As AI workloads increase server heat density, liquid cooling is moving from an optional data-centre feature to an important route for high-performance computing. Yet “server cooling fluid” is not one fixed chemical product. Water-based, silicone-based, hydrocarbon, ester and phase-change fluids can have very different properties and SDS hazards.

Why use liquid cooling?

Air has limited heat capacity and thermal conductivity. At high rack power, increasing airflow adds noise and fan energy without always delivering enough cooling. Liquids can carry more heat and shorten the path between the heat source and the heat exchanger. The engineering goal is to balance thermal performance, electrical safety, material compatibility, maintainability and lifecycle cost.

Three common cooling architectures

Cold-plate cooling

Water, water-glycol or another coolant circulates inside a plate attached to CPUs or GPUs. The fluid normally does not contact the circuit board, so leak prevention, corrosion, microbial control and long-term compatibility are central.

Single-phase immersion

Equipment is immersed in a dielectric liquid that remains liquid as it absorbs heat. Candidate fluids include silicone liquids, hydrocarbon oils, synthetic oils and esters. Important parameters include insulation performance, viscosity, flash point, volatility, oxidation stability and compatibility with seals, plastics, coatings and cables.

Two-phase immersion

A dielectric fluid boils at the equipment surface, condenses and returns to the bath. Phase change transfers heat efficiently but creates stricter requirements for containment, recovery, environmental assessment and maintenance.

Properties that must be evaluated

• thermal conductivity and specific heat;
• viscosity and pumping energy;
• boiling point, freezing point or pour point;
• flash point, combustion behaviour and volatility;
• dielectric strength and its sensitivity to moisture and contamination;
• acid value, purity and batch consistency;
• compatibility with copper, aluminium, solder, elastomers, plastics and coatings;
• oxidation, thermal ageing, waste recovery and environmental impact.

A transparent appearance does not prove that a fluid is safe or suitable. Products that look like water may differ completely in conductivity, flammability, toxicity and disposal requirements.

What is special about silicone-based fluids?

Silicone fluids can offer good electrical insulation, a broad operating-temperature range, low surface tension and chemical stability. However, base structure, viscosity grade, low-molecular-weight volatiles, additives, impurities and water content all affect performance. A high flash point does not mean non-combustible, and leaked silicone fluid can create a serious slip hazard.

SDS and TDS serve different purposes

An SDS communicates hazards, composition, first aid, firefighting, spill response, handling, PPE, transport and regulatory information. A technical data sheet (TDS) describes performance such as viscosity, thermal conductivity, heat capacity, dielectric properties and test methods. Neither replaces the other. Equipment selection should also consider compatibility and ageing reports and the equipment manufacturer's requirements.

What should be reviewed in the SDS?

1. Section 1: identify whether the product is for cold plates, single-phase immersion or two-phase service.
2. Section 2: classify the actual formulation. “Not classified as hazardous” does not mean risk-free.
3. Section 3: disclose required hazardous ingredients while protecting legitimate confidential information.
4. Sections 5 and 6: address fire, decomposition products, ventilation, slip hazards, recovery and environmental release.
5. Sections 7 and 8: cover moisture and particle control, container closure, temperature, static control and maintenance exposure.
6. Section 9: provide product-specific physical data and test conditions instead of copying raw-material values.
7. Section 10: state incompatible materials, conditions to avoid and hazardous decomposition products.
8. Sections 11-15: assess health, environmental, disposal, transport and target-market requirements.

Before entering the liquid-cooling market

Define the target cooling architecture; control moisture, particles, acid value and batch consistency; complete thermal, electrical, ageing and compatibility tests; align the SDS, label and TDS; prepare spill and fire procedures; establish a waste-fluid route; and separately review the requirements of each sales market.

Sources

• ASHRAE Datacom Series
• Open Compute Project: Advanced Cooling Solutions

Related services: Read our SDS FAQs or contact us for cooling-fluid SDS and multi-market compliance support.

Disclaimer: This article is general information and is not product-selection advice, equipment certification, legal advice or a formulation-specific SDS. Assess the actual composition, test data, equipment and target-market rules.