A demand in-flow or demand out-flow can be set at any join point in the system, or at the end of a single pipe if flow is entering or leaving the system at that point. A demand can also be the pressure required at an end node, however a node cannot have both a demand flow and a demand pressure.


A demand in-flow is the volume of fluid that enters the system at a join point (from an external source).

 

A demand out-flow is the volume of fluid that leaves the system at a join point (discharge or flows in to some external system).

 

Demand flows may also be used to specify the required flow rate at the end of a pipe where fluid is flowing out of the system, or to specify the flow rate at the start of a pipe where fluid is entering the system (from some external source). A pipe can have a demand flow or a demand pressure at the end of a pipe but it cannot have both. 


Demand flows can be added to a join point from the Node pane or the Drawing pane. Demand flow values are set on the Set Flow Demands dialog. The demand flows are then shown at the appropriate node on the Drawing pane.


NOTE: Be sure to enter the value for the required fluid flow rate in the units displayed next to the field. For example, if you are using imperial units, and ft3/sec for cubic feet per second is displayed next to the In Flow and Out Flow fields, enter the value in cubic feet per second.


Compressible Gas Flow:


If you are working with a compressible gas and you want to set the demand flows in volume of gas at standard conditions such as SCFM, SCMH, or other standard volume units, then you must ensure that the current fluid is a gas. If the current fluid data is a liquid then the units for gas flow at standard volume do not appear in the drop down list of units for demand flows.