In order to characterize the heat transfer of heat exchangers employed by pulse tube refrigerators, an experimental apparatus was built to investigate the heat transfer performance of a water-cooled finned heat exchanger operating in laminar oscillating flow. The test results summarized into the Nusselt number with respect to the maximum Reynolds number and the Valensi number were presented. The increases in the maximum Reynolds number and the Valensi number both lead to a rise in the Nusselt number. The comparisons of the experimental results and the available typical correlations were conducted and discussed. A new correlation of the Nusselt number to the maximum Reynolds number and the Valensi number was proposed, with which the results have a maximum deviation of 6.3% compared with the experimental values. (C) 2013 Elsevier Ltd. All rights reserved.