Mass transfer from spheres in various regular packings to a flowing fluid

Mass transfer coefficients have been determined for fluids flowing around single spheres, which were part of a regular arrangement of similar, but inactive spheres. Eight different kinds of packing were used. The experiments were carried out with solid spheres dissolving into a stream of water, and with porous spheres soaked with a liquid, which evaporated into a stream of gas. The results are tentatively explained on the assumption that the total mass transfer from the sphere surface is the sum of three different contributions : one for laminar convective transfer, one for turbulent convection transfer and one for diffusion in the stagnant regions near the contact points with adjacent spheres. The latter contribution would only be important for gas flow at not too high Reynolds numbers (Re < 500).