The influence of the phase transition model on the carbon dioxide (R744) converging–diverging nozzle performance simulation was investigated in this study. The nozzle model utilised the delayed equilibrium model with two distinct nucleation approaches: solely homogenous nucleation and a superposition of homogeneous and heterogeneous nucleation. The homogeneous equilibrium model approach was considered a reference case. A correlation for the heterogeneous nucleation work reduction factor was developed and validated for a typical range of operating conditions, achieving good consistency between the simulation and the experimental results for the critical mass flux. Copyright © 2012 Elsevier Ltd. All rights reserved.