Numerical Investigation of Laminar Flow and Heat Transfer in Rectangular CrossSectional Ducts

Abstract

In this study, hydrodynamically and thermally developing laminar flow and heat transfer in a rectangular cross-sectional duct have been numerically investigated for steady state and constant surface temperature boundary condition. Numerical solutions have been made for three different aspect ratios (α=0.25, 0.50 and 1.0) and in the Reynolds numbers range of 600 to 2000. Air (Pr0.72) is used as working fluid. A commercial CFD program ANSYS Fluent 13.0 has been employed to carry out the numerical study. Results are given in terms of Nusselt number Nu, Darcy friction factor f, hydrodynamic Lhd and thermal entrance Lth lengths as a function of Reynolds number Re. Also, velocity and temperature contours in the duct are given for different Reynolds numbers. It is seen that the general equation given for circular ducts does not give a true hydrodynamic and thermal entrance length for rectangular ducts. The present results obtained from numerical study are correlated as a function of aspect ratio and Reynolds number involving all aspect ratios and Reynolds numbers used in this study

Keywords

• Rectangular cross-sectional
• duct
• Developing flow
• Laminar flow
• Numerical study
• Fluent

Dikdörtgen Kesitli Kanallarda Laminer Akış ve Isı Transferinin Sayısal Olarak İncelenmesi

Abstract

Bu çalışmada, dikdörtgen kesitli kanaldaki hidrodinamik ve ısıl olarak gelişmekte olan laminer akış ve ısı transferi sayısal olarak incelenmiştir. Çalışma sabit duvar sıcaklığı sınır şartı için kararlı rejim şartında gerçekleştirilmiştir. Sayısal çalışma üç farklı en/boy oranında (α=0.25, 0.50 ve 1.0) ve Reynolds sayısının 600-2000 değerlerinde gerçekleştirilmiştir. Akışkan olarak hava (Prï€0.72) kullanılmıştır. Çalışma, Sayısal Akışkanlar Dinamiği (SAD) programı olan ANSYS Fluent 13.0 paket programı kullanılarak gerçekleştirilmiştir. Sonuçlar, Nusselt sayısı Nu, Darcy sürtünme faktörü f, hidrodinamik Lhd ve ısıl gelişme Lth uzunluklarının Reynolds sayısı Re ile değişimi biçiminde ifade edilmiştir. Buna ilaveten, kanaldaki hız ve sıcaklık dağılımları farklı Reynolds sayılarında verilmiştir. Dairesel kanallarda hidrodinamik ve ısıl gelişme uzunluklarını veren denklemlerin dikdörtgen kanallarda doğru sonuç vermediği görülmüştür. Sayısal çalışmadan elde edilen sonuçlar bu çalışmada kullanılan bütün en/boy oranlarını ve Reynolds sayılarını kapsayacak şekilde en/boy oranı ve Reynolds sayısının fonksiyonu şeklinde genel bir korelasyon ile verilmiştir.

Keywords

• Dikdörtgen kesitli kanal
• Gelişmekte olan akış
• Laminer akış
• Sayısal çalışma
• Fluent

References

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