Steady State tells you where a process settles. Dynamics follows it there. A vessel fills and drains, a heater’s contents warm over their residence time, a valve passes what the pressures on either side push through it, and a PID controller moves a valve or a duty to hold what it measures at its set point. Change a feed, a set point or a valve’s opening while the run goes on, and watch the plant find its new state.
A benzene and toluene feed into a separator, its gas and liquid leaving through valves: a pressure controller on the gas valve, a level controller on the liquid valve. Solved in Steady State, then switched to Dynamics.
Before the run, the app checks what decides every flow, which vessels need a size and which controllers cannot act
Accept All Defaults and Switch gives each stream entering or leaving the case the specification it needs
The run starts at the steady state and stays there until something changes
Step the feed up 25 %: the level rises, the controller opens the liquid valve, and the level comes back to its set point
Captioned, no sound needed.
What it does today
A flowsheet you have solved, run through time
Dynamics starts from the case you already have: solve it in Steady State, click Dynamic Mode, and the run begins from that steady state. Every picture below is from the app.
The video’s separator in a run, 22 minutes in: V-100’s icon shows its level, every stream’s values follow the run, and the toolbar shows the run’s time.
Ready to run
The app checks the case before every run
Each flow in a run is decided by exactly one thing – a valve, a pump on its curves, a flow held at a stream entering or leaving the case – and the pressures follow from where they are fixed. The Dynamics Readiness window lists what is missing or decided twice, which vessels and exchangers need a size, and which controllers cannot act, each with what Accept All Defaults would set. One click usually makes the case ready.
The Dynamics Readiness window, before Accept All Defaults and Switch.
Vessels
Separators and tanks that fill and drain
A separator, a tank or a three-phase separator holds its liquid, its vapour and its water; its level and pressure follow what flows in and out. Give it a diameter and a height, or let Size from Steady State size it from its steady flow. Each liquid outlet carries the weight of what stands above it, so a tank drains faster when it is full. On the drawing, each vessel’s icon shows its level as the run goes on.
V-100’s Dynamics tab, four minutes after the feed step. Click for the whole tab.
Control
PID controllers, with face plates
Place a PID controller from the palette, pick what it measures and what it moves – a valve’s opening, a heater’s, cooler’s, exchanger’s or reactor’s duty, a pump’s or compressor’s speed on its curves, or a flow – and tune it in the ISA or the parallel form. Its face plate shows the measured value against the set point and the output, with the last five minutes as a trend; type a new set point on it at any time. An Adjust you already have becomes a PID controller in one click, and Build with AI can plan controllers too.
LIC-100’s face plate at the level’s peak, the valve opening to bring it back.
Watching a run
Strip charts, tables and the worksheet follow the run
Add any variable in the case to the Strip Chart: each kind of quantity gets its own axis in your unit set, the hover reads every line at that moment, and Export CSV writes the whole run. Canvas tables, datasheets and the PFD Worksheet follow the run too; a table and a datasheet say which moment of the run their numbers are from, and the worksheet can show the run’s time beside them.
The Strip Chart after a 25 % feed step at 2 minutes.
Valves as they behave
On the Pressure Flow Relation a valve passes the flow its pressures and opening give (ISA-75.01), choking where a liquid or a gas chokes. Size Valve sizes it at its steady flow; linear, equal-percentage or quick-opening; an actuator that moves it at once, with a lag, or at a set rate.
Heat transfer
Heaters, coolers and each side of a heat exchanger hold their contents, so outlets warm and cool over their residence time. An exchanger’s duty follows its UA and the temperatures at its ends, its UA following each side’s flow, or a duty you or a controller set.
Reactors
The CSTR, the PFR and the conversion, equilibrium and Gibbs reactors run in Dynamics: a CSTR’s kinetics in what it holds, a PFR as one well-mixed cell per slice of its steady solve, the equilibrium and Gibbs reactors bringing their contents to equilibrium every step.
Pumps, compressors, expanders
On their performance curves – flow, head and efficiency at each speed – a machine’s rise follows its flow, and a controller can move its speed. A valve and a machine on one line are solved together each step.
Pipes and scripts
A pipe holds one well-mixed cell per increment, its pressure drop following its flow. A Python Script unit is given the run’s time, its step and a memory kept from one step to the next.
The integrator
Run, pause and step; run for a time or until a time; a step size, and a guard that splits a step where a valve and a vessel would interact too fast for it. A run saved part-way reopens exactly where it stopped.
Columns and the extractor today. In a run, a distillation column, a Shortcut Column and the liquid-liquid extractor each split their feeds as their steady solve did, product by product and component by component, and the app marks them so on the drawing. Tray-by-tray dynamics for the column is on the horizon, below.
Compared with DWSIM
DWSIM’s own run, drawn beside ours
Import one of DWSIM’s dynamic cases and its PID controllers, valves, vessels and events come with it, together with the run DWSIM saved. On the Strip Chart, DWSIM’s run is drawn dashed beside the app’s, and a column says how far apart the two are.
Fed DWSIM’s own recorded measurements, each imported controller gives DWSIM’s recorded valve openings to rounding
On DWSIM’s separator sample, the level stays within 2 % of DWSIM’s run and the pressure within 12 %, as the From DWSIM column shows
Agreement with another simulator, not proof of correctness – which is why the checks below come first
Captioned, no sound needed.
DWSIM’s separator sample after its 20-minute run: solid lines are the app’s, dashed lines DWSIM’s recorded run. The From DWSIM column gives each line’s average difference, in % of its range.
More to watch
Two more short videos
Build with AI adds a controller
One sentence to Claude becomes a level controller, planned, built and tuned – and it works in the run.
A tank draining through a valve
With its feed stopped, a water tank empties; its outflow falls with its level, driven by the weight of the water above the outlet.
How it is checked
Answers worked by hand, then DWSIM
Every release runs the program’s own validation suite, and the Dynamics checks have a section of their own in the report.
A tank draining through a valve follows Torricelli’s law, its error halving with the step
A PI loop settles on the textbook first-order response
A valve’s flow matches the ISA-75.01 equation worked by hand
Mass and energy close through every holdup’s streams, and a case entered at its steady state stays there
The tank from the video: its outflow falls in a straight line while its level curves down – Torricelli’s law.
Dynamics today is flow-driven: each flow is decided by one thing, and the pressures follow. Planned, with no dates promised:
Pressure-driven dynamics – a pressure-flow network solved every step, so flows reverse, pressure controllers act between valves, mixers equalise and vessels vent
A Dynamics Assistant that proposes the sizes and specifications a case needs
Cascade control and set-point ramps on the PID controller
The dynamic distillation column – tray holdups, condenser drum and reboiler sump levels, and the column’s own control loops
Later, in the order users ask for them: an event editor, split-range and ratio control, start-up from empty vessels, compressor surge, heat loss to the air and a PID tuning helper
Getting a Dynamics version
Dynamics is not part of the free download. If you are interested in obtaining a Dynamics version, please contact ruebenm@therqon.ca.
