IJE TRANSACTIONS A: Basics Vol. 31, No. 10 (October 2018) 1749-1759   

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N. Jahantigh, A. Shahriari and F. Rakani
( Received: November 18, 2017 – Accepted in Revised Form: February 05, 2018 )

Abstract    The investigation of the effect of nanoparticles’ mean diameter and temperature of Al2O3–water nanofluid on velocity and energy field using the lattice Boltzmann method is the main objective of this study. The temperature of the vertical walls is considered constant at Tc and Th, respectively, while the up and the down horizontal surfaces are smooth and insulated against heat and mass. The influences of Grashof number (103, 104, 105) Prandtl number (Pr=3.42, 5.83), the various volume fraction of nanoparticles (φ=0, 0.01, 0.03, 0.05) and particle-size (dp= 24, 47, 100 nm) were carried out on heat transfer and flow fields. It was concluded that addition of nanoparticles causes a significantly affect on temperature and flow fields. The decrement of heat transfer is observed with the increment of solid volume fraction, but it increases when Grashof number and nanoparticles’ mean diameter increase. The decrement of nanoparticles’ mean diameter and Prandtl number have the same effect on Nusselt number. In addition, it was resulted that the thermal conductivity model had insignificantly impact on the mean Nusselt number than the dynamic viscosity model.


Keywords    Nanoparticles Mean Diameter, Natural Convection, Nanofluid, Lattice Boltzmann Model


چکیده    هدف مطالعه حاضر بررسی اثرات قطر متوسط نانوذرات و دمای نانوسیالآبی اکسید آلومینیم (Al2O3) بر روی میدان سرعت و توزیع دما با استفاده از روش شبکه بولتزمن است. دیواره‌های سمت راست و چپ محفظه به ترتیب در دمای گرم و سرد قرار دارند در حالی که دیواره بالا و پایین هر دو صاف عایق شده‌اند. اثر پارامترهایی نظیر عدد گراشف (Gr= 103, 104,105)، عدد پرانتل (Pr= 3.42, 5.83)، کسر حجمی نانوذرات(φ = 0, 0.01, 0.03, 0.05) اندازه ذرات(dp= 24, 47, 100 nm) بر روی میدان جریان و میدان دما مطالعه شده است.می¬توان نتیجه گرفت که میدان¬هایجریان و توزیع دما متاثر از اضافه شدن نانوذرات می¬باشند.با افزایش کسر حجمی نانوذرات انتقال حرارت کاهش می-یابد،بااین‌حال با افزایش عدد گراشف و قطر متوسط نانوذرات مشاهده می¬شود کهانتقال حرارت افزایش می¬یابد. کاهش قطر متوسط نانوذرات و عدد پرانتل اثر مشابهی بر روی عدد ناسلت دارند. هم¬چنین مشاهده شد که عدد ناسلت میانگین نسبت به مدل هدایت حرارتی حساسیت کمتری نسبت به مدل ویسکوزیته دینامیکی دارد.


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