1. Research activities

2. Rational Thermodynamics
Physical chemistry is the ancestor of chemical engineering thermodynamics:
=> Inheritance of definitions originally introduced to please the experimentator.
=> Theory is adequate for hand calculations, but quite disadvantageous for general computer programming.

3. Rational Thermodynamics
Let the following VLE condition serve as an illustration:
The fundamental EOS equilibrium condition is:
For activity coefficient models an equivalent expression becomes:

4. Rational Thermodynamics
For supercritical components a Henry reference state will be more appropriate:
There is now a bewildering number of symbols & indices:

5. Rational Thermodynamics
Complex notation => model errors may occur at two different levels:
1) Inconsistent approximations made at the implementation level (semantic bugs).
2) Inconsistent use of model features in the user interface (syntactic bugs).

6. Rational Thermodynamics
In both cases the errors will be hard to capture. Typically they require the presence of an expert (programmer) to be solved.
Conclusion: Thermodynamic modelling is an old subject ready for a thorough face-lift.

7. Rational Thermodynamics
Identify the canonical variables of the
model. In practice either or
These are homogeneous functions which can be added to yield a total contribution:

8. Rational Thermodynamics
The standard state contribution can be split into new (sub)contributions following the same rules:

9. Rational Thermodynamics
Proposition: Only two algebraic operators are needed for a general thermodynamic model setup!
1) The chain operator for doing things like:
2) The patch operator for defining sub-graphs:

10. Rational Thermodynamics
Operator precedence: chain > patch
For programming reasons overload * as chain and + as patch
The equation of state VLE model can now be written:
Where the standard state is defined as:

11. Rational Thermodynamics
The operators are type safe:

12. Rational Thermodynamics
Note that a list operator has been introduced to make the expression more legible.
Similar, albeit more complex, expressions can be written for Gibbs energy models.

13. Rational Thermodynamics
An equivalent calculation graph is: * +

14. Rational Thermodynamics
Example code (in Ruby for a change):
mix = [”H2O”,”CH3OH”,”C2H5OH”]
A0 = MuT.new(mix) * [[:cpDippr,”ig”] +
Mu.new(mix) * [:HoSo,”ig”]]
A = Helmholtz.new(mix) *
[:cubicEOS,”fl”] *
[:idealGas,”ig”] + A0

15. Rational Thermodynamics
The thermodynamic object A is explicit in (T,V,N). For practical use the output needs to be transformed into (H,P,N), (S,P,N), (T,P,N), etc:
Legendre: extensive <=> intensive variable.
Massieu: function <=> extensive variable.
A new object is required to take care of the transformations => thermodynamic surface.

16. Rational Thermodynamics
More program code (x is a coordinate vector provided by e.g. the flow sheet solver):
S = Surface.new(mix) + A
S = S.legendre(”-T”).legendre(”-V”)
.massieu(”S”) .legendre(”-P”)
g = S.gradient(x)
H = S.hessian(x)

17. Rational Thermodynamics
Thermo-objects are made by operators but modified by methods => clean interface.
Use of operators => thermodynamic frameworks can be broken down into small, manageable, sequences.
Model description is not tied to any particular implementation => easy to export, exchange and update model info.

18. Rational Thermodynamics
Example: Propane-butane splitter with multiple coordinate specifications. T P H

19. Rational Thermodynamics
Thermodynamic surface transformations => canonical (& aesthetically pleasing) equation system.