Data center cooling systems: coolant distribution unit liquid cooling

The ever-increasing demands of data center infrastructure management (DCIM) create a scorching challenge: heat. Traditional air-cooling struggles to keep pace, threatening data center performance and equipment lifespan. Liquid cooling is the most effective solution for modern data centers with enhanced efficiency and higher cooling capacity. To keep high-powered CPUs, GPUs and network switches within thermal specification, coolant distribution units (CDUs) deliver broader cooling capacity to liquid cooling loops and cold plates that thermally interface directly with heat sources for increased efficiency and greater flexibility than traditional air-cooling.

The Data Center Cooling Market is projected to reach USD 30.2 Billion by 2030, growing at a CAGR of 13.8 % during the 2024-2030 forecast period and the industry is witnessing a significant shift towards liquid cooling solutions to meet the escalating cooling demands of modern data centers. The global data center liquid cooling market is expected to grow at a 23.31% CAGR from 2024 to 2029. Eaton designs CDUs to optimize these liquid cooling systems, ensuring precise temperature control and efficient heat removal in data centers.

Coolant distribution units (CDUs) or cooling distribution units orchestrate precise thermal management within high-performance environments. Coolant distribution units actively distribute coolant water or other fluids to various components of a machine or process that need liquid cooling. This process begins with the liquid coolant absorbing heat from high power equipment through a liquid cold plate or a series of cold plates called a liquid cooling loop. The heated coolant then flows through heat exchanging technology within or outside the CDU, dependent on the configuration, dissipating the heat. Typically integrated into large-scale data center infrastructure, data center racks, laboratories and semiconductor fabrication factories, CDUs are essential to maintain optimal operating conditions in data centers, industrial settings and other environments where precise temperature control is critical. CDUs ensure that next-level performance cooling is efficiently and safely delivered to system components and heat sources, safeguarding against overheating and optimizing performance and longevity.

Coolant distribution units operate through a sophisticated pump system that circulates coolant, typically water or specialized fluids, through an intricate network of pipes or channels. This circulating coolant, essential for thermal dissipation, targets critical components like processors and switches in large-scale, high-power data center systems. CDUs integrate additional components such as valves, filters and monitoring mechanisms to optimize cooling efficiency and system reliability. Precisely calibrated valves allow for dynamic coolant distribution adjustments tailored to individual component needs, while filters ensure purity by sieving out impurities and contaminants. Equipped with sensors, CDUs continuously monitor coolant parameters like temperature, flow rate and pressure levels, enabling real-time interventions to maintain peak thermal performance and reliability in complex environments.

Coolant distribution units maintain optimal temperatures within data centers, ensuring servers and other IT equipment operate efficiently. Different types of CDUs meet various cooling needs and configurations. The main types include in-row, in-rack, liquid-to-air (L2A), Sidecar and liquid-to-liquid (L2L) CDUs. Each type offers unique features and applications, tailored to specific cooling requirements.

In-row CDUs sit between server racks or at the end of a row of server racks and cool a series of server racks. They absorb heat directly from servers using chilled water or refrigerant. Cooled liquid circulates in a closed-loop system on the secondary cooling side, while facility water is used on the primary heat rejection side. In-row CDUs can cool up to 2300KW and are able to an array of 10 high-power server racks.

In-rack CDUs provide highly localized cooling to equipment since they are installed within the server rack. These units feature liquid-to-liquid or liquid-to-kair cooling. Liquid cooled CDUs circulate coolant through a liquid-to-liquid heat exchanger within the rack unit, cooling the secondary loop with the primary facility water system. For air-cooled facilities, liquid-to-air coolant distribution units draw from the cool air in the facility, cool the liquid loop through a liquid-to-air heat exchanger and discharge the heated air into the facility. In-rack CDUs seamlessly integrate into high-power devices like cloud data center servers or medical and industrial models. They simplify server rack cooling with easy installation and maintenance. These systems offer a cost-effective and reliable cooling upgrade by fitting standard server configurations and offering flexibility for self-contained or integrated setups.

Liquid-to-air (L2A) CDUs efficiently transfer heat from a liquid coolant, typically water or a water-glycol mixture, to the surrounding air. This process begins with the liquid coolant absorbing heat from data center equipment through a liquid cold plate or a series of cold plates called a liquid cooling loop. The heated coolant then flows through a heat exchanger within the CDU, where fans blow air over the exchanger, dissipating the heat. L2A CDUs leverage facility air conditioning to dissipate heat from server rows, enabling localized liquid cooling for high-output data center equipment. They maximize cooling potential in air-cooled data centers, reducing thermal management equipment and installation costs while providing higher cooling capacity than air alone. Liquid-to-air CDUs are seen as a cost effective retrofit to bring liquid cooling technology into existing data centers without needing to upgrade the full facility’s systems.

Liquid-to-liquid (L2L) CDUs transfer heat between two separate liquid cooling loops, requiring facility water to remove heat from rack and row equipment. Despite added system complexity, L2L CDUs offer numerous benefits. Fully liquid-cooled data centers maximize energy efficiency due to the higher heat capacity of liquid. These systems enable smaller footprints and lower total cost of ownership, making them ideal for various applications such as artificial intelligence, blockchain, mainframe servers and supercomputers. They offer the most sustainable cooling for high powers.