ESDU 81044 provides, directly, heat transfer coefficient data and enthalpy data specifically for the fully-developed turbulent flow of water or steam in plain circular tubes. The data are presented in the easy-to-use form of charts and tables in which internationally-agreed values of the variation of the physical properties of water substance with temperature and pressure have already been taken into account. The data are applicable for any process involving single-phase heat transfer where the working fluid is water or steam, e.g. process heat exchangers where cooling water is used on one side. Data are provided for (i) water or steam on the saturation line for temperatures between 0 and about 320 degrees C and pressures between 0.01 and 100 bar, (ii) water or steam for non-saturation conditions for temperatures between 0 and 800 degrees C and pressures between 0.01 and 100 bar. Correction factors required to account for radial variation of fluid properties are also given. The data presented may be used for calculating heat balances when enthalpy data can be used directly or for design calculations when heat transfer coefficient data can be used directly.