The paper provides details of a numerical study of the bayonet tube during the laminar-turbulent transition 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 several parameters on the overall heat transfer rate, represented by a Nusselt number. Specifically discussed are the effects of inner tube conductance, Reynolds number, and length-diameter ratio. Results are interpreted in terms of the origin and spread of turbulence, as revealed by the turbulence intensity contours calculated from the k-epsilon model. Comparisons are made with available experimental data.