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Merged
g-bauer merged 3 commits into from
Dec 4, 2025
Merged

Entropy scaling correlation functions for mixtures #323

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18fe534
Entropy scaling correlation functions (viscosity, thermal conductivity,
Nov 28, 2025
be1f67c
Added test for mixture and pseudo mixture (pure substance as mixture)…
Dec 4, 2025
de63532
Changelog updated.
Dec 4, 2025
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
## [Unreleased]
### Fixed
- Updated to `ndarray` 0.17 and `num-dual`0.13 to fix a broken dependency resolution. [#327](https://github.com/feos-org/feos/pull/327)
- Fixed calculation of parameter combination in entropy scaling for mixtures in `viscosity_correlation`, `diffusion_correlation`, `thermal_conductivity_correlation`. [#323](https://github.com/feos-org/feos/pull/323)

## [0.9.1] - 2025-11-24
### Fixed
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63 changes: 43 additions & 20 deletions crates/feos/src/pcsaft/eos/mod.rs
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Expand Up @@ -266,13 +266,13 @@ impl EntropyScaling for PcSaft {
.viscosity
.as_ref()
.expect("Missing viscosity coefficients.");
let m = (x * &self.params.m).sum();
let m = x.dot(&self.params.m);
let s = s_res / m;
let pref = (x * &self.params.m) / m;
let a = coefficients.row(0).dot(x);
let b = coefficients.row(1).dot(&pref);
let c = coefficients.row(2).dot(&pref);
let d = coefficients.row(3).dot(&pref);
let pref = x.component_mul(&self.params.m) / m;
let a = coefficients.row(0).transpose().dot(x);
let b = coefficients.row(1).transpose().dot(&pref);
let c = coefficients.row(2).transpose().dot(&pref);
let d = coefficients.row(3).transpose().dot(&pref);
a + b * s + c * s.powi(2) + d * s.powi(3)
}

Expand Down Expand Up @@ -307,14 +307,14 @@ impl EntropyScaling for PcSaft {
.diffusion
.as_ref()
.expect("Missing diffusion coefficients.");
let m = (x * &self.params.m).sum();
let m = x.dot(&self.params.m);
let s = s_res / m;
let pref = (x * &self.params.m).map(|v| v / m);
let a = coefficients.row(0).dot(x);
let b = coefficients.row(1).dot(&pref);
let c = coefficients.row(2).dot(&pref);
let d = coefficients.row(3).dot(&pref);
let e = coefficients.row(4).dot(&pref);
let pref = x.component_mul(&self.params.m) / m;
let a = coefficients.row(0).transpose().dot(x);
let b = coefficients.row(1).transpose().dot(&pref);
let c = coefficients.row(2).transpose().dot(&pref);
let d = coefficients.row(3).transpose().dot(&pref);
let e = coefficients.row(4).transpose().dot(&pref);
a + b * s - c * (1.0 - s.exp()) * s.powi(2) - d * s.powi(4) - e * s.powi(8)
}

Expand Down Expand Up @@ -371,13 +371,13 @@ impl EntropyScaling for PcSaft {
.thermal_conductivity
.as_ref()
.expect("Missing thermal conductivity coefficients");
let m = (x * &self.params.m).sum();
let m = x.dot(&self.params.m);
let s = s_res / m;
let pref = (x * &self.params.m).map(|v| v / m);
let a = coefficients.row(0).dot(x);
let b = coefficients.row(1).dot(&pref);
let c = coefficients.row(2).dot(&pref);
let d = coefficients.row(3).dot(&pref);
let pref = x.component_mul(&self.params.m) / m;
let a = coefficients.row(0).transpose().dot(x);
let b = coefficients.row(1).transpose().dot(&pref);
let c = coefficients.row(2).transpose().dot(&pref);
let d = coefficients.row(3).transpose().dot(&pref);
a + b * s + c * (1.0 - s.exp()) + d * s.powi(2)
}
}
Expand All @@ -386,7 +386,8 @@ impl EntropyScaling for PcSaft {
mod tests {
use super::*;
use crate::pcsaft::parameters::utils::{
butane_parameters, propane_butane_parameters, propane_parameters,
butane_parameters, nonane_heptane_parameters, nonane_parameters, propane_butane_parameters,
propane_parameters,
};
use approx::assert_relative_eq;
use feos_core::*;
Expand Down Expand Up @@ -545,6 +546,28 @@ mod tests {
Ok(())
}

