Optimization of heat transfer and flow in a helical duct of rectangular cross-section used to cool the stators of electric machines is studied using computational fluid dynamics (CFD) techniques. Realizable turbulent model is used with water and oil as working fluids for two different designs (Spiral (S) and Reverse Annulus (RA) designs) and total of five configurations of the helical duct at small pitch size of 0.00254 m. The Reverse Annulus (RA) is a new design proposed by the author. Due to the curvature of the ducts, as fluid flows through curved tubes, a centrifugal force is generated. A secondary flow induced by the centrifugal force has significant ability to enhance the heat transfer rate. Results showed that the spiral design provides better heat transfer in terms of lower surface temperatures at the expense of higher pressure drop for the same flow rate of fluid.

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