🧪 Binary Diffusivity Estimator
Estimate the binary diffusion coefficient DAB as a function of temperature, pressure, and species properties using Chapman–Enskog for gases and Wilke–Chang for liquids.
🌫️ Molecular Diffusion Schematic
📝 Configuration
Key Equations:
Gas, Chapman–Enskog:
DAB = 0.001858 T3/2 √(1/MA+1/MB) / [P σAB² ΩD] [cm²/s]
Liquid, Wilke–Chang:
DAB = 7.4×10−8 (φ MB)1/2 T / [μB VA0.6] [cm²/s]
Gas, Chapman–Enskog:
DAB = 0.001858 T3/2 √(1/MA+1/MB) / [P σAB² ΩD] [cm²/s]
Liquid, Wilke–Chang:
DAB = 7.4×10−8 (φ MB)1/2 T / [μB VA0.6] [cm²/s]
📊 Results & Visualization
Configure inputs and click Calculate to view results.
ℹ️ About Binary Diffusivity
DAB quantifies how fast species A diffuses through species B. Gas diffusivity increases strongly with temperature and decreases with pressure. Liquid diffusivity is much smaller and depends strongly on solvent viscosity and solute molar volume.
DAB quantifies how fast species A diffuses through species B. Gas diffusivity increases strongly with temperature and decreases with pressure. Liquid diffusivity is much smaller and depends strongly on solvent viscosity and solute molar volume.
📘 Calculation Methodology
Mathematical Model & Theory
The gas model uses Lennard-Jones collision parameters and a diffusion collision integral. The liquid model estimates infinite-dilution diffusivity of a dilute solute in a liquid solvent.
Worked Engineering Example
Oxygen in water at 25°C: using Wilke-Chang with μ = 0.890 cP, φ = 2.26, MB = 18.015 g/mol and VA = 25.6 cm³/mol gives DAB on the order of 2×10−9 m²/s.
Assumptions & References
- Chapman-Enskog: dilute, non-polar gas pair, ideal-gas pressure dependence.
- Wilke-Chang: dilute solute, empirical liquid diffusivity near ambient liquid conditions.
- Use measured diffusivity data when high accuracy is required.