Numerical investigation of high pressure condensing flows in supersonic nozzles

High-pressure non-equilibrium condensing flows are investigated in this paper through a quasi-1D Euler model coupled to the method of moments for the physical characterization of the dispersed phase. Two different numerical approaches, namely the so-called (a) the mixture and (b) continuum phase model, are compared in terms of computational efficiency and accuracy. The results are verified against experimental data of high-speed condensing steam measured at high pressure (100.7 bar). The analysis demonstrates that Model (b) markedly outperforms the mixture model in terms of computational cost, while retaining comparable accuracy. However, both models, in their original formulation, lead to considerable deviations in the nucleation onset prediction as well as an overestimation of the average droplet radius. A further investigation is then conducted to figure out the main physical parameters affecting the condensation process, i.e. the surface tension, the growth rate and the nucleation rate. It is eventually inferred that applying proper correction to these three quantities allows to obtain best fit with the experimental data. A final calculation is carried out to show the dependence of these three correcting factors from the thermodynamic conditions of the mixture.