Immersion cooling
Beginner
Dunking whole computers in a special liquid that doesn’t carry electricity. The liquid soaks up all their heat.
Novice
Servers sit in a tank of dielectric (electrically insulating) fluid. In single-phase immersion an oil-like fluid is pumped to a heat exchanger; in two-phase immersion a fluid boils on the hot parts and condenses on a coil above.
Expert
Captures nearly all heat with no server fans and tolerates high temperatures, but complicates service (lifting boards out of fluid), material compatibility and warranties. Many two-phase fluids are fluorinated chemicals, whose supply is shrinking under PFAS pressure.
Explained in Power and cooling (Systems).
See also: Direct-to-chip liquid cooling (cold plates).