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Article
Phase Change Materials for Thermal Energy Storage

Author: Mohammed Jafer Ali AL-Ataby Collage
Journal: Journal of Petroleum Research & Studies مجلة البحوث والدراسات النفطية ISSN: 22205381 Year: 2012 Volume: 261 Issue: 5th Pages: 69-92
Publisher: Ministry of Oil وزارة النفط

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Abstract

Salt hydrate phase change materials used for thermal storage in space heating and cooling applications have low material costs, but high packaging costs. A more economic installed storage may be possible with medium priced, high latent heat. Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. This paper work on latent heat storage and provides an insight to recent efforts to develop new classes of phase change materials (PCMs) foruse in energy storage. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. Hydrated salts have larger energy storage density and higher thermal conductivity but experience super cooling and phase segregation, and hence, their application requires the use of some nucleating and thickening agents. Sodium carb-onate, sodium phosphate and sodium sulfate tested as phase change material by crystallization in this work.


Article
Investigation of Thermal Performance of Finned,Water-PCM,Double Tube Heat Recovery
الأداء الحراري لمنظومة استرجاع الطاقة مكونة من انبوب مزدوج مزعنف

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Abstract

In this work, focus is taken on developing a waste heat recovery system for capturing potential of exhaust heat from an air conditioner unit to be reused later. This system has the ability to store heat in phase change material (PCM) and then release it to a discharge water system when required. To achieve this goal, a Finned, Water-PCM, Double tube (FWD) system has been developed and tested. Different profiles of fins attached to the (FWD) system have been investigated for increasing the thermal conductivity of the PCM. These include using Circular Finned, Water-PCM, Double tube (CFWD) system; Longitudinal Finned, Water-PCM, Double tube (LFWD) system; Spiral Finned, Water-PCM, Double tube (SFWD) system; as well as; Without Fins, Water-PCM, Double tube (WFWD) system. An experimental test rig that attached to an air-conditioner unit has been built to include 32 tubes of the FWD systems for both vertical and horizontal layouts during charging and water discharging processes. Transient 3-D, numerical simulations using (ANSYS Fluent14.0 software) have been developed to predict the thermal behavior for all types of FWD systems under investigation. Results show a significant performance improvement when using spiral and circular fins during charging process at vertical position. However, longitudinal and without fins showed better performance in horizontal position. Overall, SFWD system in vertical position has been found to exhibit the most effective type due to the fastest PCM melting and solidification. As compared to the WFWD system, the FWD systems have been found to increase the PCM temperature gain of about 15.3% for SFWD system; 8.2% for CFWD; and 4.3% for LFWD system. Also, comparisons between numerical and experimental results for both (measurement data and thermal camera photos) have been found reasonably matched.

في هذه البحث تم التركيز على خزن الطاقة الكامنة للهواء الخارج من منظومة تبريد لاستعمال هذه الطاقة لاحقا. لانجاز هذا الهدف, تم تصنيع منظومة خزن الطاقة الحرارية(FWD)لاستخلاص طاقة الهواء الخارج من مكثف مكيف هواء. هذه المظومة لها القابلية على خزن الطاقة الحرارية واعادة تحريرها الى منظومة الماء عند الحاجة .تم اختبار اشكال مختلفة لزعانف بعد تثبيتها الى منظومة FWD)) لغرض زيادة الموصلية الحرارية لمادة متغيرة الطور(PCM) داخل المنظومة. الأشكال تشمل منظومة ثنائية الانابيب ذو زعانف دائرية(CFWD), منظومة ثنائية الانابيب ذو زعانف طولية(LFWD), منظومة ثنائية الانابيب ذو زعانف لولبية(SFWD), و منظومة ثنائية الانابيب بدون زعانف(WFWD). تم أنشاء موديل الأختبار العملي الذي يحوي على(FWD) ومن ثم تثبيته على منظومة تبريد الهواء بترتيب عامودي وافقي خلال عملية الشحن والتفريغ. ايضآ تم بناء نظام محاكاة عددي باستخدام (ANSYS Fluent 14.0) لتخمين التصرف الحراري لمختلف انواع منظومات (FWD)التي تحت الدراسة. النتائج أظهرت تحسين هام عند أستعمال زعانف لولبية ودائرية أثناء عملية الشحن عند الوضع العمودي اما بالنسبة للزعانف الطولية وبدون زعانف أظهرت أداء افضل عند الوضع الافقي. عموماً، نظام SFWD في الموقعِ العموديِ وُجِدَ لعَرْض النوعِ الأكثر فاعليةِ بسبب ذَوَبان وتجمّدِ PCM الأسرع . تطور ملحوض بالأداء عند استعمال منظومات SFWD,CFWD,LFWD مقارنة بمنظومة WFWD. بصورة عام نسب الزيادة الحاصلة في درجة الحرارة المكتسبة لل PCM كانت 4.3%, 8.3%, و15.3% على التوالي بالمقارنة مع المنظومة بدون زعانف. كذالك وجد بان المقارنة بين النتائج النظرية والعملية متناظرة الى حد معقول.


