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Article
EXPERIMENTAL INVESTIGATION OF ENHANCEMENT HEAT TRANSFER OF INSERT TWISTED TAPE OF CIRCLAR CUT WITH WIRE COIL IN THE DOUBLE PIPE HEAT EXCHANGER

Author: Hisham Assi Hoshi
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 3 Pages: 23-33
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

: The combined effect of wire coil with twist tape inserted in a circular tube using hot air as the test fluid on heat transfer rate and pressure drop were investigated experimentally. The twisted tape used in this work is made of an aluminum sheet with dimensions (1250 mm length, 18 mm wide, 1 mm thick, twist ratio y =8 and y=5.8). The wire coil was made of copper with diameter (d=3mm), the wire coil with two coil pitch ratio (CR=p/d=10 and CR= p/d=5). Reynolds number used in experiments ranged between (9648 to 18144) and the inlet temperatures for hot and cold fluid are 750C and 300C respectively. The experimental results showed that combined wire coil with twisted tape gives 1.268 enhancement efficiency higher than those with each device alone and plain tube, also give better performance as compared to the twisted tape and wire coil alone.


Article
NUMERICAL STUDY FOR INTERRUPTED RECTANGULAR FINS IN A NATURAL CONVECTION FIELD

Authors: Abbas Jassem Jubear --- Ali Hameed Abd
Journal: Al-Qadisiyah Journal for Engineering Sciences مجلة القادسية للعلوم الهندسية ISSN: 19984456 Year: 2018 Volume: 11 Issue: 2 Pages: 216-228
Publisher: Al-Qadisiyah University جامعة القادسية

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Abstract

The heat sink with vertically rectangular interrupted fins investigated numerically in a natural convection field, and with steady-state heat transfer. Numerical study has been conducted using ANSYS Fluent software (R16.1) in order to develop a 3-D numerical model. The dimensions of fins are (305 mm length, 100 mm width, 17 mm height, and 9.5 mm space between fins). The number of fins used on the surface are eight. In this study, the heat input that is used as follow (20, 40, 60, 80, 100, and 120 watts). The study is focused on interrupted rectangular fins with different arrangement of fins. The results show that the addition of interruption fins in various arrangements will improve the thermal performance of the heat sink, and through the results, a better interruption rate obtained as an equation.


Article
FORCED CONVECTION HEAT TRANSFER OF AXIAL AIR FLOW WITH HEATSINK ON UNIFORM HEAT FLUX

Authors: Adil Abbas Mohammed --- Saad Abdulwahab Razuqi
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 2 (Part-3) Pages: 10-21
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

The heat sink is used to increase heat transfer from heated surface to air. The seize and the geometry of the fins affect on the heat transfer coefficient. The heat transfer prediction represents the first step to get the optimal design. The purpose of the present study is to predict the effectiveness of two types of closely spaced fins, the first arrangement is parallel cylindrical fin array and the second type is hollow parallel cylindrical fin array. Also there are two types of heat sink with respect to the fan location, the first type is the cooling fan attached in order to draw the hot air up and away from the heatsink fixed outside on the heat sink to let the axial air flow and the other with enclosure cutout template. The heat sink geometry are designed with Solidworks 14 and exported to ANSYS FLUENT 15.0.7 CFD code. Reynolds number were taken at a range 4000-16000, so k-Ԑ model turbulence model was used in to simulate mean flow characteristics for turbulent flow conditions. Constant heat flux condition was proposed with range between 1000-10000 kW/m2. The Results of temperature contour lines depicted a variation from the base to the extended surfaces tips especially with the fins from outside to the core of the heat sink. This explain that the heat sink with a cooling fan fixed in the enclosure cutout template more effect than the second type with second fan fixation for the two types of fins. Nusselt numbers indicated that cylindrical fins performed better in heat transfer than the hollow fins.


