Experimental investigation on phase split of gas-liquid two-phase flows at a T-junction on a 180°return bend

In order to explore the phase split mechanism of two-phase flow at T-junction,a T-junction on a 180°return bend was employed to provide additional forces,such as centrifugal, gravitational and/or buoyant forces when two-phase mixture flows passing through it.The fac-tors,such as the resultant force at the branch direction,inlet momentums of the two phases,and inlet flow patterns at the phase separation were investigated experimentally.Using air and water as two working fluids,the inlet flow patterns for the two-phase flows were set as bubble and annular flows,respectively,and the inlet tube for the bend was placed vertically upward or downward .The phase split data were measured under varying the inlet flow pattern and gas and/or liquid velocities and the flow pattern transition around the bend and at the T-junction was carefully examined.The results show that under the condition of vertically upward inlet tube and the bub-ble flow pattern,the gas is mainly subjected to buoyant force and the liquid to gravitational force.Thus gas takes off preferentially under the condition of the branch.Increasing gas or liquid velocity is harmful to the gas take-off.Whereas at vertically upward inlet tube and annular flow, the liquid is mainly subjected to centrifugal force,and thus the liquid preferentially takes off from the branch.Increasing gas or liquid velocity is beneficial to the liquid take-off.In the case of vertical-ly downward annular flow,liquid is mainly subjected to downward centrifugal and gravitational forces,thus liquid preferentially takes off from the branch.Increasing gas or liquid velocity is harmful to the liquid take-off since the bubbles entrained in the liquid flow in the branch are in-creased and the liquid drops generated by the gas core at the bend are also increased.That which phase preferentially takes off depends mainly upon the resultant force at the branch direction. The phase split phenomena can be explained by analyzing the resultant forces,the flow pattern, and the momentums of the two phases at the T-junction.