A property of a Fluid Mixture represented by the junction point of Vapour Liquid Equilibrium (VLE) area on PT diagram of Fluid Mixture (see Fig. 1).

It is characterized by pseudo-critical temperature and pseudo-critical pressure .

GLOSSARY > Pseudo-Critical Point = (Tpc, Ppc) > image2020-12-4_22-24-12.png

Fig. 1. Schematic PT diagram with Vapour Liquid Equilibrium and Pseudo-Critical Point (T_pc, P_pc).

The simplest estimate (also called Linear Blending Rule) of Pseudo-Critical Point is the mole fraction weighted average of the critical temperature and critical pressure of fluid components (which are pure substances) :

T_{pc} = \sum_i x_i \, T_{c,i}

P_{pc} = \sum_i x_i \, P_{c,i}

where

	mole fraction of the -th mixture component
	critical temperature of the -th mixture component
	critical pressure of the -th mixture component

There are other no-linear methods to blend the components to estimate the Pseudo-Critical Point but many engineering applications use and as the seed and then fit the values to match lab test data.

In case the fluid composition is not known one can use empirical Pseudo-Critical Point Correlations to assess the Pseudo-Critical Point.

See also