Numerical investigation of nitrogen spontaneous condensation flow in cryogenic nozzles using varying nucleation theories

The thermodynamic irreversible loss by condensation can have an important influence on the flow characteristics and thermal efficiency in air or nitrogen cryogenic turbo-expander involving spontaneous condensation flow. However, the design of wet type turbo-expander for cryogenic liquid plants has been constrained due to the complexity of nucleation theory and the difficulty of data measurement in cryogenic environments. This paper presents numerical simulations for prediction of nitrogen spontaneous condensation flow in cryogenic nozzles. The non-equilibrium simulations were performed using three nucleation theories with the help of ANSYS CFX solver. The standard Redlich-Kwong gas state equation and Eulerian-Eulerian governing equations were used in simulations. Comparison with the equilibrium condensation model the non-equilibrium condensation model achieves a better prediction of the flow characteristics for spontaneous condensation flow in cryogenic environments. The nucleation theory which is based on classical nucleation theory (CNT) and improved by Kantrowitz for non-isothermal effects shows a better prediction of pressure drop, location of condensation onset and supercooling compared with experimental data. The influence of varying nucleation theories on the calculation of nucleation rate, the supercooling distribution and the liquid mass fraction distribution were also analyzed.