Immersion Cooling Tank For Data Center: Single-Phase And Two-Phase Tank Design
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Immersion Cooling Tank For Data Center: Single-Phase And Two-Phase Tank Design
An immersion cooling tank for a data center is the containment vessel that holds servers fully submerged in dielectric fluid, transferring their heat directly to the liquid instead of to air. In single-phase immersion the fluid is pumped away to be cooled and returned; in two-phase immersion the fluid boils at the chip and the vapour condenses back to liquid within the tank. The tank is a leak-tight, often custom vessel whose material, sealing and fluid compatibility dominate the design — stainless steel and custom fabricated vessels are typical, with ASME construction referenced where the design is pressurised and ISO 28765 relevant where a vitreous-enamelled shell is considered.
Immersion cooling moves heat removal from the air side to the liquid side by submerging the server in a dielectric fluid that does not conduct electricity. The "tank" is therefore not a water store but the primary thermal and mechanical enclosure of the IT itself. Get the vessel wrong — a leaky seam, an incompatible gasket, a tank that cannot contain a fluid spill — and you have turned a cooling advantage into a containment liability. The two architectural choices, single-phase and two-phase, change the tank's internals, pressure regime and material demands. Specifiers need to understand both before selecting a vessel.
This guide works the immersion cooling tank for a data center from containment through the single-phase / two-phase split to material and leak control.
The Tank As Dielectric-Fluid Containment
An immersion tank is first a sealed vessel that contains a dielectric fluid and the servers within it; its primary job is leak-tight containment, not structural water storage. Every joint, sight glass and penetrator is a potential leak path.
1. Fluid boundary. The tank wall and lid form the primary containment of the dielectric fluid, which must not escape to the data hall floor or the electrical envelope.
2. Server enclosure. The tank also houses the IT; its geometry, rack interface and access covers are part of the vessel design, not an add-on.
3. Secondary containment. A drip or bunded layer beneath or around the tank captures minor leaks so a seal failure is a maintenance event, not an outage.
Because the fluid is valuable and the hall is sensitive, containment integrity and serviceability are designed in from the first sketch.
Single-Phase Versus Two-Phase Immersion
The defining design split is whether the dielectric fluid changes phase at the chip, and that choice reshapes the entire tank. Single-phase and two-phase tanks are different machines.
· Single-phase immersion. The fluid stays liquid; it absorbs heat, is pumped to an external heat exchanger (often via a CDU), cooled, and returned. The tank is essentially a leak-tight bath with inlet/outlet manifolds and no internal boiling — lower internal pressure, simpler vapour management.
· Two-phase immersion. The fluid boils at the hot component, vapour rises, and a condenser coil or surface inside the tank returns it to liquid. The tank must manage vapour space, condensation, and a pressure regime that can be above atmospheric, with stronger sealing and often a pressure-rated vessel.
· Trade-offs. Single-phase is simpler and easier to seal; two-phase has higher heat-transfer density but a more complex, pressure-aware vessel.
The choice drives material grade, sealing philosophy and whether the vessel needs pressure-vessel classification.
Aspect | Single-phase | Two-phase |
Fluid state | Liquid only | Boiling + condensing |
Internal pressure | Near atmospheric | Can exceed atmospheric |
Vapour management | Minimal | Condenser + vapour space |
Vessel complexity | Lower | Higher, pressure-aware |
Leak Containment And Fluid Compatibility
Dielectric fluid must be contained and must not degrade the tank, so the vessel material, seals and any coating are selected for fluid compatibility and long-term leak resistance. Immersion fluids are engineered liquids, not water.
· Stainless steel shell. 304/316 stainless is the common custom-vessel material, inert to most immersion dielectric fluids and capable of precise, weld-tight fabrication.
· Seals and gaskets. Fluoropolymer or fluid-rated elastomers at lids and penetrators; the seal selection is validated against the specific fluid to avoid swelling or leaching.
· Coatings where used. If any internal coating is applied, it must be fluid-compatible and non-contaminating to the dielectric; ISO 28765 vitreous enamel may be relevant where a lined shell is considered, but fluid compatibility governs.
· Bund and leak detection. A secondary containment layer and leak sensing turn a slow seep into an early alarm.
Fluid compatibility is verified, not assumed, because a reactive seal or coating can foul the dielectric and the servers it protects.
Material And Fabrication Route
Immersion tanks are typically custom fabricated vessels, and the fabrication route follows the pressure regime and fluid demands. Stainless dominates; pressure-rated construction is referenced where the design requires it.
· Stainless custom fabrication. Passivated 304/316 vessels with welded, leak-tight seams; the default for both single- and two-phase units where pressure is modest.
· ASME-rated construction. Where the two-phase vapour space or system design places the vessel under significant pressure, construction is referenced to the ASME Boiler and Pressure Vessel Code (Section VIII) so the shell, lid and relief are properly classified.
· ISO 28765 relevance. Where a vitreous-enamelled (GFS) shell is considered for any lined variant, the enamelled-tank design standard applies; immersion duty more often uses stainless, but the standard is available where relevant.
· Access and service. Covers, lifting points and drain provisions let servers be inserted, removed and the fluid changed without breaching containment.
