K&K Data Service Inc.Data Center Engineering Lab

Data Center Lab

Direct Liquid Cooling and CDU

This series publishes working engineering analysis from K&K's data center program. Numbers are labeled [TARGET], [MODELED], [SENSITIVITY] or [FACT]; nothing here is field-measured data, and no article is a sealed engineering document. Each article states its own limits and open items.

Equipment cross section through the IT main hall and UPS and power room, with rack, battery and UPS envelope heights
Equipment cross section through the IT hall and power room (coordination study — not release).
  1. KK-DCL-023N+1 on the CDU List Is Not N+1 in the PipesAn N+1 equipment count does not survive contact with in-row zoning, valve granularity and pipe routing, which is where redundancy is actually decided.
  2. KK-DCL-024Eleven 1.5 MW CDUs Equaling 12 MW Is Coincidence, Not MarginEleven nameplate units happen to sum to the target, but the coincidence is not margin once redundancy groups and zone loads are applied.
  3. KK-DCL-025The Liquid Fraction f Mixes Design, Sensitivity, and OEM ValuesThe symbol f carries three non-substitutable calibres in one document - a hydraulic representative value, a set of sensitivity steps and an unobtained equipment-supplier input - and a neighbouring schedule uses two of them in adjacent columns.
  4. KK-DCL-026Why 100% Liquid Cooling Is Not a Design CaseThe 100 % row of the sensitivity table prints zero air-side heat and is labelled a theoretical limit; the same section bounds design at f no greater than 0.97 on an assumed 3 % to 8 % residual, and the white-space geometry is drawn to that bound rather than to the row.
  5. KK-DCL-027The 385 kW CDU Pump Budget Exists Only at a Rejected 6 K ΔTThe pump power budget that makes the PUE case work belongs to a delta-T that the hydraulic basis already rejected.
  6. KK-DCL-028PG25 Is Not Water Plus 4.5% VolumePG25 changes density, viscosity, specific heat and freeze behaviour together, so treating it as water with an additive is a property error, not a rounding one.
  7. KK-DCL-029A Water-Rated 1.5 MW CDU Is 1.20–1.28 MW on PG25Water-basis nameplate capacity derates on PG25, and the derate band is wide enough to change the unit count.
  8. KK-DCL-030Same-Day Plate Heat Exchanger Datasheet and Drawing DisagreeTwo vendor documents dated the same day carry the same model name under different item identifiers and different duty points.
  9. KK-DCL-03196 Isolation Valves Turn a Weld Repair Into Zero IT ImpactIsolation granularity, not spare capacity, decides whether a weld repair is a maintenance task or an IT outage.
  10. KK-DCL-032Automatic Leak Isolation Can Drop a 130 kW Rack on a False TripAn automatic isolation response to a leak signal without qualification can remove a loaded rack on a single false detection.