DATA CENTER
LIQUID COOLING

A continuous, measurable path for heat — from the cold source through the CDU to the cold plate.

How the loop runs

The system starts at the IT load and works outwards: cold source, primary distribution, CDU, secondary ring, and the rack itself.

  1. Cold source Tower · dry cooler · chiller
  2. Primary loop Facility-side distribution
  3. CDU Isolates the two sides
  4. Secondary loop Manifolds to the rack
  5. Cold plate / rack Where the heat is made

Precision air conditioning and the liquid loop carry the IT load together; the cold source rejects it continuously.

Cold source

Towers, dry coolers, chillers and condensers combined to suit the climate, the load and the water available.

Dry cooler

Outdoor air cools the liquid in the coil. Modular fans keep it serviceable and the corrosion-resistant build suits open-air siting; fan speed control and adiabatic pre-cooling extend it into hot weather.

Cooling tower

Evaporative rejection, and the efficient choice where water is available. Selection has to account for water quality, consumption, drift control and winter protection.

01 Chiller

Carries year-round or peak mechanical load; selected on supply temperature, efficiency and redundancy.

02 Condenser

For direct-expansion or refrigerant systems, configured by heat rejection, noise and ambient.

03 Free cooling

Uses low outdoor air or water-side free cooling to cut compressor hours.

04 Sequencing

Switches between cold-source modes on load, climate and supply/return temperature.

Primary loop

The facility-side system that ties cold source, pump sets and CDUs into one supply and return.

Prefabricated mains, hydraulic balancing, sectioning valves and online monitoring meet today's load while leaving a clear boundary for phased expansion and for switching a branch out to work on it.

Twin supply and return mains, branch isolation and the key measuring points are laid out together, so flow can be balanced, a fault located and a zone maintained without draining the rest.

  • Large-bore mains prefabricated in the factory, cutting site welding
  • Welds and flange joints inspected as a step in the process
  • Sectioning valves, bypasses and monitoring points detailed together
  • Cross-checked against the CDUs, pump sets and cold-source plant

Secondary loop

Stainless prefabricated pipework, distribution manifolds and quick connectors between the CDU and the rack.

Assembled, cleaned and tested in the factory, then fitted on site as modules. The pipework takes glycol, propylene glycol or deionised water, and integrates ports for temperature, pressure, flow and leak detection. Valves allow a section to be isolated and worked on while the rest keeps running.

Clean delivery

Prefabricated in the factory, which takes the welding and the contamination risk off the site.

Even flow, isolatable

Manifold distribution and sectioning valves: steady supply, and a branch that can be worked on.

Instrumented, extensible

Sensor ports left in place, so the loop grows with the rack count instead of being rebuilt.

CDU

The unit that separates facility water from the fluid touching the servers — and takes on circulation, filtration, make-up, monitoring and control.

01

In-row liquid-to-liquid CDU

The central heat-exchange hub for a mid-to-large liquid-cooled cluster.

Cabinet, circulation pumps, plate heat exchanger, valves, expansion tank, filter and controls. Secondary fluid runs from the CDU to the cold plates, picks up the heat, and hands it to the primary side across the plate exchanger — a closed loop.

  • Dual power feed; single or dual-pump redundancy
  • 10%–100% flow turndown to follow the load
  • Condensation, overpressure and leak protection
  • Optional 25 μm filtration and online water-quality monitoring
  • Automatic make-up; key parts serviceable in place
In-row liquid-to-liquid CDU reference configurations
Item 300 kW600 kW800 kW1400 kW2500 kW
Rated flow L/min450900100012003700
Primary supply32℃32℃32℃32℃32℃
Secondary supply36℃36℃36℃36℃36℃
Flow turndown10%–100%
Supply380–480V
02

Rack-mount liquid-to-liquid CDU

4U, sited next to the IT load so the secondary run stays short.

