Chiller to Chip: Glycol Selection and the Role of Castrol ON Primary Cooling Fluid DTX

Thermal fluids are at the heart of every primary cooling system (from a full infrastructure perspective). In most data centres, this is a glycol-water mixture, and its selection has a direct impact on cooling efficiency, pumping energy, safety and environmental risk.

Glycol does far more than provide freeze protection. It alters the thermal and physical properties of water, influencing heat transfer performance, viscosity and hydraulic behaviour across the entire primary cooling system infrastructure (chillers, facility cooling loops, dry coolers and hybrid heat rejection systems etc). In continuously operating data centres, these characteristics directly affect efficiency and Power Usage Effectiveness (PUE).

For modern hybrid and AI-driven data centres, this trade-off is increasingly restrictive.

Historically, designers have faced a compromise:

• Ethylene Glycol (EG) delivers strong thermodynamic performance and low viscosity, supporting efficient pumping and heat transfer, but introduces toxicity and environmental compliance risks.
• Propylene Glycol (PG) offers significantly lower toxicity and improved safety alignment, but typically with higher viscosity and reduced heat transfer efficiency.

Castrol ON Primary Cooling Fluid DTX has been developed specifically for data centre closed-loop cooling systems to address this challenge. It combines the low toxicity characteristics of propylene glycol with thermodynamic and hydrodynamic performance that closely approaches ethylene glycol. This enables operators to reduce pumping penalties, maintain predictable flow behaviour and improve safety — without sacrificing cooling efficiency.

In Chiller to Chip architectures, where the same primary cooling system supports air cooling, direct-to-chip and immersion systems, this balanced fluid performance is critical. Glycol selection is therefore a strategic engineering decision, not a commodity purchase.