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NUCLEATION LABORATORY
TRANSPORT IN THE STATIC DIFFUSION CLOUD CHAMBER REVISITED
J. Chem. Phys. 114(2) 899 (2001)
M.P.
Anisimov, S D. Shandakov, Yu.I. Polygalov and R.H. Heist
RESEARCH
SUMMARY
The static diffusion chamber (SDC) allows measurement of critical
supersaturation and of nucleation rates, and it is a powerful instrument for the
study of vapor to liquid nucleation. Earlier, within the scope of the
International Nucleation Workshop Group, nucleation rates for 1-pentanol in
helium as the background gas have been measured using different experimental
techniques.
The disagreement of the nucleation data obtained using the SDC and that obtained
using other experimental techniques, e.g. expansion-based devices and laminar
flow devices, can be explained by re-examining the mass and energy transport
model used to describe operation of the SDC.
In this paper, we present as a model for mass and energy transport in the SDC an
effectively open system with transport in one direction and a non-zero diffusion
flux at the system boundaries. Calculated values for vapor supersaturation are
compared with the 1-pentanol nucleation rate experimental results from the
American and Czech groups and also with a nucleation rate reference equation
obtained from an earlier investigation involving the 1-pentanol - helium system.
From our results one can see that there is a significant difference in the
calculated supersaturation for all of the data. The magnitude of this difference is large even for the
relatively small vapor mass fractions at a nucleation temperature of 260 K.
We also note that the calculated nucleation temperatures from our
analysis are slightly larger than those reported by both groups.
We performed our calculations with and without the thermal diffusion
term. We observed that the effect
of thermal diffusion on the transport process is relatively small.
The key effect arises due to our new flux boundary conditions.
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