The paper provides details of a numerical study of the bayonet tube under steady, laminar conditions when the fluid is air. Attention is focused on the heat transfer characteristics of the tube. The data constitute a systematic investigation of the effect of the principal parameters on the overall heat transfer rate, represented by a Nusselt number. Specifically discussed are the effects of Reynolds number, length-diameter ratio, the ratio of annular to inner tube area, the ratio of the end clearance to the tube diameter, and the Rayleigh number. Comparisons with experimental data are also made.