Performance of supersonic steam ejectors considering the nonequilibrium condensation phenomenon for efficient energy utilisation

Yan Yang, Xiaowei Zhu, Yuying Yan, Hongbing Ding, Chuang Wen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Supersonic ejectors are of great interest for various industries as they can improve the quality of the low-grade heat source in an eco-friendly and sustainable way. However, the impact of steam condensation on the supersonic ejector performances is not fully understood and is usually neglected by using the dry gas assumption. The non-equilibrium condensation occurs during the expansion and mixing process and is tightly coupled with the high turbulence, oblique and expansion waves in supersonic flows. In this paper, we develop a wet steam model
based on the computational fluid dynamics to understand the intricate feature of the steam condensation in the supersonic ejector. The numerical results show that the dry gas model exaggerates the expansion characteristics of the primary nozzle by 21.95%, which predicts a Mach number of 2.00 at the nozzle exit compared to 1.64 for the wet steam model. The dry gas model computes the static temperature lower to 196 K, whereas the wet steam model predicts the static temperature above the triple point due to the phase change process. The liquid fraction can reach 7.2% of the total mass based on the prediction of the wet steam model. The performance analysis indicates that the dry gas model over-estimates a higher entrainment ratio by 11.71% than the wet steam model for the steam ejector.
Original languageEnglish
JournalApplied Energy
Volume242
Pages (from-to)157-167
ISSN0306-2619
DOIs
Publication statusPublished - 2019

Keywords

  • Steam ejector
  • Condensation
  • Dry gas
  • Wet steam
  • Entrainment ratio

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