Reduced properties

Reduced pressure

The reduced pressure is defined as its actual pressure p divided by its critical pressure p_{\rm c}:

:p_{\rm r} = {p \over p_{\rm c}}

Reduced temperature

The reduced temperature of a fluid is its actual temperature, divided by its critical temperature:

:T_{\rm r} = {T \over T_{\rm c}}

where the actual temperature and critical temperature are expressed in absolute temperature scales (either Kelvin or Rankine). Both the reduced temperature and the reduced pressure are often used in thermodynamical formulas like the Peng–Robinson equation of state.

Reduced specific volume

The reduced specific volume (or "pseudo-reduced specific volume") of a fluid is computed from the ideal gas law at the substance's critical pressure and temperature:

:v_{\rm r} = \frac{vp_{\rm c}}{RT_{\rm c}},

This property is useful when the specific volume and either temperature or pressure are known, in which case the missing third property can be computed directly.

References

References

1. (1976). "A New Two-Constant Equation of State". Industrial and Engineering Chemistry: Fundamentals.
2. [[Hagen Kleinert]] and Verena Schulte-Frohlinde, ''Critical Properties of φ⁴-Theories'', pp.8, [http://www.worldscibooks.com/physics/4733.html World Scientific (Singapore, 2001)]; {{ISBN. 981-02-4658-7 ''(Read online at [http://www.physik.fu-berlin.de/~kleinert/b8] {{Webarchive. link. (2008-06-29 )'')
3. (2002). "Thermodynamics: an engineering approach". McGraw-Hill.