Immersion Cooling:
Facility Infrastructure
Design Guide

The data centre industry has reached a thermal inflection point. Air cooling — the default since the first raised-floor computer rooms of the 1960s — is structurally incapable of serving the rack densities that AI and HPC workloads demand. A rack of NVIDIA H100 GPUs draws 10–14 kW per server; a fully populated 42U rack exceeds 60–80 kW. Air, with its poor volumetric heat capacity, cannot remove that heat without airflow velocities that create acoustic, structural, and operational problems.

Immersion cooling removes heat directly from the chip surface through a liquid medium with heat capacity 1,200× greater than air. But immersion cooling is not simply a matter of replacing the CRAC units. It rewrites the infrastructure design of a data centre from the floor slab upward. This article is the engineering reference for facility designers, MEP consultants, and data centre operators moving from technology selection into facility design.

Technology Types: What the Facility Sees

There are three commercially deployed immersion cooling technologies. The technology choice must be locked before facility design begins — each imposes fundamentally different infrastructure requirements that are not interchangeable at fit-out stage.

The CDU and Secondary Water Loop

In single-phase immersion, the Coolant Distribution Unit (CDU) sits between the dielectric fluid loop (primary, in contact with servers) and the facility water loop (secondary, connecting to chillers or cooling towers). Designing this interface correctly determines system efficiency, redundancy, and maintainability for the facility’s lifetime.

CDU Thermal Sizing

// CDU Thermal Capacity Sizing

Q_CDU = N_tanks × P_rack × LF × SF

Where:
  N_tanks  = Number of immersion tanks served
  P_rack   = Max IT power per tank             (kW)
  LF       = Load factor (0.85–0.95 for AI)
  SF       = Safety factor                     (1.15–1.25)

// Example: 10-tank deployment, 100 kW/tank, LF=0.90, SF=1.20
Q_CDU = 10 × 100 × 0.90 × 1.20 = 1,080 kW

// Secondary-side flow rate  (ΔT = 10°C, water)
V_sec = Q_CDU / ( ρ × Cp × ΔT )
       = 1,080 / ( 1000 × 4.18 × 10 ) = 25.8 L/s  →  ~93 m³/hr

• 01

  Supply Temperature — The Free Cooling Opportunity

  Unlike air-cooled servers requiring 7–12°C chilled water, single-phase immersion tanks typically accept secondary water supply at 25–45°C. This opens free cooling for 6,000–8,000 hours/year in most Indian climates — dramatically reducing chiller run hours and delivering the biggest PUE gain from immersion cooling beyond eliminating CRAC units entirely.

• 02

  Variable Flow — Mandatory

  AI server loads vary significantly with job scheduling — 100% during training, less than 30% during inference idle. Fixed secondary flow wastes pump energy and causes low-delta-T syndrome, forcing oversized chiller capacity. VFDs on all secondary loop pumps are mandatory, controlled by differential pressure setpoint across the CDU manifold.

• 03

  N+1 Redundancy with Hot-Swap Isolation

  CDUs must be N+1 for Tier III. Pump sets N+1 with auto-changeover. Fluid loop isolation valves at each CDU inlet and outlet allow hot-swap maintenance without draining immersion tanks — operationally non-negotiable. Include sample and drain valves at low points for fluid quality testing without full system shutdown.

Dielectric Fluid Selection and Management

Fluid selection affects material compatibility, fire risk classification, environmental liability, supply chain logistics, and spill cost. The three primary single-phase fluid categories each make different trade-offs that must be evaluated against the specific facility context.

Every immersion installation requires dedicated fluid management infrastructure that is frequently omitted from concept designs: a fluid storage tank sized at 110% of the largest single tank volume; a fill/drain station with pump, hose reel, and drip trays at each tank row; bunded floor containment with a blind sump not connected to site sewer; and fluid quality monitoring ports for dielectric strength, viscosity, and particle count sampling at CDU inlet and outlet.

Structural and Civil Requirements

This is where immersion cooling most frequently catches facility designers by surprise. A filled immersion tank is extraordinarily heavy — and most existing data centre floor slabs are not designed for it.

Electrical Infrastructure Modifications

Immersion cooling changes the electrical design of a data centre in several significant ways beyond simply removing CRAC unit power circuits.

Busway Sizing for High-Density Rows

An immersion-cooled row supporting 10 tanks at 100 kW each draws 1,000 kW per row. Standard data centre bus ducts rated for 100–250A tap-offs are undersized for this density. Row-level busway must be resized — typically 630A or 800A busbars with 250A or 400A tap-offs per tank. Voltage drop along the busbar run must be calculated; immersion tank OEMs specify maximum supply impedance to maintain server input voltage within ±5%.

