Effect of outflow orientation on heat transfer and pressure drop in a triangular duct with an array of tangential jets

Experiments are conducted to study the heat transfer and pressure drop char acteristics in a triangular duct cooled by an array of tangential jets, sim ulating the leading-edge cooling circuit of a turbine blade. Coolant ejecte d from a high-pressure plenum through an array of orifices is aimed at the leading-edge apex and exits from the radial outlets. Three different outflo w orientations, namely coincident with the entry flow, opposed to the entry flow and both, are tested for various Reynolds numbers (12600 less than or equal to Re less than or equal to 42000). A transient liquid crystal techn ique is used to measure the detailed heat transfer coefficients on two wall s forming the leading-edge apex. Flow rate across each jet hole and the cro ssflow development, which are closely related to the local heat transfer ch aracteristics, are also measured. Results show that increasing Re increases the heat transfer on both walls. The outflow orientation affects significa ntly the local heat transfer characteristics through influencing the jet fl ow, together with the crossflow in the triangular duct. The triangular duct with two openings is recommended since it has the highest wall-averaged he at transfer and the moderate loss coefficient among the three outflow orien tations investigated. Correlations for wall-averaged Nusselt number and los s coefficient in the triangular duct have been developed by considering the Reynolds number for three different outflow orientations.