Abstract: The angle θbetween dimensionless time-averaged temperature gradient and velocity vector is one of the main factors to dominate the heat transfer ability of fully-turbulent flow. Numerical investigations are carried out to examine the angle in a 2-D flow passage of two kinds of tubes, transversely corrugated and convergent-divergent tube. The calculated results indicate that the variations of T / cos θ are similar to the local Nusselt number along the stream-wise direction while Reynolds number is constant. The geometrical parameters, for example, rib height or converging length can change the angleθ

Key words: heat transfer, fully-turbulent, field-synergy theory, hetero-shaped tube