The fluid flow and heat transfer characteristics of a rectangular air jet impinging on a heated flat plate have been investigated experimentally. The effects of jet Reynolds number and nozzle-to-plate spacing on local and average Nusselt number were studied. Results show that both have a significant influence on heat transfer behaviors of impinging jets. Local and average heat transfer data along the axial and lateral directions were correlated and compared with the previous data. The local Nu number and the free-stream turbulence intensity of impinging jets exhibit a relationship: Nu/Re-1/2 = 0.014 Tu Re-1/2 + 0.517. The corresponding average Nu number and turbulence intensity have a relationship: Nu/Re-1/2 = 0.014 Tu-Re-1/2 +0.472. Heat transfer mechanics was analyzed in terms of the turbulence intensity. (c) 2006 Elsevier Ltd. All rights reserved.