STUDY OF GAS-LIQUID INTERFACES USING UNIFIED AND COUPLED MACRO-MICRO SIMULATIONS

Abstract

Interfacial interactions are critical for mass, momentum, and energy transport applications involving multiple phases. These interactions become complex when a wide range of scales are involved. In the present study, meshes having a wide range of scales and meshless microscale techniques are used to understand interfacial interactions. Further, these two extreme methodologies are coupled to explore interactions of wider-scale differences. A bubble column with concentrically arranged orifices has been simulated numerically with Finite Volume based methodology. Stage-wise bubble growth, departure, and rise have been studied to understand the effect of the neighboring orifice and bubbles on these phenomena. The effect of interfacial interactions on the overall performance of the bubble column in the case of asymmetric gas inflow has been explored. Bubble column has been also simulated under reduced gravity to determine bubble departure volume, frequency, and mutual interactions has also been analyzed. A new scheme of intermittent inflow has been proposed to reduce the bubble size and improve the bubble column performance. For further improvement of bubble column performance, the effect of inflow velocity and on-time for intermittent flow has been studied, and the rationale for choosing those parameters has been discussed. Pool boiling around a heated cylinder having a diameter larger than the departure diameter of the bubbles has been simulated numerically with finner cell discretization near the heater wall. The bubble life cycle around the horizontal cylinder has been analyzed to understand the growth, sliding, and merging stages before departure. An effort has also been made to characterize the bubble population, emerging from different sites over the cylindrical surface. The influence of cylinder inclination along its axis from the horizontal direction on these interfacial features has also been discussed using representative numerical simulation. Temperature profiles of the cylinder surface have been portrayed for both horizontal and inclined situations before presenting respective heat transfer coefficients.