Measured streamwise (longitudinal) heat transfer variations, spanwise (transverse) averaged and resolved to single row spacings, are presented for large aspect ratio ducts containing staggered arrays of circular pin fins which span the entire duct height. A number of different array geometries have been investigated in an experimental program, including uniformly spaced arrays in constant cross sectional area ducts with streamwise row spacings over the range 1.5 to 5.0 pin diameters. Such arrays, with pin length-to-diameter ratio of order unity, are often used to enhance heat transfer in internal cooling passages of gas turbine engine airfoils. The effects of various length interruptions in the pin pattern and of abrapt changes in pin diameter are presented for constant cross sectional area ducts. In addition, results are presented for the effect of duct convergence, a common situation in the cooled turbine airfoil application. A concise summary of all the observed behavior is given, useful for predicting the performance of arbitrarily spaced pin fin arrays that may be specified to produce a particular cooling distribution. Predictions are compared with two final test, configurations which combine aspects of all of the effects investigated in the experimental program.

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