This work experimentally investigates the heat transfer characteristics of Taylor-Couette-Poiseuille flow in an annular channel by mounting longitudinal ribs on the rotating inner cylinder. The ranges of the axial Reynolds number (Re) and the rotational Reynolds number (Re-Omega) are Re = 30-1200 and Re-Omega = 0-2922, respectively. Three modes of the inner cylinder without/with longitudinal ribs are considered. A special entry and exit design for the axial coolant flow reveals some interesting findings. The value of Nusselt number ((Nu) over bar) is almost minimal at the inlet of the annular channel, and then sharply rises in the axial direction. The average Nusselt number (Nu) increases with Re. Nu increases rapidly with Re-Omega at low Re (such as at Re = 30 and 60) but that the effect of Re-Omega decreases as the value increases (such as at Re = 300-1200). The ratio (Nu) over bar/(Nu) over bar (0) increases with Re-Omega and exceed two at all Re and in the test modes. The heat transfer is typically promoted by mounting longitudinal ribs on the rotating inner cylinder, especially at Re = 300 and 600. When Re = 300 or 600 and Re-Omega > 2000, the (Nu) over bar of the system with ribs reaches around 1.4 times that of (Nu) over bar (A) ((Nu) over bar in mode A). Under a given pumping power constraint (PRe3), the (Nu) over bar of the system with ribs (modes B and C) generally exceeds that without ribs (mode A), while the difference between the values of (Nu) over bar in modes B and A slowly falls as PRe3 increases. Additionally, mode B (with ribs) is preferred for high heat transfer when PRe3 < 4.5 x 10(13) but mode C (with cavities on ribs) is optimal for high heat transfer when PRe3 > 4.5 x 10(13). (c) 2006 Elsevier Ltd. All rights reserved.