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Data center · liquid cooling

Metering a data center CDU loop without risking the coolant

The problem

A colocation operator deploying direct-to-chip liquid cooling needed to verify the coolant flow their CDUs were delivering to each rack manifold. The stakes made every inline option a non-starter: a leak in a live cooling loop can take out a rack of hardware, and a turbine meter in the loop is both a moving part and a debris source in a fluid path that has to stay pristine.

The approach

Portable clamp-on transit-time measurement on the secondary loop distribution. The transducers mount on the outside of the pipe — nothing wetted, nothing to leak, nothing shed into the propylene-glycol/water coolant. The METRI Ultra ProLite suited the job: light enough to move rack to rack, and precise enough to confirm each CDU against its own internal reading.

What mattered in the detail

Glycol concentration. Speed of sound in a glycol/water mix depends on the mix ratio and temperature. The concentration was confirmed and entered correctly — a guessed value would have produced a confident wrong reading.

Pipe size. The secondary runs were on the small side for clamp-on, so the transducer frequency and mounting were confirmed on a sample line before the survey, not assumed.

The lesson

In liquid cooling, the feature that sells clamp-on is the one it refuses to do: touch the coolant. Confirm pipe size and glycol mix up front and it is close to the ideal instrument for the job.

Have a line like this one?

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