AbstractThe time‐averaged void fraction, pressure drop and flow regime transition behavior of horizontal air‐water two‐phase flows is studied experimentally and numerically for 2‐cm‐inner‐diameter tubes with various flow dividing junctions at its end. The time‐average void and pressure drop behavior along the channel is simulated using a two fluid separated flow model. The results show that two‐phase behavior (flow regime, void fraction, and pressure drop) is affected strongly by the presence of a flow division in the system. These effects extend far upstream of the junction for low‐momentum flows and far downstream for high‐momentum flows. Both numerical and experimental results show that there occurs a large increase in void just downstream of the junction owing to the halving of the fluid volume flow rates and the