A New Four-Parameter Equation of State and its Application in Predicting the Spinodal Temperature of Water
Eberhart JG1
1 Department of Chemistry, University of Colorado at Colorado Springs, Colorado Springs, CO 80933-7150
1 Correspondence: jeberhar@uccs.edu
Key words: water, equation of state, liquid spinodal temperature, limit of superheat, explosive boiling, mechanical stability condition, critical constants, Riedel factor
Received: 27 June 2009; revised 24 July; accepted 14 August. Published 1 November. Available online 1 November 2009.
Summary
A new four-parameter equation of state (EoS) is presented here. It has the form p = RT/(υ – b) – a/Tmυ(υ + c), which can be thought of as a modified Redlich-Kwong equation. This EoS is designed to permit a special parameter adjustment technique that leads to great accuracy in the calculation of the spinodal temperature (or limit of superheat) of a liquid. This p-υ-T relationship yields a predicted spinodal temperature of 331.7˚C for water at 1 atm, which is in good agreement with an extrapolation of experimental kinetic limits of superheat that fall in the range of 330 ± 2˚C. A knowledge of the spinodal temperature of water is an important dimension in the understanding of the vapor explosions (or steam explosions, in the case of water) that sometimes occur in marine volcano eruptions, nuclear-reactor accidents, and foundry molten-metal spills.