MECHANISTIC NONEQUILIBRIUM MODELING OF CRITICAL FLASHING FLOW OF SUBCOOLED LIQUIDS CONTAINING DISSOLVED NONCONDENSABLES

A mechanistic, nonequilibrium model is presented, addressing the flash ing and critical channel flow of initially subcooled water containing dissolved noncondensable gas. The model, which is based on the iterati ve numerical solution of and the imposition of critical flow condition s on, one-dimensional two-fluid conservation equations, accounts for t hermal, mechanical, and noncondensable species concentration nonequili brium between the two phases. A two-phase flow regime map including bu bbly, churn / slug, and annular patterns is applied, and flow regime-d ependent heat, mass, momentum, and mass species transfer correlations are used for representing the interfacial transfer processes. The deve loped model is validated against experimental data. Parametric calcula tions assessing the significance of dissolved noncondensables in criti cal flow are then presented. it is shown that, for flashing and critic al flow of subcooled water, the desorption of dissolved noncondensable s reduces the critical mass flux slightly.