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Article
Thermal Behavior in Dimple Square Duct with Inclined Perforated Baffles

Author: Abeer Hashim Falih
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 11 Part (A) Engineering Pages: 2047-2056
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This research presents a study of heat transfer enhancement and pressure drop in a dimple square duct fitted with∝ =30◦,60◦and 90◦ inclined perforated baffles(baffles open area ratio of 26.17 %). The baffle to duct height ratio (w/a) of 0.3 and the baffle pitch to duct height ratio, PR=1, 2 are introduced in the present work. The tested duct has a constant wall heat flux condition. The experiments are carried out by varying airflow rate in terms of Reynolds number ranging from 1147.8 to 15304. The experimental data of heat transfer and pressure drop of the duct fitted withthe inclined perforated baffles are compared with those of the dimple smooth duct under similar condition. The inclined baffles with PR=1 gives higher heat transfer rate than the one with PR=2 and the smooth ductrespectively ,andthe highest heat transfer and pressure drop is found by using baffle with 30◦.


Article
Thermal and Hydraulic Response of Turbulent Flow inside Hexagonal Duct Fitted with Various Inserts
التصرف الحراري والهيدروليكي لجريان اضطرابي داخل مجرى سداسي مزود بحشوات مختلفة

Author: Abeer Hashim Falih عبير هاشم فالح
Journal: Wasit Journal of Engineering Sciences مجلة واسط للعلوم الهندسية ISSN: 23056932 Year: 2016 Volume: 4 Issue: 1 Pages: 147-162
Publisher: Wassit University جامعة واسط

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Abstract

The present work shows the results obtained from experimental investigations of the augmentation of turbulent flow heat transfer in a horizontal hexagonal duct fitted with combined wire coil tabulators and a perforated twisted-tape swirl generator. Water is used as a working fluid for Reynolds number range between 2480-9922 under constant wall heat flux thermal boundary condition. In this study, two enhancement heat transfer devices are used. One is the constant/ periodically varying two wire coil pitch ratio that arranged into two different forms; I-coil (Increasing coil pitch ratio arrangement) and ID-coil (Increasing/decreasing coil pitch ratio arrangement). The other type of inserts is the perforated twisted- tape with constant twist ratio (Y = 5.3 and PR= 4.5%) that placed at the core of the coil wire. The experimental data obtained for each enhancement device are compared with those obtained from the plain duct and also from the available literature to ensure the validation of experimental results. The results show that the heat transfer process have been enhanced with by using combined wire coil and twisted-tape inserts or by using each one alone with compared to plain duct. The highest thermal performance factor of around 2.18 is found by using ID-coil in common with the twisted-tap .

يبين العمل الحالي النتائج التي تم الحصول عليها من التحريات العملية لتحسين انتقال الحرارة لجريان مضطرب داخل مجرى سداسي افقي مزود بمضطربات سلكية ومولدات دوامة عبارة عن شريط ملتو مثقب .استخدم الماء كمائع الاختبار لرقم رينولدز يتراوح بين 2480-9922 تحت فيض حراري منتظم حدي حراري. في هذه الدراسة تم تحسين عملية انتقال الحرارة باستخدام وسيلتين . الاولى عبارة عن لفائف سلكية ثابتة/ ومتغيرة نسبة خطوة اللفة, والمتغيرة تكون بشكلين الاول المتزايد والاخر المتزايد المتناقص . الوسيلة الاخرى عبارة عن شريط ملتو مثقب مولد للدوامات يوضع في قلب اللفائف السلكية بنسبة التواء ثابتة Y=5.3 و PR = 4.5% . تم مقارنة القيم التجريبية التي تم الحصول عليها لكل جهاز مع تلك التي تم الحصول عليها من المجرى الخالي من هذه الوسائل ومن الادبيات السابقة للتأكد من صحة النتائج العملية . لوحظ ان عملية انتقال الحرارة يتحسن باستخدام اللفائف السلكية والشريط الملتو معا او كل على انفراد مقارنة بحالة المجرى الخالي. ان اعلى عامل أداء حراري حوالي 2.18 وجدت باستخدامم ID-coil مع الشريط الملتوي رينولدز.

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