Physical Chemistry of Aqueous Systems: Meeting the Needs of Industry

ISBN Print: 978-1-56700-034-4

ISBN Online: 978-1-56700-445-8

SOME OBSERVATIONS ON THE THERMODYNAMIC PROPERTIES OF STEAM AND THE INTERPRETATION OF SOME THERMODYNAMIC DIAGRAMS

DOI: 10.1615/ICPWS-1994.190
pages 139-148

Resumo

Prior to the application of electronic computers, engineers developed compact and accurate charts of thermodynamic properties of steam in which enthalpy, h, rather than temperature, T, was an independent variable. The charts included the pressure volume product (pv), critical flow and critical velocity, for example. These charts facilitated the development of steam properties subroutines for computer applications. Further improvements in correlating some of these same quantities in specific regimes were made by using superheat or moisture (quality) as independent variables. Improved accuracy in the values obtained from computer subroutines were realized with indirect functions {T,h and v = f(p,s) or T,s and v = f(p,h)} by modifying the converged values (when the allowable convergence error was satisfied) through simple adjustments to the final results. Some observations are made on the shape of the various thermodynamic surfaces. Points of inflection of the T-s diagram (steam dome) and h-s diagram are discussed and the accompanying maximization of other parameters such as pv product, hg, is entropic exponent and specific heat, as well as the effect on the Joule-Thomson coefficient.