Article
THE EFFECT OF FINS PERFORATION AND MATERIAL TYPE ON THERMAL PERFORMANCE OF A HEAT SINK UNDER NATURAL CONVECTION
تأثير الشكل الهندسي ونوع المعدن للزعانف على الاداء الحراري لمبدد حرارة تحت الحمل الحراري الطبيعي

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Abstract

An experimental study was done to investigate the effect of fin geometry modification and material type on heat dissipation from a heat sink under natural convection. v-corrugated solid fin and v-corrugated perforated fin were designed for this purpose. Aluminum and Copper metals were selected in designing the fins because their wide application in cooling and heating equipment. Three different voltages 110, 150 and 200 V supplied to the heat sink to study their effects on the fins performance. Each experiment repeats two times to reduce the error and the data recorded after reaching the steady state conditions. The utilization of solid and perforated v-corrugated fins is compared. The results showed that perforated fins dissipated heat more than corresponding solid by 15.4, 34 and 32% for aluminum, and 2.7, 2.1 and 4.3% for copper fin in the three voltages. Also, the results indicated that the heat loss by solid copper fin is greater by 56, 72 and 92% than corresponding solid aluminum fin and for perforated fin case by 38, 31.7 and 51.9 % at 110,150 and 200 V respectively.

اجريت دراسة تجريبية للتحقق في تأثير الشكل الهندسي للزعنفة و نوع المادة المستخدمة على فقدان الحرارة بواسطة مبدد حرارة مزعنف تحت الحمل الحراري الطبيعي . تم تصميم زعانف مموجة حادة صلبة ومثقبة لهذا الغرض . تم اختيار معدن الالمنيوم والنحاس في تصميم الزعانف بسبب تطبيقاتها الواسعة في معدات التبريد والتدفئة. تم تجهيز مصدر الحرارة بثلاثة فولتيات مختلفة 110, 150 و 200 فولت لدراسة تأثيرها على اداء الزعانف . كل تجربة تم اعادتها مرتين لتقليل الخطأ وتم استحصال القراءات بعد الوصول الى مرحلة الاستقرار الحراري. تم مقارنة اداء الزعنفة المموجة المثقبة مع نظيرتها الصلبة واظهرت النتائج ان الزعانف المثقبة تبدد الحرارة اكثر من الزعانف الصلبة بنسبة 15.4, 34 و 32 % في حالة الالمنيوم و 2.7, 2.2 و 4.3 % في حالة النحاس لقيم الفولتيات الثلاثة. كما اشارت النتائج ان فقدان الحرارة بواسطة زعنفة النحاس الصلبة اكثر بنسبة 56, 72 و 92 % من زعنفة الالمنيوم الصلبة وفي حالة الزعنفة المثقبة بنسبة 31, 38 و 51.9 % عند 110, 150 و 200 فولت على التوالي.


Article
Effect of Using Combined Square Nozzle & winglet with Helical Tape on Thermal Characteristics in Tube Heat Exchanger
تأثير استخدام المركب لفوهة مربعة ذو جنيح مع شريط حلزوني على الخصائص الحرارية في أنبوب مبادل حراري

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Abstract

Influence of combined square nozzle with helical tape inserted in a constant heat flux tube on heat transfer enhancement for turbulent airflow for Reynolds number ranging from 7000 to 14500 were investigated experimentally. Three different pitch ratios for square nozzle (PR = 5.8, 7.7 and 11.6) according to three different numbers of square nozzle (N = 3, 4 and 5) and constant pitch ratios for helical tape were used. The results observed that the Nusselt number and friction factor for combination with winglets were found to be up to 33.8 % and 21.4 %, respectively higher than nozzle alone for pitch ratio PR=5.8. The maximum value of thermal performance for using combination with winglets was about 1.351 for pitch ratio= 5.8. Nusselt number and friction factor correlations from experimental data were developed for turbulent flow.

