Numerical investigation on shock waves generated by flashing water jet

Abstract

Numerical study has been conducted to investigate shock waves generated by flashing water jet. This study presents results of a numerical simulation of flash evaporation phenomena occurring when a jet of superheated water is injected through a nozzle into low-pressure water vapor. Due to the sudden pressure drop, flashing takes place, and the sensible heat of the water converts into latent heat of evaporation. The multiphase flow field in the evaporation zone and induced shock waves are explored via a 2D transient investigation in Ansys Fluent. The Mixture model is applied with slip velocities to model the non-homogeneous multiphase flows. Resulting distributions of the fluid properties velocity, Mach number, pressure, liquid volume fraction, density, and in addition to speed of sound inside the flashing chamber at different time steps are presented and discussed. The results show that once the superheated water is injected, it flashes immediately and generates a shock wave. The primary and reflected shock waves are characterized by discontinuous fluid properties in a narrow region across the shock. The generated shock waves are moving shock waves and can be useful to transfer energy directly between fluids without using mechanical components such as pistons or vaned impellers, which can be exploited in industrial and technological applications such as utilizing resulting shock waves in creating useful compression.

Keywords

• Flash Evaporation
• Pressure Drop
• Phase Change
• Mass Transfer
• Moving Shock wave