Elementary case

With elementary, the liquid density is independent of T and the liquid bulk modulus is constant, we obtain a density of:

Or

Equation 18: Case 2: fluid density at P and T for elementary

and a bulk modulus of

Equation 19: Case 2: fluid bulk modulus at P and T for elementary

Note that if the equations as displayed above are used with zero air content, there is no reduction in bulk modulus below the saturation pressure. It is of course not possible in normal engineering situations to have zero air content and in any case, at very low pressures, vapor would form from the liquid. To achieve reasonable results under these conditions the fractional air content should be limited to a minimum value of 0.0001 %.