Calculation of Two-Phase Critical Flow from a Long Pipe

Abstract

A computer simulation model (BIRD - Break Initial Bate of Discharge) has been developed for estimating the two-phase critical flow rate from along pipe (length-to-diameter ratio >> 12), based upon upstream fluid conditions at a stagnant source. Accuracy of the model in predicting the fluid pressure along a flow path and the discharge mass flux is shown to be very good over a wide range of stagnation conditions (subcooled and saturated liquids. and saturated steam at up to 17000 kPa pressure). The developed model (BIRD) has been applied to design assist and safety analyses of CANDU reactors such as estimating the initial discharge rate from ruptured feeder piping for small loss of coolant accidents.