# Immersion Cooling Immersion cooling removes the question of where to put the plumbing by putting the computer in the liquid. Boards sit submerged in a bath of electrically non-conductive fluid, which carries heat away from every component at once: processors, memory, voltage regulators, and network interfaces together. It is the most thermally complete answer available, and its costs are operational rather than thermal. > [!note] The one-sentence version > Put the whole board in a fluid that does not conduct electricity, and every hot thing on it is cooled without a single cold plate or fan. ## Why it exists Cold plates cool the components they are attached to and leave the rest to air, so a liquid-cooled rack still runs an air system for its residue; see [[wiki/Air Cooling|Air Cooling]]. Immersion captures everything, eliminates fans entirely, removes the acoustic and vibration problems that come with them, and holds every component at a uniform temperature, which is good for reliability. It also allows extremely dense arrangements, because the geometry no longer has to leave air channels. ## Prerequisites - **Dielectric fluid:** a liquid that does not conduct electricity, so live electronics can sit in it. Single-phase baths typically use synthetic or mineral-based hydrocarbon oils; two-phase systems use engineered fluorinated fluids chosen for their boiling point. - **Single-phase:** the fluid stays liquid, is circulated by pump through a heat exchanger, and carries heat by rising temperature. - **Two-phase:** the fluid boils at the component surface, absorbing a large amount of heat as latent heat of vaporization, and condenses on a coil above the bath. It handles higher heat flux and requires a sealed, pressure-managed vessel. - **Materials compatibility:** every gasket, label, thermal pad, optical transceiver, and plastic clip in the bath must tolerate the fluid for years; qualification is the central engineering task. - **Fluid handling:** drip trays, lifting gear, and drain time, because a board removed from a bath is wet and must be handled. ## How it works Servers, usually stripped of fans and heatsink shrouds, are mounted vertically in a sealed tank. Fluid circulates past them, either pumped through a heat exchanger that transfers the heat to a facility water loop, or in a two-phase tank by boiling at the components and condensing against a water-cooled coil overhead. The facility side is comparatively simple, because the tank presents a single warm water connection. Maintenance is where the design is felt: a board is lifted out with a hoist, allowed to drain, serviced, and reinstalled, which is a different operation from sliding a tray out of a rack. ## Where it fits Immersion is well established in specific settings: high-density computing where every watt of fan power matters, edge installations where sealed enclosures suit a harsh or unattended environment, and deployments where a uniform component temperature is prized. In mainstream accelerator facilities, cold plates have taken the production default, because they preserve conventional serviceability and because accelerator vendors ship trays with plates pre-installed. Immersion's advocates have the stronger thermal argument; cold plates have the stronger operational one, and operations usually decide. ## Stack position - **Upstream:** facility water, fluid supply and reclamation. - **Downstream:** every component on the board. - **Function and vendor:** one of three valid liquid approaches alongside cold plates and rear-door exchangers; the choice follows density, serviceability, and the hardware vendor's support. - **Degraded case:** a facility choosing immersion inherits a different maintenance regime and a materials-qualification obligation; a facility choosing against it accepts an air system for the residue. ## Lineage and trajectory Oil immersion is old; transformers have been immersed since the nineteenth century, and immersed computing appeared in supercomputing decades ago. The modern revival came from cryptocurrency mining, where fan power and density dominated economics, and moved from there into high-performance and edge computing. The trajectory depends substantially on fluid chemistry, since environmental and regulatory attention to certain fluorinated fluids has pushed two-phase development toward alternative chemistries, while single-phase hydrocarbon systems continue to deploy steadily. ## Relationships - **alternative to:** [[wiki/Direct-to-Chip Liquid Cooling|Direct-to-Chip Liquid Cooling]] · [[wiki/Air Cooling|Air Cooling]] - **part of:** [[wiki/Data Center Cooling|Data Center Cooling]] - **connects to:** [[wiki/Chilled Water Plant|Chilled Water Plant]] · [[wiki/Heat Reuse|Heat Reuse]] - **applied in:** [[wiki/Edge Inference|Edge Inference]] - **source articles:** [[articles/Vertically Integrating an AI Superpower from AI Factory to Citizen|Vertically Integrating an AI Superpower from AI Factory to Citizen]] · [[articles/The Gigawatt Is the New Measure of War|The Gigawatt Is the New Measure of War]] - **collection route:** [[collections/American Infrastructure|American Infrastructure]] · [[collections/American|American Collection]] ## Evidence posture - **Established:** single-phase and two-phase immersion operation; dielectric fluid classes; materials compatibility as the central qualification task; fan elimination and uniform component temperature; hoist-and-drain maintenance; deployment in high-density, edge, and mining installations. - **Established (datestamped):** as of October 2026, cold-plate direct liquid cooling is the production default in mainstream accelerator facilities while immersion serves specific settings. - **Unresolved:** the long-term role of two-phase immersion given regulatory attention to certain fluorinated fluids; the deciding evidence is the qualification of alternative chemistries at production scale. ## Sources - Thermal engineering literature and vendor documentation on single-phase and two-phase immersion systems, as of October 2026.