Makale Koleksiyonu
https://hdl.handle.net/11491/3262
Article Colleciton2024-03-29T07:24:24ZExperimental and numerical analysis of the splay impact on the performance of splayed cross-cut fin heat sink
https://hdl.handle.net/11491/7269
Experimental and numerical analysis of the splay impact on the performance of splayed cross-cut fin heat sink
Şevik, Seyfi; Özdilli, Özgür
In this study, splayed effects on the thermal performance of standard cross-cut heat sink (S-CCHS), fixed-array splayed (FAS-CCHS), and full splayed (FS-CCHS) under natural and forced conditions are studied experimentally and numerically. For this purpose, variable parameters such as splayed ratio, different powers of LEDs, natural and forced conditions, and blowing direction have been studied. The results showed that the thermal performance is significantly impacted by the spread position of the fins, blowing direction, natural and forced conditions of the CCHS but is not very sensitive to LEDs' powers. The results show that the full splayed heat sink occupies the highest physical volume, thus, provides the highest thermal performance by efficiently dissipating heat compared to other heat sinks designs. Experimental and numerical results show that the full splayed effect provides 5.46% and 2.59% lower junction temperature in natural and forced, respectively. Also, FS-CCHS achieved a 7.09% reduction in thermal resistance at natural convection 3 W and a 2.62% reduction at 10 W, respectively, compared to the flat fins and the fixed array wide fin heat sink. For this study, while the most suitable flow direction was determined as push, the most suitable orientation was found to be upward, and the splayed impact was also beneficial.
2021-01-01T00:00:00ZThermal performance analysis of a novel linear LED housing with inner and outer fins
https://hdl.handle.net/11491/7085
Thermal performance analysis of a novel linear LED housing with inner and outer fins
Şevik, Seyfi; Abuşka, Mesut; Özdilli, Özgür
There is an inverse relationship between the junction temperature of the light-emitting diode (LED) and its lifetime therefore, it is significant to operate it at low junction temperature. In this study, three different natural convection linear housing models were developed to cool mid-powered LED arrays, focusing on basic parameters such as fin structure, surface area, and wall thickness in the design of the models and thermal performance has been tested numerically and experimentally. The performance tests were carried out at five different ambient temperatures, 20, 25, 30, 35, and 40 degrees C. Compared to Model-1 (standard housing without fin) and Model-2 (thin housing with inner fin), the cooling effect of Model-3 (thin housing with inner + outer fin) is remarkably high, and this effect was more evident with the increase in ambient temperature. This impact has been achieved by increasing the surface area of Model-3 by almost 50%, although its mass has decreased more than twice. The maximum junction temperatures of Model-3 were approximately 2 degrees C lower than Model-1 and 5 degrees C lower than Model-2 in all experiments, with the presence of fins and the development of geometry. When the maximum allowable temperature rise is 94.68-101.25 degrees C and the 35 watts dissipated in the package, the average thermal resistances were found to be 1.12-1.38 degrees C/W. It is thought that these new-generation LED-based linear designs can be used to illuminate the work areas and they can replace compact lamp-based luminaires that work with direct and indirect lighting principles.
