Impingement cooling effectiveness of gas turbine vanes and blades can be further increased due to the manufacturing feasibility of integrally cast airfoils which can provide narrow impingement cooling cavities. This study examines experimentally using the transient liquid crystal technique, and numerically using a commercial CFD package, the heat transfer characteristics of narrow impingement channels over their complete heat transfer area. The baseline configuration consists of a narrow impingement channel with a single row of five impingement jets. Effects of channel height (Z/D) and impingement hole offset position from the channel centerline (Delta y/D) are investigated over a range of engine representative Reynolds numbers (10,000-40,000) based on the jet diameter. The CFD simulations are compared to the experiments aiming to quantify the degree of accuracy to which the local and averaged heat transfer rates can be predicted. The results are analysed by various post-processing procedures and compared to existing multi-array impingement cooling correlations. (C) 2013 Elsevier Ltd. All rights reserved.