n A dimensionless group relevant for heat transfer in flowing viscous liquids such as polymer melts. It is defined by NBr = μ·V2/(k·ΔT), in which μ = viscosity, V = velocity, k = thermal conductivity, and ΔT = the difference in temperature between the stream and the confining wall. The number represents the ratio of the rates of heat generation and heat conduction. (Shenoy AV (1996) Thermoplastics melt rheology and processing. Marcel Dekker, New York).