2020-01-01T00:00:00ZAnkara ve ilçeleri için Güneş kolektörü optimum eğim açısının belirlenmesi
https://hdl.handle.net/11491/3661
Ankara ve ilçeleri için Güneş kolektörü optimum eğim açısının belirlenmesi
Koçer, Abdülkadir; Şevik, Seyfi; Güngör, Afşin
Öz: Ankara merkez ve ilçeleri bazlı olan bu çalışma, güneş kolektörü ve güneş paneli performanslarını en
üst düzeye çıkarmak için optimum eğim açısının belirlenmesi ile ilgilidir. Ankara ilinde sabit güneş
kolektörleri genellikle yaklaşık 40 eğim açısında yerleştirilmektedir. Bu çalışmada, Ankara il ve ilçeleri
için yıllık optimum eğim açısı 34°1 olarak hesaplanmış buna karşın yıl içerisindeki optimum eğim
açılarının 1-67° arasında değiştiği hesaplanmıştır. Bu çalışmanın sonuçları literatürdeki benzer çalışmalar
ile karşılaştırıldığında bu çalışmaların sonuçları ile uyumlu olduğu görülmüştür. Ayrıca, altı aylık
periyotlar için 15 ve 56, mevsimlik (kış, ilkbahar, yaz, sonbahar) periyotlar için ise sırasıyla 62, 23, 6
ve 49 olarak hesaplanmıştır ve optimum eğim açıları için güneş ışınım değerleri bulunmuştur. Sadece
yılda iki kez eğim açısı değiştirildiğinde birim alana düşen enerji miktarı arttırıldığından yıllık eğim açısı
sabit olanlara göre yaklaşık % 5 verim artışı sağlar. Diğer taraftan eğim açısı her ay değiştirildiğinde ise
bu oran yaklaşık % 8’e ulaşabilir. Güneş kolektörleri ve panellerin kullanım verimliliğini arttırmak için,
eğim açısını ayda bir kez veya yılda en az iki kez ayarlanması tavsiye edilir.; Abstract: This study that is Ankara province and districts based deals with the determination of the optimum tilt angle to maximize the performances of solar collector and solar panel. In Ankara, fixed solar collectors are usually placed at slope of 40. In this study, annual optimum tilt angle for Ankara province and districts was calculated as 34°1 however the optimum angles during the year were calculated between 1° and 67°. The results of this study are compared with similar studies in the literature they were found to be consistent with the results of similar studies. Also, the tilt angle was calculated for the six months periods as 15° and 56°, for seasonal periods (winter, spring, summer, autumn) as 62°, 23°, 6° and 49°, respectively and solar radiation for optimum angles of inclination were found. When the tilt angle is changed only twice a year, due to increasing the amount of energy per unit area, according to the annual tilt angle fixed product they provides energy efficiency by about 5%. On the other hand, when the tilt angle is changed every month this ratio can be reached approximately 8%. For increasing the utilization efficiency of solar collectors and panels, it is recommended adjusting of the tilt angle once a month or at least twice a year.
note
2016-01-01T00:00:00Zİl bazında enerji dengesi analizi: Karabük örneği
https://hdl.handle.net/11491/3372
İl bazında enerji dengesi analizi: Karabük örneği
Şevik, Seyfi
Bu çalışmanın amacı; Karabük ilinin enerji arz-talep dengesini ortaya koymak, bu denge içerisinde kahverengi ve yeşil enerjilerin payını ve bunların genel eğilimini değerlendirmek ve bir enerji akış şeması oluşturmaktır. Karabük ilinde, kurulu gücü 122 MW olan 4 adet lisanslı ve 1 adet lisanssız olmak üzere toplamda 5 adet aktif elektrik enerji santrali ile yıllık yaklaşık 530 GWh elektrik üretimi yapılmaktadır. Bu üretim ile, kendi elektrik tüketiminin % 45'i karşılanabilmektedir. Karabük ili elektrik kurulu gücünün Türkiye kurulu gücüne oranı % 0.17 iken Türkiye tüketimine oranı % 0.21'dir. Yenilenebilir enerjinin toplam kurulu güç içerisindeki payı % 58.8 iken toplam enerji üretimi içerisindeki payı ise % 32'dir. Karabük, yeterli enerji kaynaklarına sahip olmayıp bununla birlikte, fosil yakıt tüketimi de oldukça yüksektir. Karabük, yerli olmayan enerji kaynaklarının ağır bir sömürüsü ile karşı karşıyadır. Yenilenebilir enerji ve etkili enerji verimliliği programları, yerli olmayan enerji kaynakları üzerindeki ülkenin bağımlılığını azaltabilir; The purpose of this study; to reveal the energy supply-demand balance of the Karabük province, to evaluate their overall trends and the share of brown and green energy in the balance and to create an energy flowchart. Karabük province has an installed capacity of 122 MW with 4 licensed and 1 unlicensed power plants. It is carried out about 530 GWh of electricity generation annually. With this generation, 45% of own electricity consumption can be met. Ratio of Karabük electricity installed capacity to installed capacity of Turkey is 0.17%, it's ratio is 0.21% to consumption in Turkey. While share in the total installed capacity of renewable energy is 58.8%, the share in total energy generation is 32%. Karabük haven't energy resources however, fossil fuel consumption is also very high. Province of Karabük is characterized by a heavy exploitation of non-domestic energy resources. Karabük does not have sufficient energy sources. Effective energy efficiency programs and renewable energy can reduce country's reliance on non-domestic energy sources
research
2017-01-01T00:00:00Z