Predicting the rate of mass transfer in liquid-liquid systems is of crucial importance for the study of ground water contamination by hydrocarbons. Proposed correlations assume that mass transfer is strongly related to the interfacial area between the two immiscible fluids. In this paper, we present results of column experiments on the dissolution of pure hydrocarbons as well as a 1D model. Experiments were conducted for small values of the Peclet number (Pe < 1). The model involves a classical convection-dispersion-mass transfer equation. Mass transfer coefficient was calculated for various periodical simplified porous systems on the basis of theoretical results from the volume averaging theory. Results show that the transport model simulates correctly the shape and dynamics of the dissolution front. It is shown that an average value of the distance between two NAPL blobs can be a key parameter for the estimation of the mass transfer coefficient rather than the interfacial area.