A 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. Two separate functions for predicting the relative permittivity of water and steam in two distinct thermodynamic regions are 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 these two functions is evaluated by comparing the values for the relative permittivity calculated using the evolved functions and the values calculated using the latest formulation of Fernandez et al., found in [Fern97] to the aforementioned data set. In both regions, the newly evolved functions outperform the most current formulation in terms of difference between calculated and experimentally obtained values for the dielectric constant.