Two-Phase Flow, Boiling, and Condensation In Conventional and Miniature Systems

Two-phase flow model transport equations are discussed. Local-instantaneous single-phase conservation equations and interfacial balance relations are presented in general mathematical forms. We then focus on 1D flows, and principles of flow area-averaging are reviewed. Using a simple and heuristic approach based on applying mass, momentum and energy balances on a slice of a flow channel, tractable model conservation equations are derived. These include mass, momentum, and energy conservation equations for homogeneous-equilibrium two-phase flow model; and phasic (i.e., separately for gas and liquid phases) mass, momentum and energy conservation equations for separated flow (two-fluid) model. The conservation equations are first derived for pure (single component) fluids, and are then expanded to two-component fluids. The interfacial processes (heat, mass, momentum transfer, virtual mass effect) are discussed for the separated-flow model. Two-fluid model equations for multi-dimensional flows are presented, followed by a simple method for the numerical solution of steady, 1D conservation equations. Three solved example problems and 14 end-of-chapter problems are provided.