Mixing Rules Package

Documentation for mixing rules in NeqSim equations of state.

Table of Contents

Overview

Location: neqsim.thermo.mixingrule

Mixing rules define how pure component EoS parameters combine in mixtures.

Classic Mixing Rules

Van der Waals One-Fluid Rules

\[a_m = \sum_i \sum_j x_i x_j \sqrt{a_i a_j}(1 - k_{ij})\] \[b_m = \sum_i x_i b_i\]

Usage

// Classic mixing rule
fluid.setMixingRule("classic");
// or
fluid.setMixingRule(2);

Asymmetric kij

// Set binary interaction parameter
fluid.getInterphaseProperties().setParameter("kij", "CO2", "methane", 0.12);

CPA Mixing Rules

For associating systems (water, alcohols, amines).

Usage

// CPA-specific mixing rule
SystemSrkCPAstatoil fluid = new SystemSrkCPAstatoil(T, P);
fluid.setMixingRule(10);

Cross-Association

Cross-association between different associating molecules is handled via combining rules:

\[\epsilon^{A_iB_j} = \frac{\epsilon^{A_i} + \epsilon^{B_j}}{2}\] \[\beta^{A_iB_j} = \sqrt{\beta^{A_i}\beta^{B_j}}\]

Activity Coefficient Mixing Rules

Huron-Vidal

// SRK with Huron-Vidal mixing
SystemSrkHuronVidal fluid = new SystemSrkHuronVidal(T, P);
fluid.setMixingRule("HV");

Wong-Sandler

// Wong-Sandler mixing rule
fluid.setMixingRule("WS");

Schwarzentruber-Renon

Combines EoS with UNIFAC.

SystemSrkSchwartzentruberRenon fluid = new SystemSrkSchwartzentruberRenon(T, P);

Binary Interaction Parameters

Accessing kij

double kij = fluid.getInterphaseProperties().getParameter("kij", "CO2", "methane");

Setting kij

fluid.getInterphaseProperties().setParameter("kij", "CO2", "methane", 0.12);

Temperature-Dependent kij

\[k_{ij}(T) = k_{ij}^0 + k_{ij}^1 \cdot T + k_{ij}^2 \cdot T^2\]

Mixing Rule Numbers

Number Mixing Rule
1 No mixing
2 Classic (Van der Waals)
4 Huron-Vidal
7 Wong-Sandler
9 Schwarzentruber-Renon
10 CPA