مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

دلایل تفاوت نتایج مدل‌های یکفازی و دوفازی در انتقال حرارت نانوسیالات

نویسندگان
جواد رستمی 1
عباس عباسی 2
مجید صفاراول 2
1 دانشگاه رازی
2 دانشگاه صنعتی امیرکبیر
چکیده
در این مقاله انتقال حرارت مزدوج نانوسیالات در یک میکروکانال موجی شکل با استفاده از مدل یکفازی به روش همگن و مدل دوفازی به روش اویلری-لاگرانژی بصورت عددی بررسی و تفاوت نتایج با استفاده از تحلیل های فیزیکی مطالعه شده است. سیال پایه آب و نانوذرات از دو جنس اکسید آلومینیوم و مس است. غلظت حجمی نانوذرات تا 2% و قطر آنها 100 نانومتر است. معادلات سه بعدی حاکم شامل پیوستگی، ممنتوم و انرژی در سیال از دیدگاه اویلری به روش حجم کنترل (سیمپل) حل شده‌اند. معادلات حاکم بر حرکت و انرژی ذرات نیز به روش لاگرانژی جداسازی و به روش رنگ-کوتای مرتبه 4 حل شده‌اند. چون در روش لاگرانژی معادلات حرکت در سه بعد و معادله انرژی برای تک‌تک ذرات حل می‌شود، از روش پردازش موازی و با استفاده از ابر کامپیوتر این معادلات حل شده‌اند. نتایج نشان می‌دهند که تحت تاثیر نیروی درگ توزیع ذرات بصورت همگن نیست و این موضوع منشا اختلاف نتایج روش همگن و مدل دوفازی است. توزیع ناهمگن ذرات بر میدانهای سرعت و دما نیز تاثیر می‌گذارد و باعث می-شود نتایج حاصل از مدل دوفازی متفاوت از نتایج مدل یکفازی (همگن) شود و در بعضی حالات این اختلاف به حدود 20% نیز می‌رسد.
کلیدواژه‌ها
نانوسیال
مدل یکفازی
روش همگن
مدل دوفازی
روش اویلری-لاگرانژی

عنوان مقاله English

The Reasons of Differences between one phase and two phase Models of Nanofluids Heat Transfer Characteristics

نویسندگان English

Javad Rostami 1
Abbas Abbassi 2
majid safar avval 2
1 Razi university
2 Amirkabir university of technology
چکیده English

in this paper, conjugate heat transfer in wavy microchannels filled with nanofluid is studied numerically. Homogeneous single-phase models underestimate the experimental results. Then, nanofluid simulated by two-phase model using an Eulerian-Lagrangian approach. Nanofluids are water-Cu or water-Al2O3 suspensions with a particle diameter of 100-150nm and a volume fraction of up to 2%. The three-dimensional governing equations including continuity, Navier-Stokes and energy equations are solved by the well-known SIMPLE method. The governing equations for particles are solved by a 4th order Runge-Kutta algorithm. due to the 3-D governing equation four equations includinf velocity components and energy should be solved for all particles. the computer program has been written in parallel processing method (MPI). Then a super computer with several CPU,s should be used. In one phase model there some supposes, one of them is that the velocty and temperature of a particle is equal to the velocity and temperature of its surrounding fluid. But the main suppose is that the particle distribution is homogeneous. Results show that the main reason of difference between the results of Homogeneous single-phase models and two-phase model is non-homogeneous particle distribution in the domain.

کلیدواژه‌ها English

Nanofluid
one phase model
homogeneous method
two-phase model
Eulerian-Lagrangian method
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مهندسی مکانیک مدرس
دوره 18، شماره 3
خرداد 1397
صفحه 228-236