Interphase Mechanical Energy Transfer of Gas-Liquid Flow in Variable Cross-Section Tubes

Abstract

The use of gas energy includes a wide range of applications to directly accelerate the liquid in a pipeline without the aid of mechanical equipment, such as marine gas-liquid jet propulsion. To clarify the characteristics of energy transfer by interphase forces for gas-liquid flows in variable cross-section tubes, two-fluid models of annular flow, bubbly flow and homogeneous flow were adopted, respectively, along with four newly elaborated coefficients, which are the work factor of gas $f_g$, reflecting the relative ability of gas to power liquid, the interface work transfer coefficient $k_g$ (representing the relative magnitude of mechanical work received by liquid from gas), the interphase work-to-energy conversion coefficient $k_l$ (denoting the capability of energy transfer through work performed by interphase forces) and the interphase mechanical efficiency ${\eta }_w$. The results reveal the interphase work transfer is strongly influenced by the structural parameters of the tubes (or nozzles), and an optimized design is necessary to improve the performance. The higher the degree of gas dispersion in the liquid, the more advantageous the conversion of gas work into the liquid’s mechanical energy. Of these three flow patterns, annular flow has the lowest $k_l$ and ${\eta }_w$ ($k_l$ = 0.0797, ${\eta }_w$ = 0.9885 in present example), while homogeneous flow displays the limit of interphase mechanical energy conversion because the gas-liquid momentum coupling reaches the maximum ($k_l$ = 0.9979, ${\eta }_w$ = 1).