Annular flow : a mechanistic suite of co-validated methods for two-phase flow and boiling/condensation heat transfer

Abstract

The present paper focuses on the unified modeling suite for annular flow that the authors have been developing in the last few years. Annular two-phase flow is one of the most important of the gas-liquid two-phase flow regimes because of the large range of industrial applications in which it occurs, such as refrigeration and air conditioning systems, nuclear reactors and chemical processing plants, and high heat flux cooling applications. Sound design and safe operation of two-phase flow systems require accurate modelling of annular flows, and this motivated the development of the mechanistic modelling suite for annular two-phase flows that is discussed here. First, the unified suite of annular flow prediction methods is presented, illustrating in particular the most recent updates. Then, selected results for convective evaporation and condensation in tubes and channels are presented and discussed. Presently, the annular flow suite includes prediction methods for the void fraction, the entrained liquid fraction, the pressure gradient, and a turbulence model for momentum and heat transport inside the annular liquid film. This turbulence model, in particular, allows prediction of the local average liquid film thicknesses and the local heat transfer coefficients during convective evaporation and condensation. The benefit of a unified modeling suite is that all the included prediction methods are consistently formulated and are proven to work well together, and provide a platform for continued advancement based on the other models in the suite.