Numerical simulation of trans-critical carbon dioxide (R744) flow through short tube orifices

A detailed one-dimensional numerical simulation of the fluid-dynamic behaviour of short tube orifices expansion devices working with trans-critical carbon dioxide (CO2 or R744) has been developed. The discretized governing equations are coupled using an implicit step by step method. A special treatment has been implemented in order to consider transitions (subcooled liquid region and equilibrium two-phase region). The numerical model allows analysis of aspects such as geometry, different working conditions, critical or non-critical flow conditions, etc. Comparison of the numerical simulation with experimental data presented in the technical literature will be shown in the present article.