Pressure drop and heat-transfer characteristics of axial air flow through an annulus with a deep-slotted outer cylinder and a rotating inner cylinder (second report - heat-transfer characteristics)

To design rotating electrical machines, the heat-transfer characteristics of axial air flow through an annulus with a rotating inner cylinder were studied experimentally. The following results were obtained: (1) When only one wall (inner or outer) is heated and the outer cylinder surface is smooth, the Stanton number can be expressed as a function of a dimensionless number X ≡ Rea2/R$-ω/ (Rea - axial Reynolds number; R$-ω/ - rotating Reynolds number). (2) When the outer cylinder surface is deep-slotted, the Stanton number can be expressed as a function of X. (3) When the inner cylinder is rotating, the Stanton number obtained when both walls are heated is nearly the same as that obtained when only one wall is heated.