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Linear headloss in Watergems/Hammer?

Hello!

In order to study a reverse osmosis plant, I need to represent linear headlosses (the flow in the membrane cartridge is laminar).

How  to do so in WaterGems and Hammer ? 

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  • In WaterGEMS (or with a steady state or EPS in HAMMER initial conditions), you can model a specific rating table of flow vs. headloss with the GPV element, but if you want a constant headloss for all flows, use a PBV (pressure breaker valve). 

    Note though that these will not work the same during a transient simulation in HAMMER. HAMMER always uses the pair of initial flow and initial headloss through each valve element, to calculate a discharge coefficient which it uses during the transient simulation. This means that even if you use a PBV for the initial conditions, the headloss will vary during the transient simulation. 

    See: Modeling a Constant Headloss


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Hello and thanks for those helpful answers!

    I understand that the GPV can represent alinear headloss (Darcy-like) in Watergems, but that Hammer will use a quadratic headloss calibrated on the initial configuration. The difference will be around 1 bar in my system during the shutdown transient (at half discharge, the headloss in the real system will be 1/2 of the initial headloss; 1/4 following the quadratic assumption used by Hammer). If not any other idea, I will have to make some sensitivity analysis to understand the incidence of  this assumption on the design of the  surge protection.

    Regards,

Reply
  • Hello and thanks for those helpful answers!

    I understand that the GPV can represent alinear headloss (Darcy-like) in Watergems, but that Hammer will use a quadratic headloss calibrated on the initial configuration. The difference will be around 1 bar in my system during the shutdown transient (at half discharge, the headloss in the real system will be 1/2 of the initial headloss; 1/4 following the quadratic assumption used by Hammer). If not any other idea, I will have to make some sensitivity analysis to understand the incidence of  this assumption on the design of the  surge protection.

    Regards,

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