Quadratic mixing rule for liquid molar volume (VLQMR)

The following equations show the quadratic mixing rule for liquid molar volume:

where

n is the number of components

vmix is the liquid molar volume of the mixture

vi is the liquid molar volume of component i

xi is the liquid molar composition of component i

kij is the binary interaction parameter between components i and j

aij, bij, cij, and dij are constant coefficients taken from the VLQMR data bank that the Fluid Type uses

Currently, AVEVA Thermodynamic Data Manager (TDM) does not include controls to create VLQMR data banks. However, we provide the System:ELECTRL data bank that contains VLQMR binary interaction data for select components for electrolytic processes.

If you want to use the quadratic mixing rule for components other than those in the System:ELECTRL data bank, you can provide the binary interaction data as thermodynamic data overrides on the VLQMR tab in the Method Data section of the Fluid Editor. You can also override any data from the System:ELECTRL data bank on the VLQMR tab. See Override the binary interaction parameters for the quadratic mixing rule for liquid molar volume (VLQMR) for more information.

If kij = 0 for all component pairs, then vmix assumes ideal mixing. We then obtain the liquid density of the mixture (rmix) according to the following equation:

where

ri is the liquid molar density of component i

For ions, the molar volume can be negative. For these cases, we can't calculate the square root term in the quadratic mixing rule. Therefore, if one of the volumes is negative, we ignore that i-j term in the total summation. This is also the case when we regress the binary interaction parameters.

We can generically use the quadratic mixing rule for systems with typical components. However, for electrolyte systems, we recommend that you regress the binary interaction parameters on a system-by-system basis.