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# Conservation of energy: Bernoulli’s equation Consider the most important case of steady,

الكلية كلية التربية للعلوم الصرفة     القسم قسم الفيزياء     المرحلة 7
أستاذ المادة بهاء حسين صالح ربيع الحسيني       14/01/2018 08:03:43
Conservation of energy: Bernoulli’s equation Consider the most important case of steady,

Several renewable energy resources derive from the natural movement of air and water. Therefore the transfer of energy to and from a moving fluid is the basis of meteorology and of hydro, wind, wave and some solar power systems. Examples of such applications include hydropower turbines (Figures 8.3, 8.5 and 8.6), wind turbines (picture on front cover and Figure 9.4), solar air heaters (Figure 6.1) and wave energy systems (Figure 12.14). Tounderstandsuchsystems,wemuststartwiththebasiclawsofmechanics as they apply to fluids, notably the laws of conservation of mass, energy and momentum. The term fluid includes both liquids and gases, which, unlike solids, do not remain in equilibrium when subjected to shearing forces. The hydrodynamic distinction between liquids and gases is that gases are easily compressed, whereas liquids have volumes varying only slightly with temperature and pressure. Gaseous volumes vary directly with temperature and inversely with pressure, approximately as the perfect-gas law pV =nRT . Nevertheless, for air, flowing at speeds <100ms?1 and not subject to large imposed variations in pressure or temperature, density change is negligible; this is the situation for the renewable energy systems analysed quantitatively in this book. It does not apply to the analysis of gas turbines, for which specialist texts should be consulted. Therefore, throughout this text, moving air is considered to have the fluid dynamics of an incompressible fluid. This considerably simplifies the analysis of most renewable energy systems.

المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .