The geometric shape of a passage’s cross-section has an effect on its convective heat transfer capabilities. For concentric annuli, the diameter ratio of the annular space plays an important role. The purpose of this investigation was to find a correlation that will accurately predict heat transfer coefficients at the inner wall of smooth concentric annuli for turbulent flow of water. Experiments were conducted with a wide range of annular diameter ratios and the Wilson plot method was used to develop a convective heat transfer correlation. The deduced correlation predicted Nusselt numbers accurately within 3 percent of measured values for annular diameter ratios between 1.7 and 3.2 and a Reynolds number range, based on the hydraulic diameter, of 4 000 to 30,000.