Immersion Cooling

Immersion cooling places entire server boards, with or without modification, into tanks containing a non-conductive dielectric fluid. Heat is transferred directly from components to the fluid, eliminating the need for fans and dramatically improving thermal efficiency.

Two variants exist. Single-phase immersion uses a fluid (typically engineered fluorocarbon or synthetic oil) that remains liquid; heat is removed by pumping fluid to an external heat exchanger. Two-phase immersion uses a fluid with a low boiling point — vapour bubbles form at hot components, rise to a condenser at the top of the tank, and liquid rains back down. Two-phase offers higher heat flux capability but is more complex to operate and has higher fluid cost.

Immersion cooling can support rack densities of 200 kW and above, enables the use of much warmer supply temperatures (up to 45°C), and eliminates fan power. Server vendors are increasingly certifying hardware for single-phase immersion, making it more accessible for production AI workloads.