Wave characteristics of vertical upward adiabatic annular flow in pipes

Abstract

Annular flow exists in many engineering applications, such as refrigerators, oil extraction, nuclear reactors and so on, due to its high heat and mass transfer efficiencies. Annular flow is characterized by liquid film on the wall and gas core at the center of the flow duct. The interface between the gas and liquid is composed of many different waves that play important role in mass, momentum and energy transfers between gas and liquid phases. Here three important parameters regarding wave characteristics, namely, wave velocity, base film thickness and wave height have been studied. For wave velocity, correlation has been proposed by two methods which are derived from liquid interfacial velocity and interfacial shear stress, respectively. For correlations of base film thickness and wave height, they are proposed in similar forms as that of average film thickness previously developed by the authors. These newly proposed correlations are functions of gas and liquid Weber numbers, and are simpler and more straightforward to use as compared to the existing ones. The newly proposed wave velocity, base film thickness and wave height correlations, respectively, have mean absolute percentage errors of 9.56%, 14.6% and 12.1% compared to current databases. They have shown an improved prediction accuracy compared to the other correlations in the literature.