Effect of diffusion on electron density across the nonequilibrium MHD channel

This paper presents an investigation of the effect of thermal diffusion of charge carriers on the electron density in a nonequilibrium MHD generator. The source of diffusion is the inhomogeneity in the background temperature and/or the nonuniform heating of electrons across the MHD channel cross section on account of the velocity boundary layer. The continuity equation of electrons has been solved in conjunction with the diffusion velocity equation to obtain the steady state electron density distribution in an MHD generator. As a result of diffusion, the electron density is found to increase with the distance from the channel axis, while the reverse is predicted from the assumption of local equilibrium. Further, it is seen that the increase in the values of Hall parameter, boundary layer thickness and the flow velocity enhances the effect of diffusion. Decrease in the wall temperature is also found to have a similar effect. The diffusion of the carriers is most prominent in the segmented geometry. It is concluded that overall electron density gets enhanced if recombination and diffusion times are of the same order.