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| Titel |
Partial Derivative Fitted Taylor Expansion: an efficient method for calculating gas/liquid equilibria in atmospheric aerosol particles – Part 2: Organic compounds |
| VerfasserIn |
D. Topping, D. Lowe, G. McFiggans |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 5, no. 1 ; Nr. 5, no. 1 (2012-01-04), S.1-13 |
| Datensatznummer |
250002289
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| Publikation (Nr.) |
 copernicus.org/gmd-5-1-2012.pdf |
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| Zusammenfassung |
| A flexible mixing rule is presented which allows the calculation
of activity coefficients of organic compounds in a multi-component aqueous solution.
Based on the same fitting methodology as a previously published inorganic model (Partial
Differential Fitted Taylor series Expansion; PD-FiTE), organic PD-FiTE treats interactions
between binary pairs of solutes with polynomials of varying order. The numerical framework
of organic PD-FiTE is not based on empirical observations of activity coefficient variation,
rather a simple application of a Taylor Series expansion. Using 13 example compounds
extracted from a recent sensitivity study, the framework is benchmarked against the UNIFAC model.
For 1000 randomly derived concentration ranges and 10 relative humidities between 10 and 99%,
the average deviation in predicted activity coefficients was calculated to be 3.8%. Whilst
compound specific deviations are present, the median and inter-quartile values across all
relative humidity range always fell within ±20% of the UNIFAC value. Comparisons
were made with the UNIFAC model by assuming interactions between solutes can be
set to zero within PD-FiTE. In this case, deviations in activity coefficients as
low as −40% and as high as +70% were found. Both the fully coupled and uncoupled
organic PD-FiTE are up to a factor of ≈12 and ≈66 times more efficient
than calling the UNIFAC model using the same water content, and ≈310 and
≈1800 times more efficient than an iterative model using UNIFAC. The use of
PD-FiTE within a dynamical framework is presented, demonstrating the potential
inaccuracy of prescribing fixed negative or positive deviations from ideality when
modelling the evolving chemical composition of aerosol particles. |
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