Documenting the fabrication standard and fluid validation prevents a vessel that looks right but cannot be classed or serviced.
Material / route | Best fit | Standard reference |
Stainless 304/316 | Custom single/two-phase vessel | Material cert, weld QA |
ASME-rated vessel | Pressurised two-phase design | ASME BPVC Section VIII |
GFS-lined variant | Where lined shell considered | ISO 28765 |
Sizing And Layout Considerations
An immersion tank is sized by the server load it must submerge and the fluid volume needed for heat capacity and component coverage, not by a water-storage logic. Two inputs dominate.
4. Server and rack geometry. The tank internal layout follows the IT form factor; volume is set by how many boards must be submerged and their spacing for flow.
5. Fluid inventory. Enough dielectric to cover components with margin, provide thermal capacitance, and (single-phase) feed the external loop without cavitation.
6. Heat-exchange interface. Single-phase needs manifold space for pumped flow; two-phase needs vapour space and condenser area sized to the boil-off rate.
The vessel is therefore an IT-integrated enclosure first and a tank second, and its specification is written with the server vendor, not in isolation.
Project Case
A dedicated data-center immersion-cooling reference is not yet part of the delivered portfolio, so this article is written as engineering guidance rather than a project citation. The company's capability to supply custom fabricated and lined vessels is demonstrated in adjacent sectors: overseas fire-protection programs have delivered GFS tanks up to 12,261 m³ (India, 3 tanks, 2024-06) and 1,666 m³ (Singapore, 2 tanks, 2026-01), built to the same bolted-tank standards an immersion cooling tank's containment philosophy is related to. Those references evidence large-volume vessel supply and QA; they are fire-protection projects, not data-center immersion installations, and are cited here only as capability context.
Center Enamel Engineering Capability
Center Enamel (Shijiazhuang Zhengzhong Technology Co., Ltd) has designed and fabricated bolted storage tanks since 2008. As the first glass-fused-to-steel (GFS) tank manufacturer in China, the company holds close to 200 enamel-related patents, produces roughly 300,000 enamel-coated steel plates a year, has completed more than 30,000 installed projects and supplies its tanks to over 100 countries. The new 150,000 m² production base was added to raise output capacity, and single tanks are supplied up to 60,000 m³. Manufacturing runs under ISO 9001 and ISO 45001, with product certification including NSF/ANSI 61, WRAS, FDA, LFGB, CE (EN 1090), ISO 28765, FM, BSCI and EUROCODE, and design referenced to ASME, ISO 28765 and AWWA D103-09 where the application requires it.
For immersion-cooling containment the company supplies custom stainless and lined vessels with leak-tight fabrication, fluid-compatible seals and secondary containment, and provides material and fabrication documentation for review.
Frequently Asked Questions
Q1: Is an immersion tank a water tank?
A1: No. It is a sealed vessel that contains a dielectric fluid with the servers submerged in it; its job is leak-tight containment and heat transfer, not water storage.
Q2: What is the difference between single-phase and two-phase?
A2: Single-phase keeps the fluid liquid and pumps it to an external cooler; two-phase lets it boil at the chip and condense back inside the tank, requiring vapour management and often a pressure-aware vessel.
Q3: What material is the tank made from?
A3: Usually stainless steel (304/316) custom-fabricated for leak-tight containment; ASME-rated construction is referenced where the design is pressurised, and a GFS-lined variant may use ISO 28765 where relevant.
Q4: Why is fluid compatibility critical?
A4: The dielectric fluid must not degrade seals, gaskets or any coating; an incompatible seal can swell or leach and foul the fluid and the servers, so compatibility is verified, not assumed.
Q5: How is leak risk managed?
A5: Through weld-tight stainless fabrication, fluid-rated seals, secondary bund/containment and leak detection, so a slow seep becomes an early alarm rather than a hall-floor spill.
Q6: Is two-phase immersion pressurised?
A6: It can operate above atmospheric because of the vapour space and boiling, so the vessel and its relief are often classified to ASME where the pressure regime requires it.
Q7: How is an immersion tank sized?
A7: By the server/rack geometry to be submerged, the dielectric fluid inventory for coverage and thermal capacitance, and the heat-exchange interface (manifolds for single-phase, vapour space and condenser for two-phase).
An immersion cooling tank for a data center is the dielectric-fluid containment vessel that makes direct liquid cooling possible, and its design turns on the single-phase versus two-phase split. Choose stainless custom fabrication for leak-tight containment, validate every seal and coating against the dielectric fluid, add secondary containment and leak detection, and reference ASME or ISO 28765 where the pressure regime or lined variant demands it. Specified that way, the tank is a reliable enclosure for the IT rather than a hidden liability.
Talk to an Engineer
For an immersion cooling tank for a data center, send us the server/rack geometry to be submerged, the dielectric fluid specification, whether you plan single-phase or two-phase, and any pressure-regime or relief requirements. We will return a stainless or lined vessel specification with fluid-compatible seals and secondary containment, a sizing study for fluid inventory and heat-exchange interface, and fabrication documentation referenced to ASME and ISO 28765 as needed.
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