Effect of Rotation on Heat Transfer in Rectangular Channels with Pin Fins

摘要

The effect of rotation on smooth narrow rectangular channels and narrow rectangular channels with pin fins is investigated in this study. Pin fins are commonly used in the narrow sections within the trailing edge of the turbine blade; the pin fins act as turbulators to enhance internal cooling while providing structural support in this narrow section of the blade. The rectangular channel is oriented at 150 deg with respect to the plane of rotation, and flow through the channel is radially outward. The focus of the study involves narrow channels with aspect ratios of 4:1 and 8:1. The enhancement due to both conducting (copper) pin fins and nonconducting (Plexiglas~(~R)) pins is investigated. Because of the varying aspect ratio of the channel, the height-to-diameter ratio (h_p/D_p) of the pins varies from two, for an aspect ratio of 4:1, to unity, for an aspect ratio of 8:1. A staggered array of pins with uniform streamwise and spanwise spacing (x_p/D_p = s_p/D_p = 2.0) is studied. With this array, 42 pin fins are used, giving a projected surface density of 3.5 pins/in.~2 (0.543 pins/cm~2), for the leading or trailing surfaces. The range of flow parameters include Reynolds number (Re_(Dh) = 5 X 10~3-2 x 10~4), rotation number (Ro = 0.0-0.302), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). Heat transfer in a stationary pin fin channel can be enhanced up to 3.8 times that of a smooth channel. Rotation enhances the heat transferred from the pin fin channels to 1.5 times that of the stationary pin fin channels. Overall, rotation enhances the heat transfer from all surfaces in both the smooth and pin fin channels. Finally, as the rotation number increases, spanwise variation increases in all channels.