Extended Time Simulation (XTS)

An AFT Arrow Add-on Module

The AFT Arrow Extended Time Simulation (XTS) Module helps
engineers answer design and operating simulation questions by
simulating how critical parameters vary over time. Perform a
series of steady-state gas flow solutions with variables changing
automatically to achieve a dynamic simulation of your system.

With AFT Arrow Extended Time Simulation Module you can define a wide range of operational changes during the time simulation, including:

  • Tank pressure tracking (predict how long to fill and empty tanks)
  • Compressor start/stop and speed variation
  • Valve position changes
  • Control valve setpoint variation

Reporting Features

  • Text and graphical output clearly displays time varying parameters such as:
    • gas pressure in tanks
    • flow and pressure in pipes
    • compressor operating conditions
    • valve position and more
  • Unique animation feature that dynamically displays time varying parameters along selected flow paths

AFT Arrow Extended Time Simulation FAQ's

What kinds of transients can the AFT Arrow XTS Module model?

A wide range, including tank pressure, valve open/close, compressor speed changes, relief valve opening and more. Just as important, the AFT Arrow XTS module can model time transients, event transients and inherent transients. Time transients are changes that are specified to occur based on the model time. Event transients, on the other hand, are triggered by an event that occurs in the system.

Many kinds of events can be used, such as pressure, flow, velocity and tank pressure. Inherent transients are changes that occur by the very nature of a system component.

Two examples would be the pressure level change that occurs in a finite tank, while another would be a check valve opening and closing as a result of flow reversals.

AFT Arrow models heat transfer, so does this mean Arrow XTS does as well?

AFT Arrow XTS does not include heat transfer models on pipes. Arrow XTS works by adjusting boundary conditions and running steady-state simulations. Therefore, changes in pressure and temperature instantly propagate through the entire system. Due to the complexities of this instantaneous effect combined with the fact that changes in pipe wall temperature are generally very slow, AFT feels it is better to restrict the capabilities rather than forcing the user to make additional far-reaching assumptions.

Many junctions in Arrow XTS do allow the user to impose thermal conditions on the model. For example, a known pressure can vary its temperature over time, a heat exchanger can represent exchange with an external fluid with changing conditions, and a finite tank can have a user defined heat rate applied to it. Arrow XTS does not model the effect of stored heat in these components.

Do I have to have one AFT Arrow XTS module license for each AFT Arrow license?

This is true only for standalone licenses. For network licenses, there does not need to be a one-to-one relationship. This provides users the flexibility to choose the level of capability they need.

For example, you may have several AFT Arrow licenses deployed on your network but only need to use AFT Arrow XTS half the time and, therefore, have a correspondingly lower number of module licenses. If you open a model previously saved using the AFT Arrow XTS, AFT Arrow will first try to activate the module. If all of the module licenses are being used, a message will be displayed telling you a AFT Arrow XTS license is not available and provide you a choice of continuing to open the model or canceling the load.

This same message will remind you that if you do open and work with the model, AFT Arrow Extended Time Control Module specifications contained in the model may be lost.

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