Hydronic systems behave differently depending on load conditions, control actions and thermal inertia. This article explains when to use dynamic simulation and when imposed load simulation (ILS) gives better insight.
Hydronic HVAC systems contain pumps, valves, emitters and thermal masses that interact dynamically. No single simulation type covers every aspect of system behaviour.
A dynamic simulation captures time-dependent behaviour: how flows, temperatures and control actions evolve minute by minute.
Imposed load simulation (ILS), on the other hand, applies predefined loads to evaluate how the system responds under simplified operating conditions. Each method provides valuable but different insight depending on the design question.
Dynamic simulation models the real sequence of events in a system:
This makes it ideal for verifying comfort performance, control strategy robustness and transient behaviour. Engineers use it to check how the system handles real-world disturbances, such as recovery after night setback or sudden demand spikes.
An imposed-load model focuses on how the hydronic system behaves when heat or cooling demand is specified directly, instead of being determined by control loops or dynamic conditions.
The practical value of this approach becomes clear in imposed load simulation, where the focus is on system capacities, temperature regimes and hydraulic responses under controlled load scenarios.
It allows engineers to:
In many early project phases, ILS provides fast and clear feedback.
The distinction between both methods is outlined in RTS vs ILS.
A simple rule of thumb helps:
For complete system design, both methods complement each other rather than compete.
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