Cooling & Water for data centers in India

Designing for an Indian summer and an AI hall

Thermal design in India starts from two facts. Ambient temperatures exceed 40 degrees for weeks in most metros, so free cooling delivers a few hundred hours a year and chiller capacity must be rated at 45 degrees, not at the standard conditions on a catalogue page. And rack densities have moved from 6 to 8 kW for enterprise workloads to 40 kW and beyond for GPU clusters, with the latest accelerators exceeding 100 kW per rack.

Air cooling with containment and raised supply temperatures remains the right answer for storage, network and general compute rows up to roughly 25 to 30 kW per rack. Above that, direct-to-chip liquid cooling through coolant distribution units, or immersion, becomes the design basis. Most new Indian campuses are being designed as hybrid halls: an air-cooled envelope with a facility water loop and CDU connections ready for liquid-cooled rows.

The design target that matters commercially is PUE at the sold load, not at nameplate. A well-executed air-cooled facility in an Indian metro lands between 1.4 and 1.6; liquid cooling with warm-water loops at 30 to 40 degree supply can bring high-density halls below 1.3 and cuts the chiller energy that drives the rest.

Plant selection

Chilled water with water-cooled chillers and cooling towers gives the lowest energy use but the highest water consumption. Air-cooled chillers or dry coolers eliminate most water at a PUE penalty of roughly 0.1 to 0.2 in Indian conditions. Adiabatic assist and hybrid coolers sit between. The choice is a water decision as much as an energy one, and it should be made with a contracted water supply in hand.

Specify chillers by part-load performance at the site's actual ambient profile rather than by nameplate capacity. Magnetic-bearing centrifugal and high-efficiency screw machines with variable-speed drives earn their premium in India because the plant spends most of its life between 30 and 70 percent load. Demand the manufacturer's performance curves at 45 degrees and N+1 redundancy at that condition.

In the white space, CRAH units on the chilled-water loop with EC fans and containment are the standard; direct-expansion CRAC units suit small or edge facilities. Raise the supply air temperature to the top of the ASHRAE allowable range for the equipment class; every degree of warmer supply reduces chiller energy and extends economiser hours.

Liquid cooling: what to specify

A liquid cooling package has four parts: the facility water loop (treated, filtered, at a controlled supply temperature), the coolant distribution units that isolate the technology loop, the rack-level manifolds and cold plates or rear-door heat exchangers, and leak detection with automated isolation. Specify CDU redundancy per row, pressure and flow monitoring with BMS integration, and a water quality regime, because cold-plate loops are unforgiving of corrosion and biological growth.

Immersion cooling, single-phase in practice, suits homogeneous high-density compute where the operator controls the hardware. It brings its own fluid handling, hardware compatibility and maintenance considerations and is less common in multi-tenant colocation. India now has integrators with delivered references above 80 kW per rack in both direct-to-chip and immersion; verify those references by visit.

Water: supply, treatment and discharge

A 20 MW evaporatively cooled facility consumes 1 to 2 million litres of make-up water a day in summer. Municipal supply is unreliable in several metros and tanker supply is expensive and insecure, so the serious options are a contracted treated or recycled supply from a municipal sewage treatment plant, on-site treatment of borewell or surface water, or dry cooling. Water usage effectiveness, in litres per kWh of IT energy, is becoming a reportable metric for customers and a consent condition for pollution control boards.

The treatment chain is sized for the cooling towers' cycles of concentration: softening or reverse osmosis for make-up, side-stream filtration, chemical dosing, and blowdown handling. Where discharge is restricted, zero liquid discharge through evaporators or crystallisers adds capital and operating cost but removes a consent risk that has stopped projects in Tamil Nadu and Karnataka.

Procurement sequence and evaluation

Chillers, cooling towers and large pumps lead at 5 to 8 months and should be ordered against a performance specification before the mechanical contractor is appointed. CRAH units from Indian manufacture run 3 to 5 months; CDUs and liquid cooling kits 4 to 7, with integrator capacity rather than hardware as the constraint. Water treatment plants are typically 4 to 6 months including civil work.

Evaluate bids on performance at Indian ambient, controls integration (chiller plant optimisation, BMS protocols, leak detection), commissioning support and service presence. Chillers are the most frequent cause of thermal events in operation, so an OEM technician within the city and compressor and pump spares in stock are worth more than a few percent on price.