A New GP-evolved Formulation for the Relative Permittivity of Water and Steam

The relative permittivity (or static dielectric constant) of water and steam has been experimentally calculated at a relatively wide range of temperatures and pressures. A single function for predicting the relative permittivity of water and steam in three distinct thermodynamic regions is evolved using genetic programming. A data set comprised of all of the most accurate relative permittivity values, along with temperature, pressure, and density values from the entire experimentally calculated range of these values, found in [Fern95], is used for this task. The accuracy of this function is evaluated by comparing the values for the relative permittivity calculated using the evolved function and the values calculated using the latest formulation of Fernandez et al., found in [Fern97] to the aforementioned data set. In all regions, the newly evolved function outperforms the most current formulation in terms of difference between calculated and experimentally obtained values for the dielectric constant.