Results from experimental and numerical studies of the transient heat-transfer characteristics of circular air-jet impingement are presented. The circular nozzle has an inner diameter of 6 mm. The Reynolds number is defined based on the nozzle diameter varied from 14,000 to 53,000. The nondimensional distance between the nozzle exit and the target plate is varied from 4 to 8. The local Nusselt number variation with the time obtained from the experimental and numerical studies are presented. The local Nusselt number rapidly increases when the air jet began its impingement. The increasing speed of Nu(loc) slows down as the jet impingement continues to cool down. At the 50-80 s region, the Nu(loc), at various radii R/D-n get the maximum point and remain almost constant from 80 s until the end of the experiment. (C) 2016 Elsevier Ltd. All rights reserved.