FLOW AND HEAT TRANSFER IN RADIAL CHANNELS OF ELECTRIC MACHINES

Abstract

This article deals with the combined hydraulic-thermal effects in radial channels of electric machines.

The introductory part describes survey information gathered from the relevant literature and gives the objective as well as purpose of the presented article.

This is followed by a description of the model facilities after which the author describes the method of measuring. The results are given in the form of dimensionless relations and coefficients which make their practical application much more easier.

For the evaluation and comparison purposes the following data were used:

• - Characteristics of the heat transfer in rotating channels, both in laminar and turbulent region of flow.

• - Data for the computation of the hydraulic resistance of the air gap between rotor and stator, above all when taking the effect of rotation into account.

• - Basic information on the effects of filling the channels round stator coils.

• - Data on the existence of pressure pulsations in the radial channels of both stator and rotor brought about by periodically changing the conditions in the region of the air gap.

In the article some till now not published effects are being described, especially as to the flow in the stator channels. From these effects it follows that an unsuitable structure of the system coil - spacer causes in certain speed range that only one side of the stator winding is being cooled.

The existence of pressure pulsations shows that they actually may be responsible for the Increased heat transfer in the rotating channel rather than the Coriolis forces as recognized till now. The pressure pulsations change the dynamics as well as thermal boundary layers at the walls of the channels.

The Information gathered in this paper can be used in the design of electric rotating machines with radial channels in both rotor and stator.