A Comparison of Three Different Flow Solvers For Simulating Steam Condensation Inside a Nozzle

Abstract

In this work the condensation process of steam inside a converging diverging nozzle is simulated, the experiments on which were performed by Moses and Stein [1]. Three different flow solvers are used for this purpose, namely, Ansys Fluent, Ansys CFX and the open source flow solver OpenFOAM. The aim of the current work is to narrow down the choice of the flow solver which can finally be used for simulating non-equilibrium condensation of Carbon Dioxide inside ejectors. The pressure distribution predicted inside the nozzle by the three solvers follow closely the experimental one. However, the location and amount of pressure rise due to the condensation onset are differently predicted by the flow solvers. Only one plateau is observed in the pressure curve experimentally while at least two different plateaus are predicted numerically. For the vapor temperature and supercooling, the three solvers predict similar values before the condensation onset. After start of condensation, Ansys Fluent and OpenFOAM give similar results while Ansys CFX predicts at least 10 degree higher values. Ansys CFX predicts a wider nucleation zone compared to the two other solvers. The highest discrepancy being displayed by the solvers appears in the distribution of droplet diameter and droplet number density. However, the three solvers predict similar trend for the liquid mass fraction distribution inside the nozzle