Immersion Cooling — Servers submerged in dielectric fluid
Immersion cooling is a method where complete servers are fully submerged in a non-conductive dielectric fluid. The fluid absorbs heat directly at the components — no fans, no air conditioning, significantly higher power density. Common in HPC, AI training clusters and hyperscale data centers.
How does immersion cooling work?
Cross-section of a single-phase immersion tank — servers submerged in dielectric fluid, a cooling loop transports heat to the facility water loop.
- 1 Sealed tank
Sealed steel or polycarbonate tank with lid — prevents evaporation and splashes of the coolant.
- 2 Dielectric fluid
Non-conductive oil (e.g. 3M Novec, Shell Immersion Cooling Fluid). Heat capacity 1200× higher than air.
- 3 Servers submerged vertically
Standard servers without fans, modified for direct fluid contact. Up to 20× higher power density vs. air cooling.
- 4 Cooling loop
Pump circulates heated fluid to heat exchanger and back to tank cold.
- 5 Heat exchanger / CDU
Liquid-to-liquid heat exchanger — transfers heat to facility water loop. No compressor needed.
- 6 Facility cooling outlet
Connection to free-cooling tower or outdoor air cooling. PUE values of 1.03 to 1.1 achievable.
Single-Phase vs. Two-Phase
With Single-Phase Immersion the fluid stays liquid — a pump circulates it continuously to the heat exchanger and cold back into the tank. Simpler setup, proven fluids, lower investment costs. Standard in mid-market data centers and dedicated AI cluster deployments.
With Two-Phase Immersion the fluid evaporates at hot components — the vapour rises, condenses at the cooled tank lid and drips back. Higher thermal transfer efficiency, but: significantly more expensive fluid (often fluorinated compounds), sealed tank mandatory, higher regulatory requirements (PFAS class). Mostly used in hyperscale deployments like Microsoft Azure and Google Cloud.
Efficiency metrics
- PUE 1.03 to 1.1 — almost no overhead, vs. ~1.5 in classic data centers
- 20× higher power density — up to 200 kW per tank instead of 10–15 kW/rack
- 30–50 % lower power consumption — no CRAC AC, no server fans
- Silent operation — no fan noise, allows office co-location
- Longer hardware lifetime — no temperature spikes, less thermo-mechanical stress
Practical hurdles in DACH
Despite technical advantages, immersion cooling is still rare in DACH enterprise data centers. Reasons: standard servers must be modified for immersion (remove fans, redo cable management), classic hardware suppliers offer few pre-validated configurations. Co-location providers must first install tank infrastructure. EU PFAS regulation additionally complicates the choice of cooling fluid — two-phase systems with fluorinated fluids are under pressure.
Realistic use today: dedicated AI/HPC clusters, crypto-mining farms, hyperscale pilots. For classic enterprise workloads (SAP, mail, office) conventional air cooling with free-cooling loop remains the most economical path.
TPM maintenance for immersion-cooled hardware
Servers submerged in immersion tanks still need hardware maintenance — DIMM failures, disk replacements and PSU defects occur at similar rates as with air cooling. We service servers in single-phase immersion configurations vendor-independently, with special procedures for cleanly extracting and drying components before replacement. For two-phase systems with fluorinated fluids additional handling requirements apply — talk to us before pilot.