Overall mass transfer in the swirling flow induced by a tangential inlet between coaxial cones

An electrochemical method is used to measure mass transfer coefficients bet ween an electrolytic solution and the inner core of a system formed by stat ionary coaxial cones of the same apex angle. A swirling decaying flow is in duced by means of a tangential inlet at the system base. The average mass t ransfer coefficients are measured at three axial positions from the tangent ial inlet for both laminar and turbulent flow regimes. Pressure drops betwe en the inlet and the outlet of the experimental device are also investigate d. Flow visualization revealed the existence of axially fixed toroidal vort ices. The overall mass transfer coefficients along the conical gap are foun d to be greater than those measured in annular swirling decaying flow for t he same values of the annular gap thickness, of the tangential inlet diamet er and of the Reynolds number based on the mean axial velocity at the botto m of the conical gap. The enhancement in mass transfer, up to 50% compared with that measured in a cylindrical arrangement, is not counter-balanced by an increase in pressure drop, which remains of the same order of magnitude as that measured in a classical annular configuration.