Visualization study of evaporation of single n-pentane drops in water

A laser shadowgraph system was constructed to enable successive filming of a drop or a bubble rising or falling in an immiscible liquid confined within a vertical column. The assembly was applied to a study of the evaporation of n-pentane drops in a stagnant medium of water. The liquid/vapor two-phase bubble evolving from each pentane drop was observed together with its wake, the morphology and the dynamics of which are our primary concern in considering the mechanism of the medium-to-bubble heat transfer.List of symbols a minor axis of ellipsoidal two-phase bubble - b major axis of ellipsoidal two-phase bubble - D ₀ diameter of saturated-liquid drop set to vaporize - Re Reynolds number based on instantaneous, volume-equivalent spherical diameter and rise velocity of two-phase bubble and kinematic viscosity of the continuous phase - t time lapse after the start of evaporation - T ^* excess of undisturbed continuous-phase temperature above the temperature at which the sum of the saturated vapor pressures of the dispersed- and the continuous-phase fluids is equal to the pressure at the position where evaporation starts - opening angle of wake-covered region on bubble surface - _w zenith angle at flow-separation ring on bubble surface - mass fraction of vapor in two-phase bubble