THERMAL HYDRAULIC SUBCHANNEL MODEL BASED ON VOID-DRIFT
An improved thermal hydraulic subchannel model is presented for the calculation of two-phase flow and enthalpy in the subchannels of a rod bundle. The flow model uses a mixture formulation for the conservation of mass, momentum, and energy and includes provision for both axial and lateral relative velocity. The relative velocity in the lateral direction accounts for the counter-current liquid and vapor flow associated with "void-drift;" this lateral relative velocity is defined in terms of void diffusion toward a specified equilibrium void fraction. Computation results using this model have been successfully compared to all of the known subchannel data.