında analiz edilmiştir. Yatay yüzey eğimli yüzeyden daha sıcak olup, düşey yüzey ise adyabatik sınır koşuluna sahiptir. Diferansiyel korunum denklemleri ticari bir hesaplamalı akışkanlar dinamiği programı olan Fluent 13.0. programı ile çözülmüştür.Yürütülen çalışma neticesinde, üçgenin eğimi ve engel parametrelerinin doğal taşınım üzerinde önemli etkisinin olduğu belirlenmiştir. Eğim açısının 90°'ye kadar olan ve 270°'den sonraki değerlerinde ısı transferi daha yüksektir, ancak 90° ile 270° arasında ısı transferi azalmaktadır. Ayrıca engel kullanımına bağlı olarak ısı transferinde %24.9 oranına varan bir düşüş meydana gelmektedir.Anahtar Kelimeler: Doğal taşınımla ısı transferi, üçgen kapalı ortam, eğimli üçgen kapalı ortam, engel kullanımı.

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