Where it fits

Integrated liquid-cooled cabinets High-density single racks or small clusters Edge compute and modular data centres
  • 304 stainless pipework — corrosion resistant, serviceable long-term
  • Dual-pump redundancy, flow following the load automatically
  • Modbus / SNMP monitoring, 4.3-inch display
  • Leak detection, automatic make-up, condensation control
  • Optional 50 μm secondary filtration and hot-swap pumps
Rack-mount CDU reference configurations
Item 40 kW80 kW160 kW
Secondary flow L/min6099160
Primary supply35℃35℃30℃
Secondary supply40℃40℃35℃
PumpsDual
Supply220V AC48V DC48V DC
03

Liquid-to-air CDU

A way into liquid cooling for a room that has no facility water to connect to.

Rack-mount L2A

Pumps, a liquid-to-air exchanger, fans, filter, expansion tank and controls. Simple to install, and aimed at single-rack liquid cooling inside a conventional data hall.

  • Reference capacity 16 / 20 kW
  • Dual-pump circulation, 100-mesh secondary filtration
  • Fits OCP ORV3 liquid-cooled racks
  • 220V AC or 48V DC

In-row L2A

Rear-door fans, a liquid-to-air exchanger, pumps, controller and pipework, cooling the fluid with cold-aisle air. Suits high-density rows and retrofits into an existing room.

  • Reference capacity per rack 120 kW
  • Two high-performance pumps
  • N+1 fans, hot-swappable
  • Total draw below 5% of the heat load

Choosing between them Where facility water is not available or the retrofit window is short, L2A is worth evaluating. Where there is a stable cold source, L2L comes first.

Reference configurations transcribed from the GPTECH liquid-cooling brochure. Final model, medium and operating conditions are set by the technical selection document, not by this page.

Precision air conditioning

Room, row and rack level — chosen on the size of the hall, the heat density, the airflow you can organise and the cold source available.

01 Small room unit 17.5–20.2 kW

Small rooms, telecom nodes

02 Modular room unit 25.4–100.4 kW

Scale halls, phased build-out

03 In-row unit 13–60.3 kW

High-density row cooling

04 Rack unit 3.5–12.5 kW

Standalone racks, local hot spots

Room level

The small unit is built for continuous year-round duty in a tight footprint, single-cool or close-control as the site needs. The modular unit covers scale halls and phased projects, with module redundancy, inverter control and several supply-air arrangements.

Close-coupled

In-row units sit in the rack line, pushing cold air straight into the cold aisle and taking hot air back nearby, which removes the losses of a long path. Rack units serve a single enclosure in a closed loop, out of reach of whatever the room air is doing.

Selected on Per-rack heat load, airflow organisation, cold-source type, the temperature and humidity band you can allow, and the redundancy grade.

Monitoring and control

Leak, water quality, condensation and plant sequencing — across the rack, the CDU and both loops.

Leak detection, end to end

Coverage runs from the server and manifold through the CDU to both the primary and secondary pipework. Sensing cable and point sensors are zoned by area, and an alarm can drive valves, pumps or the supervisory system rather than only lighting a lamp.

Online water quality

pH, conductivity and turbidity measured continuously, so degradation, contamination or corrosion shows up as a trend — and a fluid change is scheduled on evidence rather than on the calendar.

01 Condensation control

Operating limits move with supply temperature, room conditions and dew point.

02 Plant sequencing

CDU, pumps, valves, cold source and BMS held to one operating mode.

03 One view

Temperature, pressure, flow, water quality, alarms and plant state on one screen.

04 Running it well

Load tracking and inverter control, to cut the hours spent running inefficiently.

From brief to handover

Six stages, each with an input, an output and something to verify — so equipment interfaces and system boundaries do not come apart at the seam.

  1. 01 Brief

    Heat load, room conditions, cold source, redundancy and growth targets

  2. 02 Design

    System boundary, hot and cold paths, pipe sizing and hydraulics, control logic

  3. 03 Selection

    CDU, ring mains, cold-source plant and precision AC matched to the duty

  4. 04 Detailing

    Drawings, BOM, interface review, factory assembly and test

  5. 05 Install & commission

    Site connection, hydraulic balancing, alarm and mode-switch verification

  6. 06 Support

    Training, maintenance plan, spares advice and continuing technical response

The delivery rule Clear boundaries · clear interfaces · clear responsibility · clear verification.

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HEAT LOAD

Rack density, room conditions and the cold source you have — enough to come back with a loop.

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