Two-Phase Immersion Cooling

Two-phase immersion cooling removes heat by submerging electronic components in an electrically non-conductive dielectric liquid that boils at operating temperatures. It is called two-phase because the coolant repeatedly changes between liquid and vapour while transporting heat away from the equipment.

Heat removal through phase change

Heat from processors and other components raises the nearby liquid to its boiling point. The liquid then absorbs energy as latent heat of vaporisation, expressed as Q = mL, while changing into vapour with little temperature change.

• Boiling occurs most strongly near hotter surfaces, carrying heat directly away from those locations.
• Because phase change absorbs substantial energy without requiring a large rise in temperature, component temperatures can remain comparatively uniform.

Cooling cycle

The generated vapour rises to a condenser, where heat is transferred to air or a secondary liquid-cooling circuit. The vapour releases latent heat, condenses back into liquid and returns to the immersion bath, completing a closed cycle.

• The bath coolant circulates mainly through boiling, vapour movement, condensation and gravity-driven return.
• Heat ultimately leaves the system through the condenser; immersion merely provides the efficient internal path from components to that heat-rejection system.

Design requirements and distinction

The fluid must have a suitable boiling point, strong electrical insulation and compatibility with circuit boards, seals and other materials. Condenser capacity must match the equipment heat load so that vapour is continuously condensed.

• Unlike single-phase immersion cooling, which keeps the coolant liquid and removes sensible heat through circulation, two-phase cooling deliberately uses boiling and condensation.
• Fluid containment, pressure control, material compatibility and environmental and safety properties are important engineering considerations.