What are the specific functions of the CDU in the liquid cooling system?

The CDU (Coolant Distribution Unit) serves as the core hub of the data center liquid cooling system. Its specific functions are listed below:

1. Heat isolation & heat transfer via built-in plate heat exchanger It separates the facility primary chilled water loop and the IT secondary coolant loop. Heat absorbed by secondary coolant from racks (RDHX, GPU cold plates, optical module cold plates) is transferred to the primary facility water, without mixing the two fluids. This prevents impurities from building water entering IT-side piping.

2. Coolant circulation & pressure maintenance Integrated circulating pumps provide stable flow and pressure for the secondary loop, delivering temperature-controlled coolant to all racks. An expansion tank compensates volume changes caused by coolant thermal expansion and maintains stable system static pressure.

3. Precise temperature regulation of secondary coolant It controls the supply temperature of the secondary loop. Keeping coolant temperature above the dew point avoids condensation on cold plates or RDHX coils, protecting IT hardware.

4. Filtration and water quality protection Built-in fine filters capture solid particles in returning coolant. It prevents micro-channel cold plates and RDHX coils from clogging, reducing abrasion on pumps and seals.

5. Automatic air venting Air vent valves remove trapped air from the secondary loop. Air bubbles can cause unstable flow, local overheating and pump cavitation.

6. System monitoring, alarm and safety interlock Sensors continuously collect data: supply/return temperature, flow rate, pressure, liquid level and filter differential pressure. It triggers alarms for abnormal conditions such as low flow, pressure loss and filter blockage. Linked with rack leak detection signals, it can close isolation valves to cut off coolant to faulty racks.

7. Coolant distribution for multi-rack parallel operation It distributes balanced coolant flow to multiple racks in a row. It supports mixed cooling loads: RDHX, GPU cold plates and optical module liquid cooling on the same secondary loop.

8. Communication with upper management platform It communicates with BMS / DCIM via Modbus TCP or RS485. It uploads operating data, receives setpoint adjustments and records fault logs.