Thermal conductivity enhancement by the use of nanoparticles has remained a long debatable area of research. Using a modified heat transport model considering the interfacial effects via Kapitza resistance, the effective thermal conductivity of different nanofluids in an aqueous medium is predicted. Kapitza resistance stems due to density stratification at the interface owing to the interfacial wettability and the Brownian motion of nanoparticles. We introduce a fitting parameter ε which represents density stratification. A positive and a negative value of ε represents higher and lower density respectively at the interface with respect to the bulk. We find different values of ε for different nanofluids by comparing the predicted value with the existing experimental values in the literature and observe the variation of ε with nanoparticle diameter to predict the effect of density stratification.