Effective chimney height
The effective stack height ( English effective plume height ; also: effective emission amount, effective source height) indicates height to which exhaust gases ascend before they propagate approximately horizontally. This value is required to calculate exhaust plumes in dispersion models .
calculation
The effective chimney height is made up of two components:
- Chimney height h
- Corresponds to the physical height of the chimney, i.e. the vertical distance from the floor to the height of the chimney opening.
- Chimney elevation (also "exhaust plume elevation") H
- This size takes into account that the exhaust gases continue to rise above the chimney. H can be calculated according to various theoretical and empirical exaggeration formulas from the exit momentum of the chimney air and the heat emission.
The effective chimney height is therefore dependent on the exit temperature of the exhaust gas as well as the exit speed, the water vapor content and the amount of the exhaust gas, but is also influenced by the atmosphere ( wind , temperature stratification ).
With a low exit speed of the flue gases, low flue gas temperature and wind, the effective chimney height can be reduced if the air flows downwards on the leeward side of the chimney or another flow obstacle. This effect is also known as downwash (Engl. For downdraft , with obstacles such as chimneys "thin") and downdraught (also downdraft, with larger obstacles) called.
meaning
As the effective chimney height increases, exhaust gases and pollutants from industrial plants are distributed over ever greater distances and thereby more diluted (see also the policy of tall chimneys ).
literature
- http://bfw.ac.at/rz/wlv.lexikon?keywin=1544 - Austrian Federal Office for Forests
- Spread of pollutants in the atmosphere ; Heiner Geiß, KTG seminar Volume 1; Kerntechnische Gesellschaft eV, Verlag TÜV Rheinland, 1983