A macroscopic model of heterogeneous nucleation is used for a theoretical study of condensation of water-vapor/carrier-gas mixtures in a nonequilibrium nonstationary rarefaction wave generated in a shock tube. The results are compared with those from homogeneous nucleation. It is assumed that nucleation takes place heterogeneously on idealized smooth, spherical solid particles of Aitken nuclei, which are chemically and electrically inert. In the processes of heterogeneous condensation, the controlling factors are the size-distribution of nuclei, the concentration of monomers on the surface of the substrate and the activation energy of nucleation, which is greatly dominated by the contact angle of embryos. Of these factors, the most dominant is the contact angle. Due to the reduced activation energy, heterogeneous condensation results in less supercooling of the mixture and a faster approach to the equilibrium state. By choosing a suitable value for the contact angle, the numerical results can be made to fit some recent experimental data. Although this is not entirely satisfactory, it is probably preferable to changing the value of surface tension, which was done in the homogeneous-nucleation model in order to obtain agreement with the same experimental results.