Dear Bentley Team,
I am having confusion in input parameters of Hydropneumatic Tank.
HGL Initial =
Liquid Volume =
Pressure (Gas-Preset) =
For example, consider a tank that has been given a full volume of 500 L and the initial conditions pressure head is 50 m. Assume that the pre-charge pressure is 5% of the steady state pipeline pressure. (This is a number that you would know ahead of time.) So, the gas preset pressure is set to 2.5 m (50 m times 5%). In this case, HAMMER computes the 'K' constant as (2.5 m + 10.33 m)(0.5 m3) = 6.415. Since K is known now, the initial gas volume for the transient simulation after the bladder is submitted to pipeline pressure is computed as V = K/P = (6.415)/(50 m+10.33 m) = 0.106 m3 = 106 L.
By keeping above example in mind I am assigning following parameter in my calculation.
Elevation = 200m (Tank Location) Steady state pressure 10 bars
HGL Initial = (200+100) =300
Liquid Volume (initial)= 200L (?)
Tank Volume = 500L (Assume)
Pressure (Gas-Preset) = 5m (5% of Steady State Pressure)
Please correct me if my calculation is wrong.
Regards,
SA
Hello Syed,
The example that you use above is from the hydropneumatic tank modeling reference and is used to calculate the gas volume in the hydropneumatic tank. The values for the parameters mentioned may be dependent on the tank and the overall system. For instance, the HGL (Initial) is based on the initial water elevation of the tank.
The Liquid Volume (Initial) is the volume of liquid in the tank at the start of the initial conditions calculation and is based on the initial HGL. It is mainly used during an EPS run in WaterGEMS or WaterCAD. It is used in a transient simulation when "Treat as Junction" is set to "False". In this case, the Liquid Volume (Initial) value and the tank volume is used to calculated the initial gas volume. When "Treat as Junction" is set to "True" (which it is in many modeling cases), the initial liquid volume field is not directly used by the transient simulation.
The Pressure (Gas-Preset) is pressure of the gas before exposing the tank to the system. You can make an assumption like in the example you reference.
Scott Kampa
Bentley Technical Support
Thanks Scott for clearing confusion.