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Article
Dynamics and Control of Heat Exchanger Networks
السلوك الديناميكي و السيطرة على شبكة المبادلات الحرارية

Authors: Duraid Fadhil Ahmed --- Cizan A. Ali
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2014 Volume: 32 Issue: 2 Part (A) Engineering Pages: 465-480
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

In this paper dynamics of plate heat exchanger networks is given by combining dynamic models of plate heat exchangers in the network. A mathematical model for plate heat exchanger is developed based on energy balance. Dynamic simulation of plate heat exchanger networks to different step changes in flow rate of both process fluid and utility fluid is conducted using MATLAB simulink. Plate heat exchanger networks has been controlled using split range control method with two manipulated variables which are process fluid and utility fluid. The simulation results showed that split range controller is the best action and gives better response compared with conventional controller.

تم في البحث الحصول على النموذج الديناميكي لشبكة المبادلات الحرارية الصفائحية من خلال الجمع بين النموذج الديناميكي لمبادلات الحرارية الصفائحية الموجودة في الشبكة. تم تطوير نموذج رياضي لمبادل الحراري الصفائحي بالاعتماد على موازنة الطاقة. أجريت محاكاة ديناميكية لشبكة المبادلات الحرارية الصفائحية باستخدام برنامج ماتلاب من خلال اجراء اضطراب درجي في معدل الجريان لمائعي العملية والخدمات. تمت السيطرة على شبكة المبادلات الحرارية الصفائحية باستخدام مسيطر المدى المنفصل ذو متغيرين للمعالجة و أظهرت نتائج المحاكاة بأن مسيطر المدى المنفصل هو أفضل أداء وأعطت استجابة جيدة مقارنة مع المسيطر التقليدي.


Article
Performance Evaluation of Three Phase Spray Direct Contact Heat Exchanger

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Abstract

The present investigation deals with experimental study of three-phase direct-contact heat exchanger, for water-Freon R11 system, where water is the continuous phase (liquid) and Freon R11 (liquid-gas) is the dispersed phase. The test section consisted of a cylindrical Perspex column with inner diameter 8cm and 1.2m long, in which, water was to be confined. Liquid Freon R11 drops were injected into the hot water filled column, through a special design of distributors at the bottom of the column. The liquid Freon R11 drops rose on their way up and evaporated into two-phase bubbles at atmospheric pressure. The study was devoted to express the effect of process variables such as column height, Freon R11 mass flow rate and initial temperature of water on the average percentage holdup, heat transfer rate, volumetric heat transfer coefficient and effectiveness. The obtained experimental results showed that the average percentage holdup increased with increasing in the process variables. The heat transfer rate increased clearly with increasing in mass flow rate of Freon R11 while it increased very little when column height and initial temperature of water increased, it increased two times when increase the mass flow rate from 1.8 to 5.4 kg/hr. The volumetric heat transfer coefficient was found to decrease with increasing in column height and initial temperature of water, while it was increased with increasing in mass flow rate of Freon R11. The effectiveness was found to increase (maximum 90%) with increasing in column height and decreasing in the mass flow rate of Freon R11 and initial temperature of water. A statistical analysis was performed to get general correlations for the average percentage holdup, heat transfer rate, volumetric heat transfer coefficient and effectiveness as a function of the studied parameters


Article
Application of Earth Tube Heat Exchanger and Solar Chimney for Natural Cooling System in Basrah City

Authors: Salman H. Hammadi --- Alaa Hlaichi Mohammed
Journal: Basrah Journal for Engineering Science مجلة البصرة للعلوم الهندسية ISSN: Print: 18146120; Online: 23118385 Year: 2014 Volume: 14 Issue: 2 Pages: 23-32
Publisher: Basrah University جامعة البصرة

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Abstract

Solar chimney (SC) together with earth to air heat exchanger (EAHE) is being employed as a low-energy consuming technique to remove undesirable interior heat from a building in the hot seasons. A numerical program "FLUENT 6.3 code" of an earth to air heat exchanger (EAHE) is studied for predicting the outlet air temperature and cooling potential of these devices in Basrah climate. Theoretical analyses have been conducted in order to investigate the ventilation in a solar chimney. The investigation into the viability of Low Energy Earth Pipe Cooling Technology in providing thermal comfort in Basrah. The demand for air-conditioning in buildings in Basrah affects the country escalating energy consumption. Therefore, this investigation was intended to seek for an alternative passive cooling to air-conditioning. The passive technology, where the ground was used as a heat sink to produce cooler air, has not been investigated systematically in hot and humid countries. A sub-soil temperature model adapted for the specific conditions in Basrah is presented and its output compared with CFD modeling. The results have shown that the potential of Earth Pipe is providing lower output temperature of air inlet to the room. We found that the resulting temperature at the buried pipe outlet decreases with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air in the pipe and increasing depths up to 4m.

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