Mass transfer enhancement associated with sudden flow expansion

The limiting diffusion current technique (LDCT), based on reduction of ferricyanide species on nickel electrodes of a novel approach, has been used to investigate the effect of an axisymmetric sudden how expansion on mass transfer rates under highly turbulent flow conditions (25 000 less than or equal to Re-d less than or equal to 90 000). Sudden expansion of diameter D has a significant effect on the local mass transfer rate, the peak rate of the Sherwood number, Sh(p), approximating to twice the steady state fully developed flow value, Sh(FD), further downstream. The mass transfer enhancement for single-phase liquid flow is correlated by the dimensionless equation: SHp/Sh(FD) = 2.55 x Re-D(-8.1) x (d/D)(0.7) x Sc-0.33 Additionally, the present work has shown that the mass transfer enhancement after sudden flow expansion is inversely proportional to the Reynolds number. Sh(p)/Sh(FD) = 100.2 x Re-D(-0.188) Copyright (C) 1996 Elsevier Science Ltd