This simulator models a closed chilled-water cooling loop — chiller, circulating pump, CRAH coil, supply/return headers and an expansion vessel — with lumped room and water thermal masses, letting you fail the pump or lose heat rejection and watch the water-side energy balance respond over simulated time.
• 01 Facility laboratory tab: a real-time 3D workbench of the chiller and heat-rejection assembly, the chilled-water pump and valves, the CRAH water-side heat exchanger (coil), the supply and return headers and an expansion vessel, with Home view, Focus selected part, Show full enclosure, Exploded view, Auto rotate, Expand and Hide/show labels camera controls, clickable numbered components with callouts, live stats, a sequence readout, switch-state tokens and a readings table. Experiment controls include Pause/resume, Advance 10 ms, Advance 1 s, a playback-speed selector (10× slow motion, real time, 10× faster, 1 minute per second), Enable facility / Stop experiment / Stop water pump / Lose heat rejection actions, an IT load slider (10–240 kW), water mass flow (0.5–10 kg/s), chilled-water setpoint (5–20°C), coil/chiller capacity (40–240 kW), Pump running / Chiller available checkboxes, and chiller COP (2–7 kW/kW). • 02 Curves & measurements tab: a torque/load operating-point chart, a speed-and-current history chart, model equations (coil heat transfer limited by rated capacity, water-side heat balance, room and water thermal-mass differential equations and chiller electrical input from COP) and snapshot readouts for server inlet temperature, hot return air, coil leaving air (supply), heat removed, chilled-water supply temperature and water return temperature. • 03 Experiments tab: guided presets (loop reaches equilibrium, chiller failure, pump failure, compare electrical efficiency) plus a Model verification bench ("Run model checks") using independent fresh models, and a timestamped event log with trial-report export. • 04 Learn & assess tab: lessons on following the closed water circuit, closing the transport heat balance, storing excess thermal energy, and how COP connects heat rejection to electrical demand, a two-question knowledge-check quiz with reset, and a scope-and-references note.
Chilled water leaves the chiller, is circulated by the pump through the supply header to the CRAH coil, absorbs heat from the room's hot return air at the coil, and returns warmer through the return header to the chiller's evaporator, where the cycle repeats. Heat transfer at the coil follows an effectiveness-limited exchange (εCmin times the return-to-water temperature difference, capped by rated capacity), and the water-side heat gained equals mass flow times water heat capacity times the temperature rise across the loop.
Because the water loop has finite thermal mass (850 kJ/K in this model) and the room has its own thermal mass (400 kJ/K), the room-return and water temperatures don't jump instantly — they evolve according to differential heat balances, which is why failing the chiller doesn't immediately overheat the room: heat accumulates in the water loop first, gradually raising water temperature and reducing the coil's effectiveness before room temperature climbs. Stopping the pump instead removes forced water circulation entirely, halting heat transport even while the chiller itself remains available.
The stats panel reports server inlet temperature, hot return air, coil leaving air, heat removed, chilled-water supply temperature and water return temperature. The compare-electrical-efficiency experiment preset shows how chiller electrical input scales inversely with COP for the same heat-rejection rate (Pchiller = Qchiller / COP) — raising COP from 4 to 6 reduces electrical demand for identical cooling output, which is the core lever this simulator lets you explore.
The Run model checks button in the Experiments tab exercises the coil, water-loop and room thermal-balance equations against independent model instances without disturbing your current trial. This is a lumped sensible-heat model using fixed nominal air flow (8 m³/s), a fan multiplier of 1, containment of 0.9 and uncontained recirculation of 0.2 — it excludes CFD, humidity, condensation, refrigeration-cycle detail and hydraulic network effects, and its temperature alarms are teaching thresholds rather than manufacturer setpoints.
The water loop has its own thermal mass (850 kJ/K in this model), so heat accumulates there first, gradually raising water temperature and reducing coil effectiveness before room return-air temperature climbs. This lets you observe the chiller-failure experiment preset play out over simulated time rather than as an instant spike.
Stopping the pump halts forced water circulation entirely, so no water-side heat transport occurs even if the chiller itself is still available. Losing the chiller (heat rejection) keeps water flowing through the coil but stops removing heat from the water loop, so heat accumulates over time instead of stopping instantly.
Chiller electrical input equals the heat-rejection rate divided by COP (Pchiller = Qchiller / COP). At 100 kW of heat rejection, a COP of 5 needs 20 kW of electrical input, while a higher COP of 6 needs proportionally less for the same cooling output — that's the comparison the "compare electrical efficiency" preset demonstrates.
The Run model checks button in the Experiments tab runs automated checks against independent, freshly created model instances, confirming the coil heat-transfer, water-loop and room thermal-balance equations behave correctly.