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Cooling

Delta-T

ΔT

The temperature difference between the supply and return of a cooling circuit; a key indicator of how efficiently heat is being transferred.

Unit: Kelvin (K) or °C

Full Definition

<p>Delta-T (ΔT) is the temperature differential between the supply and return of a fluid circuit — chilled water, condenser water or coolant in a CDU loop. A higher ΔT on the chilled water side means more heat is being extracted per litre of water pumped, improving system efficiency and reducing pump energy. A low ΔT indicates bypassing, short-circuiting or oversized flow relative to the heat load.</p><p>In direct liquid cooling systems, the CDU ΔT is a critical commissioning and monitoring parameter. Typical chilled water supply/return temperatures might be 7°C/12°C (5K ΔT) in a conventional plant. CDU secondary loops for high-density GPU racks often target 20–40°C supply with a 10–20K ΔT to maximise free cooling hours and reduce pump energy.</p>

Also Known As

temperature differentialsupply/return delta

Source Reference

ASHRAE TC9.9 Liquid Cooling Guidelines

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