Impingement heat transfer for linearly stretched arrays of holes is investigated. In real engine configurations, impingement arrays are not always square with evenly spaced holes both in streamwise and spanwise direction. They are primarily directed to hot spot locations thus producing nonsquare arrays. In this study, the spacing between the holes increases in both the streamwise and spanwise direction simulating the stretching of the hole arrays downstream. Two different arrays are investigated with the first array having uniform diameter holes through the array placed in a stretched format. The second array has holes placed in the same locations with increasing diameter along the streamwise direction. The measured heat transfer coefficients for these arrays are then predicted using existing impingement heat transfer correlations based on regular evenly spaced arrays. Results show that the published correlations over-predict the effect of cross-flow. Also, the correlation was extrapolated for this study due to lack of information for extremely strong cross-flow effects. All measurements were obtained using the transient liquid crystal technique.

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