Subchannel analysis by the FIDAS code based on the three-fluid model

The Film Dryout Analysis Code in Subchannels, FIDAS, has been developed with the main objective of predicting dryout and post-dryout heat transfer in channels and in rod bundles. In FIDAS, two-phase flow consisting of continuous liquid film, continuous vapor and entrained droplets is modeled by a three-fluid, three-field representation of 12 field equations, i.e. three continuity, three energy and six momentum equations. In this validation study of the code, inter-subchannel mixing models were examined. FIDAS satisfactorily predicted flow quality and mass flux in subchannels under typical operating conditions of a boiling water reactor, as comparisons with the experimental data of GE 3x3 and ISPRA 4x4 tests. (orig.)