Numerical Investigations of the Deposition of Unattached {sup 218}Po and {sup 212}Pb from Natural Convection Enclosure Flow
We report numerical predictions of the deposition to enclosure surfaces of unattached {sup 218}Po and {sup 212}Pb, short-lived decay products of {sup 222}Rn and {sup 220}Rn, respectively. The simulations are conducted for square and rectangular two-dimensional enclosures under laminar natural convection flow with Grashof numbers in the range 7 x 10{sup 7} to 8 x 10{sup 10}. The predictions are based upon a finite-difference natural-convection fluid-mechanics model that has been extended to simulate the behavior of indoor radon decay products. In the absence of airborne particles, the deposition velocity averaged over the enclosure surface was found to be in the range (2-4) x 10{sup -4} m s{sup -1} for {sup 218}Po and (1-3) x 10{sup -4} m s{sup -1} for {sup 212}Pb. In each simulation, the deposition rate varied by more than an order of magnitude around the surface of the enclosure with the largest rates occurring near corners. Attachment of decay products to airborne particles increased the deposition velocity; for example, attachment of {sup 218}Po at a rate of 50 h{sup -1} increased the predicted average deposition velocity by 30-70% over values in the absence of attachment. The simulation results have significance for assessing the health risk associated with indoor exposure to {sup 222}Rn and {sup 220}Rn decay products and for investigating the more general problem of the interaction of air pollutants with indoor surfaces.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Environmental Energy Technologies Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 939272
- Report Number(s):
- LBL-30249; JALSB7; TRN: US200912%%76
- Journal Information:
- Journal of Aerosol Science, Vol. 23, Issue 4; ISSN 0021-8502
- Country of Publication:
- United States
- Language:
- English
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