Numerical investigation on submerged steam jet condensation in subcooled water flow in a restricted channel with the presence of non-condensable gas

Abstract

Submerged steam jet in subcooled water flow is widely used in many industrial processes. When non-condensable gas is involved in the steam jet, the mechanisms of heat and mass transfer become more complicated due to the added non-condensable components and the strong effect of water turbulence. In present work, a three-dimensional steady numerical simulation is conducted to study the steam jet condensation in subcooled water flow in a vertical pipe with the presence of non-condensable gas based on inhomogeneous multiphase model. The effects of non-condensable gas on steam plume shapes, distributions of static pressure, velocity, temperature and heat transfer characteristics are investigated. As air contents increases, steam plume transforms from ellipsoidal shape to divergent shape and the peak value of static pressure decreases. The mechanism of the peak phenomenon of static pressure at the end of steam plume is revealed to be the squeezing effect of water flow towards the nozzle axis. Since air mass fraction rises to 1%–9%, the average heat transfer coefficient declines by 24.5%–54.9%. The local heat transfer coefficient is evaluated by using thermal equilibrium model at phase interface. Numerical results show a self-intensifying effect on heat transfer, indicating that the distribution of local heat transfer coefficient is highly similar to that of water turbulent kinetic energy near phase interface, decreasing first and then rising to a high level at the tail of steam plume. The local heat transfer coefficient and steam condensation rate decrease with air concentration and increase with water mass flow rate.