Article
Experimental and Numerical Study of Closed Loop Solar Chimney Assisted with PCM and CFM as Thermal Energy Storage Collector

Authors: Talib K. Murtadha --- Hussien M. Salih --- Ali D. Salman
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 13 Part (A) Engineering Pages: 2450-2463
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

In this work, a test room was built in Baghdad city, with selective dimensions, while the solar chimneys (SC) where designed with aspect ratio (ar) bigger than 12 and setup to the oriented wall to the south. Collector of SC consist of paraffin wax as a phase change material (PCM) and supported by copper foam matrix (CFM), to enhance the combined of thermal energy storage material box (TESMB). Double transparent acrylic sheets covered the collector from outside. TESB supported by array of evacuated tubular collector with thermosyphon to sincere heat storage in the TESB. Results of experimental work that achieved in 25 January and 26 February refer to effectiveness using TESM in closed loop SC in day time and its effect cover the night time also. The heating system of test room is arrived to the biggest room temperature after sun set, at that moment the difference between indoor and outdoor approximately 15oC, and room temperature value still bigger after five hours from sun- set with a different in temperature by approximately 8 oC. Numerical solution done by employing CFD with solution the PDE’s that present continuity, momentum, energy equations, by using the FVM with algebraic forms of turbulent viscosity and diffusion coefficient and employing turbulent standard (k-ε)model. The comparison between numerical and experimental results indicated that the heat transfer inside test room is dominate by condition, also results shows acceptable convergence in velocity and temperature profile, while the experimental results for air flow inside SC gap appears the turbulent behavior in most duration time.


Article
The Impact of Width of the Air Gap Channel on the Mass Flow Rate, Rayleigh Number, and Efficiency of Passive Solar Heating System

Authors: Ehsan F. Abbas --- Shayma A. Azat
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 3 Pages: 47-52
Publisher: Tikrit University جامعة تكريت

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Abstract

The mass flow rate and Rayleigh number has been investigated experimentally on the passive solar using Trombe wall consist of (industrial wax) used as phase change material (PCM). A test rig of a cubicle was made of PVC sandwich panel except the south wall, Trombe wall; covered with a clear glass of 6 mm thickness. The six experiments were carried out during the winter season in Kirkuk city with six different widths of the air gap channel (10, 15, 20, 25, 30, and 35) cm. The experimental resultts show that the mass flow rate proportional directly to a width of the channel and inversely with Rayleigh number. Moreover, the highest efficiency was obtained at a depth of 30 cm, where it was about 2.45 times the efficiency of 10 cm.


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
DEVELOPMENT OF A WASTE HEAT RECOVERY SYSTEM

Authors: Maathe Abdulwahwd Theeb --- Ali Shukor Golam --- Mohammed Hamid Alhamdo
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 2 (part-6) Pages: 166-182
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

In this work, focus is taken on developing a waste heat recovery system for capturing potential of exhaust heat from an air conditioner unit to be reused later. This system has the ability to store heat in phase change material (PCM) and then release it to a discharge water system when required. To achieve this goal, a Finned, Water-PCM, Double tube (FWD) system has been developed and tested. Spiral fins attached to the (FWD) system have been investigated for increasing the thermal conductivity of the PCM with and without copper network (CN). An experimental test rig that attached to an air-conditioner unit has been built to include 32 tubes of the FWD systems for both vertical and horizontal layouts during charging and water discharging processes. Transient 3-D, numerical simulations using (ANSYS Fluent14.0 software) have been developed to predict the thermal behavior for all types of FWD systems under investigation. Results show a significant performance improvement when using spiral fins with 6% (CN) during charging process at vertical position. As compared to the WFWD system, the FWD systems have been found to increase the PCM temperature gain of about 15.3% for SFWD system; 18.6% for SFWD system with 6% (CN) during charging process.


