Effect of solute concentration level on the rate of coupled mass and heat transfer during solid sphere dissolution in a uniform fluid flow

We studied nonisothermal dissolution of a solvable solid spherical particle in a uniform fluid flow when the concentration level of the solute in the solvent is finite (finite dilution of solute approximation). Coupled therma l effects during dissolution and solute concentration level effect on the r ate of mass transfer is investigated. It is found that the rate of mass tra nsfer between a solid sphere and a flowing fluid increases with the increas e of the solute concentration level. The suggested approach is valid for hi gh Peclet and Schmidt numbers. Isothermal and nonisothermal cases of dissol ution are considered whereby the latter is described by the coupled equatio ns of mass and heat transfer. It is shown that for positive dimensionless h eat of dissolution K thermal effects cause the increase of the mass transfe r rate in comparison with the isothermal case. On the contrary, for negativ e K thermal effects cause the decrease of the mass transfer rate in compari son with the isothermal case. The latter effect becomes more pronounced wit h the increase of the concentration level of the solute in a solvent. Theor etical results are consistent with the experimental data of Petrescu et al. (Chemical Engineering Journal, 66 (1997) 57-63) for falling urea particles dissolution in water and in aqueous urea solutions. (C) 2001 Published by Elsevier Science Ltd.