Heat load & loop

IT heat load (kW) ?Heat load — total rack/cold-plate heat the CDU must remove. The denominator for flow-per-kW. AI racks today run 60–130 kW.

Secondary ΔT (K) ?ΔT — secondary supply-to-return rise. Band 8–12 K (cdu-checklist §01). Higher ΔT = lower flow for the same heat.

Fluid ?Secondary fluid — water or PG-25 (25% propylene glycol, OCP direct-to-chip grade). PG-25 carries ~9% less heat per litre.

Glycol % (PG only) ?Glycol fraction — band 20–35% vol. 25% freezes near −10 °C. Affects cp, density and viscosity.

Secondary supply T (°C) ?TCS supply — temperature delivered to the cold plates. Band 17–45 °C (ASHRAE W-classes). Must stay above room dew point.

Hydraulics

Pipe size (secondary) ?Nominal pipe — sets internal diameter for velocity + Darcy-Weisbach friction. Velocity band 1.5–3.0 m/s.

Run length, one-way (m) ?Pipe length — straight-run length for friction loss. Total developed length of the worst secondary leg.

Fittings (sum K) ?Fitting loss — sum of minor-loss K-values (elbows ~0.9, tee ~1.8, valve, QD couplers ~1.5). Crane TP-410 typical.

Pump / motor efficiency ?Efficiencies — pump BEP (~0.70) and motor (~0.92). Used for shaft and electrical pump power.

Per-pump capacity (LPM) ?Duty pump flow — capacity of one pump; drives the N+1 count (OCP Deschutes mandates N+1).

Heat exchanger & environment

Facility supply T (°C) ?FWS supply — primary/facility water temperature into the CDU heat exchanger. The cold side of the approach.

HX NTU ?NTU — heat-exchanger size (UA/Cmin). Higher NTU → higher effectiveness → smaller approach. Typical CDU plate HX 1.5–3.

Room air T / RH (°C / %) ?Dew-point inputs — room air temperature and relative humidity set the dew point. Supply must stay ≥2–3 °C above it.

Sizing results

engine —

How to read this. Every figure is Derived by the validated CDU engine (js/cdu-engine.js, 40/40 tests) from your inputs and the bands in the checklist. A cyan rail = within band, amber = watch, red = out of band. Flow uses Q = ṁ·cp·ΔT; pressure drop uses Darcy-Weisbach with Haaland friction; approach uses ε-NTU; dew point uses the Magnus formula; NPSH per the Hydraulic Institute. PG-25 properties are handbook-class (ILLUSTRATIVE) — confirm against your fluid's datasheet. Pro analysis (TCO/NPV, Monte-Carlo, sensitivity and a PDF tech-spec) is coming next. Not procurement or safety advice.

Pro Analysis

Lifecycle TCO & NPV, a 10,000-run Monte-Carlo on pump energy, sensitivity ranking, and a PDF tech-spec.

TCO & ROI (10-yr)

Capex/maintenance defaults per CDU type are illustrative; energy from computed pump power × $/kWh. vs an air-cooled baseline.

CDU sizing & thermohydraulic calculator

Heat load & loop

Hydraulics

Heat exchanger & environment

Sizing results

TCO & ROI (10-yr)

Monte-Carlo — pump energy (10k)

Sensitivity — drivers of pump kW

Engineering assessment