Compressibility Factor

COMPRESSIBILITY FACTOR

The perfect gas equation is given by

pv = RT

But for real gas, a correction factor has to be introduced in the perfect gas equation to account the deviation of the real gas from the perfect gas equation. This factor is known as compressibility factor (Z) and it is defined by

Z = pv / RT    ... (5.32)

The general compressibility chart is plotted with compressibility factor (Z) versus reduced pressured (pr) for various values of reduced temperature (Tr). It is constructed by plotting the known data of one or more gases which can be used for any gas. Such chart is shown in Figure 5.5.

The equation of state for real gas at any state becomes

pv = ZRT  ... (5.33)

Similarly, the equation of state for the same real gas at critical point becomes, 

pcvc = Zc RTc    ... (5.34)