A numerical model is used to study the effect of the height and position of an overflow sill on glass melt hydrodynamics and heat transfer in a glass-melting tank furnace. A differentiated effect of the overflow sill on the formation of convection flows and heat and mass transfer in various parts of the tank is established. It is demonstrated that the considered parameters of the sill have virtually no effect on the intensity of the charge convection cycle. At the same time, they have a significant effect on melt hydrodynamics past the sill. The quantitative correlations between the design parameters of the sill and certain characteristics of heat and mass transfer in the melting tank are identified. © Springer Science+Business Media, Inc. 2006.