تمت دراسة عملية تأثير اتحاد فوهة مربعة ذات جنيح مع شريط حلزوني مدرج في أنبوب ذي تدفق حراري ثابت على تحسين نقل الحرارة لتدفق هواء مضطرب ولعدد رينولدز يتراوح من 7000 إلى 14500.حيث تم استخدام ثلاث نسب خطوة مختلفة للفوهة المربعة وهي (5.8, 7.7 و11.6) على وفق ثلاثة أعداد مختلفة من الفوهات المربعة وهي (5, 4 و3) واستخدامت نسبة ثابتة واحدة للشريط الحلزونية. ولاحظت النتائج أن عدد ناسلت وعامل الاحتكاك للاتحاد مع الفوهة ذات الجنيح وجد أنه يصل إلى 33.8% و 21.4% على التوالي أعلى من الفوهة وحدها لنسبة خطوة هي (5.8). كانت القيمة القصوى للأداء الحراري لاستخدام الاتحاد مع الفوهة ذات الجنيح حوالي 1.351 لنسبة خطوة هي ( 5.8). تم تطويرعلاقات تجريبية لعدد ناسلت ومعامل الأحتكاك للنتائج التجريبية ولجريان مضطرب.


Article
Effect of the Circular Perforations on the Heat Transfer Enhancement by the Forced Convection from the Rectangular Fins

Author: Wadhah Hussein Abdulrazzaq Al-Taha وضاح حسين عبد الرزاق الطه
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2018 Volume: 11 Issue: 3 Pages: 62-70
Publisher: Diyala University جامعة ديالى

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Abstract

This study aims to investigate the effect of the circular perforation of the rectangular fin on the enhancement of the heat transfer by forced convection. The solid rectangular fin considered as a reference for comparison purpose with the perforated fin. The parameters taken into consideration are thermal properties and geometrical dimensions of the fin and its perforations. The area and heat transfer gain of the perforations fins were considered being the main parameters in this study. The results of this study showed that the heat dissipation was improved when used the perforation fins compared with the equivalent solid fin. The enhancement quantity of the heat dissipation from the fin depends on the thermal conductivity, the perforation dimension, thickness, longitudinal and lateral spacing. Finally, the perforating of the fins enhances the rate of heat dissipation as well as decreases the weight of the fin.


Article
Simulation of Turbulent Heat Transfer Augmentation with Hybrid Nanofluid

Authors: Adnan Mohammed Hussein عدنان محمد حسين --- Jasim Ibrahim Musa جاسم ابراهيم موسى
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2018 Volume: 11 Issue: 4 Pages: 28-34
Publisher: Diyala University جامعة ديالى

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Abstract

Study of heat transfer augmentation with hybrid nanofluid represents a new class of heat transfer augmentation. The CFD model by using commercial software depending on finite volume technique and adopting SIMPLE algorithm is performed. Mixture of Aluminum Nitride (AlN) and alumina (Al2O3) nanoparticles into water as a basefluid is classified as a new class of hybrid nanofluids that can augment heat transfer. The nanofluid volume fraction and Reynolds number are in the range of (1% to 4%) and (5000 to 17000) respectively. The size diameter of nanoparticles and heat flux around a horizontal straight tube are fixed at 30 nm and 5000 w/m2 respectively. The numerical solution has been successfully validated by using an experimental data available in the literature. Results show that combination of AlN - Al2O3 nanoparticles into water basefluid tends to augment significant heat transfer performance.

Keywords

Nanofluid --- Hybrid --- Turbulent --- CFD --- ANSYS --- Heat transfer.


Article
Effect of Fluidized Bed Particle Size on Heat Transfer Coefficient at Different Operating Conditions
تأثير حجم جسيمات الطبقة المميعة على معامل انتقال الحرارة عند ظروف تشغيلية مختلفة

Authors: Ehsan Fadhil Abbas --- Sarah Burhan Izat
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 4 Pages: 24-29
Publisher: Tikrit University جامعة تكريت

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Abstract

The aim of this study is to investigate the effect of gas flow velocity, size of sand particles, and the distance between tubes immersed in a fluidized bed on heat transfer coefficient. Experimental tests were conducted on a bundle of copper tubes of (12.5 mm) diameter and (320 mm) length arranged in a matrix (17×9) and immersed in a fluidized bed inside a plastic container. One of the tubes was used as a hot tube with a capacity of (122 W). (25 kg) of sand with three different diameters of sand particles (0.15, 0.3 and 0.6 mm) was used in these tests at ten speeds for gas flow (from 0.16 m/s to 0.516 m/s). The results showed a significant inverse effect of fluidized bed particles diameter on the heat transfer coefficient. Accordingly, the heat transfer coefficient for (0.15mm) diameter sand was found to be higher than that of (0.3 mm) and (0.6 mm) sand by about (3.124) and (6.868) times respectively, in all tests. The results showed good agreement with results from other studies conducted under the same conditions but with different sandparticle size.

