Major change on the API soon to be ducumented - just a draft now.

[viniviena]

I'll create a clean PR message without the emoji icons:

New Features: Steady-State Flash Drum, Three-Port Architecture & Enhanced Base Components

Summary

This PR introduces major enhancements to ProcessSimulator.jl, extending the modeling capabilities with steady-state separation equipment, improved base components architecture, and comprehensive testing infrastructure. The key additions follow the established design patterns from CSTR implementations and EMSO manual specifications.

New Features

Steady-State Flash Drum Components

• SteadyStateFlashDrum: Base component for steady-state vapor-liquid equilibrium separation
• FixedPressureSteadyStateFlashDrum: Wrapper with pressure constraint following CSTR wrapper patterns
• Mathematical Model: Based on EMSO manual formulations with proper VLE calculations using flash_mol_fractions_vapor
• Energy Balance: Internal energy calculation accounting for both liquid and vapor phases

Three-Port Control Volume Architecture

• ThreePortControlVolume_: Dynamic three-port control volume (1 inlet, 2 outlets)
• ThreePortControlVolume_SteadyState: Steady-state version for flash separations
• Phase Separation: Dedicated liquid and vapor outlet ports for proper phase handling

Enhanced Base Components

• ConstantFlowRate: Fixed flowrate boundary condition with molar/mass/volumetric basis options
• ConstantPressure: Fixed pressure boundary condition for system constraints
• ConnHouse: Generic connection point for flowsheet termination
• Boundary_pTzn: Comprehensive boundary condition with state specification options

Solid Properties & Adsorption Framework

• BasicMaterialConstants: Enhanced material properties structure for adsorbents
• SolidEoSModel: Polynomial-based solid equation of state with temperature dependencies
• Adsorbent: Complete adsorbent medium with isotherm, EoS, and transport models
• Mass/Heat Transfer: Correlations for particle-based systems with proper area calculations

Geometry Utilities

• CylindricalTank: Tank geometry with discretization capabilities
• Volume/Area Functions: volume_(), surface_area_(), cross_section_area_() for design calculations

Implementation Details

Mathematical Foundation

# VLE equilibrium constraint
ControlVolumeState.z[:, end] .~ flash_mol_fractions_vapor(...)

# Internal energy balance (both phases)
U ~ (LiquidOutPort.h[2] - p/ρ[2])*nᴸⱽ[1] + (VaporOutPort.h[3] - p/ρ[3])*nᴸⱽ[2]

# Conditional heat specification (following CSTR pattern)
if !isnothing(Q)
    q_eq = [Q ~ Q]
else
    q_eq = [ControlVolumeState.T ~ state.T]
end

Wrapper Pattern Consistency

The new flash drum components follow the exact same architectural patterns as the existing CSTR implementations:

• resolve_guess!(medium, state) for initialization
• extend(System(constraints...), odesystem) for wrapper construction
• Conditional specification of thermal conditions (Q vs T)

Testing Infrastructure

Flash Drum Test (test/separation/flash_drum_test.jl)

• EMSO Manual Example: 6-component system with realistic industrial conditions
• Components: 1,3-butadiene, isobutene, n-pentane, 1-pentene, 1-hexene, benzene
• Conditions: 496.3 kmol/h feed at 338 K, flash at 2.5 atm pressure
• Validation: Proper VLE calculations with Peng-Robinson EoS

Enhanced Test Coverage

• Valve Test: Isenthalpic expansion with pressure drop validation
• CSTR Test: Steady-state reactor with ethylene oxide hydration
• Adsorption Test: Well-mixed adsorber with Langmuir isotherms
• Boundary Test: Fixed boundary conditions with multiple phases

Files Modified/Added

Core Implementation

• FlashDrum.jl - New steady-state flash drum components
• basecomponents.jl - Enhanced base components and three-port architecture
• Geometry.jl - Tank geometry utilities
• SolidsProp.jl - Solid properties and adsorption framework

Testing

• flash_drum_test.jl - Comprehensive flash drum testing
• valve_test.jl - Valve performance validation
• ss_cstr_test.jl - Steady-state CSTR validation
• fixed_pTzN_boundary.jl - Boundary condition testing

Configuration

• Updated exports in all relevant modules
• Project.toml dependency management maintained

Technical Validation

Compilation Success

All new components successfully compile with mtkcompile() and pass structural validation.

Mathematical Consistency

• Degrees of Freedom: Proper balance achieved through adiabatic + pressure specification
• VLE Calculations: Thermodynamically consistent using Clapeyron.jl backend
• Energy Conservation: Internal energy correctly calculated for multi-phase systems

Design Pattern Adherence

• Wrapper Architecture: Consistent with existing CSTR implementation patterns
• Component Structure: Follows AbstractSeparator hierarchy
• State Management: Proper resolve_guess!() integration

Benefits

1. Expanded Modeling Capabilities: ProcessSimulator.jl now supports steady-state flash separations
2. Architectural Consistency: All new components follow established design patterns
3. Industrial Relevance: Test cases based on realistic process conditions from EMSO manual
4. Extensibility: Framework established for additional separator types (distillation columns, etc.)
5. Multi-phase Support: Three-port architecture enables proper phase separation modeling

Breaking Changes

None. All changes are additive and maintain backward compatibility with existing code.

This PR significantly expands ProcessSimulator.jl's capabilities while maintaining the high-quality architectural standards established in the existing codebase.