Thermal Dependent Physical Properties of Water

Most physical properties of water are thermal dependent. In many instances of hydraulic engineering, this dependency is considered to be significant. In other instances, the dependency is recognized, necessitating manual modification of constants when problems are solved for nonstandard temperature conditions. There is need for a set of mathematical estimators describing thermal dependence, suited for rapid employment in engineering algorithms. Using such estimators, overall thermal sensitivity can be readily specified. Six equations are proposed describing the thermal variability of fundamental water properties. These equations are empirical approximations based on zero or one temperature transformation and two or three constants. These equations were determined through a search of functional relationships minimizing squared deviations from a regressed line. Each equation, linearly transformed, yielded an R² correlation term greater than 0.999. The six equations are substantially shorter than mathematical models found in physical literature. These equations describe the thermal dependence of properties with a degree of accuracy more than adequate for most hydraulic engineering computations. The thermal dependence of many other physical properties of water can be derived from the six properties evaluated.