Heat-transfer and flow-friction design data are presented for flow normal to circular tube bundles for the Reynolds-number range, 500 to 20,000 (based on tube diameter). Six staggered circular tube patterns and one in-line arrangement were tested. Tentative correlations are presented for the staggered arrangements allowing interpolation of the test results to obtain design data partially covering a transverse pitch-ratio range from 1.25 to 2.50, and a longitudinal pitch-ratio range from 0.75 to 1.50. Data also are provided so that the influence of the number of tube rows on the mean coefficient may be estimated accurately. These results are of interest in applications involving small-diameter tubes and low-density fluids, as, for example, the gas-turbine regenerator. They supplement the high Reynolds-number data of Pierson, Huge, and Grimison, and the low Reynolds-number viscous-flow-range data of Bergelin, Colburn, et al., by providing needed information for the intermediate range. A transient-test technique was employed in obtaining these data. Several tests employing a conventional steady-state technique also were made to demonstrate the validity of the transient method. The advantages and limitations of the transient method are considered in detail.