The design, construction and investigation of experimental study of two compound parabolic concentrators (CPCs) with tubular absorber have been presented. The performance of CPCs have been evaluated by using outdoor experimental measurements including the instantaneous thermal efficiency. The two CPCs are tested instantly by holding them on a common structure. Many tests are conducted in the present work by truncating one of them in three different levels. For each truncation the acceptance half angle (θc) was changed. Geometrically, the acceptance half angle for standard CPC is (26o). For the truncation levels for the other CPC 1, 2 and 3 the acceptance half angle were 20o, 26o and 59o, consequently. A significant difference between the instantaneous thermal efficiency of 3.86× CPC (θc=20o) and 2.32× CPC (θc=26o), and between that for 3.61× CPC (θc=26o) and 2.32× CPC (θc=26o). It's noticed that the difference between the instantaneous thermal efficiency of 2.32× CPC (θc=59o) and 2.32× CPC (θc=26o) is small compared with the difference of the first and second cases, the instantaneous thermal efficiency of 2.32× CPC (26o) was higher than those for other three CPCs. The experimental results show that the maximum thermal efficiency of the full 2.32×CPC (26o) is 0.708, the maximum thermal efficiency of the 3.93×CPC (15o), when it's truncated to 3.84× CPC (20o), 3.61× CPC (26o) and 2.32× CPC (59o) are 0.51, 0.52 and 0.66, respectively. As the concentration ratio decreases from (3.93× to 1×), the thermal efficiency, energy losses and optical efficiency increase from (0.47 to 63), (1.58 to 7.2 K.m2/W) and (0.494 to 0.797), respectively.
Baalbek ( Heliopolis- the City of the Sun), one of the most important historical cities in Lebanon, has known as multiple civilizations in successive historical periods, which have left many archaeological evidences, the most important ones are the castle and the roman temples.
The Islamic architectural and artistic heritage in Baalbek was consisted from different types of buildings: religious, civil, military and social in addition to many archaeological arts that were mastered by the Muslims.
The calamities, calamities, problems and constant dilemmas that society is experiencing have made it the responsibility of professors and researchers to find appropriate and effective solutions to these issues, and among those calamities that our societies faced was the problem of the epidemic represented by (Corona-Covid-19),
Karbala is one of the oldest cities in Iraq. It was named after the name of the child. This is the saga that Imam Hussein was martyred in
This Research on (Ayat of Advice and Guidance of Morals
Included in Sorat Al-Baqara) is a study for the virtual of Ayat
dealing with advice and guidance.
The importance of this research title comes from the study of
the Holy Quran from one side and the importance of advice and
guidance from the other side, besides, we are truly in need for
such study in our life.
Andalucía, dentro del mapa lingüístico español, es una región con muchas variaciones dialécticas. En muchos casos contiene una gran variedad de términos propios de la zona, ya que en esta misma zona se pueden observar muchas subdivisiones dialectales.
En este trabajo, hemos seguido dos tipos de fuentes:
- Directa: Se trata de conseguir la información por medio de cuestionarios distribuidos a informantes de edades y localidades diferentes.
- Indirecta: Consultando libros para conseguir información y datos básicos del tema, e información sobre las voces y nombres dialectales en la geografía estudiada.
There are words that are described in certain words that are not described in other words, so the relationship between two words that accompany a habit is strengthened, which leads to the emergence of a conjunction or an idiomatic expression
Praise be to God, Lord of the worlds, and may blessings and peace be upon the most honorable of all creation, Abi Al-Qasim Muhammad, and the God of the good and pure
اصبح مصطلح الصورة الذهنية من المصطلحات الشائعة التي يتزايد استخدامها في المجالات السياسية والإعلامية والعلاقات الدولية اذ اصبح يشكل اهمية كبرى لدى دراسي السلوك الانساني، فقد احتلت دراسة المصادر المتعددة التي يستقي منها الافراد انطباعاتهم عن الاخرين، وتعاظم الدور الذي تلعبه وسائل الاتصال في تدفق الصور عن الشعوب في ظل التطور التكنولوجي الهائل الذي يشهده عالم الاتصال حاليا، والذي يسمى بعصر السموات المفتوحة
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