Multiphase flows and phase-change phenomena are often encountered in many engineering systems, such as CCUS (carbon capture, utilization, and storage); the exploitation of oil, natural gas, and other underground resources; the utilization of geothermal energy and hydrogen energy, etc. Multiphase flows refer to the interactive flow of distinct phases, and each phase discriminated by common interfaces in a channel represents a mass or volume of matter. Multiphase flows can occur in single-component or multi-component systems. Possible phase combinations in our Reprint include the following: solid-liquid-gas, where solid particles and gas bubbles are mostly dispersed in liquid; solid-gas, solid-liquid, and liquid-gas, where the volume fraction of one phase is relative to other results for different flow regimes; and phase change and miscibility phenomena involved in a combination of the above. We hope that our Reprint will act as a guide for researchers and engineering technicians.