Hidrolik Çap Kullanarak Dairesel Kanal ve Gerçek Altıgen Kanal Sonuçlarının Karşılaştırılması

Öz

Dairesel kanallar için türetilmiş türbülanslı akış korelasyonlarının hidrolik çap kullanılarak altıgen kesitli kanallar için kullanılıp kullanılamayacağını görmek için ANSYS Fluent 17.0 yazılımı kullanılarak altıgen kanallardaki türbülanslı akış sayısal olarak incelenmiştir. 30o ile 90o arasında kanal yanal açıları ve 10×103Re50×103 arasındaki Reynolds sayısı parametreleri incelenmiştir. Türbülans modeli olarak standart k-ε modeli kullanılmıştır. Altıgen kesitli kanallar için Reynolds sayısına ve yanal açıya bağlı tam gelişmiş boyutsuz ısı transfer katsayısı olan Nusselt sayısı ve tam gelişmiş Darcy sürtünme faktörü için genel ifadeler önerilmiştir. Sonuçlar, altıgen kanal yanal açısının kanal boyunca basınç düşümünü ve kanaldaki ısı transfer katsayısını etkilediğini göstermiştir. Ayrıca sonuçlar =60o olan eşkenar altıgen kanalın minimum basınç düşüşü ve maksimum Nusselt sayısı verdiğini göstermiştir. Literatürde türbülanslı akış koşullarında dairesel kanallar için verilen korelasyonların gerçek altıgen kanal akışına göre %14 daha yüksek boyutsuz ısı transfer katsayısı olan Nusselt sayısı sağlayabileceği sonucuna varılmıştır.

Anahtar Kelimeler

• Altıgen kesitli kanal
• ısı transferi
• türbülanslı akış
• sayısal analiz

A Comparison of Circular Duct and Real Hexagonal Duct Results Using Hydraulic Diameter

Öz

To see whether the turbulent flow correlations derived for circular ducts can be used for hexagonal cross-sectional ducts using hydraulic diameter, turbulent flow in hexagonal ducts is numerically investigated under constant wall temperature boundary condition using ANSYS Fluent 17.0 software. Investigated parameters are the Reynolds number between 10×103Re50×103 and side angle of the duct varying between 30o and 90o. Standard k-ε model is used as turbulence model. General expressions are proposed for fully developed dimensionless heat transfer coefficient Nusselt number and fully developed Darcy friction factor in terms of Reynolds number and side angle for hexagonal-shaped cross-sectional duct. Results show that side angle of hexagonal duct affects the pressure drop along duct and heat transfer coefficient in duct. Results point out that regular hexagonal duct, =60o, gives minimum pressure drop and maximum Nusselt number. It is concluded that correlations given in the literature for circular ducts in turbulent flow can give 14% higher dimensionless heat transfer coefficient, Nusselt number, than that of actual hexagonal duct flow.

Anahtar Kelimeler

• Hexagonal duct
• heat transfer
• turbulent flow
• numerical analysis

Kaynakça

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