Graetz problem with non-linear viscoelastic fluids in non-circular tubes

► Numerical study, of fully developed Nusselt number in circular, rectangular, square and triangular ducts. ► Axisymmetric case contrasted against analytical solutions. ► New values for the Nusselt number for PTT viscoelastic fluids are obtained. ► A parametric study of the influence of elasticity and shear thinning is conducted. ► Difficulties in analyzing such flows at high We numbers are discussed.