Dynamic Drift Effects in CANDU Reactor Thermal Hydraulics

Abstract

In this paper, a realistic velocity difference Scheme will be presented in both horizontally and vertically oriented sections of the primary heat transport systems of the CANDU reactors. This scheme predicts the unequal velocity effects: spatially and temporally. It can be used to describe the slip in transient and multi purpose thermohydraulic codes. The transient velocity difference equation of this model is an arrangement of the two fluid model equations. The equation describes the time dependent relation between the phase velocities. This is a function of the pressure gradient, phase interties, volume fraction, the flow regime and additional constitutive relations. In addition, the model includes a package of momentum exchange constitutive laws to calculate the interphase momentum exchange parameters and virtual mass coefficient. The parameters necessary for the integration of this model into CANDU thermohydraulic codes (SOPHT, FIREBIRD) are expressed in terms of the dynamic difference velocity. These parameters are the drift mass flow rate, drift velocity, distribution parameter, flow quality, effective density and flow enthalpy. Preliminary results revealed that this model fairly predicts the dynamic drift flux parameters.