Natural convection mass transfer behaviour of long vertical annuli

Abstract

The natural convection mass transfer behaviour of the inner cylinder of a vertical annulus was studied by measuring the limiting current of the cathodic deposition of copper from acidified copper sulphate solution. Active cylinder height and copper sulphate concentration were varied to provide a (Sc.Gr) range of 1.8 × 10 10 − 3.3 × 10 14; under these conditions which lie in the transition region, the data were found to fit the equation: Sh = 0.325(Sc. Gr) 0.28 Comparison between the present data and previous related data in mass and heat transfer confirmed the fact that the product Sc.Gr is not the sole criterion for laminar-turbulent transition but the value of Sc or Pr plays also an important role. The technical importance of the present work in the design and operation of annular mass transfer equipments, e.g., electrochemical reactors and dialyzers was highlighted.