Enhancement of forced convection in wide cylindrical annular channel using rotating inner pipe with interrupted helical fins

• Plain and finned inner pipe of wide annular channel are tested under rotation and at rest.
• Inner pipe rotation doubled heat transfer coefficient at rotation speed of 400 rpm.
• Interrupted helical fins enhances the heat transfer up to 280% under stationary conditions.
• Rotating finned pipe enhances Nu by a factor of 7.5 compared to plain stationary pipe.
• Rotating finned pipe boosts the ratio of heat exchange to pumping power by a factor of 7.6.

This paper presents the results of heat transfer and pressure drop in concentric annular wide channel with inner plain or finned pipe under stationary and rotating conditions in Taylor–Couette–Poiseuille flow. The experiments are conducted for one plain pipe and three finned pipes with helical fin spacing of 75, 110 and 150 mm at rotating speeds of 0, 200, 250, 300, 350 and 400 rpm. The experiments cover axial Reynolds number of 8.07 × 104–1.82 × 105, rotational Reynolds number of 0 and from 1428 to 3008, corresponds to Taylor number of 0 and from 1.22 × 106 to 8.32 × 106. The reported results in the form of Nusselt numbers and friction factors are correlated in terms of Re, Ta, Pr and fin geometrical parameters. The results proved that at Re = 1.5 × 105, the wide annular channel with inner pipe of helical fin spacing 75 mm that rotates at 400 rpm enhances Nu by a factor of 7.5 and also boosts the ratio of heat exchange to pumping power by a factor of 7.6, compared to the case for plain stationary pipe.