MASS TRANSFER IN TURBULENT PIPE FLOW MEASURED BY THE ELECTROCHEMICAL METHOD

Abstract Various factors affecting mass transfer measurements in electrochemical systems are discussed. Ways are indicated for increasing the values of “critical” flow rates and Reynolds numbers up to which meaningful results can be obtained. Mass-transfer coefficients were measured in fully developed flow in smooth pipes over the range 8 × 10 3 Re 5 at Schmidt numbers varying between 1000–6000. When the concentration boundary layer was fully developed the results could be represented by the expression St d = 0.0165 Re −0.14 Sc −0.67 . Using the current results together with published data an empirical relation has been developed in the form Nu = 2 + cRe a Pr 1 3 where c = 0.0165 + 0.011 Pre − pr a = 0.86 − 10 (4.7 + Pr) 3 which can be recommended for predicting heat- and mass-transfer rates over the range 0.6 Pr or Sc 4 and 10 4 Re 6 . The mean Stanton numbers measured in the entrance section (developing concentration boundary layer) agree well with the integrated turbulent Leveque equation St d = 0.276 Re −0.417 Sc − 2 3 ( L d ) − 1 3 .

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