Chapter 12 is focused on multiphase flows with phase changes, where the phase interactions are further complicated by the mass transfer and mass-transfer-induced momentum and energy transfer.Basic topics include the regime classification and flow characteristics in each regime for boiling and spray dispersion, phase interaction mechanisms involving phase changes, flow characteristics of atomized spray jetting with evaporation, characteristics of gas–solid reacting flows in risers, characteristics of bubbling flow in sparged stirred tanks, and their impact on reactions, and combustion characteristics and coupling of transport mechanisms of dispersed fuel particles. Multiphase flow modeling with phase changes is quite incomplete compared to that without phase changes. More physical understanding is necessary and hence the mathematical descriptions of flow-influence phase changes, multiscaled phase changes, and transport phenomena of multiphase flows under highly pressurized and high-temperature operation conditions.Progress in both modeling and numerical solution techniques is evidenced in the case studies as given for the applications of multiphase flows with phase changes.