Jet-array impingement heat transfer in a concentric annular channel with rotating inner cylinder

Abstract

As a new cooling scheme for electric rotor machines, the impinging jets issued from the armature onto the stator with the spent flows directed toward two annular exits at both ends can convect the Joule heat out of the rotor machinery effectively. An experimental study is accordingly devised to investigate the heat transfer performances over the outer cylinder of a concentric annulus with an impinging jet-array issued from the rotating inner cylinder. Intermittencies of impinging jets and spent flows in the Taylor–Couette–Poiseuille annular flow feature the dominant flow physics that affect the heat transfer performances. A set of selected experimental data illustrates the isolated and interdependent influences of jet Reynolds number ( Re), Taylor number ( Ta) and rotating Grashof number ( Gr ω ) on local and area-averaged Nusselt numbers ( Nu and Nu ¯ ). With the present parametric conditions examined, the coupled Re, Ta and Gr ω effects have led the ratios of rotational and non-rotational Nu ¯ in the range of 0.75–1.48. In conformity with the experimentally revealed heat transfer physics, the heat transfer correlation that permits the evaluation of Nu ¯ over the outer cylinder of the concentric annulus subject to jet-array impingement from the rotating inner cylinder is generated.