Mass transfer equations are derived and compared with dissolution experiments of C
6H
5COOH-H
2O and Cu-H
2SO
4-K
2Cr
2O
7 systems on single spheres (6 different sizes from 3/4" to 3"). In region I (long contact time with smooth laminar film), Sh converges
Sh=1.608 (GaSc/Pe
*)
1/3 or k=2.01 D√δ
(δ: mean film thickness) and increases with decreasing volumetric flow rate Q. In region II (short contact time with smooth laminar film), Sh converges
Sh=0.716 Pe
*1/9(GaSc)
2/9The transition from region I to II occurs around Pe
*/(GaSc)
1/4≤10. In region III (short contact time with wavy film surface), Sh increases with Pe
* to the 1/3 - 1/2 power and is substantially higher than that in region II. A generalized short contact time equation using the measured local film thickness δ
Sh=0.501 Pe
*1/3{∫
π0(d/δ)sinθdθ}
2/3is valid in this region. Thus, main cause for enhancement in Sh is the reduction in film thickness relevant to the wave formation. The II-III transition is somewhere between wave inception and wave coverage flow rates. In the above, Sh=kd/D, Pe
*=Q/dD and Ga=gd
3/v
2, in which k is based on a log-mean driving force.
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