Article
Theoritical Analysis on Thermal Energy Storage using Phase Change Materials Capsules for Solar Organic Rankine Cycle Power Generation System
التحلیل النظري لخزن الطاقة الحراریة باستخدام كبسولات المواد متغیرة الطور في نظام تولید الطاقة بدورة رانكن العضویة الشمسیة

Author: Hayder Mohammad Jaffal حيدر محمد جفال
Journal: AL-NAHRAIN JOURNAL FOR ENGINEERING SCIENCES مجلة النهرين للعلوم الهندسية ISSN: 25219154 / eISSN 25219162 Year: 2014 Volume: 17 Issue: 1 Pages: 15-35
Publisher: Al-Nahrain University جامعة النهرين

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Abstract

This paper presents a theoretical analysis on packed bed thermal energy storage using phase change material (PCM) to improve the performance of solar organic Rankine cycle power generation system by extending its operational time demand to the night. The transient behavior of packed bed thermal energy storage using spherical capsules filled with paraffin wax as a storage unit has been studiednumerically by finite difference technique for charging and discharging process .The effects of different parameters such as inlet temperature, mass flow rate, bed porosity , diameter of capsule and turbine inlet temperature have shown to be dominant parameters in determining the effective thermal efficiency of the solar ORC. It is seen that, turbine inlet temperature is plays animportant role in the geometrical parameters of the packed bed.Comparison between theoretical results and experimental results of previous study for solar water heating system has been carried out where good agreement is noticed.

یعرض ھذا البحث تحلیلاً نظریاً لخزن الطاقة الحراریة في مھد محشو بمادة متغیرة الطور لتحسین أداء دورة رانكن العضویة الشمسیة لنظام تولید الطاقة الكھربائیة وذلكبتمدید وقت التشغیل المطلوب إلى اللیل .السلوك الغیر مستقر لخزن الطاقة الحراریة في مھد محشو بكبسولات مملوءة بشمع البرافین كوحدة خزن تم دراستھ عددیاً باستخدام طریقة الفروق المحددة لعملتي الشحن والتفریغ.تأثیرات محددات مختلفة مثل درجة حرارة الدخول ,معدل التدفق ,مسامیة المھد ,قطرالكبسولة ودرجة حرارة الدخول للتوربین وضحت لتكون محددا مھیمناً في إیجاد الكفاءة الحراریة الفعالة لدورة رانكن العضویة الشمسیة .لوحظ إن درجة حرارة الدخولالى التوربین تلعب دورا قویا في المعاییر الھندسیة للمھد المحشو.تمت مقارنة النتائج النظریة مع نتائج عملیة لدراسة سابقة لنظام تسخین المیاه وظھر توافق جید بین الدراستین.


Article
Study of the Performance of Paraffin Wax as a Phase Change Material in Packed Bed Thermal Energy Storage System

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Abstract

The present work deals with an experimental investigation of charging and discharging processes in thermal storage system using a phase change material PCM. Paraffin wax was used as the PCM which is formed in spherical capsules and packed in a cylindrical packed column which acted as an energy storage system. Air was used as the heat transfer fluid HTF in thermal storage unit. The effect of flow rate and inlet temperature of HTF on the time of charging and discharging process were studied. The results showed that the faster storage of thermal energy can be made by high flow rate of heat transfer fluid HTF and high inlet temperature of heat transfer fluid. It was found that at 65°C HTF inlet temperature, the melting and solidification processes accelerated by 27.9% and 57.14% respectively, when the flow rate was increased from 9 to 24 L/s. Also, when the HTF inlet temperature changed from 65°C to 80°C, the time needed to complete melting process decreased by 38.8%.


