Heat transfer experiments of forced turbulent and laminar, and combined laminar downflows of water are conducted in a uniformly heated, triangularly arranged, seven-rod bundle having a P/D ratio of 1.38. In the forced flow experiments Re ranged from 1200 to 24 800 and Pr from 6.8 to 9.0, while in the combined convection experiments Re varied from 148 to 3800, Grq from 1.3 × 105 to 3 × 106, and Ri from 0.01 to 9. The data in the forced turbulent and the laminar flow regimes are in good agreement with the upflow correlations (within ±10%). Also, the transition between these two regimes, occurring at Re = 3800, is the same as that for the upflow condition. In the laminar flow regime, the flow entering the heated section is hydrodynamically developing while the flow in the heated section is thermally developed. The transition from forced laminar to combined convection occurred at Ri = 0.1, which is an order of magnitude lower than that for upflow. The combined convection data are correlated by superimposing the correlations for forced laminar and natural laminar flows as: NuC,L = [NuF,L3 + NuN,L3]13, for upflow NuC,L = [NuF,L2 + NuN,L2]12, for downflow. These correlations are within ±11 and ±15% of the uplow and downflow data, respectively.