Two-phase flows in pipes and capillary channels

This review is devoted to analysis of two-phase flow patterns in capillary channels. Studies are considered in which flow pattern maps are obtained of two-phase flow in channels of different cross sections with the transverse dimension ranging from $20$ $\mu$m to $255$ mm. Data on flow patterns are systematized and given in tables. The impact made by capillary effects is analyzed compared to the influence of other factors under conditions of two-phase flow in channels. The classification of channels based on the degree of manifestation of capillarity is validated. Characteristic features of two-phase flow in channels of noncircular cross section are considered. It is demonstrated that thermocapillary effects may be significant under conditions of nonisothermal two-phase flow in microchannels and under conditions of weak effect of gravitation.