Article
THERMAL CHARACTERISTICS OF PHASE CHANGE MATERIAL USED AS THERMAL STORAGE SYSTEM BY USING SOLAR ENERGY
الخواص الحرارية للمواد متغيرة الاطوار المستخدمة كنظام خزن حراري باستعمال الطاقة الشمسية

Authors: Kadhim F. Nasir كاظم فاضل ناصر --- Munir Ali منير علي --- Ameer H. AL Mamoori امير حسن حمزة المعموري
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2018 Volume: 9 Issue: 1 Pages: 1-22
Publisher: University of Kufa جامعة الكوفة

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Abstract

In this paper, the melting processes of phase change material in a shell and tube heat exchanger by using solar thermal energy have been investigated numerically and experimentally. All experimental were outdoor tested at AL-Mussaib city-Babylon-Iraq (Lat 32.5 º North, and long 44.3 º East) with N-S collector direction at tilt angle of 32.5 º with the horizontal. The phase change material used in this work is black color Iraqi origin pure Paraffin with amount of 12 kg. In the experimental setup evacuted tube solar collector is employed for melting phase change material in shell regime. Different volume flow rates for the water flow inside the inner tube of heat exchanger namely (200, 300, and 500 LPH) for Reynolds number namely (15000, 23000, 38000) respectively were used for each season from August 2016 to January 2017. The numerical investigation involves a three dimension numerical solution of model by a commercial package ANSYS FLUENT 15.0. The boundary conditions of the model that solved by the numerical solution have been taken from the experimental tests. The experimental results indicated that the inner tube inlet and ambient temperatures has a significant effects on the melting process compared with the volume flow rates. Studying phase change material temperature distribution, it is exposed that a melting temperature of the phase change material in summer season needed time of (3-4) hours only, while it needed more time; (14-16) hours in winter season. Increasing solar radiation and ambient temperature reduces the melting time of phase change material. Increasing water temperature difference of inner tube increased the heat gained for phase change material. The results obtained from numerical solution presented the static temperature contours and showed that the temperature distribution of phase change material give good validations with experimental results with percentage deviation of 2.7%. The present experimental results have been compared with the previous studies and give a good agreement with increasing for present work of 25.9 %.

في هذه البحث تم دراسة عملية وعددية لعمليات انصهار المواد متغيرة الاطوار باستخدام الطاقة الشمسية في مبادل حراري من نوع الغلاف والانبوب. انجزت الدراسة العملية في الاجواء الخارجية بمدينة المسيب- محافظة بابل- العراق (خط عرض 2016 مع الافق باتجاه الجنوب خلال الفترة من شهر اب 32.5° شرقا) عند زاوية ميلان 44.3° شمالا وخط طول 32.5° . تضمن الجانب العملي استخدام مجمع شمسي من نوع الانابيب المتفرغة بدون استخدام منظومة 2017الى كانون الثاني كيلوغرام كمادة متغيرة 12 توجيه لصهر المادة متعددة الاطوار. استخدم البارافين النقي اسود اللون وعراقي الانتاج بكمية 500, و300 ,200 الاطوار في منطقة الغلاف. استخدمت معدلات تدفق متغيرة للماء داخل الانبوب للمبادل الحراري وهي لنموذج يمثل المبادل ANSYS FLUENT 15.0لتر لكل ساعة. الدراسة النظرية تضمنت عمل محاكات باستخدام برنامج الحراري, الظروف الحدية للنموذج اخذت من التجارب العملية. اظهرت النتائج المستحصلة من الاختبارات العملية ان درجة حرارة الماء الداخل للانبوب الداخلي للمبادل الحراري ودرجة حرارة الطقس لها تاثير كبير في عملية انصهار المادة متغيرة الاطوار مقارنة بتاثير معدلات جريان الماء. واظهرت النتائج ان عملية انصهار البارافين في فصل الصيف تحتاج الى فترة ساعة, زيادة الاشعاع الشمسي 16-14 ساعة فقط بينما تحتاج في فصل الشتاء الى فترة زمنية مقدارها 4-3زمنية مقدارها ودرجة حرارة الطقس تؤدي الى تقليل الفترة الزمنية اللازمة لانصهار البرافين. اظهرت النتائج النظرية تطابقا مع النتائج %. تم مقارنة النتائج العملية لهذه الدراسة مع نتائج بحوث سابقة في 2,7العملية لدرجات حرارة البرافين مع فرق مقداره % زيادة في25,9 مجال انصهار المواد متغيرة الاطوار وقد اظهرت المقارنة افضلية جيدة في النتائج للدراسة الحالية بنسبة درجات حرارة البارافين.


Article
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

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