| Abstract: | Heat transfer and naphthalene sublimation experiments have been conducted to study the effects of varying the flow Reynolds number, the pin configuration, the pin length-to-diameter ratio, the entrance length, the exit geometries, and lateral flow ejection on the detailed distribution of the local endwall heat transfer and the overall heat transfer for turbulent flow in a channel with short pin fins. The pin fin channel resembles the internal cooling passage near the trailing edge of a typical high-performance gas turbine blade. The heat transfer and mass transfer experiments were complemented by pressure measurement experiments. The results of the investigation have been obtained for staggered and aligned arrays of pin fins with L/D = 0.5 and 1.0, X/D = 1.25 and 2.5, and S/D = 2.5. The Reynolds number ranged from 6,000 to 60,000. The results show that the local endwall heat transfer is generally very high immediately upstream of a pin and is relatively high in the wake region downstream of a pin. The distributions of the local endwall heat transfer coefficient for a staggered array and for an aligned array are very different from that for a plain channel with no pin fin and from each other. Furthermore, the effect of the entrance length on the endwall heat transfer in a channel with a staggered array of pin fins is limited to the small region near the leading edge. For any given ejection ratio, the overall Nusselt number increases with increasing Reynolds number according to an equation of the form Nu = aRe[superscript b], where a and b are constants. The overall Nusselt number is reduced by as much as 25 percent as the ejection ratio increases from 0 to 1. The Nu-Re-[epsilon] relationship is insensitive to varying the ejection exit cross section geometry. The overall friction factor is independent of the flow Reynolds number over the range of Reynolds number studied. However, the friction factor is strongly dependent on the ejection ratio as well as the straight flow exit and lateral ejection flow exit geometries. |
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