Condensation core

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A condensation nucleus or condensation nucleus facilitates nucleation (also called nucleation) and the subsequent condensation of a gaseous substance. Such a germ can be pollution, such as a dust , salt or soot particle , or ionized gas molecules, as in the cloud chamber . PJ Coulier succeeded in detecting condensation nuclei in 1875.

With greater oversaturation or hypothermia , nucleation also occurs spontaneously from local density fluctuations , i.e. H. without nucleus or nucleus.

Conversions in condensed phases are influenced in a similar way by foreign substances (e.g. crystal nuclei ).

Examples

  • Aerosol particles, which have certain chemical and physical properties, act as condensation nuclei in the earth's atmosphere and contribute to the formation of clouds .
  • When measuring particles with the condensation particle counter, the property of the particles as a condensation core is used in a targeted manner in order to enlarge them through condensation and to make them visible for the counting optics.
  • For the production of test aerosols (i.e. aerosols with defined properties) that are based on condensation processes, condensation cores are used.

Individual evidence

  1. ^ Carsten Möhlmann: Dust measurement technology - then until now . In: Hazardous substances - cleanliness. Air . 65, No. 5, 2005, ISSN  0949-8036 , pp. 191-194. (PDF; 335 kB)
  2. ↑ VDI 3491 sheet 4: 2018-03 measurement of particles; Manufacturing process for test aerosols; Condensation methods (Measurement of particles; Methods for generating test aerosols; Condensation methods). Beuth Verlag, Berlin, p. 4.
  3. ↑ Alfred Wiedensohler : Particle counting in the outside air - a measuring task with a future. In: Hazardous substances - cleanliness. Air. 64, No. 7/8, 2004, ISSN  0949-8036 , p. 313.
  4. ↑ VDI 3867 sheet 2: 2008-02 Measurement of particles in the outside air; Characterization of test aerosols; Determination of particle number concentration and number size distribution; Condensation Particle Counter (CPC) (Measurement of particulate matter in ambient air; Methods for characterizing test aerosols; Determination of the particle number concentration and particle size distribution; Condensation Particle Counter (CPC)). Beuth Verlag, Berlin, pp. 3-4.
  5. ↑ VDI 3491 sheet 4: 2018-03 measurement of particles; Manufacturing process for test aerosols; Condensation methods (Measurement of particles; Methods for generating test aerosols; Condensation methods). Beuth Verlag, Berlin, pp. 9-10.