THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS

Thermodynamic (compressibility, specific heat, enthalpy, entropy) and transport (density, viscosity, thermal conductivity) properties of fluids are essential to countless engineering applications. While steam is the most common fluid, air, natural gas, and refrigerants are also vital to many designs. I have been supplying such properties in computationally convenient forms to the power and process industries over four decades. I began supplying steam properties coded entirely in assembler and requiring only 4 kB memory from the earliest days of DOS and moist air properties similarly encoded requiring less than 1 kB. My refrigerant properties (available free at the link below) have been used to design and test organic Rankine cycles and geothermal systems around the world.

In 2020 I undertook the task of updating the properties of steam for the first time in 25 years since the IAPWS-SF95 formulation was published. The SF95 formulation extended to 1273 K and 1 GPa. The 2020 formulation extends to 6000 K and 150 GPa, making it suitable for extreme applications, such as fracking, deep wells, and shock waves. One such application is cooling the launch pad beneath the updated Saturn V booster. Deficiencies in the pre-2020 properties of steam were only noticeable above the critical point and in specialized graphs. Isotherms up to 100 GPa are shown in the figure below along with the spinodal lines (locus of inflection points):

Steam Isotherms

Perhaps the most significant deficiency of pre-2020 formulations was incorrect behavior below the vapor dome (between the saturated liquid and saturated vapor), which illustrates Maxwell's Equal Areas along any subcritical isotherm. The yellow and green shaded regions must be the same (note that this is a log-log scale and so the areas may not appear equal):

Maxwell's Equal Areas

This relationship can be expressed by the following integral:

The correct metastable states under the vapor dome and spinodals are shown in this next figure:

Spinodals and Metastable States of Steam

Note that the behavior under the vapor dome of every other steam formulation pre-2020 is a complete mess, a deficiency ignored in the literature. The compressibility is shown in this next figure:

Compressibility of Steam

I have never seen a graph showing the fugacity of steam in the literature:

Fugacity of Steam

Many of these topics are described with more detail in my book, Thermodynamic and Transport Properties of Fluids, https://www.amazon.com/dp/B07Q5L1CHT and also Steam 2020: to 150 GPa and 6000 K, https://www.amazon.com/dp/B086TYQMFM both of which are free from time-to-time, in accordance with Amazon's policy. The latest version of the refrigerant and steam properties can be found on the software page: software