Vapor-liquid two-phase flow and thermodynamic loss of multi-stage high temperature and pressure reducing valve based on evaporation model

A three-dimensional simulation model of multi-stage high temperature and pressure reducing valve (MSHTPRV) was established via the combination of Euler-Lagrange two-phase flow and droplet evaporation model. The simulation model was verified by a DN10 temperature and pressure reducing valve (TPRV) experiment. Then the vapor-liquid two-phase flow model with droplet evaporation was applied to the MSHTPRV. The complex flow and working performance of the MSHTPRV are demonstrated. The key influence of water spray parameters on the flow characteristics and thermodynamic loss was analyzed. The results show that the steam flow evolves the strong vortex in front of each stage orifice, and the droplet evaporates faster in the large vortex. The entropy production in MSHTPRV is mainly from the vortex motion and droplet evaporation. With the increasing of droplet diameter, the evaporation rate of droplet decreases, and the steam work capacity loss decreases. When the injection velocity of droplet exceeds the steam velocity, the evaporation rate of droplet can be increased. The increasing of injection temperature leads to the decreasing of steam work capacity loss. The latent heat of vaporization absorbed by the droplet is the main mechanism to reduce the steam temperature, and the evaporation of smaller droplet diameter can produce more steam work capacity loss.