Hole Staggering Effect on the Cooling Performance of Narrow Impingement Channels

This study examines experimentally the cooling performance of integrally cast impingement cooling channels which provide increased heat transfer area compared to traditional impingement configurations. For the evaluation of the heat transfer coefficient, the transient liquid crystal method was used. Full surface heat transfer coefficient distributions on the target plate and the side walls of the channel have been measured by recording the temperature history of liquid crystals using a frame grabber. Several impingement cooling geometries have been tested composing a test matrix of nine different geometrical configurations. The experimental data are analyzed by means of various post-processing procedures and aim to clarify and quantify the effect of hole staggering on the overall cooling performance, a variable which has been little addressed in the open literature. The experiments were carried out in a low speed wind tunnel over a wide range of Reynolds numbers between 15’000 and 100’000. The results indicated similarities with convectional multi-jet impingement cooling systems as well as a noticeable effect of the cooling hole pattern. Finally, an error propagation analysis of the experimental uncertainties was performed providing information for the significance of scatter on repeated experiments.