Coolant Distribution Unit (CDU)
System Overview
The HD-CDU is the heat-transfer heart of a liquid cooling loop. It isolates the facility water
from the secondary coolant that runs through the racks, holds the pressure differential stable, filters the loop and
reports every alarm back to the building management system.
Units are built in a welded stainless frame with a brazed plate heat exchanger, two variable speed pumps in N+1 arrangement, a 50 micron filter, an expansion vessel and a 7 inch HMI. The secondary circuit runs at 40 to 45 °C supply, within the ASHRAE W45 envelope, which keeps the facility loop on a free-cooling design for most of the year and drives PUE down to 1.1 to 1.2.
Both in-row (rack width) and in-rack (1U to 4U) formats are available, together with containerised skids for edge deployments.
Units are built in a welded stainless frame with a brazed plate heat exchanger, two variable speed pumps in N+1 arrangement, a 50 micron filter, an expansion vessel and a 7 inch HMI. The secondary circuit runs at 40 to 45 °C supply, within the ASHRAE W45 envelope, which keeps the facility loop on a free-cooling design for most of the year and drives PUE down to 1.1 to 1.2.
Both in-row (rack width) and in-rack (1U to 4U) formats are available, together with containerised skids for edge deployments.
Basic Parameters
| Cooling capacity | 60 / 120 / 300 / 600 kW per unit, parallel up to 2 MW |
| Heat exchanger | Brazed plate, 316L, counter flow |
| Pumps | 2 x variable speed, N+1, dry-run protected |
| Working pressure | 1.0 MPa design, 1.6 MPa test |
| Secondary supply | 40 - 45 °C, ASHRAE W45 class |
| Primary side | 32 - 45 °C facility water, 25 - 30% PG |
| Secondary fluid | Deionized water or PG25 |
| Filtration | 50 micron standard, 25 micron option |
| Flow rate | 8 - 60 m3/h depending on model |
| Connections | DN50 - DN100 flange or grooved |
| Instrumentation | Pressure, differential pressure, flow, temperature, leak sensor |
| Communication | Modbus RTU / TCP, SNMP, dry contacts to BMS / DCIM |
| Enclosure | IP54, RAL 7035, stainless frame |
| Options | Redundant power, UPS interface, remote HMI, containerised skid |
Values above are typical ranges. Final selection is confirmed against the project datasheet, flow rate, coolant and rack layout before order.
Redundancy Without Downtime
One pump runs, one pump stands by. On loss of flow, differential pressure or a leak alarm the controller switches over in under two seconds and logs the event, so a single pump failure does not take the rack down.
Condensation Control
Supply temperature is held above the calculated dew point of the room. The controller reads room humidity from the BMS and raises the set point automatically, so cold plates stay dry in humid climates.
Factory Testing
Every unit is hydrostatically tested at 1.6 MPa for 30 minutes, flow tested on a calibrated bench, and shipped with a FAT report, wiring diagram and material certificates for the wetted parts.
Application Notes
Size the CDU on the design heat load plus a 15 to 20% margin, and check that the secondary flow stays inside the
cold plate supplier's pressure drop limit. Where the facility loop is shared between several CDUs, specify a common
header with isolation valves so one unit can be serviced while the rest carry the load. Provide a make-up water point
and a drain at the lowest point of the loop for commissioning.