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Article
Hybrid CFD-ANN Scheme for Air Flow and Heat Transfer Across In-Line Flat Tubes Array

Authors: Tahseen Ahmad Tahseen --- M. Ishak --- Khalaf Ibrahim Hamada --- M.M. Rahman --- et al.
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 2 Pages: 59-67
Publisher: Tikrit University جامعة تكريت

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Abstract

Flat tubes are vital components of various technical applications including modern heat exchangers, thermal power plants, and automotive radiators. This paper presents the hybridization of computational fluid dynamic (CFD) and artificial neural network (ANN) approach to predict the thermal-hydraulic characteristics of in-line flat tubes heat exchangers. A 2D steady state and an incompressible laminar flow in a tube configuration are considered for numerical analysis. Finite volume technique and body-fitted coordinate system are used to solve the Navier–Stokes and energy equations. The Reynolds number based on outer hydraulic diameter varies between 10 and 320. Heat transfer coefficient and friction are analyzed for various tube configurations including transverse and longitudinal pitches. The numerical results from CFD analysis are used in the training and testing of the ANN for predicting thermal characteristics and friction factors. The predicted results revealed a satisfactory performance, with the mean relative error ranging from 0.39% to 5.57%, the root-mean-square error ranging from 0.00367 to 0.219, and the correlation coefficient (R2) ranging from 99.505% to 99.947%. Thus, this study verifies the effectiveness of using ANN in predicting the performance of thermal-hydraulic systems in engineering applications such as heat transfer modeling and fluid flow in tube bank heat exchangers.


Article
Tensile Strength, Micro-hardness and Microstructure of Friction-Stir-Welding AA6061-T4 Joints
مقاومة الشد، الصالدة المجهرية، والبنية المجهرية لوصالت (T4-AA6061) ملحومة باللحام الخلط االحتكاكي

Authors: Najeeb S. Abtan --- Ataalah Hussain Jassim --- Mustafa S. M. Al-Janabi
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 4 Pages: 51-56
Publisher: Tikrit University جامعة تكريت

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Abstract

Welding of aluminum alloys by traditional welding methods creates some defects such as hot cracks, porosity, and void that led to decreasing of mechanical properties. Friction Stir Welding (FSW) gives good mechanical properties of aluminum alloy welds. In this paper, FSW worked in 4 mm thick plate of 6061-T4 aluminum alloy, with two welding parameters are used (tool rotational speed and feed rate) was investigated, were analyzed the microstructure and mechanical properties by carried out microstructural, microhardness, and tensile strength tests. From results are found defect-free of welds at a wide range of parameters. Stir zone shows a fine-equiaxed grain and high hardness, not significantly change between heat affected zone and base metal in size grain. Tensile strength of welds was lower than base metal and fracture location was occurred at a low hardness region for the welds.

لحام سبائك االلمنيوم بالطرق التقليدية يخلق بعض العيوب مثل الشقوق الحارة والمسامية والفراغات التي تعمل على خفض الخواص الميكانيكية للملحومات، لحام الخلط االحتكاكي يعطي خواص ميكانيكية جيدة لملحومات سبائك االلمنيوم. في هذا البحث دراسة للحام سبائك االلمنيوم (T4-AA6061) بسمك (4mm) بوساطة لحام الخلط االحتكاكي تحت متغيرات) السرعة الدورانية ومعدل التغذية(، وحللت الخواص الميكانيكية والبنية المجهرية من خالل اجراء فحوصات البنية المجهرية والصالدة المجهرية ومقاومة الشد. من خالل النتائج وجد ان البنية المجهرية لمنطقة الخلط ذات حجم حبيبي ناعم-ومتساوية المحاور وذات صالدة عالية وليس هناك اختالف مميز في الحجم الحبيبي بين منطقة المعدن األساس والمنطقة المتأثرة بالحرارة، مقاومة الشد للملحومات أدنى من مقاومة الشد للمعدن األساس وموقع الكسر للملحومات حدث في منطقةالصالدة المنخفضة.

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