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Equation 1 · Part 5 · The Physical Plant: Power, Cooling, and Networks in an AI Datacenter

Fluid density

Q˙=m˙ cp ΔT=ρ V˙ cp ΔT,\dot{Q} = \dot{m}\,c_p\,\Delta T = \rho\,\dot{V}\,c_p\,\Delta T,
ρ\rho

What this part means

Mass per unit volume of the cooling fluid. Its SI unit is kilograms per cubic metre.

Its job in the formula

ρ is an input to the expression that computes the quantity on the left.

The passage around this formula

The rate at which a fluid stream removes heat is Q˙=m˙ cp ΔT=ρ V˙ cp ΔT\dot{Q} = \dot{m}\,c_p\,\Delta T = \rho\,\dot{V}\,c_p\,\Delta T. with mass flow m˙\dot{m} , specific heat capacity cpc_p , and the temperature rise Δ\Delta T across the load. What matters for a datacenter is not cpc_p per kilogram but the volumetric heat capacity ρ\rho cpc_p , because the room has to physically contain the flow.

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Learn the underlying idea

Units describe how a quantity is measured. A valid physical equation must combine compatible dimensions.

Open the illustrated units and dimensions: a formula’s consistency check guide →

See this notation across published equations →

Sources cited in the article section

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Further reading for this equation