Heat Transfer in Rotating Cylindrical Cavities

Abstract

Nusselt numbers are measured on the heated disc of a rotating cylindrical cavity, with either an axial throughflow or a radial outflow of coolant, over a range of gap ratios, 0.13 ≤ G ≤ 0.4, flow rates up to Re _z ≈ 1.8 × 10⁵, rotational speeds up to Re_ø ≈ 2.5 × 10⁶, and Grashof numbers up to Gr ≈ 1.7 times 10¹². For the axial throughflow case, dramatic increases in the values of local Nusselt numbers are observed at certain Rossby numbers; these increases are consistent with the vortex breakdown observed on a separate, isothermal, laser Doppler anemometry (L.D.A.) rig For the radial outflow case, the mean Nusselt numbers show three separate régimes which depend on Re _z and Re_ø but are only weakly affected by G. These three régimes have been identified on the L.D.A. rig and are associated with the presence or absence of Ekman layers on the rotating discs.