Abstract    In this paper, the heat transfer to the fluid, passing through the double forward facing step (FFS) channel with square obstacle is enhanced by Taguchi’s S/N ratio analysis. Flow through the forward facing step channel has a wide range of applications in thermal systems due to its flow separation and subsequent reattachment, which in turn enhances the heat transfer. Flow separation and reattachment mainly depends on the channel geometry, obstacle and flow parameters. Hence, in this study, step height in the channel, obstacle size, Reynold’s number and gap between the obstacle and step are included as control paramters in the S/N ratio analysis for maximizing the heat transfer. These parameters are varied through three levels of values and L9 orthogonal array is employed. Numerical simulation technique is applied to analyze the L9 cases through computational fluid dynamics code. From the simulation, the rise in temperature at the channel exit with reference to the inlet is predicted. The best values for the identified control parameters conclude to a temperature raise of about 2.86°C. The optimum result obtained from the S/N ratio analysis is also compared with response surface methodology technique. Finally, analysis of variance (ANOVA) is conducted and identified that step height and flow Reynold’s number affect the heat transfer by about 79 and 19%, respectively.

Keywords    Double forward facing step flow, Square obstacle, Taguchi’s S/N ratio analysis, Response surface methodology technique, ANOVA, Numerical simulation.

چکیده    در این مقاله، انتقال حرارت به مایعی که از کانال دو طرفه رو به جلو (FFS) با مانع مربعی عبور می‌کند با آنالیزS/N تاگوچی افزایش داده می شود. جریان در کانال گام رو به جلو کاربرد گسترده ای در سیستم های حرارتی دارد چرا که جداسازی جریان و اتصال مجدد آن، به نوبه خود انتقال حرارت را افزایش می دهد. جداسازی جریان و اتصال مجدد به طور عمده به هندسه کانال، مانع و پارامترهای جریان بستگی دارد. از این رو، در این مطالعه، ارتفاع گام در کانال، اندازه مانع، عدد رینولدز و فاصله بین مانع و گام به عنوان پارامترهای کنترل در آنالیز نسبت S/N برای به حداکثر رساندن انتقال حرارت بررسی می شود. این پارامترها در سه سطح مقادیر تغییر داده شده و در آرایه افقی L9 استفاده می شوند. شبیه سازی عددی برای تحلیل موارد L9 از طریق کد دینامیک سیالات محاسباتی استفاده می شود. از شبیه سازی، افزایش دما در خروجی کانال با توجه به ورودی پیش بینی شده است. با استفاده از بهترین مقادیر برای پارامترهای کنترل، افزایش درجه حرارت در حدود 2.86درجه سانتیگراد است. نتیجه مطلوب حاصل از آنالیز نسبت S/N با روش پاسخ سطح مقایسه شده است. در نهایت، آنالیز واریانس (ANOVA) انجام می شود و مشخص می شود که ارتفاع گام و عدد رینولدز روی انتقال حرارت به ترتیب به میزان 79 و 19٪ تاثیرگذار هستند.

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