Block Solver

Jasper uses a sequential modular solver that processes unit operations one at a time in topological order, with recycle convergence for cyclic flowsheets.

Algorithm

1. Select property package from project.thermodynamics.propertyMethod
2. Initialize feed streams (T, P, flow, composition → enthalpy)
3. Topological sort with tear stream detection
4. If no recycles:
     Solve blocks in order → done
5. If recycles detected:
     Initialize tear streams with defaults
     Loop (max 50 iterations):
       a. Solve all blocks in topo order
       b. Compare tear stream values (T, P, flow, composition)
       c. Apply Wegstein acceleration
       d. If max relative change < 1e-4 → converged

Property Package Threading

The solver creates a PropertyPackage from the project settings and passes it to every block solver. This means:

• Flash drums use the correct K-value model (Ideal, PR, or NRTL)
• Compressors use rigorous entropy for isentropic calculations
• Distillation columns use property-package K-values for relative volatilities
• Absorbers use K-values for equilibrium slope in Kremser

const methodName = project.thermodynamics?.propertyMethod ?? 'Ideal';
const pkg = getPropertyPackage(methodName);

Recycle Convergence

Tear Stream Detection

During topological sort, back-edges in the DFS identify recycle loops. These edges become tear streams — the solver breaks the loop at these points and iterates.

Wegstein Acceleration

After 2+ iterations, Wegstein acceleration is applied to tear stream variables:

slope = (g(x2) - g(x1)) / (x2 - x1)
q = slope / (slope - 1)
x_new = (1 - q) · g(x2) + q · x2

Where q is bounded to [-5, 0] for stability.

Convergence Criteria

• Tolerance: max relative change < 1e-4
• Max iterations: 50
• Variables checked: T, P, flow, all mole fractions

SolverResult

interface SolverResult {
  converged: boolean;
  streams: Map<string, StreamState>;
  blockResults: Map<string, any>;
  error?: string;
  recycleIterations?: number;
}

StreamState

interface StreamState {
  id: string;
  name: string;
  T: number;           // K
  P: number;           // bar
  flow: number;        // kmol/h
  composition: Record<string, number>;  // mole fractions
  phase: 'V' | 'L' | 'VL';
  H: number;           // kJ/mol
}

Supported Block Types

Type	Solver	Key Feature
Feed	Initialize	Reads params or edge spec
Flash / Separator	VLE flash	Property-package K-values
Mixer	Enthalpy balance	Newton iteration for T
Splitter	Flow division	Split ratio parameter
Pump	ΔP + power	Rackett liquid density
Compressor	Isentropic + efficiency	Entropy-based Newton iteration
Valve	Isenthalpic	Pressure drop
Heater / Cooler	Energy balance	Rigorous enthalpy duty
DistillationColumn	Fenske-Underwood-Gilliland	Shortcut distillation
RStoic / RCSTR / RPfr / etc.	Stoichiometric + heat of rxn	Adiabatic or isothermal
REquil / RGibbs	Equilibrium	Keq from ΔG, bisection
Absorber	Kremser	General multi-solute
Stripper	Kremser	General stripping
HeatExchanger	Counter-current	80% effectiveness

Source

src/sim/solver/blockSolver.ts