IJE TRANSACTIONS A: Basics Vol. 28, No. 10 (October 2015) 1408-1414   

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R. Davarnejad and M. Kheiri
( Received: July 24, 2015 – Accepted: September 03, 2015 )

Abstract    Turbulent heat transfer in Helically Corrugated Tubes (HCT) was numerically investigated for pure water and SiO2 nanofluid using Computational Fluid Dynamics (CFD). This study was carried out for different corrugating pitches (5, 7, 8 mm) and heights (0.5, 0.75, 1.25 mm) at various Reynolds numbers ranging from 5000 to 13300. The effect of nanoparticles on heat transfer augmentation for plain tube and HCT was considered and the relative Nusselt numbers were also compared. However, the heat transfer extremely increased with increasing the volume fraction of nanoparticles in the plain tube but, the effect of helical corrugation on the heat transfer increment was much more than that of the nanoparticles enhancement in the HCT. It was concluded that the corrugated height increment and the corrugated pitch reduction increase the heat transfer process. The maximum heat transfer was obtained at Reynolds number of 13300, HTC with p=5 mm and e=1.25 mm, and SiO2 volume fraction of 1%.


Keywords    CFD, Helically corrugated tubes, Plain tube, Turbulent heat transfer


چکیده    مدل سازی عددی انتقال حرارت جریان آشفته در لوله های چین دار حلزونی با استفاده از نرم افزار فلوینت، برای آب خالص و نانو ذره اکسید سیلسیم انجام شد. مطالعه صورت گرفته بر روی گام های مارپیچ مختلف (5،7،8 میلی متر) و ضخامت های مارپیچ (0.5،0.75،1.25 میلی متر) در اعداد رینولدز بین 5000 تا 13300 در نظر گرفته شد. تاثیر افزودن نانو ذره بر روی انتقال حرارت برای لوله ساده و پیچ دار در نظر گرفته شد و اعداد ناسلت مربوطه اندازه گیری شد. در لوله ساده انتقال حرارت با افزایش میزان نانو ذره به شدت افزایش یافت. این درحالی است که تاثیر گام مارپیچ و ضخامت مارپیچ در لوله پیچ دار، بیش از افزودن نانو ذره است. افزایش ضخامت و کاهش گام باعث افزایش انتقال حرارت در لوله های پیچ دار شد. بیشترین عدد ناسلت در رینولدز 13300، گام 5 میلی متر،ضخامت 1.25 میلی متر و یک درصد حجمی از نانو ذره اکسید سیلسیم به دست آمد.



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