بررسی تجربی انتقال حرارت و افت فشار در کانال گرمکن هوای خورشیدی دارای دندانههای سوراخدار

نوع مقاله : مقاله پژوهشی

نویسندگان

1 صنعتی خواجه نصیرالدین طوسی

2 دانشکده مهندسی مکانیک دانشگاه صنعتی خواجه نصیرالدین طوسی

چکیده

در مطالعه حاضر انتقال حرارت و افت فشار جریان هوا در داخل کانال مربعی با دندانه‌های دارای سوراخ به شکل تجربی بررسی می‌شود و فرضیه تأثیر ایجاد سوراخ در ازبین‌بردن یا کاهش اثر مخرب ناحیه‌ی کم فشار در پشت دندانه که باعث کاهش افت فشار می‌شود، مورد واکاوی قرار گرفت. محدوده رینولدز 15000 تا 50000، نسبت ارتفاع دندانه به قطر هیدرولیکی کانال 11/0 و 14/0، نسبت قطر سوراخ به ارتفاع دندانه 3/0 و 5/0 و نسبت گام دندانه به قطر کانال در مقادیر 20، 25 و 30 بررسی شد. نتایج به منظور اعتبارسنجی با نتایج دندانه معمولی مطالعات پیشین مقایسه شدند که صحت نتایج تجربی تأیید شد. نتایج نشان داد که با ایجاد سوراخ در دندانه، افت فشار و مقدار ناسلت توأمان کاهش می‌یابد؛ این تأثیر نامطلوب در گام‌های کوچکتر مشهودتر است. از طرف دیگر، ایجاد سوراخ در دندانه‌های بلندتر باعث بهبود عملکرد حرارتی می‌شود. ضریب عملکرد در بهترین حالت تا 17درصد افزایش یافت. در مواردی که گام دندانه‌ها بزرگتر است، دندانه‌های دارای سوراخ می‌تواند در کاربردهایی که نیاز به افزایش انتقال حرارت یا کاهش دمای دیواره است و مصرف انرژی دمنده اهمیت کمتری دارد، عملکرد سیستم مربوطه نظیر گرمکن خورشیدی را تا حد چشمگیری افزایش دهند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental investigation of heat transfer and pressure drop in perforated ribs in the solar air heater channel

نویسندگان [English]

  • Majid Bazargan 1
  • Faraz Mirali 2
  • Elham Mohammadi 2
  • Mohammad Ansari 2
2 Mechanical Engineering Department K. N. Toosi University of Technology
چکیده [English]

In the present study, heat transfer and pressure drop inside the square channel are investigated experimentally with perforated ribs. The Reynolds range was between 15000 and 50,000. The ratio of ribs height to channel hydraulic diameter was 0.1 and 0.13 and ribs pitch to height ratio was 20, 25, and 30, respectively. The ratio of hole diameter to rib height was 0.3 and 0.5, respectively. The results obtained from the experimental setup developed in the laboratory compared with the results of previous studies, which confirmed the accuracy of the experimental results. The results show that the use of ribs in the channel surfaces results in a significant improvement in the heat transfer rate in the canal as well as an increase in the pressure drop. The perforated ribs resulted in less pressure drop, however, the Nusselt decreased. As well The effect of perforation on the indentation was more evident in the smaller pitch ratio. The results show that in applications where there is a need to lower the wall temperature or increase the heat transfer and the blower energy consumption is less important, using holes in the ribs, the performance of the relevant system such as gas turbine or heaters can be improved.

کلیدواژه‌ها [English]

  • Convection heat transfer
  • perforated ribs
  • Pressure drop
  • Experimental investigation
  • Solar air heater
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