#[test]
fn viscosity_mix() -> FeosResult<()> {
// Test case: compare fig 15 of Lötgering-Lin 2018 (https://doi.org/10.1021/acs.iecr.7b04871)
let e = &nonane_heptane_parameters();
let nonane = &nonane_parameters();

let t = 303.15 * KELVIN;
let p = 500.0 * BAR;
let n = dvector![0.25, 0.75] * MOL;
let viscosity_mix = State::new_npt(&e, t, p, &n, None)?.viscosity();
let viscosity_paper = 0.68298 * MILLI * PASCAL * SECOND;
assert_relative_eq!(viscosity_paper, viscosity_mix, epsilon = 1e-8);

// Make sure pure substance case is recovered
let n_pseudo_mix = dvector![1.0, 0.0] * MOL;
let viscosity_pseudo_mix = State::new_npt(&e, t, p, &n_pseudo_mix, None)?.viscosity();
let n_nonane = dvector![1.0] * MOL;
let viscosity_nonane = State::new_npt(&nonane, t, p, &n_nonane, None)?.viscosity();
assert_relative_eq!(viscosity_pseudo_mix, viscosity_nonane, epsilon = 1e-15);
Ok(())
}

#[test]
fn diffusion() -> FeosResult<()> {
let e = &propane_parameters();
Expand Down
75 changes: 75 additions & 0 deletions crates/feos/src/pcsaft/parameters.rs
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Expand Up @@ -391,6 +391,33 @@ pub mod utils {
PcSaft::new(PcSaftParameters::new_pure(butane_record).unwrap())
}

pub fn nonane_parameters() -> PcSaft {
let nonane_json = r#"
{
"identifier": {
"cas": "111-84-2",
"name": "nonane",
"iupac_name": "nonane",
"smiles": "CCCCCCCCC",
"inchi": "InChI=1S/C9H20/c1-3-5-7-9-8-6-4-2/h3-9H2,1-2H3",
"formula": "C9H20"
},
"molarweight": 128.258,
"m": 4.2079,
"sigma": 3.8448,
"epsilon_k": 244.51,
"viscosity": [
-1.4629,
-3.0058,
-0.5842,
-0.1222
]
}"#;
let nonane_record: PureRecord<PcSaftRecord, PcSaftAssociationRecord> =
serde_json::from_str(nonane_json).expect("Unable to parse json.");
PcSaft::new(PcSaftParameters::new_pure(nonane_record).unwrap())
}

pub fn dme_parameters() -> PcSaftPars {
let dme_json = r#"
{
Expand Down Expand Up @@ -522,6 +549,54 @@ pub mod utils {
PcSaft::new(PcSaftParameters::new_binary(binary_record, None, vec![]).unwrap())
}

pub fn nonane_heptane_parameters() -> PcSaft {
let binary_json = r#"[
{
"identifier": {
"cas": "111-84-2",
"name": "nonane",
"iupac_name": "nonane",
"smiles": "CCCCCCCCC",
"inchi": "InChI=1S/C9H20/c1-3-5-7-9-8-6-4-2/h3-9H2,1-2H3",
"formula": "C9H20"
},
"molarweight": 128.258,
"m": 4.2079,
"sigma": 3.8448,
"epsilon_k": 244.51,
"viscosity": [
-1.4629,
-3.0058,
-0.5842,
-0.1222
]
},
{
"identifier": {
"cas": "142-82-5",
"name": "heptane",
"iupac_name": "heptane",
"smiles": "CCCCCCC",
"inchi": "InChI=1S/C7H16/c1-3-5-7-6-4-2/h3-7H2,1-2H3",
"formula": "C7H16"
},
"molarweight": 100.204,
"m": 3.4831,
"sigma": 3.8049,
"epsilon_k": 238.4,
"viscosity": [
-1.2979,
-2.6936,
-0.4951,
-0.0988
]
}
]"#;
let binary_record: [PureRecord<PcSaftRecord, PcSaftAssociationRecord>; 2] =
serde_json::from_str(binary_json).expect("Unable to parse json.");
PcSaft::new(PcSaftParameters::new_binary(binary_record, None, vec![]).unwrap())
}

#[test]
pub fn test_kij() -> FeosResult<()> {
let ch3: String = "CH3".into();
Expand Down