Numerical simulation and design of ejector for solar air conditioning systems

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题名:	Numerical simulation and design of ejector for solar air conditioning systems
作者:	費浦納;fistianduta,prana
贡献者:	機械工程學系
关键词:	噴射器設計;?值模擬;太陽能空調;Ejector Design;Numerical Simulation;Solar Air Conditioner
日期:	2013-10-07
上传时间:	2013-11-27 11:34:43 (UTC+8)
出版者:	國立中央大學
摘要:	在這篇論文中，廣義的太陽能空調系統噴射器研製成功利用FLUENT。噴射器的一維分析進行這項工作。在使用氨蒸汽作為工作流體的情況下，顯示操作壓力和噴射器幾何形狀對流動結構和噴射器空調系統性能的影響。主噴嘴幾何參數變化為2.90 mm2,2.93 mm2和2.96 mm2。對於一個給定的噴射器，存在一個最佳的主要流體壓力在得到最大霧沫比(entraintment ratio)的情況下。隨著增加主要流體壓力，霧沫比下降；降低排出壓力時，霧沫比增加。最好性能的操作條件是Pg= 0.4MPa,Tg= 100℃, Pe=0.04MPa, Te=4℃, Pc= 0.06MPa，Tc= 28℃在2.90 mm2的主噴嘴幾何參數下，得到最高的霧沫比以獲得更好的性能。一個二維軸對稱，理想氣體模型的發展，計算噴射器空調系統的流場。藉由它的結果討論，預測空調系統噴射器的操作條件，來得到噴射器的性能在雙哽塞(choking)或臨界模式條件(critical mode condition)和變化操作條件的情形下，影響主要流體壓力和馬赫數來進行觀察和分析，結果發現噴射器的性能，經由混合室中的混合流體衝擊(shock)的位置和超音速主要流體的擴展直徑，扮演非常重要的角色。在不同的噴射器喉部直徑(A3)，能得到臨界背壓(Pc)。當噴射器喉部直徑(A3)增加時，臨界背壓(Pc)就下降；噴射器喉部直徑(A3)下降時，臨界背壓(Pc)就增加，又當噴射器喉部直徑(A3)小於12.7 mm時，即使背壓非常低時噴射器還是不能工作，噴射器性能的變化引起衝擊波的變化。這是導致噴射器部直徑(A3)的變化。 In this thesis a generalized ejector for solar air conditioning system was successfully developed by using FLUENT. A 1-D analysis for ejector is carried out in this work. It revealed the influence of operating pressures and ejector geometries on the flow structure and the performance of an ejector air conditioning system using ammonia vapour as the working fluid. The primary nozzle geometries parameter was varied as 2.90 mm2, 2.93 mm2 and 2.96 mm2. For a given ejector, there exists an optimum primary fluid pressure at which maximum entrainment ratio is obtained. Entrainment ratio is decreased by increasing the primary fluid pressure and entrainment ratio is increased by decreasing the discharge pressure. The best performance was obtained by operating condition Pg=0.4 MPa, Tg=100℃, Pe=0.04 MPa, Te=4℃, Pc=0.06 MPa, and Tc=28℃ with primary nozzle geometry of 2.90 mm2 gives the highest entrainment ratio for better performance. A 2D axisymmetric, ideal gas model was developed to calculate the flow in the ejector air conditioning system. Predictions at the operating conditions in the ejector air conditioning system were discussed to obtain the ejector performance in the double choking or critical mode condition and variable operating condition. The effects on the primary fluid pressure and Mach number were observed and analyzed. It was found that shock’s position of the mixed fluid and the expansion diameter of the primary fluid supersonic stream within the mixing chamber played a very important role in the ejector performance. The critical back pressure Pc^ on the different ejector throat diameters A3 have obtained. When the ejector throat diameter A3 is larger, the critical back pressure (Pc^* ) is lower. When the ejector throat diameter A3 is smaller, the critical back pressure Pc^* is higher. When the ejector throat diameter A3 < 12.7 mm^2, ejector can’t work even if the back pressure is very low. The change of the ejector performance is caused by the change of shock wave. Which is the result of the change of ejector throat diameter A3.
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