A paraffin wax and copper foam matrix were used as a thermal energy storage material in the double passes air solar chimney (SC) collector to get ventilation effect through daytime and after sunset. Air SC collector was installed in the south wall of an insulated test room and tested with different working angles (30o, 45o and 60o). Different SC types were used; single pass, double passes flat plate collector and double pass thermal energy storage box collector (TESB). A computational model based on the finite volume method for transient tw dimensional domains was carried out to describe the heat transfer and storage in the thermal energy storage material of collector. Also, equivalent specific heat method was employed to describe the heat storage and release in the mushy zone. Experimental results referred to an increase in thermal conductivity of paraffin wax that supported by copper foam matrix more than ten times. While the ventilation effect was still active for hours after the sun set, depending on the heat storage amount. Maximum ventilation mass flow rate with TESB collector was recorded with value equals to 36.651 kg/hr., when the overall discharge coefficient that was calculated for the system equals to 0.371. Experimental results showed that the best working angle range was 45~60o, and the highest air to the collector approaching temperature appeared to the double passes flat plate collector. Results gave greater heat storage efficiency of (47)% when the maximum solar radiation was 780 W/m2 at 12.00pm, while the energy summation through duration charge time was 18460 kJ. Computational results, depending on the equivalent heat capacity method for heat storage or release from phase change material that supported by copper foam matrix, showed the behavior of paraffin wax melting and solidification situation through periodic for charge and released heat from the solar collector. Also, these results gave agreement approaching the experimental results for the heat storage in the combined heat storage material, with standard error of 16.8%.
Abstract:
The hotel sector is one of the most vital sectors exposed to risks, and the authorities concerned with control must take their active and influential role in putting the hotel sector on the right track and compatible with the internationally approved approaches, and the importance of auditing the performance of the hotel sector in light of the (Covid-19) pandemic is embodied in the fact that it gives a clear and realistic picture to the management and regulatory bodies about the performance and activities of this sector and the shortcomings and deviations that must be addressed, and also helps government decision makers to ob
... Show MoreBarium–doped TiO2 / n-Si photodetector was fabricated by spray pyrolysis exhibited visible enhancement responsivity profile with peak response at 600 nm flat response between 650 and 900 nm. The quantum efficiency was 30% and specific detectivity was 5x1012 W-1Hz1/2cm at peak response. The GaAlAs laser diode was used to estimate the rise time of the detector.
The weak and strong forms are so called because it is not their lexical content that primary matter, but the role they have in the sentence. The problematic confusion, our students encounter, in recognizing and producing the correct pronunciation of weak and strong forms of the English function words is the main incentive behind conducting this study. In order to gather the data, this paper used two types of tests: a recognition test and a production test. The general results reached through the analysis of the students' answers seem to conform to the researcher's assumption: students face a critical problem in recognizing and producing correct pronunciation of the weak and strong forms of the English funct
... Show MoreThe importance of economic and technical feasibility studies include all of the investor, the society, the banks, the project and the government. As it will assist in achieving the optimal use of the available economic incomes on the national level and arranging the projects in priority which participates in achieving the government benefit without wasting the amounts .This is the research goal So, the research covered its theoretical aspect, of SAIs and the economic and technical feasibility studies then the role of the auditors in auditing those studies Then a mechanism was proposed includes a guidebook that provides guidelines for organizing the process of preparing and auditi
... Show MoreNuclear shell model is adopted to calculate the electric quadrupole moments for some Calcium isotopes 20Ca (N = 21, 23, 25, and 27) in the fp shell. The wave function is generated using a two body effective interaction fpd6 and fp space model. The one body density matrix elements (OBDM) are calculated for these isotopes using the NuShellX@MSU code. The effect of the core-polarizations was taken through the theory microscopic by taking the set of the effective charges. The results for the quadrupole moments by using Bohr-Mottelson (B-M) effective charges are the best. The behavior of the form factors of some Calcium isotopes was studied by using Bohr-Mottelson (B-M) effective charges.
مشكلة البحث:
يبقى الفن ولا زال في جميع حالات التعاقب البشري ومراحل التطور الانساني الاكثر انطلاقة وتميزاً في التعبير عن واقع الانسان وعن مشاعره وانفعالاته وافكاره ذات الصلة بتأثيرات البيئة المحيطة به.
والفن ولاسيما (الرسم) يمثل وسيلة من وسائل التعبير الفني بل يكاد يكون الرسم وسيلة الانسان الاولى التي عبر فيها بخطوط مرئية عن مجالات حياته وعلاقته بالبيئة التي عاش فيها، ويقينا
... Show Moreهدف البحث التعرف على الذكاء الروحي لدى عينة من طلبة جامعة بغداد فضلا عن التعرف على الفروق بين الطلبة في الذكاء الروحي وفق متغير النوع ( الذكور- الإناث) ، ومتغير التخصص الدراسي ( علمي – إنساني) ومتغير المرحلة الدراسية ( المرحلة الأولى-المرحلة الرابعة) تألفت عينة البحث من (300) طالباً وطالبة ، وتم تطبيق - مقياس الذكاء الروحي وهو ( من إعداد الباحثة) ، وقد اسفرت نتائج البحث عن:--إن طلبة جامعة بغداد( عينة البحث) تمتعوا بمست
... Show Moreيستهدف البحث الحالي التعرف إلى 1 .بناء مقياس سمات الشخصية المفضلة لدى معلمي ومعلمات التربية الخاصة في العراق من وجهة نظر ذوي اإلختصاص والعاملين في هذا المجال. 2 .مستوى توافر سمات الشخصية المفضلة لدى معلمي ومعلمات التربية الخاصة في العراق من وجهة نظر ذوي اإلختصاص والعاملين في هذا المجال. 3 .داللة الفروق اإلحصائية في سمات الشخصية المفضلة لدى معلمي ومعلمات التربية الخاصة ً في الع ارق من وجهة نظر ذوي اإلختصاص والعا
... Show MoreThe aim of the research was to know the effect of the inquiry wheel model on chemical enlightenment among second-grade middle school female students in government daytime middle and secondary schools. Umm AlQura Middle School was chosen by intentional selection to be its students as the research sample for the academic year (2024-2025). Two groups were chosen, one of which was the experimental group studying using the inquiry wheel model and the other the control group studying in the usual way. The equivalence of the two research groups was verified by a set of variables, which were (chronological age in months, previous information test, Raven's intelligence test, chemical enlightenment scale). As for the research tool, the researchers bu
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