Asymmetric BIPs

[alex-s-v]

Description of the Change

Some new mixing rules require the matrix of binary interaction parameters (BIPs) to be asymmetric, so I have done my best to add such functionality. Methods set_binary_interaction_double were overwritten to accept an additional (optional) parameter which specifies whether to set Kij symmetrically or not (symmetrically by default).

Benefits

Now you can specify the matrix of BIPs asymmetrically.

Possible Drawbacks

Adds new ways to inexperienced users to ruin their calculations =D

Verification Process

The following python script shows the use and effect of the introduced changes.

import CoolProp.CoolProp as CP

AS = CP.AbstractState("PR", "benzene&toluene")
AS.set_binary_interaction_double(0, 1, "kij", 0.05)  # symmetrically
k01 = AS.get_binary_interaction_double(0, 1, "kij")
k10 = AS.get_binary_interaction_double(1, 0, "kij")
print(f"k01 = {k01}; k10 = {k10}")
# Output: k01 = 0.05; k10 = 0.05
AS.set_mole_fractions([0.3, 0.7])
AS.update(CP.PQ_INPUTS, 101325, 0)
ys = AS.mole_fractions_vapor()
print(ys)
# Output: [0.5042805536100579, 0.49571944638994214]

AS.set_binary_interaction_double(0, 1, "kij", 0.1, False)  # asymmetrically
k01 = AS.get_binary_interaction_double(0, 1, "kij")
k10 = AS.get_binary_interaction_double(1, 0, "kij")
print(f"k01 = {k01}; k10 = {k10}")
# Output: k01 = 0.1; k10 = 0.05
AS.update(CP.PQ_INPUTS, 101325, 0)
ys = AS.mole_fractions_vapor()
print(ys)
# Output: [0.5050982763042872, 0.49490172369571284]

Applicable Issues

My own old issue #1890

[ibell]

I have a new idea: what if rather than adding a new argument, you could add :asymmetric (or something similar) to the key, so the API could be identical, but the same effect could be realized? Boolean arguments are always challenging to document because I see a True in the code, and it is not clear what is going on there. My proposal should propagate to the linked states for VLE, for instance, and I'm not sure that would necessarily work with what you have implemented.