Separation of different molecules in a liquid or in a gas in the presence of a carrier is a challenging task if a separation is desired by physical separation methods. Now there is experimental and theoretical evidence that mass transfer can be enhanced with the aid of oscillating flows. The magnitude of the enhancement depends on the carrier's kinematic viscosity, species' diffusion coefficients, oscillation amplitude and the flow geometry. Thus species of different diffusion coefficients can be separated with oscillating flows since the mass transfer enhancements differ for them. Analytical solutions for the mass transfer in circular tubes and between parallel plates are well known and the physics of separation is well explained. This work focuses on the effect of extra side walls of a two dimensional cross sectional channel on the separation. The theoretical mass transfer is obtained for rectangular channels using Chebyshev Spectral methods. With the oscillating flows, a separation of species in a liquid or in a gas phase is possible, but due to significant difference in the diffusion coefficients, the channel sizes required differ significantly. Two dimensional channels introduce competing velocity and concentration gradients along the width or height of the channel at various frequencies. Due to this, multiple optima in separation can be observed. The use of oscillating flows to separate species would be relevant for microfluidic applications such as molecule separation or for macro scales such as in air revitalization for space missions.

Separation of species in square and rectangular channels with the aid of oscillating flows

248th National Meeting (2014)

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