Heat of mixing

In the Fluid Editor, you can choose to include the heat of mixing (excess enthalpy) in the calculations for liquid enthalpy for liquid activity methods. You use the Include Heat of Mixing (Excess Enthalpy) in Liquid Enthalpy Calculations checkbox to include or exclude the heat of mixing in the liquid enthalpy calculations. The default selection status (selected or cleared) for this checkbox changes based on your Phases and Vapor Equilibrium selections. When you clear this checkbox, the liquid enthalpy calculations do not include the heat of mixing (HE = 0).

When you select the Include Heat of Mixing (Excess Enthalpy) in Liquid Enthalpy Calculations checkbox, we incorporate the heat of mixing (excess enthalpy) in the final liquid enthalpy (HL) calculations by using the following equation:

where

HiL is the liquid enthalpy contribution of component i

HE is the heat of mixing

We calculate HE by using the following equation:

For Henry's solutes, the activity coefficient is typically equal to one. Therefore, the contribution of Henry's solutes to the heat of mixing is typically zero. For the Electrolyte NRTL (eNRTL) method, the activity coefficient may not equal one for all cases, and the Henry's solutes may contribute to the heat of mixing. See Equations for the eNRTL method for more information.