Peculiarities of unsteady mass transfer in flat channels with liquid and gel

The rate of the unsteady mass-transfer process in horizontal flat channels filled with viscous liquid (water) and in channels filled with gel has been measured experimentally. It has been established that the rate of propagation of a substance through a channel under the unsteady one-dimensional mass transfer conditions depends on its width and exceeds the value corresponding to the rate of diffusion. The measured mass transport rate in an open channel is less than in a closed channel. The reason for the increased mass-transfer rate with regard to the diffusion mechanism is the slow convective flow of liquid caused by the difference between the densities of a diffusing substance and water. The presence of the surface concentration gradient of liquid gives rise to the appearance of surface forces that significantly affect the mass transport rate. The similarity of the mass-transfer behavior in channels filled with pure liquid and gels is found experimentally, which allows one to talk about their presence, as well as of convective transport in them.