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Parametric Study of the Flow Characteristics and Heat Transfer from Circular Intermittent Jet Impinging on a Concave Surface | ||
| Journal of Heat and Mass Transfer Research | ||
| دوره 8، شماره 2 - شماره پیاپی 16، بهمن 2021، صفحه 173-186 اصل مقاله (2.09 M) | ||
| نوع مقاله: Full Length Research Article | ||
| شناسه دیجیتال (DOI): 10.22075/jhmtr.2021.22009.1319 | ||
| نویسندگان | ||
| Mehran Rajabi Zargarabadi* 1؛ Saeed Rakhsha2؛ Syfolah Saedodin3 | ||
| 1Faculty of Mechanical Engineering | ||
| 2Faculty of Mechanical Engineering, Semnan University, Semnan, Iran | ||
| 3Faculty of Mechanical Engineering, Semnan University, Iran | ||
| تاریخ دریافت: 13 آذر 1399، تاریخ بازنگری: 02 آبان 1400، تاریخ پذیرش: 28 آبان 1400 | ||
| چکیده | ||
| The main purpose of the current work is the analysis of the pulsating effect on the flow and heat transfer from impinging jet on a concave surface. In this way, the heat flux of 2300 W/m2 has been applied constantly on the surface with the radius of 120mm. The intermittent jet has been created for the frequency range of 1-100Hz by the pulsed-jet generator. Nusselt number distribution and flow field have been investigated for dimensionless distance of nozzle to surface (H/d) 2 to 5 and Reynolds number from 7000 to 13000. The comparison of the experimental data with Numerical simulation shows that the k-ε RNG turbulence model is appropriately capable of predicting the Nusselt number on the concave surface under the pulsed jet impinging. Results of the present research indicate that, pulsating the jet is more effective on the concave surface in comparison with a flat surface. Also as compared to steady jet, when pulsating applies to the inlet jet with low frequency, reduction in Nusselt number is acquired. Furthermore, at each Re number and H/d, a threshold Strouhal number is found above which the Nusselt number of the pulsed jet is greater than that of the steady jet. Moreover, for the low nozzle to surface distance, Nu of stagnation point at low and high frequency is varied with Sr=0.05 and Sr=0.15, respectively. At Re=10000, pulsating the impinging jet with f =100Hz causes an increase in the time and area-averaged of Nusselt number by 22% and 20% in comparison to steady jet at H/d=5 and 2, respectively. | ||
| کلیدواژه‌ها | ||
| Impinging jet؛ Nusselt number؛ pulse frequency؛ concave surface | ||
| عنوان مقاله [English] | ||
| مطالعه مشخصه های جریان و انتقال حرارت جت برخوردی دایروی متناوب به سطح مقعر | ||
| چکیده [English] | ||
| هدف مطالعه حاضر، بررسی و تحلیل اثر نوسانی کردن جت ورودی بر روی جریان و انتقال حررات جت برخوردی دایره ای بر سطح مقعر است. به این ترتیب، شار حرارت W/m2 2000 بر روی سطح با شعاع 120 میلی متر اعمال شده است. جت نوسانی برای محدوده فرکانس 1-100 هرتز توسط دستگاه تولید جریان نوسانی ایجاد شده است. توزیع عدد نوسلت و میدان جریان برای فاصله بدون بعد نازل تا سطح مقعر، 2 تا 5 و عدد رینولدز از 7000 تا 13000 بررسی شده است. مقایسه داده‌های تجربی با شبیه‌سازی عددی نشان می-دهد که مدل آشفتگی k-ε RNG به طور مناسب قادر به پیش بینی عدد نوسلت در امتداد سطح مقعر می باشد. نتایج تحقیق حاضر نشان می‌دهد که، جت نوسانی روی سطح مقعر در مقایسه با سطح تخت موثرتر است. همچنین در مقایسه با جت ثابت، نوسانی کردن جت ورودی با فرکانس پایین باعث کاهش Nu می‌شود. علاوه بر این، در هر Re و H / d، یک عدد آستانه استروهال یافت می‌شود که برای مقادیر بیشتر از آن، مقدار عدد Nu جت نوسانی بیشتر از جت ثابت است. نتایج نشان می‌دهد، برای فاصله‌های کم نازل تا سطح برخورد، Nu نقطه سکون در فرکانس های کم و زیاد به ترتیب با Sr0.05 و Sr 0.15 متناسب است. در Re = 10000 ، نوسانی کردن جت ورودی با f = 100Hz در مقایسه با جت ثابت، باعث افزایش متوسط زمانی و مکانی عدد ناسلت به اندازه % 22 و %20 در H/d های 2 و 5 می گردد. | ||
| کلیدواژه‌ها [English] | ||
| جت برخوردی, فرکانس نوسان, عدد استروهال, عدد ناسلت, صفحه مقعر | ||
| مراجع | ||
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