Cooling method picker by rack kW
Select a cooling approach by your target rack density (kW per rack). Thresholds based on published vendor data, ASHRAE classes, and industry deployments.
How we calculated this
Density thresholds based on published vendor specifications and deployments: NVIDIA GB200 NVL72 at ~140 kW/rack (TrendForce, 2024; NVIDIA, 2026); Schneider Electric and NVIDIA Vera Rubin NVL72 reference designs up to 227 kW/rack (Schneider Electric AI Factory Reference Designs 112/113, https://www.se.com/ww/en/work/solutions/ai-factory/reference-designs/); AMD Helios rack-scale reference (Mordor Intelligence, 2026); RDHx deployments up to 75 kW (Mordor Intelligence, 2026).
Air cooling limit of ~30 kW/rack reflects practical containment and fan power limits. Uptime Institute 2026 survey notes more operators reporting peak densities ≥30 kW for AI workloads (Mordor Intelligence, 2026).
W-class recommendations follow ASHRAE TC 9.9 Thermal Guidelines, 5th Edition (2021): W27-W32 enables dry cooler free cooling in most climates; W32-W45 for hot climates or maximum density.
PUE targets drive the rules: air cooling typically 1.3-1.6; RDHx 1.15-1.30; direct-to-chip 1.05-1.15; immersion 1.01-1.08 (Wikipedia PUE, 2026; industry reported values). A ≤1.05 target routes to two-phase immersion or the best end of direct-to-chip, ≤1.10 to direct-to-chip or two-phase, and any stated target rules out air.
Method checked on 2026-11-01.
Guidance only. Final cooling selection requires vendor consultation, OEM warranty confirmation, facility constraints analysis, and fluid qualification. This tool does not replace engineering design.
Questions
- Can I use air cooling at 50 kW/rack?
- Air cooling with advanced containment can reach 40-50 kW/rack, but liquid cooling is more reliable and efficient above 30 kW. Uptime Institute's 2026 survey links rising peak densities to AI workloads (Mordor Intelligence, 2026).
- What is the density limit for rear-door heat exchangers?
- RDHx typically handles 30-75 kW/rack, limited by air-side heat transfer. They are best for retrofit where server modification is not feasible. NorthC deployed RDHx at Münchenstein without downtime (Mordor Intelligence, 2026).
- When should I choose immersion over direct-to-chip?
- Choose two-phase immersion for maximum density (>100 kW/rack) and best PUE (1.01-1.05). Choose single-phase immersion if you prefer hydrocarbon fluids (Shell S3 X, Intel certified). Direct-to-chip has broader OEM warranty support and is the NVIDIA/AMD reference design choice.
Find vendors
Use this tool on your site
The snippet includes a link back to this page. Please keep it.