The 3D non-isothermal creeping flow of nylon-6 in a bent square duct with uniform temperature is studied numerically. The non-Newtonian characteristics of this fluid polymer are represented by a differential-type non-isothermal White-Metzner model. Computational results are obtained by the elastic-viscous split-stress (EVSS) finite element method, incorporating the streamline-upwind Petrov-Galerkin (SUPG) scheme. The generated thermal field is entirely due to viscous heating. Essential flow characteristics, including temperature distribution in the flow field, are predicted. The resulting average Nusselt numbers along the walls are obtained. Subsequently, the effects of flow-rate and geometry are investigated. (c) 2005 Elsevier Ltd. All rights reserved.