A Two-fluid/DQMOM Methodology for Condensation in Bubbly Flow

Paper in proceeding, 2015

n this paper a two-fluid framework for simulating two-phase bubbly flow in heated vertical channels is proposed. The aim is to simulate the two-phase flow and heat transfer of the liquid phase and the vapour phase under subcooled conditions in nuclear reactors where light water serves as coolant, namely Light Water Reactors (LWRs). The framework couples a two-fluid solver and a population balance equation (PBE) solver. A formulation of the PBE including condensation of vapour bubbles is outlined and implemented for the direct quadrature method of moments (DQMOM). Furthermore a wall boiling condition is formulated and expressed in terms of a boundary condition that allows the bubble distribution at the wall to be specified. The formu- lated system is applied to a system with condensation vapour bubbles in a subcooled liquid entering at the inlet and to a system with wall boiling, i.e emergence of vapour bubbles due to a superheated wall. The proposed DQMOM method is compared to the multiple size-group (MUSIG) method, and it is shown to capture the space dependence of the bubble size distribution with a low number of abscissas and in a computationally efficient manner.