Radially resolved measurement of stator heat transfer in a rotor–stator disc system

0017-9310/$ see front matter 2009 Elsevier Ltd. A doi:10.1016/j.ijheatmasstransfer.2009.09.006 * Corresponding author. Tel.: +44 (0) 20 7594 6215 E-mail addresses: [email protected] (D.A. ac.uk (A.S. Holmes), [email protected] (K.R. Pu This paper describes a new experimental method for measuring stator heat transfer in a rotor–stator disc system using an electrical heater array. The system is partially blocked at the periphery, with radial outflow of rotor-pumped air from an inlet at stator centre. The aim is to improve thermal performance prediction for air-cooled disc type electrical machines. Local Nusselt numbers were measured for 0:6 < r=R < 1 at three non-dimensional gap ratios G 1⁄4 g=R 1⁄4 ð0:0106;0:0212;0:0297Þ and rotational Reynolds numbers 3:7e4 6 Reh 6 5:6e5. Transition at the stator is observed to occur at Reh > 3e5 for all gap ratios. Increased Nusselt numbers at the periphery are observed for all Reh and G because of the ingress of ambient air along the stator due to the rotor pumping effect. 2009 Elsevier Ltd. All rights reserved.