تهدف هذه الدراسة الى التحقق من تأثير كل من سرعة الغاز، حجم جسيمات الرمل والمسافة بين االعمدة المغمورة في الطبقة المميعة على معامل انتقال الحرارة. حيث اجريت اختبارات تجريبية على حزمة من االنابيب نحاسية بقطر )5.12 )ملم وطول )320 )ملم ورتبت على شكل مصفوفة )17×9 )مغمورة في الطبقة المميعة داخل حاوية بالستيكية. استخدمت احدى االنابيب كمصدر للحرارة بسعة )122 )واط. استخدمت ثالثة قياسات لجسيمات الرمل )15.0 ،3.0 و6.0 )ملم وبعشر سرع تراوحت مــــن )16.0 الى 516.0 )م/ ثا. اظهرت النتائج بأن تأثير عكسي كبير لقطر جسيمات الرمل في الطبقة المميعة على معامل انتقال الحرارة. وفقا" لذلك، فان معامل انتقال الحرارة عند الرمل بقطر )15.0 )ملم الذي حصل عليه كانت اعلى عما حصل عليه عند )3.0 )ملم و )6.0 )ملم بحوالي )124.3 )و )868.6) مرة على التوالي في جميع االختبارات. تظهر النتائج بانها توافق بشكل جيد مع نتائج لدراسات اخري اجريت تحت نفس الظروف ولكن مع قياسات الرمل مختلفة.


Article
NUMERICAL INVESTIGATION OF MICROCHANNEL HEAT SINK WITH MEPCM SUSPENSION WITH DIFFERENT TYPES OF PCM

Authors: Hind Lafta TBENA --- Mushtaq Ismael HASAN
Journal: Al-Qadisiyah Journal for Engineering Sciences مجلة القادسية للعلوم الهندسية ISSN: 19984456 Year: 2018 Volume: 11 Issue: 1 Pages: 115-133
Publisher: Al-Qadisiyah University جامعة القادسية

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Abstract

The aim of this paper is to study the microencapsulated phase change materials (MEPCM) suspension as a coolant instead of pure fluid in the micro channel heat sink (MCHS) with different core and wall materials as well as different base fluids. The MEPCM suspension using in this study consist of microcapsules constructed from n-octadecane, RT44 as a phase change materials (PCM) and shell materials are poly-methylmthacrylate (PMMA), poly-alpha olefin (PAO), these capsules are suspended in (pure water, ethylene glycol and pure oil) in a concentration of (0–20)% and have been used as a cooling mediums at different ambient temperatures. Constant heat flux is applied at base of heat sink. The results obtain show that, using MEPCM suspensions as a coolant in micro heat sink instead of conventional cooling with pure fluid lead to enhance the cooling performance of micro heat sink is be 20.91% with (RT44+PMMA) pure oil, 16.91% with (RT44+PMMA) for ethyleneglycol and 12.91% with (RT44+PMMA) for pure water at concentration 2% and


Article
CONVECTION HEAT TRANSFER IN A CHANNEL OF DIFFERENT CROSS SECTION FILLED WITH POROUS MEDIA

Authors: Ahmed A. Mohammad Saleh --- Suhad A. Rasheed --- Rafel B. Smasem
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2018 Volume: 9 Issue: 2 Pages: 57-73
Publisher: University of Kufa جامعة الكوفة

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Abstract

A forced convection heat transfer in ducts (circular, triangular, rectangular) cross sections and (1m) length with hydraulic diameter (0.1m) filled with porous media (glass spheres 12 mm diameter) is investigated experimentally at constant heat flux from the wall (1070W/m²) with Reynolds number range of (12461-2500). Comparison was made between three ducts for local temperature distribution and local Nusselt number). The experimental results showed the effect of Reynolds number and cross section on the temperature profile and local Nusselt number,also empirical correlations for average Nusselt number and Peclet number were obtained for three ducts.

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