UNIQUAC Activity Coefficient Model: DETAILS

Name	TDE.UNIQUAC.ActivityCoefficients
Comment	Activity coefficients model
Variable GEX	Excess Gibbs energy
Variable T	Temperature
Variable x1	Mole fraction of component 1
Variable x2	Mole fraction of component 2
Parameter u12	Array (0 to nTerms)
Parameter u21	Array (0 to nTerms)
Constant r1
Constant q1
Constant r2
Constant q2
Constant R	Gas constant

The following expressions define the terms leading to the equation for G^EX.

t₁₂ = exp{-u₁₂/(R×T)} and t₂₁ = exp{-u₂₁/(R×T)}
t₁ = (x₁×q₁)/{x₁×q₁ + (1 - x₁)×q₂} and t₂ = {(1 - x₁)×q₂}/{x₁×q₁ + (1 - x₁)×q₂}
f₁ = (x₁×r₁)/{x₁×r₁ + (1 - x₁)×r₂} and f₂ = {(1 - x₁)×r₂}/{x₁×r₁ + (1 - x₁)×r₂}

G^EX/(R×T) = -q₁×x₁×ln(t₁ + t₂×t₂₁) - q₂×x₂×ln(t₂ + t₁×t₁₂) + x₁×ln(f₁/x₁) + x₂×ln(f₂/x₂) + 5{q₁×x₁×ln(t₁/f₁) + q₂×x₂×ln(t₂/f₂)}