Calculation of Flow Rate - Intergraph Smart Instrumentation - 13.1 - Reference - Hexagon PPM

Integraph Smart Instrumentation Sizing Equations

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  1. Calculate internal pipe diameter at floe temperature:

  2. Calculate correction factor for steam quality (For lliquid, water, and steam, Fs=1):

  3. Calculate orifice diameter at flow temperature.

    1. For Venturi tubes and Nozzles:

    2. For orifice plates:

  4. Calculate b - ratio:

  5. Checking for Critical flow and some initial calculations.

    Liquid /Water case

    1. Calculate downstream pressure:

    2. If the the flow is critical. If not then the floe is sub-critical.

      1. For critical flow:

      2. For sub-critical flow:

        Classic Venturi tube:

      1. Nozzles

      2. Orifice plates:

      3. Calculate first estimate for flow rate (W0 [kg/s]):

    3. Gas/Steam case

      1. Calculate critical pressure ratio and define whether the flow is critical.

        If the the flow is critical. If not the flow is sub-critical.

    4. Initial calculation for critical flow.

      1. Gas Expansion factor:

      2. First estimate for flow rate (W0 [1b/h], T[R], D[in], P1[psi-a])

    5. Initial calculations for sub-critical flow.

      Differential pressure to be used in flow rat calculation:

      1. For classical Venturi tube:

      2. For Nozzles:

      3. For orifice plates:

    6. Gas expansion factor:

      1. For Venturi tubes and nozzles:


      2. For orifice plates:

      3. First estimate for flow rate (W0[kg/s]):

  6. Calculate Reynolds number.

    1. For gas/steam critical flow (Bore Reynolds number):

    2. For liquid/water and gas/steam sub-critical flow (Pipe Reynolds number):

  7. Calculate discharge coefficient. See Appendix.

  8. For orifices in the case of gas/steam sub-critical flow, calculate DP and gas expansion factor:

  9. Calculate new flow rate:

    1. For gas/steam at critical flow:

    2. For other cases (W[kg/s]):

  10. Repeat steps 6 to 10 until the relative change in the flow rate is less than 0.0001.