NUCLEATION LABORATORY
THE
IMPACT OF CONVECTIVE FLOW ON THERMAL DIFFUSION CLOUD CHAMBER OPERATION
accepted
for publication in J. Phys. Chem. 2001
F.T.
Ferguson and R.H. Heist
RESEARCH
SUMMARY
We report in this paper new results that further elucidate the role of
buoyancy-driven convective flows in determining the distribution of vapor mole
fraction and temperature in the thermal diffusion cloud chamber.
A two-dimensional model describing both diffusion and convection in the
presence of chamber sidewalls is presented.
The model equations are use to analyze 1-butanol and 1-pentanol
nucleation data obtained earlier. The
results of the investigation are summarized in the figures shown below.
These results show that convective flow is nearly always present and, in the
cases considered here, result in a reduction in the value of the calculated
critical supersaturation (as compared to the one-dimensional case).
The dependence of critical supersaturation with total pressure reported
earlier is smaller but is not eliminated.
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| Variation
of critical supersaturation of 1-pentanol in helium with total pressure
for the 1-D analysis (solid symbols) and the 2-D analysis (open
symbols). The solid lines
are regression fits to the linear portions of the data sets and are
included to emphasize trends in the data.
Nucleation temperatures: diamonds
- 356K; squares - 366K; triangles - 377K.
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Variation
of critical supersaturation of 1-butanol in helium with total pressure
for the 1-D analysis (solid symbols) and the 2-D analysis (open
symbols). The solid lines
are regression fits to the linear portions of the data sets and are
included to emphasize trends in the data.
Nucleation temperatures: diamonds
- 334K; squares - 348K; triangles - 363K.
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