Limiting Separations in Parametric Pumps

It has been predicted theoretically that the proper selection of frequency and fluid displacement is critical in maximizing separation in batch, direct-thermal-mode parametric pumps. New data are presented to verify these earlier theoretical predictions. Limiting (ultimate) separation factors exceeding 3000 are reported on the system aqueous sodium chloride on BioRadAG11A8 resin for which, heretofore, researchers were able to obtain only order 10 using equivalent fluid displacements. A new-parameter estimation technique is presented which allows determination of key dissipation factors. These, in turn, can then be used to estimate conditions under which maximum separation is likely to occur. For the first time, a simple theoretically based expression is uncovered to estimate optimum velocities in parapumps. It is shown that the optimum velocity is approximately equal to the square root of the product of the coefficients of mass transfer and of molecular diffusion