بررسی عددی تأثیر هندسه فین و ضخامت فیلم بر انتقال حرارت در تبخیر فیلم ریزان روی لوله افقی

رحیمی, علی; جلال الدین ابیانه, محمد حسن; جعفرکاظمی, فرزاد

doi:10.48311/mme.2026.122000.83058

بررسی عددی تأثیر هندسه فین و ضخامت فیلم بر انتقال حرارت در تبخیر فیلم ریزان روی لوله افقی

نوع مقاله : مقاله پژوهشی

نویسندگان

علی رحیمی

محمد حسن جلال الدین ابیانه

فرزاد جعفرکاظمی

گروه مهندسی مکانیک، واحد تهران جنوب دانشگاه آزاد اسلامی، تهران، ایران

10.48311/mme.2026.122000.83058

چکیده

تبخیر فیلم‌ریزان از کارآمدترین روش‌های انتقال حرارت در مبدل‌ها و تبخیرکننده‌هاست که عملکرد آن به هیدرودینامیک فیلم مایع و توزیع سطحی آن وابسته است. در این پژوهش، اثر سه هندسه فین محیطی بر ویژگی‌های هیدرودینامیکی و عملکرد حرارتی جریان فیلم‌ریزان روی لوله افقی با شبیه‌سازی CFD بررسی شد. شبیه‌سازی‌ها در عدد رینولدز ۲۷۱ با مدل دوفازی VOF و شرط دمای ثابت دیواره انجام شد. برای ارزیابی عملکرد، توزیع کسر حجمی مایع، ضخامت فیلم، میدان‌های سرعت و دما و ضریب انتقال حرارت موضعی در زوایا و مقاطع مختلف طول لوله استخراج گردید. نتایج نشان داد هندسه فین نقش تعیین‌کننده‌ای در بازتوزیع فیلم، کنترل ترشوندگی و تغییر مقاومت حرارتی دارد. در میان هندسه‌ها، مدل F1 بهترین تعادل را بین هیدرودینامیک و انتقال حرارت ارائه داد؛ علی‌رغم افزایش ۱۵٫۴ درصدی ضخامت متوسط فیلم نسبت به لوله صاف، ضریب انتقال حرارت را حدود ۱۶٫۴ درصد افزایش داد. مدل F2 افزایش ۱۴٫۹ درصدی ضریب انتقال حرارت داشت، اما به دلیل توزیع غیریکنواخت‌تر فیلم، نوسانات موضعی بیشتری ایجاد کرد. مدل F3 به دلیل تجمع مایع و افزایش ضخامت متوسط فیلم تا ۶۹ درصد، موجب کاهش ۷۴٫۸ درصدی ضریب انتقال حرارت شد. نوآوری این پژوهش، بررسی همزمان اثر هندسه فین بر توزیع و ضخامت فیلم، ترشوندگی سطح و انتقال حرارت و تبیین نقش یکنواختی فیلم در عملکرد حرارتی است؛ نتایج نشان می‌دهد که افزایش سطح فین یا حتی افزایش ضخامت متوسط فیلم الزاماً موجب بهبود انتقال حرارت نمی‌شود و بازتوزیع یکنواخت فیلم و جلوگیری از تجمع موضعی مایع، عامل مؤثرتری در افزایش ضریب انتقال حرارت است.

کلیدواژه‌ها

تبخیر فیلم ریزان

لوله افقی فین‌دار

دینامیک سیالات محاسباتی (CFD)

روش حجم سیال (VOF)

ضخامت فیلم

ضریب انتقال حرارت

موضوعات

دینامیک سیالات محاسباتی

عنوان مقاله English

Numerical Investigation of the Effect of Fin Geometry and Film Thickness on Heat Transfer in Falling Film Evaporation on a Horizontal Tube

نویسندگان English

Ali Rahimi

Mohammadhasan Jalaleddin Abyaneh

Farzad Jafarkazemi

Department of Mechanical Engineering, ST.C., Islamic Azad University, Tehran, Iran

چکیده English

Falling film evaporation is one of the most efficient heat transfer methods in heat exchangers and evaporators. Its performance strongly depends on liquid film hydrodynamics and surface distribution. This study investigated the effect of three circumferential fin geometries on hydrodynamic characteristics and thermal performance of a falling film over a horizontal tube using CFD. Simulations were at Re=217 with VOF two-phase model and constant wall temperature. Liquid volume fraction, film thickness, velocity and temperature fields, and local heat transfer coefficient were extracted at various angles and cross-sections along the tube.

Results showed fin geometry plays a decisive role in redistribution, wettability, and thermal resistance. Model F1 gave the best balance between hydrodynamics and heat transfer. Despite 15.4% higher average film thickness than the smooth tube, it enhanced the heat transfer coefficient by 16.4%. Model F2 showed a 14.9% increase in heat transfer. However, its less uniform distribution caused greater local fluctuations. Model F3, due to accumulation and 69% thicker average film, caused a 74.8% reduction in heat transfer.

A key contribution of this study is the simultaneous assessment of the effects of fin geometry on film distribution and thickness, surface wetting, and heat transfer, thereby elucidating the role of film uniformity in thermal performance. The results demonstrate that increasing the finned surface area or even the average film thickness does not necessarily enhance heat transfer. Instead, uniform film redistribution and the prevention of local liquid accumulation play a more significant role in improving the heat transfer coefficient.

کلیدواژه‌ها English

Falling film evaporation

Horizontal finned tube

Computational Fluid Dynamics (CFD)

Volume of Fluid (VOF)

Film thickness

Heat transfer coefficient

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