مطالعه انتقال حرارت از دیواره بستر حبابی گاز-جامد به ذرات جامد درون آن به کمک دینامیک سیالات محاسباتی

نویسندگان

1 دانشگاه ایلام

2 دانشگاه ماهشهر

چکیده

بسترهای سیال به دلیل خصوصیات انتقال حرارتی مناسب در بسیاری از فرایندهای حرارتی استفاده می⁣شوند. به دلیل پیچیدگی⁣های مربوط به مدل⁣سازی انتقال حرارت در بسترهای سیال، پژوهش⁣های محدودی در این خصوص صورت گرفته است. در تحقیق موجود با استفاده از مدل دو سیالی ترکیب با تئوری جنبشی جریان دانه⁣ای یک راکتور گاز-جامد حبابی حاوی ذرات کروی با قطر میانگین 280 میکرون شبیه⁣سازی شده است. تاثیر دو مدل دراگ مهم یعنیGidaspow و Syamlal-O’Brien و برخی پارامترهای هیدرودینامیکی همچون ضریب ارتجاع ذره-ذره و نیز تاثیر شرایط مرزی ذره-دیواره بررسی شده است. نتایج شبیه⁣سازی حاکی از این است که هر دو مدل دراگ، عبور حباب از درون بستر را بخوبی نشان می⁣دهند. اگرچه هر دو مدل دراگ روند تغییرات محلی ضریب انتقال حرارت با زمان را بطور مناسبی پیش⁣بینی می⁣کنند، اما مدلGidaspow انطباق بهتری را نتایج تجربیِ ضریب انتقال حرارت از دیواره به بستر را نشان می⁣دهد. همچنین دیده شده که ضرایب ارتجاع ذره-ذره و ذره-دیواره و نیز ضریب آینه⁣ای تاثیر بسزایی بر انتقال حرارت درون بستر گاز-جامد حبابی دارند.

کلیدواژه‌ها


عنوان مقاله [English]

Numerical Study of Wall-to-Bed Heat Transfer in a Gas–Solid Bubbling Fluidized Bed by CFD

نویسندگان [English]

  • Hossein Hosseini 1
  • Ashkan Mohasseli 2
چکیده [English]

Due to the effective heat transfer in fluidized beds, these systems have been wieldy used in many thermal processes. There are limited published papers in the literature regarding heat transfer in fluidized beds, because of complexities existing in these systems. In the present study, a gas-solid bubbling fluidized bed including the spherical particles with diameter of 280 µm is simulated by a Eulerian-Eulerian Two-Fluid Model incorporating the kinetic theory of granular flow (KTGF). Influence of two important drag models of Gidaspow and Syamlal as well as some hydrodynamics parameters, namely, particle-particle restitution coefficient and solid wall boundary conditions are studied. Both drag models predict the behavior of the bubble passage through the bed reasonably. Although both drag functions show the same trend with the experimental data, Gidaspow drag model predicts the better results than the Syamlal one. The CFD results reveal that the modeling parameters of specularity coefficient, particle-particle and particle-wall restitution coefficients have a significant effect on the heat transfer coefficient between the wall and particles.

کلیدواژه‌ها [English]

  • Heat transfer
  • CFD
  • KTGF
  • TFM
  • Drag model
  • specularity coefficient

 

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