Thermolab: a thermodynamics laboratory for non-linear transport
processes in open systems
Abstract
We developed a numerical thermodynamics laboratory called “Thermolab”
to study the effects of the thermodynamic behavior of non-ideal solution
models on reactive transport processes in open systems. The equations of
state of internally consistent thermodynamic datasets are implemented in
MATLAB functions and form the basis for calculating Gibbs energy. A
linear algebraic approach is used in Thermolab to compute Gibbs energy
of mixing for multi-component phases to study the impact of the
non-ideality of solution models on transport processes. The Gibbs
energies are benchmarked with experimental data, phase diagrams and
other thermodynamic software. Constrained Gibbs minimization is
exemplified with MATLAB codes and iterative refinement of composition of
mixtures may be used to increase precision and accuracy. All needed
transport variables such as densities, phase compositions, and chemical
potentials are obtained from Gibbs energy of the stable phases after the
minimization in Thermolab. We demonstrate the use of precomputed local
equilibrium data obtained with Thermolab in reactive transport models.
In reactive fluid flow the shape and the velocity of the reaction front
vary depending on the non-linearity of the partitioning of a component
in fluid and solid. We argue that non-ideality of solution models has to
be taken into account and further explored in reactive transport models.
Thermolab Gibbs energies can be used in Cahn-Hilliard models for
non-linear diffusion and phase growth. This presents a transient process
towards equilibrium and avoids computational problems arising during
precomputing of equilibrium data.