Interface Overview

Skarstrom is organised as a set of docked windows. The Navigation panel on the left is the spine of the interface: selecting an item there brings up the corresponding editor. The items are listed roughly in the order you build a model, and each modelling stage carries a status icon — a green check when its inputs are valid, a red cross when something is missing or inconsistent. Hover the icon to see the specific problem.

A typical model is built top to bottom:

1. System Information — name and describe the simulation.
2. Fluid Package Selector — choose the gas components.
3. Adsorbent Library — define the adsorbent materials (isotherms, kinetics, heat of adsorption).
4. Column Properties — set the column geometry, energy balance, wall, voids and the packed layers.
5. Cycle Design — build the sequence of steps and their boundary conditions.
6. Solver — run the simulation and plot the results.

The Parameters, Optimisation and Parameterisation windows support advanced studies. While a job is running, the editing windows are disabled to protect the model state.

System Information

Metadata for the simulation — Title, Description and Author. These are saved with the file and are useful for keeping a library of cases organised.

Fluid Package Selector

Choose the gas-phase components. The window shows two lists — Available and Selected — and you move components between them with the arrow buttons, Enter, or a double-click. Thermophysical properties (heat capacity, viscosity, thermal conductivity, molar mass) are evaluated from CoolProp, so the component names are CoolProp fluids.

Click a selected component to open its Component Properties, where the Lennard-Jones parameters (characteristic energy and length) are set. These feed the binary-diffusion calculation used by the transport correlations.

The adsorbed-phase heat capacity is set separately, in Column Properties → Energy Balance — see the energy balance.

Adsorbent Library and Materials

The Adsorbent Library holds a reusable collection of adsorbent materials. Use Add New Adsorbent to create one, or Load Example for a starting point (Activated Carbon, Mg-MOF-74, Zeolite 13X). Each material, edited in the Adsorbent Material window, has:

• Material Properties — solid/particle density $\rho_p$, specific heat capacity, thermal conductivity, and particle void fraction $\epsilon_p$.
• Isotherms — the isotherm model for each component, with a Show Isotherm Plot option.
• Heat of Adsorption — the isosteric heat $\Delta H_i$ for each component.
• Rate Models — the kinetic rate model for each component.

Materials are defined once and then referenced (by mass fraction) from the packed layers, so the same material can be reused across layers and cases.

Column Properties

Defines the vessel and how it is packed. Tabs:

• Geometry — the Column Shape (Cylinder, Square or Rectangle) and its dimension (e.g. Column Diameter).
• Energy Balance — the thermal equilibrium model (LTE/LTNE) and the adsorbed-phase heat capacity.
• Void Spaces — optional lumped Bottom Void and Top Void regions (dead volume / manifold) at each end of the column, each with a volume and a flow resistance coefficient.
• Wall — the wall Material (a preset, or Custom with heat capacity, density, thermal conductivity), Thickness, Ambient Temperature, and the wall-temperature boundary condition.

Below the tabs is the Adsorbent Layers panel. A bed can be packed with several layers stacked along its length; add, delete and reorder them here, and click a layer to edit it in the Adsorbent Properties window.

Adsorbent Properties (a layer)

Each layer combines one or more library materials with its packing geometry:

• Properties — the layer name, the composition (a mass-fraction mix of library adsorbents; use Normalise to make the fractions sum to one), the Length, Number of cells (the finite-volume discretisation), Bed void fraction $\epsilon_b$, and Particle Diameter. Derived quantities (adsorbent mass, bulk density, layer volume) are shown read-only.
• Heat Transfer — the internal and external heat-transfer correlations.
• Dispersion — the axial mass and heat dispersion correlations.

Number of cells sets spatial resolution. More cells sharpen concentration and thermal fronts but slow the solver. Start modest (e.g. 20–50) while building a model, then refine and confirm the results no longer change.

Parameters

The Parameters window lets you define named user variables and reuse them across any numeric input. Most input fields accept an expression, including physical units in square brackets — for example 10 [bar] or 100 [degC]. Built-in read-only variables (temperature T, pressure P, concentration c, mole fraction y, velocity v, the gas constant R, and PI) can be referenced in expressions, which is powerful for making state-dependent inputs. User variables are saved with the simulation file.