Mass transfer in fluid flow from a solid sphere

The general problem of mass transfer from a solid spherical surface in a fluid is discussed following consideration of the flow patterns around a sphere and actual dissolution of solid spheres in a controlled stream of water. Experimental mass-transfer data for the dissolution of 0∙5 in. benzoic acid spheres in a stream of water at room temperature are correlated by the equation Kd/D = 44 + 0∙48 R0∙5 S0∙33, where K is the mass-transfer film coefficient, d the sphere diameter and D the diffusivity. From a consideration of mass transfer by natural and forced convection, the following general equation is proposed for the mass transfer from solid spheres in a fluid: Kd/D = 0∙50 (G' S)0∙25 + 0∙48 R0∙5 S0∙33 for G' S ⊀ 105.