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Article
THE INFLUENCE OF APEX ANGLE ON MIXED CONVECTION IN A POROUS SECTOR CHANNEL
تأثير الزاوية الرأسية على الحمل المختلط في قناة مسامية قطاعية الشكل

Author: Manar Salih Mahdi منار صالح مهدي
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2011 Volume: 4 Issue: 1 Pages: 54-70
Publisher: Diyala University جامعة ديالى

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Abstract

ABSTRACT: - The influence of apex angle on mixed convection in a horizontal porous sector channel is investigated. The analysis is performed by considering fully- developed hydrodynamically and thermally flow. The governing equations have been solved numerically using finite difference method. The channel is heated from the right surface, and cooled from the left one –both are held at constant temperature- while the top surface is adiabatic. The numerical analysis has been conducted in the following range of parameters: radius of the sector=4, (Pe=20(, (Ra*=100 and 1000(, the apex angle (Φ=30o, 60o, 75o and 90o). The results are presented to demonstrate the effect of increasing the apex angle on the streamlines, the isotherms and local Nusselt number. The highest stream function appears in a specified apex angle depending on Ra*. The local Nusselt number values are decreasing as the apex angle is increasing at (Ra*=1000), while at (Ra*=100) its values are increasing as the apex angle is increasing. A correlating equation is suggested to correlate ( (against apex angle (Φ) and (Ra*( for )Pe=20(.Keywords: - porous, mixed convection, horizontal sector channel.

الخلاصه في هذا البحث تم استقصاء تأثير الزاوية الرأسية على الحمل المختلط في قناة أفقية مسامية قطاعية الشكل، أجريت التحليلات باعتبار الجريان تام التشكيل هيدروليكياً وحرارياً، حلت المعادلات الحاكمة عددياً باستخدام طريقة الفروقات المحددة، سخن السطح الأيمن من القناة وبرد السطح الأيسر لها- كلاهما ثابتي درجة الحرارة-، بينما عزل السطح العلوي للقناة، أجريت التحليلات وفق المعاملات التالية: نصف قطر القطاع= 4، (Pe=20)، (Ra*= 100, 1000)، الزاوية الرأسية (Φ=o30، وo60، وo75، وo90). وضحت النتائج تأثير زيادة الزاوية الرأسية على خطوط الجريان، خطوط ثبوت درجة الحرارة، وعدد نسلت الموقعي. تظهر أعلى قيمة لدالة الجريان عند زاوية رأسية معينة اعتماداً على قيم عدد (Ra*) ، إن قيم عدد نسلت الموقعي تنخفض بزيادة الزاوية الرأسية عند (Ra*=1000) بينما عند (Ra*=100) تزداد قيمها بزيادة الزاوية الرأسية. أقترحت علاقة ترابطية تربط معدل عدد نسلت ( ) بالزاوية الرأسية (Φ) و(Ra*) عندما (Pe=20).الكلمات الدالة: مسامي، حمل مختلط، قناة أفقية قطاعية الشكل.


Article
Natural Convection in a Vertical Rectangular Enclosure
الحمل الحر في حيز شاقولي مستطيل

Author: Manar Salih Mahdi منار صالح مهدي
Journal: kirkuk university journal for scientific studies مجلة جامعة كركوك - الدراسات العلمية ISSN: 19920849 / 26166801 Year: 2013 Volume: 8 Issue: 4 Pages: 1-16
Publisher: Kirkuk University جامعة كركوك

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Abstract

In this paper an experimental work has been conducted to investigate the influence of heating the lower half and cooling the upper half of vertical surface of a rectangular enclosure on natural convection. The enclosure length is (100 cm) with a square cross section (10×10 cm). The tests are done for three mass flow rates (0, 0.003 and 0.03 kg/sec) and five heat fluxes (48, 187, 400, 706 and 1080 W/m2). The hottest region formed is observed at ( = 0.67) where the lowest Nux is found while the coldest region is observed at ( = 0.33) where the highest Nux is found. Increasing the water mass flow rate enhances the heat transfer. The same thing happens with increasing the heat flux. A correlation is found to relate Nu with Ra (Nu= 0.216 Ra1/4) for (4×105≤Ra≤4×106). Both the experimental results and the correlation found are compared with a previous work and fair agreement is found.

