Consistent comparison between the drift flux and two-fluid formulations of two-phase flow in LWRs

Two numerical models have been developed to simulate the non-equilibrium, non-homogeneous behavior of one dimensional two-phase flow through a heated channel. One model was developed using the drift flux formulation while the other model employed a two-fluid approach. Consistent numerics and constitutive relationships were used wherever possible for both models, allowing noted prediction differences to be attributed to fluid momentum formulation differences associated with the two models. Several transient conditions similar to thermal hydraulic conditions found in light water reactors (LWR) were then simulated to examine the differences which may arise between the two formulations. The results indicate that the two models showed good prediction agreement in all fluid properties except the relative velocity for steady-state conditions