Fluid properties pressure-enthalpy diagrams

Figure D-6 Pressure-enthalpy diagram for ethylene. (From RE Sterling, Fluid Thermal Properties for oi Petroleum Systems. Houston, TX Gulf Pub. Reprinted by permission.) - ...

FIG. 2-5 Pressure-enthalpy diagram for dry air. Properties computed with the NIST REFPROP Database, Version 7.0 (Lemmon, E. W., McLinden, M. O., and Huber, M. L., 2002, NIST Standard Reference Database 23, NIST Reference Fluid Thermodynamic and Transport Properties—REFPROP, Version 7.0, Standard Reference Data Program, National Institute of Standards and Technology), based on the equation of state of Lemmon, E. W., Jacobsen, R. T., Penoncello, S. G., and Friend, D. G., Thermodynamic Properties of Air and Mixtures of Nitrogen, Argon, and Oxygen from 60 to 2000 K at Pressures to 2000 MPa, /, Phys. Chem. Ref. Data 29 331-385, 2000. 

This thermodynamic diagram provides descriptions of fluid properties as a function of pressure and enthalpy. One can follow lines of constant temperature, density, or entropy. The (mostly) horizontal curves represent constant density, and the (mostly) vertical curves are lines of constant entropy. 

MOLLIER DIAGRAM - An enthalpy-entropy or enthalpy-pressure chart showing the thermodynamic properties of a fluid. 

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