A combined numerical and experimental study was performed to determine the turbulent heat transfer on a stationary disk, which is situated in a close distance from a rotating disk. The RNG k-epsilon model and the steady-state liquid crystal technique were employed respectively in the numerical simulation and the experiment. In the range of the rotational Reynolds number from 1.42 x 10(5) to 3.33 x 10(5), the heat transfer rate on the stator and the flow characteristics in the gap between the disks are presented. The results revealed that there exists an optimum rotor-stator distance for a given Reynolds number, at which the average heat transfer on the stator reaches maximum. When the Reynolds number increases, the maximum shifts towards smaller disk-distances. (C) 2003 Elsevier Science Ltd. All rights reserved.