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

Abstract

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 thermal effects during dissolution and solute concentration level effect on the rate of mass transfer is investigated. It is found that the rate of mass transfer between a solid sphere and a flowing fluid increases with the increase of the solute concentration level. The suggested approach is valid for high Peclet and Schmidt numbers. Isothermal and nonisothermal cases of dissolution are considered whereby the latter is described by the coupled equations of mass and heat transfer. It is shown that for positive dimensionless heat of dissolution K thermal effects cause the increase of the mass transfer rate in comparison with the isothermal case. On the contrary, for negative K thermal effects cause the decrease of the mass transfer rate in comparison with the isothermal case. The latter effect becomes more pronounced with the increase of the concentration level of the solute in a solvent. Theoretical 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.