How data center liquid cooling works

Start with heat at the GPU

Electrical power used by computer hardware becomes heat that must be removed. A cold plate provides a path from a hot component into circulating coolant. In a cold-plate system, the coolant stays inside sealed passages rather than washing over the electronics. This differs from immersion cooling, where compatible equipment is submerged in a specially selected fluid.

Supply and return form one circuit

Supply carries relatively cooler fluid toward the equipment. Return carries fluid that has absorbed heat away from it. Cool and warm are relative terms; this model does not specify operating temperatures. Blue and orange distinguish those directions in the explorer. Moving markers illustrate circulation, not actual balls or air bubbles travelling through production plumbing.

The server loop reaches a CDU

The server-side circuit connects cold plates and distribution plumbing to a coolant distribution unit, or CDU. Pumps circulate coolant, while controls monitor conditions needed for the equipment. A real installation also needs provisions for fluid quality, pressure management, leak detection and maintenance. The simplified 3D model shows the main heat-transfer route rather than every valve and sensor.

Two loops exchange heat without mixing

In the modeled arrangement, a heat exchanger in the CDU transfers heat from server coolant to a separate facility-water circuit. A physical barrier separates the fluids. This allows each circuit to be managed for its own operating requirements. The CDU is a heat-transfer interface: it does not itself dispose of all the heat outdoors.

Outdoor equipment completes the heat path

Facility water carries heat toward outdoor heat-rejection equipment. Depending on the installation, this can involve dry coolers, cooling towers, chillers or combinations of equipment. The explorer uses a simplified outdoor unit. Visible cooling water does not automatically imply evaporative water consumption: a circulating closed loop and water evaporated at a cooling tower are different things.

Fans can still be necessary

Cold plates may cool GPUs while CPUs, memory, storage, power supplies or other components use air cooling, depending on the design. Containment helps keep warm exhaust from mixing with cooler supply air. Liquid and air systems therefore often coexist. A liquid-cooled rack should not be interpreted as a rack with no remaining airflow or room-cooling requirements.

Read the explorer’s cooling view

Choose Cooling under Explore a system. Trace the outdoor unit to the CDU, then trace the separate supply and return lines serving the racks. Transparent pipes reveal the direction markers; their transparency is an educational aid. The geometry is schematic, and the animation does not calculate flow rate, pressure drop, water consumption or cooling efficiency.

Connect the steps

Follow heat across two separate circuits

Imagine tracing a drop of server coolant. It can circulate through the cold plates and back to the CDU, but it does not need to travel through the outdoor cooler. Heat crosses the CDU heat exchanger into a second fluid circuit. The water routes in this model show one possible design; other facilities use different combinations of air and liquid cooling.