CDU Power on UPS-Backed Supply

CDUs require their own power feed — typically 5–15 kW per CDU for pump motors, controls, and instrumentation. This load must appear on the electrical load schedule as a separate mechanical service load (not IT load) to avoid distorting PUE calculations. CDU feeds must be on the UPS-backed critical bus — a CDU losing power during high IT load causes rapid dielectric fluid temperature rise leading to thermal throttling or server shutdown within minutes.

Earthing and Bonding

All metallic tank bodies must be bonded to the facility equipotential earth system. The dielectric fluid is non-conductive but servers within the tank remain live — the tank body provides the grounding path for server chassis earth conductors. Static charge accumulation in flowing dielectric fluid also requires earth continuity verification across all pipe flanges and tank connections. See KVRM’s earthing and grounding design guide → for the full methodology.

Fire Suppression and Detection

Fire protection for immersion-cooled rooms requires a complete rethink from standard data centre practice. The risk profile is fundamentally different — and in some respects significantly better than air-cooled rooms.

PUE, WUE and Heat Recovery

Transition Strategy: Air to Immersion

Few data centres will be purpose-built for immersion from day one. The transition strategy requires careful MEP planning to avoid service interruption and stranded asset costs.

• 01

  Phase 1 — Purpose-Built Immersion Wing

  Designate a new data hall extension or a dedicated bay as the immersion zone. Ground slab, secondary water loop, CDU room, and modified suppression system installed to serve only that zone. Existing air-cooled halls untouched. The most common and lowest-risk entry path used by Indian colocation operators today.

• 02

  Phase 2 — DLC Overlay on Existing High-Density Racks

  Direct liquid cooling cold plates fitted to GPUs in existing racks while remaining server components continue air cooling. Facility water loop extended to rack level via manifolds. This requires the existing chilled water system to serve rack-level supply at 18–22°C — most existing 7/12°C plants are compatible with valve adjustment.

• 03

  Phase 3 — Progressive Immersion Conversion

  As servers reach end-of-life, replace air-cooled racks with immersion tanks bay by bay. Structural assessment and slab reinforcement on a bay-by-bay basis. CRAC units on converted bays decommissioned but retained on adjacent bays until full conversion. Phased approach spreads capital cost over 3–5 years.

• 04

  Phase 4 — Unified Warm Water Loop

  Once the majority of capacity is immersion-cooled, a unified secondary water loop (35–45°C) replaces the original chilled water plant serving air-cooled zones. Remaining chilled water capacity retained only for ancillary spaces. Net chiller plant typically reduced by 60–75% of original installed capacity at full conversion.

India-Specific Design Considerations

Designing immersion cooling infrastructure for Indian data centre locations introduces constraints and opportunities not present in European or North American designs.

Ambient Temperature and Free Cooling Hours

Mumbai, Chennai, and Hyderabad ambient temperatures exceed 35°C for 2,000–3,000 hours per year — limiting free cooling on warm fluid loops. Adiabatic pre-cooling of dry cooler inlet air extends free cooling hours economically. Delhi and Pune have more favourable winter profiles. Design the control system to maximise free cooling hours with automated switchover between free cooling and mechanical cooling modes based on ambient wet-bulb temperature.

Secondary Loop Water Quality

Indian municipal water supply carries high TDS in many locations. Secondary water loop requires chemical treatment and softening to prevent scale deposition on CDU heat exchanger plates. Scale buildup of even 0.5 mm increases thermal resistance by 20–40% — a common cause of CDU under-performance discovered only at full load. Specify a closed-loop glycol treatment system with continuous conductivity monitoring.

Fluid Supply Chain and Lead Times

Synthetic ester and engineered dielectric fluids are currently imported into India — no large-scale domestic production exists. For a 1 MW deployment requiring ~40,000 litres of synthetic ester, import lead times of 8–12 weeks must be factored into construction schedules. Maintain a minimum 20% buffer stock volume on site for top-up. Engage with fluid suppliers at design stage to confirm supply availability and local distribution arrangements before committing to a specific fluid type.

Engineering Specification Checklist

Before issuing the MEP design brief for an immersion-cooled data centre, confirm these parameters are resolved:

Conclusion: Infrastructure-First Thinking

Immersion cooling is not a product you install — it is a systems transformation of the facility. The tank itself is perhaps 20% of the engineering challenge. The other 80% is the secondary water loop, the structural engineering, the electrical modifications, the fluid management infrastructure, the fire suppression rethink, and the transition strategy from existing infrastructure.

Facilities that engage MEP consultants at concept stage — before technology selection is locked and before the structural engineer has signed off on a slab that cannot bear the load — complete on schedule with a system that performs as modelled. Facilities that treat immersion as a late-stage product selection discover the infrastructure implications during construction, at maximum cost.

The data centres that will define Indian AI infrastructure in 2027–2030 are being designed today. Immersion cooling is not a future option in that landscape — it is a present requirement for any facility targeting GPU rack densities above 30 kW.