BAT Model Activity Example¶

Demonstrates using ActivityNonIdealBinary for organic-water mixtures, comparing ideal vs non-ideal activity coefficients.

What is the BAT Model?¶

The Binary Activity Thermodynamic (BAT) model accounts for non-ideal interactions between water and organic species based on the organic's oxygen-to-carbon ratio.

What This Example Shows¶

• Creating a non-ideal activity strategy via builder
• Comparing ideal vs non-ideal activity at various compositions
• Understanding the effect of O:C ratio on non-ideality

In [ ]:

import numpy as np
import particula as par

import numpy as np import particula as par

1. Define Organic Properties¶

Set up properties for an organic species with a moderate oxygen-to-carbon ratio.

In [ ]:

molar_mass_organic = 200.0e-3  # kg/mol
o2c_ratio = 0.5  # oxygen to carbon ratio
density_organic = 1200.0  # kg/m^3

print("=== Organic Properties ===")
print(f"Molar mass: {molar_mass_organic * 1e3:.1f} g/mol")
print(f"O:C ratio: {o2c_ratio}")
print(f"Density: {density_organic} kg/m^3")

molar_mass_organic = 200.0e-3 # kg/mol o2c_ratio = 0.5 # oxygen to carbon ratio density_organic = 1200.0 # kg/m^3 print("=== Organic Properties ===") print(f"Molar mass: {molar_mass_organic * 1e3:.1f} g/mol") print(f"O:C ratio: {o2c_ratio}") print(f"Density: {density_organic} kg/m^3")

2. Create Non-Ideal (BAT) Activity Strategy¶

Use the builder pattern to create the BAT activity strategy.

In [ ]:

non_ideal = (
    par.particles.ActivityNonIdealBinaryBuilder()
    .set_molar_mass(molar_mass_organic, "kg/mol")
    .set_oxygen2carbon(o2c_ratio)
    .set_density(density_organic, "kg/m^3")
    .build()
)

print(f"Strategy: {type(non_ideal).__name__}")

non_ideal = ( par.particles.ActivityNonIdealBinaryBuilder() .set_molar_mass(molar_mass_organic, "kg/mol") .set_oxygen2carbon(o2c_ratio) .set_density(density_organic, "kg/m^3") .build() ) print(f"Strategy: {type(non_ideal).__name__}")

3. Create Ideal Activity Strategy for Comparison¶

Create an ideal strategy with the same molar masses to compare results.

In [ ]:

ideal = par.particles.ActivityIdealMolar(
    molar_mass=np.array([18.015e-3, molar_mass_organic]),
)

print(f"Ideal strategy: {type(ideal).__name__}")

ideal = par.particles.ActivityIdealMolar( molar_mass=np.array([18.015e-3, molar_mass_organic]), ) print(f"Ideal strategy: {type(ideal).__name__}")

4. Compare Ideal vs Non-Ideal Activity¶

Test at various organic mass fractions and compare the activity values and activity coefficients.

Note: The BAT model returns only the organic activity (scalar), not both water and organic activities like the ideal model.

In [ ]:

mass_fractions = np.array([0.2, 0.5, 0.8])
print("=== Ideal vs Non-Ideal Activity Comparison ===")
print(f"Organic O:C ratio: {o2c_ratio}")
print(f"Organic molar mass: {molar_mass_organic * 1e3:.1f} g/mol")
print("Note: BAT model returns organic activity only (scalar)\n")

for org_frac in mass_fractions:
    # Mass concentrations: [water, organic]
    mass = np.array([1.0 - org_frac, org_frac]) * 1e-9  # kg/m^3

    ideal_activity = ideal.activity(mass_concentration=mass)
    # BAT model returns only organic activity (scalar)
    bat_organic_activity = float(non_ideal.activity(mass_concentration=mass))

    print(f"Organic mass fraction: {org_frac:.1f}")
    print(
        f"  Mass conc: water={mass[0] * 1e9:.1f}, "
        f"org={mass[1] * 1e9:.1f} ng/m^3"
    )
    print(
        f"  Ideal activity:     water={ideal_activity[0]:.4f}, "
        f"org={ideal_activity[1]:.4f}"
    )
    print(f"  Non-ideal (BAT):    org={bat_organic_activity:.4f}")

    # Activity coefficient = activity / mole fraction
    moles = mass / np.array([18.015e-3, molar_mass_organic])
    mole_frac = moles / np.sum(moles)
    gamma_organic = bat_organic_activity / mole_frac[1]
    print(f"  Organic activity coeff (gamma): {gamma_organic:.4f}\n")

mass_fractions = np.array([0.2, 0.5, 0.8]) print("=== Ideal vs Non-Ideal Activity Comparison ===") print(f"Organic O:C ratio: {o2c_ratio}") print(f"Organic molar mass: {molar_mass_organic * 1e3:.1f} g/mol") print("Note: BAT model returns organic activity only (scalar)\n") for org_frac in mass_fractions: # Mass concentrations: [water, organic] mass = np.array([1.0 - org_frac, org_frac]) * 1e-9 # kg/m^3 ideal_activity = ideal.activity(mass_concentration=mass) # BAT model returns only organic activity (scalar) bat_organic_activity = float(non_ideal.activity(mass_concentration=mass)) print(f"Organic mass fraction: {org_frac:.1f}") print( f" Mass conc: water={mass[0] * 1e9:.1f}, " f"org={mass[1] * 1e9:.1f} ng/m^3" ) print( f" Ideal activity: water={ideal_activity[0]:.4f}, " f"org={ideal_activity[1]:.4f}" ) print(f" Non-ideal (BAT): org={bat_organic_activity:.4f}") # Activity coefficient = activity / mole fraction moles = mass / np.array([18.015e-3, molar_mass_organic]) mole_frac = moles / np.sum(moles) gamma_organic = bat_organic_activity / mole_frac[1] print(f" Organic activity coeff (gamma): {gamma_organic:.4f}\n")