Investigation on liquid holdup in vertical zero net-liquid flow

Zero net-liquid flow (ZNLF) is a special case of upward gas-liquid two-phas e flow. It is a phenomenon observed as a gas-liquid mixture flows in a cond uit but the net liquid flow rate is zero. Investigation on the liquid holdu p of ZNLF is conducted in a vertical ten-meter tube with diameter of 76 mm, both for Newtonian and non-Newtonian fluids. The gas phase is air. The New tonian fluid is water and the non-Newtonian fluids are water-based guar gel solutions. The correlations developed for predicting liquid holdup on the basis of Lockhart-Martinelli parameter are not suitable to ZNLF. A constitu tive correlation for the liquid holdup of vertical ZNLF was put forward by using the mass balance. It is found that the liquid holdup in ZNLF is depen dent on both the gas flow rate and the flow distribution coefficient.