Views: 0 Author: Site Editor Publish Time: 2026-06-23 Origin: Site
Optical module liquid cooling follows two main approaches: indirect liquid cooling via cold plates and full-system immersion liquid cooling. Both approaches rely on the CDU's built-in brazed plate heat exchanger for heat dissipation. The slot-mounted miniature cold plates/immersion coils are only responsible for absorbing heat from the optical modules; the CDU plate heat exchanger is responsible for transferring the total heat generated by the entire cabinet of optical modules and servers to outdoor chilled water/cooling towers, making it an indispensable core component of the entire optical module liquid cooling cycle.
Complete Heat Exchange Process (Closed-Loop Liquid Cooling for Optical Modules)
Secondary-side cryogenic coolant is output from the CDU, flows through the cold plates/immersion coils of the OSFP/QSFP optical modules in the switch, absorbing heat from the DSP and laser of the 800G/1.6T/3.2T optical modules. The water temperature rises to 28~35℃ and flows back to the CDU.
High-temperature secondary fluid enters one side of the CDU plate heat exchanger.
Primary-side chilled water (15~22℃) flows to the other side of the equipment room, with the hot and cold fluids separated by stainless steel corrugated plates for counter-current heat exchange.
The secondary-side coolant cools to 18~25℃ and is again supplied to the optical modules for heat absorption.
The heated primary-side chilled water is then supplied to the outdoor cooling tower for heat dissipation, completing the closed-loop process.
Why must CDUs use plate heat exchangers (not tubular ones)?
Corrugated plates force turbulence, resulting in heat exchange efficiency 3-5 times that of tubular exchangers. The temperature difference between hot and cold fluids can be controlled from 0.5-1℃, ensuring constant temperature of the optical module, no optical power drift, and low bit error rate.
The compact structure, with a volume only 1/4 that of a tubular exchanger for the same heat exchange power, is suitable for small server racks/server room layouts.
The brazed seal withstands pressure of 1.0-1.6MPa, suitable for high-pressure circulation in liquid cooling systems.
It is compatible with various coolants such as ethylene glycol and fluorinated liquids, is corrosion-resistant, and suitable for long-term 24/7 operation of the optical module.
