Experimental data are compared to calculations with a one-dimensional computer code (DUESE). In a systematic study, two-phase flow models (homogeneous and drift-flux) and empirical parameters in constitutive correlations of different code versions were tested. Special attention was given to the pressure rise in the diffuser, which could be calculated adequately only with the drift-flux correlation taken from the SOLA-DF code., Velocity data for choked flow conditions are compared to four different two-phase sound velocity models, which give the best agreement with the equilibrium sound velocity.