Question

Can someone please explain how to use this chart or how to get the number from it. There's so many numbers so I don't know what's going on

5.00 3.00 1.00 1.60 2 ?/ 1.40 1.30 1,20 1.15 1501 40 0.85 0.80 0.90 0.70 0.95 0.60 8 0.50 0.40 0.30 0.0 0 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1.0 Reduced pressure, pA

Answer 1

The dimensionless compressibility factor, Z, for a gaseous species is defined as the ratio Z = pv RT. If the gas behaves ideally then Z = 1. The extent to which Z differs from 1 is a measure of the extent to which the gas is behaving non-ideally. The compressibility can be determined from experimental data where Z is plotted versus a dimensionless reduced pressure P_R and reduced temperature T_R, defined as

P_R = P/P_c and T_R = T/T_c

Where P_c and T_c denote the critical pressure and temperature, respectively.

The solid lines represent reduced temperature T_R values and bottom axis represents the reduced pressure P_R values. Draw a vertical line from the calculated or given value of P_R where it cuts the solid lines T_R, draw horizontal line to get corresponding value of Z.

Looking more closely at the generalized compressibility chart we notice that there are not only TR lines, but also V_R^' lines (dotted). V_R^' is called the pseudo-reduced specific volume, since it is defined as

V_R^’ values has been seen when P_R or T_R value are not known followed by similar way of looking to the chart

It can be seen from above chart that the value of Z tends to unity for all temperatures as pressure approach zero and Z also approaches unity for all pressure at very high temperature.