🧪 Gas Mixture Properties
Compute the molar mass, specific heats, dynamic viscosity, and thermal conductivity for ideal gas mixtures using Wilke and Wassilijewa mixing rules.
Tools
📝 Configuration
μₘᵢₓ = Σ(yᵢμᵢ / Σⱼ yⱼφᵢⱼ)
kₘᵢₓ same form (Wassilijewa)
📊 Results
Configure species and click Compute.
📘 Methodology
Wilke Mixing Rule
μₘᵢₓ = Σᵢ yᵢμᵢ / Σⱼ yⱼφᵢⱼ where φᵢⱼ = [1+√(μᵢ/μⱼ)(Mⱼ/Mᵢ)¹ᐟ⁴]² / √(8(1+Mᵢ/Mⱼ)). Accurate to ~2% for non-polar gas mixtures.
Wassilijewa Rule
Thermal conductivity uses the same interaction parameter φᵢⱼ. kₘᵢₓ = Σᵢ yᵢkᵢ / Σⱼ yⱼAᵢⱼ. Originally proposed by Wassilijewa (1904), refined by Mason & Saxena.
Mixture Properties
Mₘᵢₓ = ΣyᵢMᵢ (molar average). Cpₘᵢₓ = ΣyᵢCpᵢ (molar). γ = Cp/(Cp−R). Density from ideal gas law at STP.
📘 Calculation Methodology: Gas Mixture Molar & Mass Properties
Mathematical Model & Theory
Calculates equivalent molecular weight $M_{mix}$, apparent gas constant $R_{mix}$, mass fractions $w_i$, specific heat $c_{p,mix}$, and enthalpy of ideal gas mixtures via Dalton-Amagat rules:
Assumptions
- Ideal gas mixture behavior without intermolecular interaction deviation.
- Sum of mole fractions $\sum y_i = 1.0$ and mass fractions $\sum w_i = 1.0$.
Academic References
- Moran, M. J. et al.: Engineering Thermodynamics, Ch. 12.
- Turns, S. R.: Thermal-Fluid Sciences, Cambridge.
Worked Engineering Example
A gas mixture contains $75\%\ CH_4$ ($M = 16.04\text{ g/mol}$) and $25\%\ CO_2$ ($M = 44.01\text{ g/mol}$) by mole. Calculate apparent molar mass $M_{mix}$ and gas constant $R_{mix}$.
Step-by-step Solution:
1. $M_{mix} = 0.75(16.04) + 0.25(44.01) = 12.03 + 11.0025 = 23.0325\text{ g/mol}$.
2. $R_{mix} = 8314.46 / 23.0325 \approx 361.0\text{ J/kg}\cdot\text{K}$.
Final Result:
Mixture molar mass is $\mathbf{23.03\text{ kg/kmol}}$ and gas constant is $R = \mathbf{361.0\text{ J/kg}\cdot\text{K}}$.