About the Effect of Two-Phase Flow Formulations on Shock Waves in Flash Metastable Expansions Simulations

Abstract

Two-phase expanders are promising conversion machines that could help in increasing the energy efficiency of several systems such as heat-to-power plants, liquefaction processes or chillers. Expansion of two-phase flows is complex to model since the dynamics of the liquid-gas interactions depend on several factors. This work gives a preliminary insight on the effect of various formulations for liquid-gas interaction terms on the shock waves that may appear in over-expanded flash nozzles simulations. The case study is a water thrust nozzle from literature designed for geothermal energy conversion at inlet temperatures close to 150°C. The compared formulations differ mainly on the homogeneity assumptions regarding momentum and on the interface mass transfer term. The simulations results suggest that these assumptions have a fundamental effect on the flow behavior close to the outlet of the nozzle and in particular on the presence or not of the shock waves. This has meaningful consequences on the velocity profile in the nozzle.