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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
EFFECT OF BAFFLES ORIENTATION ON HEAT TRANSFER ENHANCEMENT IN DIMPLED SQUARE DUCT
تأثير اتجاة العوائق على تحسين انتقال الحرارة داخل مجرى مربع ذي نتوءات

Author: Abeer Hashim Falih
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2017 Volume: 21 Issue: 3 Pages: 36-46
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

The article presents an experimentally investigation on turbulent flow and heat transfer behaviors in a dimple square duct fitted with inline angled baffles having a constant length for two pitch ratio , (PR= PB/a=0.83and 1.66), and three attack angle, α=45◦,60◦ and 90◦. The inline angled baffles are mounted on the lower channel walls to create longitudinal vortex flows throughout the test duct . 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 3900 to 18750. The experimental results are compared between the duct with inclined baffles and the dimple smooth duct. The duct fitted baffle gives higher heat transfer rate and friction factor than the smooth duct. The experimental results reveal that the maximum heat transfer is at PR= 0.83. For the given conditions, the maximum thermal performance enhancement factor (TEF) of the inline -angled baffle with 30◦ is found to be about 2.4 at PR= 0.83 and Re= 3900.

تقدم هذه المقالة دراسة عملية لتدفق وانتقال الحرارة لجريان اضطرابي داخل مجرى مربع ذي نتوءات مزود بعوائق مائلة ثابتة الطول وبنسبتين لل ( ( PR =0.83and 1.66 ومائلة بثلاثة زوايا ( α =45◦,60◦ and 90◦ ) . هذه العوائق مثبتة على السطح السفلي للمجرى لخلق دوامة طولية على طول مجرى الاختبار.مع تعرض مجرى الاختبار الى فيض حراري ثابت .اجريت التجارب من خلال تغيير تدفق الهواء الذي يتمثل بعدد رينولدز الذي يتراوح من 3900 الى 18750. تم مقارنة النتائج العملية بين المجرى المزود بالعوائق المائلة والمجرى الخالي من هذه العوائق حيث وجد ان المجرى المزود بالعوائق يمتلك اعلى معدل لانتقال حرارة وخسائر احتكاك مقارنة بالمجرى الخالي من تلك العوائق .كم بينت النتائج العملية ان اعلى معدل لانتقال الحرارة وجد عند PR=0.83 وان اعلى اداء حراري وجد عند استخدام العائق المائل بزاوية 30 وكانت قيمته تتراوح حوالي.4 2 عند PR=0.83 و. Re=3900


Article
EFFECT OF USING R-22, R404 AND R-407C ON PERFORMANCE OF AN AIR-CONDITIONING SYSTEM
على اداء منظومة التثليجR-22, R404 AND R-407C تاثير استخدام

Author: Abeer Hashim Falih*
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 5 Pages: 200-214
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

Due to the environment depletion, replacing chlorofluorocarbons in refrigeration industry was an important problem. In the experimental study a (1.0 TR) vapor compression system were used with original working fluid of R-22 and compared to alternatives refrigerant R-407C and R-22. The effects of the main parameters of performance analysis such as refrigerant type, compressor pressure ratio, outlet air evaporative temperature, coefficient of performance were investigated for various ambient temperatures above 50 ºC. The results showed that the compressor ratio of system using R404 and R-407C is more than the compressor ratio of system using R22 by 2% and 4% respectively. Also, the outlet air evaporative temperature of system using the alternative refrigerant R-22 is more than the outlet air evaporative temperature with system using R-407C and R-404 by 8% and 5% respectively. The coefficient of performance of R-407C was measured with the same reciprocating compressor that was supplied with the R-22 system. It could be concluded that there is a decrease of 8% in system COP as friendly environment R407C compared with system using R-22 and a decrease of 12% in system COP when using R-404. However; the result showed that R407C have thermodynamic performance similar to R-22. Engineering Equation Solver (EES) software is used for draw (p-h) diagram for the cycle


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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