Comments on paper by Wang et al.

Letters to the Editors

Comments on paper by Wang et al. (Receiued 30 June 1982)

Dear Sirs, The recent paper by Wang et a.i, A study of mass transfer in a packed bed by electrochemical technique. Chem. Engng Sci 1982 37 939 represents a careful enquiry into that issue. They find for beds of spheres & = 0.72Rs-0.J’. Apparently they failed to find a theoretical development[l, which teaches

ljD =

1.15~/(c)Re-“-5

(1)

numbers vary by a factor of 2 to 3 from stagnation point to beyond.

Theory must, of course, respect reality and all must respect the literature. Department of Chemical Engineering Universily of Notre Dame Notre Dame, IN 46556 U.S.A.

21 NOTATION

(2)

mass transfer j factor

t

or for i = 0.4

0

ljD =

JAMESJ.CARBERRY

particle Reynolds number void fraction.

0.727Re-“.5.

Both experiment and theory are macroscopic, however, as a detailed study[fI demonstrates local microscopic deviations of the transport coefficient as a function of position about a single sphere within that complexity we term the fixed bed. Local Nusselt

REFERENCES

[I]Carberry J. J., A.LCh.EJ. 1960 6 450. [2]Mkon F. 0. and Carberry J. J., Chem. Engng Sci. 1960 13 30. 131Gillespie B. G., Crandall E. and Carberry J. J., A.LClrE.J. 1%8 14 483.