Density Calculation
The average density of a mixture is calculated with the following equation:
From Mass Fractions:
From Volume Fractions:
From Molar Fractions:
Where:
xi = the mass fraction of component i
vi = the volume fraction of component i
yi = the molar fraction of component i
MWi = the molecular weight of component i
SGm = the average specific gravity (one type of density)
SGi = the specific gravity of the component
Note: There are two types of densities that can be computed using this data reference. The unit of measure of the Attribute density must belong to the Specific Gravity or Density unit-of-measure class.
EXAMPLE: Density CalculationA process stream consists of a mixture of three components: A, B and C. The following table provides the necessary information to calculate the average molecular weight.
Density Calculation – Example
| Component | Molecular Weight (lb/lbmol) | Mass Fraction |
|---|---|---|
| A | 0.1234 | 0.234 |
| B | 0.5638 | 0.132 |
| C | 0.8923 | 0.634 |
Using the equation shown above, the average density is 0.352 SG.