DEVELOPMENT OF A CORRELATION FOR AQUEOUS-VAPOR PHASE MASS-TRANSFER INPOROUS-MEDIA

In many situations vapor-phase extraction procedures (e.g., soil venti ng, air sparging, and bioventing) may be suitable methods for remediat ing porous media contaminated by volatile organic compounds. This has led to increased study of operative processes in these systems, includ ing aqueous-vapor phase mass transfer. Past work has shown the importa nce of the flow regime on this process, but a quantitative estimate of mass-transfer coefficients is lacking, especially for systems not con founded by uncertainties involving interfacial area between the phases . An experimental investigation was conducted to isolate the resistanc e to aqueous-vapor phase mass transfer at the phase boundary, using an ideal porous medium system. Mass-transfer coefficients were measured for toluene for a wide range of Reynolds numbers. An empirical model w as fit to the data in dimensionless form. The mass-transfer model was coupled with an available interfacial area model, yielding a dimension less expression for the mass-transfer rate coefficient. This expressio n was used to compare results from this work to three other experiment al studies reported in the literature. These comparisons showed that f or experiments where infiltrating water flowed uniformly within the po rous medium, the predicted mass-transfer coefficients were within a fa ctor of 5 of the measured coefficients. Mass transfer was significantl y slower than the rate predicted, using the results from this work, in experiments where infiltrating water flowed nonuniformly.