Equations of state and spinodal lines — a review

Abstract

Modern thermal processes in the power industry involve ever increasing heat fluxes and rapid transients. Simulating such processes requires accurate thermodynamic properties and correlations that encompass stable as well as metastable states. Here we review the development of cubic equations of state that can be made to yield very accurate thermodynamic properties of liquids in saturation and metastable (superheated) states. These cubic equations enable us to develop predictions and correlations for a number of other quantities which are either useful in themselves or for application to boiling and two-phase flow. Examples of such results include predictions of the saturation pressure, the limiting liquid superheat, the destructive energy available to a superheated liquid, the surface tension of a saturated fluid and the approach of the specific heat at constant pressure to infinity at the spinodal point. These topics are described and discussed, and it emerges that these seemingly separate topics can be unified by the use of cubic equations of state. We pay particular attention to the issue of a possible connection between the limit of liquid superheat and the liquid spinodal line.