AN APPROXIMATE ESTIMATION OF VELOCITY PROFILES AND TURBULENCE FACTOR MODELS FOR AIR-FLOWS ALONG THE EXTERIOR OF TEFC INDUCTION MOTORS

Compared to a number of other existing correlations for heat transfer, the empirical correlations for forced convection from a short horizontal cylinder in axial air-flows usually do not involve the effects of changes in air-flow velocity and/or air-flow turbulence. Therefore, a common analysis of the heat transfer by using only one energy balance equation for entire outer surface of a solid is considered insufficient for induction motor applications because it fails to include aforementioned effects. This paper presents a novel, empirically-based methodology to estimate approximately the values of air-flow velocities and turbulence factors, that is, velocity profiles and turbulence factor models for stationary horizontal cylinders with and without fins (frame and two end-shields) in axial air-flows. These velocity profiles and turbulence factor models can then be used in analytical modelling of steady-state heat transfer from the exterior of totally enclosed fan-cooled induction motors.