Numerical Investigation on the Effects of Operating Conditions on the Performance of a Steam Jet-Ejector

Abstract

-In this paper, the focus is on an existing steam jet-ejector, in which the primary flow is high pressure superheated steam and the suction flow is a mixture of saturated steam and air. The main goal of this work is to improve the ejector performance via proper setting of its working conditions such as setting motive, suction and discharge pressures and even primary and secondary streams composition, albeit if it is possible. From the computational perspective, the modelling and simulation of fluid flow are very complicated in an ejector because of facing with simultaneous subsonic and supersonic regimes, very high and very low pressure regions close to each other inside the ejector, complex turbulent mixing, and imperative heat transfer conditions. This study aims to improve the entrainment ratio of the existing steam jet-ejector by investigating its performance under different operating conditions and reduce the consumption of motive steam, which is a critical issue in the current human society because of facing with major global warming and water crisis conditions. The results show that by lowering the motive pressure, the achieved entrainment ratio increases up to 51% percent, while the ejector critical back pressure decreases. Obeying the current strategy, the annual water consumption of the vacuum system can be reduced about 3000 m 3 in the current combined power cycle unit.