Heat transfer characteristics of an impinging air jet are experimentally investigated under a fixed pumping power condition. The effects of dimensionless pumping power (P-pump(center dot) = 1.4 x 10(10)-6.7 x 10(12)) on the Nusselt number are considered. The focus is on cases where the nozzle-to-plate spacing is equal to or less than one nozzle diameter (H/d <= 1.0). The results show that the Nusselt number is independent of the nozzle-to-plate spacing under fixed pumping power conditions, while the Nusselt number increases with decreasing the nozzle-to-plate spacing under fixed flow rate conditions. Based on the experimental results, new correlations for the stagnation and average Nusselt numbers of the impinging jet are developed as a function of the pumping power alone. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.