Closed-Loop Cooling Can Still Use Water: Read the Facility Boundary

Separate fluid circuits can share a heat path

A technology cooling system carries heat away from selected IT components in circulating coolant. In a liquid-to-liquid CDU, an exchanger can transfer that heat to a separate facility-water circuit without mixing the two fluids. CoolIT describes this separation in its CDU overview. The coolant returning toward the IT equipment and the facility water carrying heat onward belong to different circuits.

That separation explains how a closed technology loop can coexist with water use elsewhere. Keeping its coolant inside one circuit says nothing by itself about the next system's water balance. Heat transfer and water transfer are different events: the facility can receive the heat without receiving the technology-loop fluid.

For a buyer, closed-loop is therefore an incomplete basis for a facility-wide water claim. Identify which circuit the term describes and follow the heat beyond its exchanger.

References: [C1]

Where replacement water enters the cooling chain

FEMP's Figure 1, dated January 9, 2019, illustrates air-cooled IT racks, room cooling, chilled water, a chiller, condenser water and an evaporative cooling tower. Heat passes through those stages to the atmosphere. This is the source's illustrative air-cooled-IT arrangement, rather than a diagram of every direct-liquid-cooled installation.

At the tower, evaporation removes heat and water leaves as vapor. Some circulating water is also discharged as blowdown to limit dissolved-solids concentration. FEMP's separate cooling-tower overview identifies makeup water as replacement for water leaving the tower. Recirculation and replacement can consequently occur in the same system.

A claim about retained fluid in an upstream circuit does not account for those downstream flows. Equally, the existence of water circulating in a system does not prove that it has an evaporative tower. The complete heat-rejection arrangement determines which water flows need to be explained.

References: [F1][T1]

Distinguish circulation, supply and consumption

Circulation describes fluid moving through a circuit. Counting every passage through a pipe as new water would repeatedly count recirculated fluid. A circulation flow and the volume of replacement water supplied during a year therefore answer different questions.

The USGS glossary defines withdrawal as water removed from a groundwater or surface-water source for use. It defines consumptive use as the withdrawn portion evaporated, incorporated into products or otherwise removed from the immediate water environment. Water delivered to a facility is another accounting location: it may come through a public supplier rather than a withdrawal made at the facility itself.

These distinctions matter at an evaporative tower. Evaporated water fits the consumptive-use definition. Blowdown leaves that cooling circuit as liquid; classifying its subsequent hydrological fate requires the actual discharge and return-flow boundary. A tower's makeup volume must not automatically be relabeled as its evaporated volume or as hydrological consumption.

Ask what a reported water total measures: source withdrawal, facility delivery, tower makeup or consumption under a stated definition. Preserve that meaning when comparing claims.

References: [U1][T1]

No facility-water connection is an interface claim

A liquid-to-air CDU can reject heat into room air without a facility-water connection at that unit. Eaton explicitly describes reliance on data-center air conditioning for this arrangement. The technology loop can still contain liquid; the omitted connection is between the CDU and facility water.

The room-cooling system has its own downstream heat path. If that path uses an evaporative tower, the tower's water use remains relevant even though the CDU has no facility-water connection. This is a conditional illustration, not a claim about every liquid-to-air installation.

Dry heat rejection and hybrid arrangements also exist. A 2018 NREL report describes a refrigerant-based dry cooler alongside existing cooling towers. That historical architecture shows why the presence of a dry device alone does not establish a wholly non-evaporative facility.

Read no-water language for its coverage: the CDU interface, the cooling plant, a stated operating mode or the whole site's annual use. A narrower statement needs additional evidence before it can support a broader one.

References: [E1][N1]

Read annual site WUE with its inputs

FEMP states site water usage effectiveness as annual site water usage in liters divided by annual IT-equipment energy in kWh. The resulting unit is L/kWh. It is neither a percentage nor liters per kW; the denominator is IT energy accumulated over the year.

Keep both input totals with the ratio. For comparisons, establish the same reporting period, included site boundary and water-accounting definition. A site-water numerator must not silently become an evaporation-only estimate, and an IT-energy denominator must not become total facility energy.

WUE makes the water total relative to IT energy. It does not replace the total when the question is how much water was used within the reported boundary.

References: [F1]

A fictional comparison: less total water, higher WUE

Consider two entirely fictional annual reports, A and B. Assume the same one-year period, equivalent site boundaries and the same definition of annual site water usage. Stipulate that each report includes the corresponding IT-equipment energy for that boundary. These are invented accounting inputs, with no represented facility, measurement or industry benchmark.

A reports 2,000,000 liters and 1,000,000 kWh of IT energy. Dividing those stipulated inputs gives 2 L/kWh.

B reports 1,200,000 liters and 400,000 kWh of IT energy. Its corresponding ratio is 3 L/kWh.

B has the lower annual water total and the higher water intensity. Its IT-energy denominator is smaller as well, so the lower water total alone does not produce the lower ratio. Conversely, A's lower ratio does not mean A used fewer liters. The ranking changes with the question being asked.

Neither ratio establishes peak water demand, available supply, local scarcity, water quality or water associated with electricity generation outside the site. Nor does either report contain the workload accounting needed to assign water consumption to a particular prompt. Those questions require information beyond these stipulated annual totals.

Compare the claim you are buying

For an equipment offer, a statement that no facility-water connection is needed at the CDU can be useful interface information. For a facility offer, the useful explanation continues through the receiving cooling system and identifies any evaporative stages. For an annual water-performance comparison, the useful return contains the reporting boundary, defined water total, IT-energy total and period. These are distinct answers, even when the proposal uses one low-water headline.

A no-water assertion should identify the uses and operating conditions it covers. A low-water comparison should identify its baseline and equivalent boundaries. Neither a closed-loop label nor one annual ratio supplies that missing scope. The evidence can support a precise claim without establishing an environmental certification or deciding which site should be selected.

The customer's appointed cooling and facility parties determine the actual architecture, requirements and water-supply assessment. Leviathan does not perform, coordinate or subcontract liquid-side work or offer a water-use audit. Its rack-and-stack service concerns separately agreed physical IT equipment mounting, IT cabling, labels, physical checks and handoff records.

For that surrounding installation package, use the linked rack-and-stack project inquiry to share the exact IT equipment, rack and cable inputs, requested physical tasks and customer-defined facility prerequisites. Identify the appointed cooling contacts so the physical work can be discussed against the actual interfaces, scope and availability.

References: [L1][L2]