In order to estimate the convection related radial segregation observed in an idealized horizontal Bridgman configuration, an order of magnitude analysis is carried out, assuming that diffusion is the dominant solute transport mode. The theoretical results, confirmed by means of 2D numerical simulations, indicate that segregation is proportional to the convective intensity in the fluid and that its variation with respect to the growth velocity passes through a maximum. A field of application of this work could be the modelling of crystal growth experiments in microgravity.