Cross-flow effects on impingement array heat transfer with varying jet-to-target plate distance and hole spacing

New impingement heat transfer data are presented for experimental conditions and configurations employed have not been previously examined, which illustrate the effects of impingement cross-flows on local, line-averaged, and spatially-averaged Nusselt numbers, as both jet-to-target distance and jet hole spacing are altered. Data are given for a constant impingement jet Reynolds number of 8000. In general, the impingement passage cross-flows which accumulate are detrimental to local Nusselt number performance, especially for denser hole arrays with 5D and 8D hole spacing, where D is impingement hole diameter. This is illustrated by periodic variations of surface Nusselt numbers, which generally decrease with streamwise development, and by local Nusselt number peak values for hole spacings of 5D, 8D, and 12D which generally become smaller at successive x/D locations for each value of Z/D. Also considered are unique situations where significant accumulation of cross-flow fluid results in an opposite trend, with local Nusselt numbers which increase with streamwise development for dense hole spacing of 5D, and smaller jet-to-target plate distances of 1.5D and 3.0D.