تم في هذا البحث إج ا رء د ا رسة عممية لأختبار تأثير تسخين النصف السفمي لسطح شاقولي وتبريد نصفه العموي في حيز مستطيل عمى الحملالطبيعي. طول الحيز ) 100 cm ( وهو ذو مقطع مربع ) 10×10 cm (. أجريت الاختبا ا رت لثلاث معدلات تدفق كتمية ) 0 kg/sec و 0.003و 0.03 ( وخمس قيم لمفيض الح ا رري ) 48 W/m2 و 781 و 400 و 107 و 1080 (. لوحظ تشكل أدفء منطقة عند ( = 0.67) حيث توجد أقلقيمة ل Nux بينما لوحظت أبرد منطقة عند ( = 0.33) حيث توجد أعمى قيمة ل Nux . زيادة التدفق الكتمي لمماء يحسن انتقال الح ا ررة، الشيءنفسه يحدث عند زيادة الفيض الحراري. أوجدت معادلة ت ا ربطية لربط Nu مع Ra(Nu= 0.23 (0.778 Ra)1/4) للمدى(4×105≤Ra≤4×106) . قورنت كل من النتائج العممية والعلاقة الت ا ربطية مع عمل سابق ووجد تقارب جيد بينها.


Article
Thermally Developing Forced Convection in a Horizontal Equilateral Triangular Channel
انتقال الح ا ررة بالحمل القسري لجريان متطور ح ا ررياً في قناة أفقية مثلثة متساوية الأضلاع

Authors: Manar Salih Mahdi --- Tahseen Ahmad Tahseen --- Adnan Mohamed Hussein
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2012 Volume: 19 Issue: 3 Pages: 58-67
Publisher: Tikrit University جامعة تكريت

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Abstract

An experimental investigation was carried out to study thermally developing fully developed laminar forced convection in a horizontal equilateral triangular channel where the channel surface was heated uniformly. The channel length was (1.5 m) long and constructed from three plane (100 mm) walls to form the equilateral triangular crosssection. The experiments were conducted for three mass flow rates (1.91×10-3, 2.54×10-3 and 3.03×10-3 kg/s) and four heat fluxes (91, 171, 272 and 406 W/m2). Reynolds number range was (1198  Re 1988). It was found that local Nusselt number increasing as the heat fluxes and the mass flow rate increased. Also it was found that the greatest local Nusselt number value was in the beginning of the channel then it decreased accompanied by growing the thermal boundary layer along the channel. Present experimental results have a good agreement with previous results obtained for similarly configured channels.


Article
Theoretical Study of Heat Transfer through a Sun Space Filled with a Porous Medium

Authors: Ahmed Tawfeeq Ahmed Al-Sammarraie --- Manar Salih Mahdi
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2016 Volume: 23 Issue: 2 Pages: 10-20
Publisher: Tikrit University جامعة تكريت

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Abstract

A theoretical study had been conducted to detect the effect of using a porous medium in sunspace to reduce heating load and overcoming coldness of winter in the cold regions. In this work, the heat transferred and stored in the storage wall was investigated. The mathematical model was unsteady, heat conduction equation with nonlinear boundary conditions was solved by using finite difference method and the solution technique of heat conduction had based on the Crank Nicholson method. The results had adopted on the aspect ratio (H/L=30), Darcy number (Da=10-3), porosity (φ=0.35) and particle to fluid thermal conductivity ratio (kp/kf=38.5). The results showed that using the porous medium had enhanced the heat transferred and stored in the storage wall. For the outside storage wall temperature, an increase of 19.7% was achieved by using the porous medium instead of the air, while it was 20.3% for the inside storage wall temperature.

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