Case 4: P < PLvap

In this case, all the liquid is vaporized.

Here we take the fluid density in case 3 and we set Φ=1 and giving:

Where:

which we can be written as:

Equation 28: Case 4: fluid density at P and T

From this, we obtain for the bulk modulus:

Equation 29: Case 4: fluid bulk modulus at P and T

Note that in case 4, Equation 28 and Equation 29 are valid for all types of fluid properties.