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Property Methods

Jasper uses a PropertyPackage abstraction to dispatch thermodynamic calculations to the appropriate model. Each package implements the same interface, so the solver is model-agnostic.

PropertyPackage Interface​

interface PropertyPackage {
  name: string;
  calculateKValues(components: string[], T: number, P_Pa: number): Record<string, number>;
  flash(z: Record<string, number>, T: number, P_Pa: number, components: string[]): FlashResult;
  liquidDensity(composition: Record<string, number>, T: number, P_Pa: number): number;
  vaporDensity(composition: Record<string, number>, T: number, P_Pa: number): number;
  mixtureEnthalpy(composition: Record<string, number>, T: number, P_Pa: number, phase?: 'V' | 'L'): number;
  mixtureEntropy(composition: Record<string, number>, T: number, P_Pa: number, phase?: 'V' | 'L'): number;
}

Available Packages​

IdealPropertyPackage​

  • K-values: Raoult's Law — K = Psat(T) / P
  • Enthalpy: Ideal gas — H = Hf + ∫Cp dT
  • Entropy: Ideal gas — S = ∫(Cp/T)dT - R·ln(P/Pref)
  • Density: Ideal gas law (vapor), Rackett equation (liquid)

Use when: all components are chemically similar, low pressure, no strong interactions.

PRPropertyPackage (Peng-Robinson)​

  • K-values: Fugacity-based — iterative phi-phi flash
  • Enthalpy: Ideal + PR departure function
  • Entropy: Ideal + PR departure function
  • Density: From PR compressibility factor Z

Use when: hydrocarbons, gases, high-pressure systems, supercritical conditions.

NRTLPropertyPackage​

  • K-values: Modified Raoult's — K = γ · Psat / P
  • Activity coefficients: NRTL model with BIP database
  • Enthalpy/Entropy: Ideal gas (excess enthalpy not yet included)
  • Density: Rackett equation for liquid

Use when: polar mixtures, alcohol-water, amine-water, organic-organic with known non-ideality.

Factory​

import { getPropertyPackage } from './propertyMethod';

const pkg = getPropertyPackage('PR');        // Peng-Robinson
const pkg = getPropertyPackage('NRTL');      // NRTL activity coefficients
const pkg = getPropertyPackage('Ideal');     // Raoult's Law (default)

Recognized strings: 'PR', 'PENG-ROBINSON', 'SRK', 'NRTL', 'NRTL-RK', 'IDEAL', 'RAOULT'.

Choosing a Property Method​

System TypeRecommended MethodWhy
Light hydrocarbons (C1-C10)PRHandles non-ideal vapor, high P
Natural gas processingPRCryogenic, high-pressure VLE
Alcohol-water distillationNRTLAzeotrope, strong liquid non-ideality
Amine gas treating (CO2 capture)NRTLPolar, aqueous amine solutions
Ideal mixtures (benzene-toluene)IdealFastest, accurate enough
Air separationPRCryogenic, multi-component
Classroom problems (ideal)IdealSimplest, matches textbooks

Peng-Robinson Details​

The PR EOS:

P = RT/(V-b) - a·α(T) / (V(V+b) + b(V-b))
  • Alpha function: α = [1 + κ(1 - √Tr)]² where κ = 0.37464 + 1.54226ω - 0.26992ω²
  • Mixing rules: van der Waals one-fluid (a_mix = ΣΣ xi·xj·√(ai·aj))
  • Cubic solver: Analytical Cardano's method for Z roots
  • Phase selection: smallest Z for liquid, largest Z for vapor

NRTL Details​

ln(γi) = (Σj τji·Gji·xj) / (Σk Gki·xk) + Σj [xj·Gij/(Σk Gkj·xk)] · (τij - (Σm xm·τmj·Gmj)/(Σk Gkj·xk))

Where:

  • τij = aij + bij/T
  • Gij = exp(-αij · τij)
  • Parameters from bipDatabase.ts (~20 common pairs)