A PORE-SCALE INVESTIGATION OF MASS-TRANSPORT FROM DISSOLVING DNAPL DROPLETS

Spheres and pendular rings of trichloroethylene and tetrachloroethylen e are observed dissolving in an artificial porous medium consisting of a single layer of glass beads. Given the simple geometry of the dropl ets, pore-scale mass transfer coefficients are calculated. For dissolv ing spheres, mass transfer coefficients are found to be constant over time. However, coefficients for pendular rings are found to decrease a s the rings shrink in size. This is consistent with the concept of dif fusion-controlled mass transfer in low-flow zones. Sherwood numbers me asured at Reynolds numbers between 0.0033 and 8.33 show a similar tren d to empirical relationships established by previous researchers using other techniques. As in previous experiments, considerable scatter in mass transfer rates is observed at a given mean flux. It is hypothesi zed that this variation in local mass transfer rates is caused by vari ations in local pore velocity.