The influence of the Henry number on the conjugate mass transfer from a sphere

Abstract

 Unsteady conjugate mass transfer between a sphere and a surrounding fluid flow has been analysed. Two sphere models, the sphere with rigid interface and the sphere with mobile interface and internal circulation, have been studied. Creeping flow is assumed. The mass balance equations were solved numerically by the ADI finite difference method. The influence of the parameters that characterize the coupling features of the conjugate mass transfer, diffusivity ratio (Φ_D) and Henry number (H) (0.01 ≤ H (Φ_D) ≤ 100), is studied at intermediate Pe numbers. The occurrence and evolution of mass wake phenomenon is analysed. In contradiction with the assumptions practiced in classical theories of interface mass transfer, the results obtained in this work show that the Henry number and the diffusivity ratio have a significant and distinct influence on the values of both overall and fractional (internal and external) Sh numbers. Using the additivity relation as an interpolation formula between two asymptotic solutions does not lead to accurate approximations of the numerical results on the entire domain of variation of H and Φ_D. An analogy between conjugate heat and mass transfer was established.