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Article
The Combined Effect of Rib with Single Large Eddy Break Up Devices on Flow and Heat Transfer Characteristic of Turbulent Flow in Rectangular Duct

Authors: Ekhlas Mohammed Fayyedh --- Moayed R. Hasan --- Ali Falah Mohammed
Journal: AL-NAHRAIN JOURNAL FOR ENGINEERING SCIENCES مجلة النهرين للعلوم الهندسية ISSN: 25219154 / eISSN 25219162 Year: 2017 Volume: 20 Issue: 1 Pages: 281-291
Publisher: Al-Nahrain University جامعة النهرين

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Abstract

An experimental investigation has been performed to study the effect of combined artificially roughened (ribs) with and without single Large Eddy Break-Up Devices, on flow and heat transfer characteristic of fully developed turbulent flow in rectangular duct. The aspect ratio of rectangular duct is 10, hydraulic diameter 72.72 mm, relative roughness pitch (P/e) 10 and relative roughness height (e/Dh) 0.05. The rib was in the form of circular shape with diameter of (4mm) which was mounted on heated wall of duct at spanwise direction. The experiments have been conducted by varying airflow rate in terms of Reynolds number ranging from 3.2x104 to 6.2x104 and constant heat flux of 600W/m2. The heat transfer and friction factor of the flow for rib and combined method were compared with those of a smooth duct under similar experimental conditions. It has been found that the combined method (rib with single Large Eddy Break-Up Devices) has significant effect on the friction factor and heat transfer with decreasing in friction factor with percent(1.2) and increasing Nusselt number with (4.1). Correlations for Nusselt number and friction factor in terms of (Reynolds number and Large Eddy Break-Up Devices) parameters are found which reasonably correlate the experimental data.


Article
THE COMBINED EFFECT OF RIB WITH TANDEM LARGE EDDY BREAK UP DEVICES ON FLOW AND HEAT TRANSFER CHARACTERISTIC OF TURBULENT FLOW IN RECTANGULAR DUCT : PART B
دراسة التاثير المركب للعوائق المستعرضة واجهزة تفكك الدوامة الكبيرة على خصائص انتقال الحرارة للجريان المضطرب داخل مجرى مستطيل

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Abstract

An experimental investigation was carried out to study the effect of Large Eddy Breakup Devices with of circular ribs on one heated wall of a rectangular duct with fully developed turbulent flow , on heat transfer and flow characteristic. The artificially roughened duct has an aspect ratio (W/H) of 10, hydraulic diameter of 72.72 mm, relative roughness pitch (P/e) of 10 and relative roughness height (e/Dh) of 0.05. The experiments were conducted by varying airflow rate in terms of Reynolds number ranging from 3.2x104 to 6.2x104 and constant heat flux of 600 W/m2.The heat transfer and friction characteristics of the duct were compared with those of a smooth duct under similar experimental conditions. It was found that there was a significant enhancement of Nusselt number for combined high Reynolds number (2.6) and friction factor (3.47).

تم اجراء دراسة عملية للتحقق في تأثير كل من أجهزة تفكك لدوامة الكبيرة للأسطح الساخنة مع عوائق مستعرضة ذات مقطع دائري داخل قناة ذات مقطع مستطيل للجريان المضطرب على خصائص انتقال الحرارة والجريان, المجرى الهوائي ذات نسبة باعيه (W/H =10)قطر هيدروليكي 72.72ملم ، استخدم انابيب اسطوانية ذات مقطع دائري بقطر 4 ملم و المسافة بينهما 40 ملم ، نسبة الخشونة تمثل (p/e=10)، ارتفاع الخشونة النسبي(e/Dh=0.05) . تم إجراء التجارب لمدى من عدد رينولد تتراوح بين ( 3.2x104- 6.2x104) تمت مقارنة نتائج السطح الخشن بوجود او عدم وجود اجهزة تفكيك الدوامة الكبيرة تحت فيض حراري ثابت في تحسين انتقال الحرارة ومعامل الاحتكاك. لوحظ ان عدد نزلت تزداد بمقدار(2.6) اما معامل الاحتكاك فيتحسن بمقدار (3.47) بوجود اجهزة تفكك الدوامة الكبيرة مع العوائق العرضية .

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