Figure 45  Common Gas 02 – Flow Demands

External gas out-flow leaving the system can be specified at a node.

External gas in-flow entering the system can be specified at a node.


External in-flow and external out-flow should be specified in units of Gas Flow or Mass Flow, such as SCMH or kg/hour. General volumetric flow rates would refer to the volume of gas at the density defined in the Fluid Zone data and not the volume of gas at standard conditions.


Volumetric flow rates will vary throughout a gas system. As pressure loss occurs, the gas density will decrease and the volume of the gas will expand. As the gas volume increases, the gas velocity in the pipes will increase. Even as these volume and velocity changes occur, the mass flow in (weight of flow) and mass flow out of a particular node must always be equal.