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Set Calculation for Elements

Elements that participate in the energy balance need to have both a quantity and a specific energy or total energy calculated for each flow, transfer and inventory Element in the model.

For example, ways to get a mass Attribute value are as follows:

  • Directly from a PI Point

  • Calculated from a Volume

  • From a Level Gauge

  • Determined in Self-Calculated Inventories

    Similarly, specific energy can be obtained from the following:

  • Using a formula that calculates this value considering temperature, heat capacity, and reference temperature. You can use the Formula Data Reference in this case.
  • Connecting to a PI point that historizes the specific energy that is calculated with other PI System tools, such as Performance Equations or ACE
  • Creating a data reference that estimates specific energy as a function of other attributes.

Mass - Directly from a PI Point​

When a mass is stored in a PI Server as a tag value, you can use the PI Point Data Reference to retrieve its value. It is important to know what the data is that is being stored in PI. In order to import the correct value into the analysis case, you need to know whether the value is a continuous mass rate or a mass measurement and also what the unit of measure is for the value.

\See PI Point Data Reference found under Data Reference.

Mass – Calculated from a Volume​

To calculate a mass from a volume and density, use the Unit of Measure Data Reference to calculate the Mass. The volume and density Attributes have sources for their values, and you can use the Unit of Measure Data Reference ("Unit of Measure Data Reference Appendix" in the Sigmafine Reference Guide ) to make this calculation.

It is important to determine that the volume used in this calculation is a Net Volume and not a Gross (Observed) volume. You can use the Gross to Net Volume calculation of the Sigmafine Data Reference to aid in this intermediate calculation. See the "Sigmafine Data Reference Appendix" of the Sigmafine Reference Guide for more details.

Mass – Calculated from a Level Gauge​

To calculate the mass from a level or gauge value measurement, use the Strapping Table or Polynomial Equation calculations in the Tank Volume from Gauge Data Reference.\See Tank Volume from Gauge Data Reference found under Data Reference.

Mass – Determined in Self-Calculated Inventories​

If an inventory mass is not measured and you want it to be calculated during the mass balance, there are two settings that must be made:

  • Set the Attribute SelfCalculatingFlag to True in the element.
  • Set the ReconciledMass value in the initialization case. The analysis rule uses the reconciled value Attribute in each prior Case for initialization. Therefore, the mass must be manually set in the first case. To set the value of the mass, create an adjustment in the attribute. (\Adjustments are described in Creating an Adjusted Value found under Server & Client. )