General Junction Information

The different types of junctions on the Toolbox offer a great degree of freedom in assembling a pipe network model. While there is some redundancy in capabilities between the junctions, each of the junctions offers specialized features to allow you to prepare a good conceptual model of the physical system of interest. Table 1 compares the features of the junction types.

There is a junction properties window for each junction type. Each junction Properties window falls into one of two basic window formats, depending on the number of connecting pipes allowed for that junction type.

Note: AFT Arrow does not prevent negative flow through junctions. Should this occur, AFT Arrow will use the same loss factor or pressure drop data referenced to the defined upstream pipe, just as in forward flow. Because it is possible that the loss factor or pressure drop data would not be the same for both flow directions, the flow solution could be misleading. For this reason it is important that you either properly define the pipe flow directions for junctions or pay close attention to the flow directions that result. Should negative flow occur in any junction, AFT Arrow will give a caution in the output.

Table 1: Comparison of junction capabilities

Junction Type Connecting Pipes Special Conditions CdA Custom Library Window Format
Area Change 2   Yes Yes 1
Assigned Flow 1 Yes   Yes 1
Assigned Pressure* 1/1-25   Yes Yes 1
Bend/Elbow 2   Yes Yes 1
Branch 2-25 Yes   Yes 2
Check Valve 2 Yes Yes Yes 1
Compressor/Fan 2 Yes   Yes 1
Control Valve 2 Yes   Yes 1
Dead End 1       1
General Component 2 Yes Yes Yes 1
Heat Exchanger 2 Yes   Yes 1
Orifice 1-2   Yes Yes 1
Relief Valve 1-2 Yes Yes Yes 1
Screen 2   Yes Yes 1
Separator 2 Yes   Yes 1
Spray Discharge 1-4 Yes Yes Yes 1
Tank 1-25     Yes 2
Tee/Wye** 3       2**
Valve 1-2 Yes Yes Yes 1
Venturi 2   Yes Yes 1

*Assigned Pressure Junction connects to only one pipe for static pressure, and up to 25 for stagnation

**Tee/Wye junction has a unique format closer to Format #2