  We propose a new method of estimating the mean diameter and dispersion of
clusters formed in a cooling gas, right after the nucleation stage. Using a
moment model developed by Friedlander [S.K. Friedlander, Ann. N.Y. Acad. Sci.
354 (1983)], we derive an analytic relationship for both cluster diameter and
diameter dispersion as a function of two of the characteristic times of the
system - the cooling time and primary constituents collision time. These
formulas can be used to predict diameter and dispersion variation with process
parameters such as the initial monomer pressure or cooling rate. It is also
possible to use them as an input to the coagulation stage, without the need to
compute complex cluster generation during the nucleation burst. We compared our
results with a nodal code and got excellent agreement.
