Farklı geometride akış yönlendiriciler ve çarpan jet kullanarak yüksek ısı akılı bir yüzeyden olan ısı transferinin iyileştirilmesi

Bu çalışmada sabit ısı akılı yüzeyde ısı transferinin, çarpan akışkan jet ve farklı geometride akış yönlendiricilerin birlikte kullanılarak iyileştirilmesi sayısal olarak araştırılmıştır. Çalışmada, akış yönlendirici kullanılmayarak kanal içindeki akış ve ısı transferi farklı Reynolds sayıları ve kanal yüksekliğijet hidrolik çapı (H/Dh) oranları için incelenmiştir. Sonrasında kanal içine yerleştirilen iki adet silindirik, kare ve üçgen akış yönlendiricinin akışa ve ısı transferine etkisi; farklı akış yönlendirici-jet merkezi mesafeleri için incelenmiştir. Son aşamada ise dört adet üçgen akış yönlendirici kullanılarak, ikinci grup akış yönlendiricinin ısı transferine etkisi incelenmiştir. Sonuç olarak; çarpan akışkan jet ile farklı geometride akış yönlendiricilerin birlikte kullanılarak; ısı transferinde akış yönlendirici kullanılmaması durumuna göre %28'e kadar bir artış sağlanabildiği görülmüştür. Re sayısının artması ile ısı transferinin artış gösterdiği, kanal yüksekliğindeki azalmanın yerel Nu sayısında belirgin bir artışa sebep olmadığı, silindirik akış yönlendirici merkezi; yerel Nu sayısı L/Dh=1,4 değerinde maksimum değerine ulaştığı, en etkin ısı transferinin üçgen akış yönlendirici ile elde edildiği tespit edilmiştir. İkinci grup akış yönlendirici kullanılma durumunda ise, yerel olarak %36,1'lik bir artış sağlanabilmesine karşın plaka genelinde ısı transferinde önemli bir artış olmadığı tespit edilmiştir. Ayıca; modellemede kullanılan düşük Reynolds sayılı k-? türbülans modelinin sıcaklık dağılımını ve akış özelliklerini iyi şekilde temsil edebildiği görülmüştür

Improvement of heat transfer from high heat flux surfaces by using vortex promoters with different geometries and impinging jets

In this study; the enhancement of heat transfer from a surface with constant heat flux using an impinging jet and different shapes of vortex promoters was investigated numerically. Firstly, fluid flow and heat transfer in a channel were investigated for different Reynolds numbers, and ratio of channel height to nozzle hydraulic diameter (H/Dh), without using vortex promoters. Afterwards, effects of cylindrical, square and triangular vortex promoters on fluid flow and heat transfer for ratio of distance of vortex promoter to jet center to nozzle hydraulic diameter were investigated. In the last phase; effects of second group of vortex promoters were investigated on heat transfer and fluid flow. As a result; by using impinging jets and vortex promoters an increase of 28% on heat transfer from the surface can be observed according to the condition without vortex promoter. With increasing Reynolds number an increase on heat transfer was observed. Decreasing the channel height does not increase the heat transfer significantly. For the cylindrical vortex promoters maximum local Nusselt number is obtained at L/Dh=1.4. The most effective heat transfer is obtained with triangular vortex promoters. Using second group of vortex promoters can cause an increase of 36.1 % on heat transfer locally, but cannot cause a prominent increase on heat transfer along the target plate generally. Additionally, it is observed that the low Reynolds k-ɛ turbulent model can represent temperature variation and flow characteristic quite well

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