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Article
Enhancement of Heat Transfer using Aluminum Oxide Nanofluid on Smooth and Finned Surfaces with COMSOL Multiphysics Simulation in Turbulent Flow

Authors: Hasan S. Majdi --- Hussein A. Alabdly --- Muayad F. Hamad --- Basim O. Hasan --- et al.
Journal: AL-NAHRAIN JOURNAL FOR ENGINEERING SCIENCES مجلة النهرين للعلوم الهندسية ISSN: 25219154 / eISSN 25219162 Year: 2019 Volume: 22 Issue: 1 Pages: 44-54
Publisher: Al-Nahrain University جامعة النهرين

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Abstract

Both surface extension and nanofluid methods were used to enhance the heat transfer in a double pipe heat exchanger under turbulent flow conditions. Aluminum oxide nanoparticles were used with different concentrations(0.6-3 g/l)in hot water to increase the heat transfer rate on smooth tube and circular fins tube for a range of Reynolds number4240-19790. The simulation was also performed to predict the heat transfer coefficient and temperature profile for selected conditions in which COMSOL Multiphysics is used. The experimental results revealed that the heat transfer enhancement by both circular fin and nanofluid exhibited an increasing trend with Reynolds number and nanofluid concentration. The conjoint effect of Al2O3 of 3 g/l concentration and circular fin provided largest heat transfer enhancement of 53% for the highest Re investigated. Simulation results showed reasonable agreement with the experimental values of heat transfer coefficient. The simulation showed that the presence of nanofluid on finned surface influenced the temperature profile indicating the increased heat transfer rate.


Article
Preparation of PPSU Hollow Fiber Nanofiltration Membranes for Nanofiltration Application

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Abstract

PPSU hollow fiber nanofiltration membranes are prepared by applying two concentrations and various extrusion pressures according to the phase inversion method. Cross-sectional area and outer structures were characterized by using scanning electron microscope (SEM) and atomic force microscopy (AFM). In additional to the pore size distribution, either the mean roughness or the mean pore size of the PPSU hollow fiber surfaces was evaluated by AFM. It was found that the morphology of the PPSU fibers had both sponge-like and finger-like structures through different extrusion pressures and PPSU concentrations. The mean pore size and mean roughness for inner and outer surfaces were seen to be decreased with the increase of extrusion pressure at two different PPSU concentrations. Moreover, the lead ion rejection was significantly improved from 19 to 78 % with increasing the extrusion pressure from 2.5 to 3 bar at 25 wt.% PPSU concentration.


Article
Corrosion of Carbon Steel in Oxygen and NaCl Concentration Cells: the Influence of Solution Temperature and Aeration
تاكل الفولاذ الكاربوني في خلايا تركيز الاوكسجين وكلوريد الصوديوم :تاثير درجة حرارة المحلول والتهوية

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Abstract

Corrosion rate tests were carried out on carbon steel under concentration cells conditions of oxygen and sodium chloride. The effect of aeration in one compartment on the corrosion rate of both coupled metals was determined. In addition, the effects of time and temperatures on the corrosion rate of both coupled metals and galvanic currents between them were investigated. Corrosion potentials for the whole range of operating conditions under concentration cell conditions were also studied. The results showed that under aeration condition, the formation of concentration cell caused a considerable corrosion rate of the Carbon steel specimens coupled in different concentrations of O2 and NaCl due to the galvanic effect. Aerating one compartment caused a noticeable increase in the corrosion rate of the coupled specimen in the other compartment due to the galvanic effect. Increasing temperature caused unstable trends in the free and galvanic corrosion potentials. Increasing the temperature led to an increase in the corrosion rate for both metals.

اجريت عملية قياس معدل التاكل للحديد الفولاذي تحت ظروف خلايا التركيز للاوكسجين وملح كلوريد الصوديوم. وتم دراسة تاثير عامل التهوية لاحد اجزاء الخلية على معدل التاكل لكلا المعدنين المربوطين بالاضافة الى ذلك تم دراسة تاثير الوقت ودرجات الحرارة على معدل التاكل لكلا المعدنين المربوطين وايضا تم قياس التيارات الكلفانية بينهما .تم قياس ودراسة جهود التاكل للمدى الكلي للظروف التشغيلية لظروف خلية التركيز.اظهرت النتائج انه في حالة استخدام التهوية فان تَكُون خلية التركيز يسبب زيادة معدل التاكل للعينات المربوطة وفي تراكيز مختلفة للاوكسجين وملح كلوريد الصوديوم بسبب التاثير الكلفاني. استخدام التهوية لاحد اجزاء الخلية يسبب زيادة ملحوظة في معدل التاكل للعينة المربوطة في الطرف الاخر من الخلية نتيجة التاثير الكلفاني. زيادة درجة الحرارة يؤدي الى اتجاه غير مستقر في جهود التاكل الكلفانية والحرة وان زيادة درجة الحرارة يؤدي الى زيادة معدل التاكل الكلي للمعدنين .

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