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Mass transfer from spherical particles and reservoirs into quiescent liquids
Author(s) -
Doan Huu D.,
Trass Olev,
Fayed Muhammad E.
Publication year - 1998
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450760506
Subject(s) - urea , mass transfer , diffusion , particle (ecology) , convection , chemistry , natural convection , spheres , rayleigh scattering , heat transfer , materials science , analytical chemistry (journal) , thermodynamics , chromatography , optics , geology , physics , organic chemistry , oceanography , astronomy
A continuous weighing technique was developed for measuring urea transfer (carbamide, a fertilizer) from a single opening on a coated sphere in a stagnant liquid. Urea release was determined from the changes of the particle weight with time. Mass transfer coefficients for Rayleigh numbers from 1.8 × 10 7 to 6.8 × 10 10 were measured and compared with those for uncoated urea spheres and literature data. For the opening oriented vertically upward in water, natural convection enhanced the transfer rate by 1.8 times compared to that for urea diffusion only. In other opening orientations (45°, 90°, 135° and 180° to the vertical), natural convection provided the major mechanism for the release. A model for urea diffusion was also developed. It agrees well with experimental data.