Impingement heat transfer from rib roughened surface within two-dimensional arrays of circular jet has been investigated experimentally. After the jet impinges on the rib roughened surface parallel to the jet plate, it is constrained to exit in a single direction along the channel formed by the jet plate and the rib roughened surface. An initial crossflow is present which approaches the arrays through an upstream extension of the channel. The configurations considered are intended to simulate the impingement cooling midchord region of the gas turbine aerofoils in case where an initial crossflow is also present. The study covered four different relative positions of the jet hole to the ribs: jet hole before the rib (−p/4), jet hole on the rib, jet hole behind the rib (+p/4) and jet hole between the ribs (midst,+p/2). The tests were performed for Reynolds number Re = 8000 and 15000, and the nondimensional jet-to-surface spacing z/d = 1.4, 2.0 and 3.0. The test results show that the impingement heat transfer from the rib roughened surface can be considerably improved by adequately arranging the relative position of the jet hole to the ribs.

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