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  • Author or Editor: A. M. Sinnarwalla x
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A. M. Sinnarwalla
and
D. J. Alofs

Abstract

A vertical plate, steady-flow, thermal diffusion chamber designed for use as a cloud condensation nucleus counter is described. In this instrument, phoretic forces are shown to limit the maximum available growth time to a value eight times larger than the growth time available in conventional horizontal plate chambers. This additional growth time is shown to be necessary when operating at supersaturations below 0.2%. Experiments and calculations concerning convection currents in the vertical chamber are also presented.

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P. C. Mahata
,
D. J. Alofs
, and
A. M. Sinnarwalla

Abstract

Analytical expressions are derived for temperature and vapor pressure profiles in a vertical-plate, steady-flow, thermal diffusion chamber designed to count cloud condensation nuclei. The influence of longitudinal diffusion of heat and water vapor on the supersaturation rise time is shown to be quite significant at low sample velocities. The effect of different velocity profile shapes is also investigated.

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A. M. Sinnarwalla
,
D. J. Alofs
, and
J. C. Carstens

Abstract

Growth rate measurements were made for water drops grown on nuclei in atmospheric air samples taken in Rolla, Missouri. Rolla, having a population of 15,000 and very little industry, is relatively free of urban pollutants. The measurements were made in a vertical flow thermal diffusion chamber at supersaturations of 0.5 and 1%. The time to grow from near dry radius to the final radius (6 to 7.5 µm) was measured. If one assumes the thermal accommodation coefficient is unity, the measurements indicate an average value of 0.026 for the condensation coefficient. The temperature ranged from 22.5 to 25.7°C.

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