Effect of mixing on the performance of wet steam ejectors

Ariafar, Kavous and Buttsworth, David and Al-Doori, Ghassan and Malpress, Ray (2015) Effect of mixing on the performance of wet steam ejectors. Energy, 93 (2). pp. 2030-2041. ISSN 0360-5442

Abstract

Steam ejector computational simulations using a wet steam model give higher entrainment ratios and higher critical back pressures for the ejector compared with the ideal gas model. This paper identifies the origin of these differences. Simulation results show that the wet steam model predicts an entrainment ratio for the choked flow ejector operation that is 10% higher than that for the ideal gas model. The wet steam model also gives a higher critical back pressure by about 7% relative to the ideal gas model with a closer agreement to experimental data for the unchoked ejector operation. Enhanced mixing layer growth which arises due to steam condensation in the primary nozzle is identified as the main reason for higher entrainment ratio of the ejector simulations using the wet steam model. The difference in the mixing layer growth rate between ideal gas and wet steam simulations is 21%, indicating enhanced entrainment for the wet steam model. Furthermore, the mixture at the start of the diffuser is shown to have a higher pitot pressure than in the ideal gas simulations and these elevated pitot pressures allow the ejector to operate in a choked mode to a higher critical back pressure.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Date Deposited: 14 Mar 2016 05:45
Last Modified: 01 Aug 2016 01:28
Uncontrolled Keywords: steam ejector; entrainment ratio; condensation; shear layer mixing; pitot pressure; CFD (computational fluid dynamics)
Fields of Research : 09 Engineering > 0913 Mechanical Engineering > 091305 Energy Generation, Conversion and Storage Engineering
Identification Number or DOI: 10.1016/j.energy.2015.10.082
URI: http://eprints.usq.edu.au/id/eprint/28491

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