# Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures

## Abstract

A formalism based on powerful concepts of the thermodynamics of irreversible processes is derived for calculating multicomponent diffusion flux both at the critical point and away from the critical point. The derivations are based on the entropy balance expression combined with the phenomenological equations and Onsager reciprocal relations. The formalism results in a clear expression of the thermal contribution in the diffusion flux for nonideal multicomponent mixtures. The diffusion flux analysis at the critical point showed that, unlike isothermal and isobaric conditions where molecular diffusion flux is zero, molecular diffusion flux is finite and nonzero at the critical point. The thermal contribution in the diffusion flux is also finite at the critical point in multicomponent mixtures. At nonisothermal conditions, as well as nonisothermal and nonisobaric conditions, the composition gradient reaches infinity at the critical point; therefore, the mol fraction plot vs. spatial coordinates has an inflection point.

- Authors:

- Publication Date:

- Research Org.:
- Reservoir Engineering Research Inst., Palo Alto, CA (US)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 20080304

- DOE Contract Number:
- FG22-96BC14850

- Resource Type:
- Journal Article

- Journal Name:
- AIChE Journal (American Institute of Chemical Engineers)

- Additional Journal Information:
- Journal Volume: 46; Journal Issue: 5; Other Information: PBD: May 2000; Journal ID: ISSN 0001-1541

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; RESERVOIR ENGINEERING; DIFFUSION; HYDROCARBONS; THERMODYNAMICS

### Citation Formats

```
Ghorayeb, K., and Firoozabadi, A.
```*Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures*. United States: N. p., 2000.
Web. doi:10.1002/aic.690460503.

```
Ghorayeb, K., & Firoozabadi, A.
```*Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures*. United States. doi:10.1002/aic.690460503.

```
Ghorayeb, K., and Firoozabadi, A. Mon .
"Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures". United States. doi:10.1002/aic.690460503.
```

```
@article{osti_20080304,
```

title = {Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures},

author = {Ghorayeb, K. and Firoozabadi, A.},

abstractNote = {A formalism based on powerful concepts of the thermodynamics of irreversible processes is derived for calculating multicomponent diffusion flux both at the critical point and away from the critical point. The derivations are based on the entropy balance expression combined with the phenomenological equations and Onsager reciprocal relations. The formalism results in a clear expression of the thermal contribution in the diffusion flux for nonideal multicomponent mixtures. The diffusion flux analysis at the critical point showed that, unlike isothermal and isobaric conditions where molecular diffusion flux is zero, molecular diffusion flux is finite and nonzero at the critical point. The thermal contribution in the diffusion flux is also finite at the critical point in multicomponent mixtures. At nonisothermal conditions, as well as nonisothermal and nonisobaric conditions, the composition gradient reaches infinity at the critical point; therefore, the mol fraction plot vs. spatial coordinates has an inflection point.},

doi = {10.1002/aic.690460503},

journal = {AIChE Journal (American Institute of Chemical Engineers)},

issn = {0001-1541},

number = 5,

volume = 46,

place = {United States},

year = {2000},

month = {5}

}