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NUMERICAL STUDY OF SOME INFLUENCING PARAMETERS ON MELTING PROCESS OF PHASE CHANGE STORAGE UNITS INTEGRATED WITH A SOLAR WATER HEATER

Authors: Khalid Ahmad Joudi --- Aouf Abdulrahman Al-Tabbakh
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 2 (Part-2) Pages: 47-63
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

This work theoretically analyzes the melting process of a phase change material (PCM) packed in thermal energy storage units. The units are filled with paraffin wax and inserted in the water storage tank of a solar water heater to improve the storage capacity. A computer program was built to simulate the performance of the whole system during a typical day between 8 a.m. and 3:45 p.m.. The simulation period was divided into small time intervals of 10 seconds. The Finite Difference Method (FDM) was used to analyze the melting process of the PCM units. Each unit was discretized into a large number of nodes forming a two dimensional grid. The effect of three PCM parameters were studied which are the shape, volume and surface area. The cross-sectional shape included square, annular square, circular and circular annulus bars. It was found that the circular sections provide higher melt ratio than the square sections and that the annular sections are more effective than the solid sections. Increasing the PCM surface area at constant PCM volume significantly increases the melt ratio for all PCM shapes. The system equipped with PCM having the least volume operates more effectively than a system with larger PCM volumes


Article
PERFORMANCE ANALYSIS OF A COMPACT SOLAR WATER HEATER WITH PARAFFIN WAX STORAGE UNIT

Authors: Raid Salman Fahad --- Amir Fadhil Noori --- Aouf Abdulrahman Al-Tabbakh
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2019 Volume: 23 Issue: 1 Pages: 135-144
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

The present work experimentally studies the thermal performance of a solar collector integrated with a thermal storage unit to form a compact solar water heater. The storage capacity is further enhanced by attaching a phase-change storage unit containing phase change material (PCM) which is paraffin wax. The two units (tanks) take the form of two shallow rectangular boxes (compartments) tilted at 45o to the horizon and are firmly attached to ensure complete mutual heat transfer between them. Water and PCM fill the top and bottom tanks respectively. Measurements were carried out from 8 a.m. to 4 p.m. where the temperatures at various locations in the system were measured along with ambient temperature and solar radiation intensity. Results show that the temperature of both compartments increases continuously during the simulated period with the upper tank having the higher temperatures. The PCM average temperature did not reach melting range (55oC – 60oC) which requires either decreasing the amount of PCM or using a PCM with a lower melting point. The maximum temperatures reached are 82oC for water and 47oC for PCM which are measured at 4 p.m. and the maximum overall system efficiency of the system was 74% at 11:30 a.m.


Article
A Theoretical Procedure for Estimating Saturation Temperature Inside Solar Two-Phase Loops
دراسة نظرية لتخمين درجة حرارة التشبع داخل الدورات الشمسية ثنائية الطور

Authors: Khalid Ahmad Joudi خالد احمد الجودي --- Aouf Abdulrahman Al-Tabbakh عوف عبد الرحمن احمد الطباخ
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2015 Volume: 19 Issue: 4 Pages: 219-248
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

This work presents a theoretical analysis for the prediction of refrigerant saturation temperature inside a typical solar two-phase loop. This loop may be incorporated in any solar heating system for transporting heat between the solar collector and storage tank. The procedure takes into account all influencing parameters such as:- solar irradiance, ambient temperature, heat transfer coefficients in the source (collector) and sink (condenser), collector fill ratio and the geometric parameters of the solar collector and condenser.The trend of change of saturation temperature was studied over a typical daytime period extending 8 hours. Mathematical models were formulated for the collector and condenser to take into account the most influencing parameters. The models are highly interrelated which required an iterative procedure. A computer program was built to implement the iterative procedure and simulate the change of saturation temperature during the studied period. The period was divided into small time intervals of 10 seconds.Results reveal a significant influence of condenser area, collector fill ratio and the working conditions on the calculated saturation temperature. Optimum conversion of energy occurs at a fill ratio of 0.85 at which saturation temperature is about 40oC for the system under consideration.

يتناول هذا البحث دراسة نظرية تهدف إلى تخمين درجة حرارة التشبع لمائع تبريد يجري داخل دورة شمسية نموذجية ثنائية الطور. يمكن استعمال دورات كهذه في أية منظومة تسخين شمسية لغرض نقل الحرارة بين المجمع الشمسي وخزان الماء. وقد جرى في هذه الطريقة تناول كل العوامل المؤثرة على الأداء مثل :- شدة الإشعاع الشمسي ودرجة حرارة الجو ومعاملات انتقال الحرارة في المجمع والمكثف إضافة إلى نسبة ملىء المجمع وأبعاده مع أبعاد المكثف.تم دراسة نمط تغير درجة حرارة التشبع خلال فترة نهارية نموذجية تمتد 8 ساعات حيث تم صياغة نماذج رياضية لتمثيل كل من المجمع الشمسي والمكثف تشتمل معظم العوامل الرئيسية المؤثرة على الأداء. إن النماذج الرياضية متداخلة مع بعضها مما يوجب إيجاد حل يعتمد التجربة والخطأ. لذا تم بناء برنامج حاسوبي لحل هذه المسألة المترابطة حلا يعتمد التجربة والخطأ ويخمن درجة حرارة التشبع للمائع الشغال خلال فترة المحاكاة النظرية السالفة الذكر. وقد تم تقسيم الفترة إلى فترات قصيرة بطول 10 ثواني.أظهرت النتائج تأثيرا ملحوظا لكل من مساحة المكثف ونسبة ملىء المجمع وظروف التشغيل على القيمة المحسوبة لدرجة حرارة التشبع. وظهر ان التحويل الأمثل للطاقة يتم عند نسبة ملىء 0.85 ودرجة حرارة تشبع مقدارها 40 درجة مئوية للمنظومة قيد الدراسة.

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