  For high- pressure nucleation experiments in upward diffusion cloud chamber,
there is the great deviation of predictions of classical nucleation theory from
experimental results; the discrepancy is more than 10 orders of magnitude of
nucleation rate. Experimental data for 1-propanol vapor are under investigation
in this paper. It was shown that mathematical model of a single droplet growth
and motion semi- quantitatively explained all experimentally discovered
regularities. For explanations low nucleation rate versus high supersaturation,
the coalescence mechanism in gaseous phase has been proposed. As result of
coalescence the vast majority of newly formed clusters evaporate and restore
vapor density and temperature profile in DCC. The observed picture with low
nucleation rate is result of diffusion interaction between small clusters and
droplets in nucleation zone for high- pressure nucleation experiments.
