ABSTRACT
This paper summarizes results of recent experimental studies of two-phase flow in passages containing idealized single fin and constriction elements. These studies used a phase-Doppler particle analyzer system to determine how droplet entrainment is affected by these types of internal structures. The relevance of the results of these experimental studies to annular flow vaporization processes is explored in detail. These studies imply that constrictions and expansions in plate-fin evaporators may enhance entrainment, thereby reducing the liquid film thickness on the surface. This may enhance heat transfer when the liquid inventory is high and may hurt heat transfer performance when the liquid inventory is low by inducing localized dryout of the film on the passage wall. Shedding of liquid from fin structures can produce a non-uniform entrainment field which facilitates redeposition of droplets on fins immediately downstream. This helps keep fin surfaces wetted when liquid inventory is low, improving heat transfer performance.
