Transient local thermal hydraulics data for two-phase flow instability in natural circulation

Two-phase flow instability is of increasing importance to reactor safety. New designs of LWRs employ passive safety features relying on low pressure and low flow rate which are susceptible to instability. However, data for natural circulation instability are still limited for the validation of system analysis codes and computational fluid dynamics (CFD) codes. The Multiphase Thermo-fluid Dynamics Laboratory at UIUC has collected a new dataset for natural circulation in an internally heated vertical annulus channel, which includes both stable conditions and conditions exhibiting periodical oscillations caused by instability. Flow rate at the inlet, temperature and pressure at ten locations around the test loop are recorded. Local two-phase parameters in the internally heated annulus riser are obtained with conductivity probes along with local liquid measurements with thermocouples. The data for oscillation cases are post-processed to reconstruct the transient two-phase distribution both radially and axially. Area-averaged data are also provided for the five axial locations in the two-phase region. The data provided by this research is expected to be widely beneficial to the validation of system analysis codes and CFD codes in simulating natural circulation phenomena.