The calculations incorporate use of the Ideal Gas Law and if required a custom Compressibility Factor or use of the CNGA Compressibility Factor (that is calculated based on the pressures at the start and end of the pipe).


The Compressible Flow Calculation Engine will automatically take account of pressure changes within the pipe and will automatically adjust the density properties of the gas as appropriate when performing the gas flow rate, pressure loss, diameter size, and pipe length calculations. The equations used in the calculations currently assume isothermal flow where there is no change in temperature. 


The Pipe Flow Wizard software will automatically account for changes in pressure and gas density within the pipe, however the original fluid properties must be defined for the operating temperature within the pipe (although the density may have been specified for a different pressure condition).


Normally the gas properties should be defined for the atmospheric pressure condition (0 bar.g or 0 psi.g) and the software will then automatically calculate the gas density at the start pressure condition prior to performing the appropriate calculation. 


If the start pressure is a high pressure, and the real gas density at this condition varies from the ideal gas law prediction, then a compressibility factor other than 1.0 can be specified. This will be applied when calculating the gas density at the start pressure condition prior to performing the appropriate calculation.