In the present numerical study, the equations for condensation in cooled laminar tube flows have been presented and the solutions for low vapor concentrations and variable vapor-gas thermodynamic properties have been obtained. The main results of this paper are to explore the explicit effects of the flow regime. The problem, which is coupled with the particle size distribution, is treated by the PSI-CELL (Particle Source in Cell) and Eulerian method, and no assumption on the particle size distribution is adopted. Wall loss in the upward mixed convection flow is found to be smaller than that in the downward mixed convection flow. It is pointed out that particle size dispersity in the upward flow is higher than that in the downward flow. The optimum conditions for the monodispersity of the particle size distribution are very different with respect to the flow direction. As the tube diameter increases in the same Reynolds number, the vapor wall loss and particle number concentration decrease. When inlet seed concentration is absent, total vapor wall loss increases and the particles number concentrations decrease as Reynolds number decreases in the same tube diameter although the effects of the mixed convection decreases the vapor diffusion to the wall around the tube inlet. The PSD mode locally can not be represented by a specific function. With seed nuclei in which homogeneous nucleation is fully suppressed, the vapor wall loss is very small and the homogeneity of the PSD is improved.
