Homogeneous equilibrium modeling for subcritical flows in liquid rocket engine cooling systems

During off-design operations of liquid rocket engines, the coolant operating conditions can easily extend from the subcritical to the supercritical regime. As a matter of fact, it is very useful to have a single software able to study the flow in this range of operating conditions, providing reliable simulations that are reasonably quick and able to accurately estimate and assess the increase in coolant temperature along the channel and the wall temperature field. This objective is pursued by extending an established approach for the study of supercritical flows to the case of subcritical heating, where a two-phase flow may occur. This is done by exploiting the so-called homogeneous equilibrium model, which has been shown to be sufficiently predictive and accurate for specific applications. With the aim of demonstrating and discussing the potential and limitations of such a single software approach, analyses are conducted on different test cases where two-phase flow is induced by cavitation or flow boiling, and results are compared with those of analytical models and experimental data. It is found that, in addition to some intrinsic limitations in the analysis of subcooled boiling flows, satisfactory agreement with experimental data is obtained in the post-critical-heat-flux regime.