Effects of surface roughness and temperature on non-equilibrium condensation and entrainment performance in a desalination-oriented steam ejector

Abstract

• Wet steam model was built and effects of surface conditions were fully studied. • Increase of roughness reduces the ejector performance and condensation intensity. • The performance varies within 4% as the wall temperature changes from 30 to 150 °C. • The condensation droplets occur on the inner wall when it has poor adiabatic properties. Ejectors usually act as thermal compressors to recover the superfluous water vapor in multi-effect desalination systems. However, the influences of wall conditions on the steam ejector performances were not fully understood. To investigate the effects of the surface roughness and temperature on non-equilibrium condensation and entrainment performance in the steam ejector, a wet steam model was built by a computational fluid dynamics software. Simulation results indicate that the increase of roughness height reduces the ejector performance and attenuates the non-equilibrium condensation phenomenon significantly. Furthermore, as the wall temperature changes in the range of 30–150 °C, the ejector performance varies merely within 4%; however, condensation droplets which may cause erosion damage occurs on the internal surface when the wall has poor adiabatic properties. Therefore, the wall roughness and temperature should be fully considered to enhance the ejector performance and mitigate potential condensation on the wall.