ABSTRACT
This chapter presents some representative examples of unsteady-state diffusion problems in the Cartesian, cylindrical, and spherical coordinate systems. A mathematical treatise of diffusion and heat conduction problems is completely analogous. The comprehensive book by H. S. Carslaw and J. C. Jaeger provides analytical solutions to a variety of heat conduction problems. In the absence of bulk flow, transfer of species into and/or out of the system takes place by diffusion. The Josef Loschmidt cell is used to determine the diffusion coefficients of binary gas mixtures. Initially, the cylinders are filled with pure gases, the heavier one being placed in the lower cylinder to minimize convection effects. The two gases are allowed to diffuse by removing the partition. Variation in the concentration change with time leads to the estimation of the diffusion coefficient.
