Application of a low-pressure transient subcooled void model to channel and bundle experiments

A time-dependent subcooled-void model, developed from low-pressure generation-condensation data, is applied to flow instability experiments conducted with an electrically-heated bundle. The void model, implemented in a numerical 1-D transient code, was used to perform a stability analysis of the bundle sub-channels. This paper summarizes the features of the subcooled-void model and details the application of the void model to the bundle experiments. The flow bulk outlet temperature at the bundle exit was always subcooled. However, incipient flow oscillations were observed at certain power levels and these flow oscillations resulted solely from the subcooled void present. Thus, realistic modeling of the subcooled void was critical to predicting the onset of flow oscillations. Though developed for, and applied to, a low pressure situation, the approach may be applicable to higher pressure applications. Insights into the sub-channel dynamics are also presented and discussed.