Glycol Fill method

Because petro components are characterized when you add them to your Fluid Type, binary interaction data is not readily available for binary pairs that include a petro component and a pure component. Typically, to account for the interactions between petro components and pure components, you must manually add the binary interaction data as thermodynamic data overrides in the Method Data section of the Fluid Editor. The data entry process may be time consuming and prone to typing errors. To make this data entry process easier for Fluid Types that use glycol-based pure components, you can use the Glycol Fill method to calculate certain binary interaction parameters (BIPs).

Currently, you can use the Glycol Fill method only with Fluid Types that use the Soave-Redlich-Kwong Modified Panagiotopoulos-Reid (SRKM) equation of state as their System method. The Glycol Fill method calculates BIPs only for binary pairs that include a petro component and one of the following glycol-based pure components:

• Ethylene glycol (EG)

• Diethylene glycol (DEG)

• Triethylene glycol (TEG)

The Use Glycol Fill Correlation checkbox's status in the Equilibrium Options section of the Fluid Editor determines whether the software applies the Glycol Fill method:

• If the Use Glycol Fill Correlation checkbox is clear, then the default values for the BIPs come from the SRKM data banks that the Fluid Type uses. Typically, BIP data is not available, and the BIPs are blank in the Method Data section of the Fluid Editor.

• If the Use Glycol Fill Correlation checkbox is selected, then the software calculates the default values for the BIPs according to the Glycol Fill correlations.

For the Glycol Fill method, we assume limited temperature dependence for the k-value (kij), and we use the following equations to calculate kij and aij instead of the extended SRKM equation:

Therefore, for the full set of SRKM BIPs, we do the following for those binary pairs that use the Glycol Fill method:

• Calculate the default values for the kija, kjia, kijb, and kjib parameters according to the Glycol Fill correlations, which are specific to the pure component in the binary pair.

• Set the default values for the kijc, kjic, kijd, and kjid parameters to zero.

• Set the default values for the cij and cji parameters to one.

  

Although the Glycol Fill correlations provide accurate, well-fit BIP data, you can still use the thermodynamic data overrides in the Fluid Editor to specify your own values for the BIPs as needed. Any values that you specify in the Method Data section of the Fluid Editor override any filled BIP data.

The Glycol Fill correlations calculate the BIPs from two characteristic values (np and na) for the petro component in the binary pair, which we calculate from the aromatic number (naromatic) and carbon number (ncarbon) for the petro component.

where

NBP is the normal boiling point in Kelvin (K) for the petro component.

K is the Watson K-factor for the petro component.

We use the following equation to calculate the Watson K-factor:

where

NBP is the normal boiling point in degrees Rankine (°R) for the petro component.

SG is the specific gravity at 60°F relative to water at 60°F for the petro component.

You can view and modify the NBP and SG values in the Fluid Editor, in the Component Data section, on the Constants tab, in the Basic table of constant properties, in the NBP and SG60F columns, respectively.

The Glycol Fill correlations are different for each glycol-based pure component.

Ethylene glycol (EG)

For binary pairs that include EG and a petro component, the software calculates the BIPs according to the following Glycol Fill correlations:

Diethylene glycol (DEG)

For binary pairs that include DEG and a petro component, the software calculates the BIPs according to the following Glycol Fill correlations:

Triethylene glycol (TEG)

For binary pairs that include TEG and a petro component, the software calculates the BIPs according to the following Glycol Fill correlations: