Mastering the Heat: Advanced Thermal Management Strategies for Next-Generation Data Centers

By: Allegro MicroSystems

The escalating power demands of data centers necessitate highly efficient thermal management. Hyperscalers — companies that provide massive, large-scale cloud computing services and infrastructure—are consuming vast amounts of power, a direct result of the rapid development in artificial intelligence and large language models (LLMs). Effective thermal management is essential for performance, reliability, and energy efficiency. Traditionally, air cooling has been the go-to solution, but with rising power densities, the industry is rapidly evolving towards more sophisticated liquid cooling and the adoption of efficient 48V power systems. This evolution is driven by the imperative to manage heat more effectively than ever before.

Are Air Cooling Techniques Keeping Pace with Higher Densities?

For years, data centers primarily relied on air cooling, a method utilizing massive HVAC systems and raised floors to circulate cool air. This process typically involves powerful fans, often housed within Computer Room Air Handlers (CRAHs), which draw in hot air, pass it over cooling coils that are typically supplied with chilled water, and then blow cooled air back into the data center space. Fan efficiency directly impacts overall cooling performance.

Despite its long-standing use, air cooling faces significant challenges with modern, high-density racks used in hyperscalers or AI data centers. This challenge is fundamentally tied to the thermal design power (TDP) of components like CPUs and GPUs, representing the maximum heat generated by a chip under typical workloads. Over time, the TDP of these high-performance processors has steadily increased, pushing traditional cooling boundaries. Air’s inherent properties — poor heat conduction, lower heat capacity, and higher thermal resistance compared to liquids — mean it struggles to efficiently remove heat. This often leads to hot spots and requires considerable energy to move the large volumes of air necessary for cooling, making air cooling a significant energy consumer within the data center. To optimize this, data centers often employ strategies such as alternating cold and hot air aisles. This involves arranging server racks in rows so that the front (intake) faces a cold aisle, supplied with cool air, while the rear (exhaust) faces a hot aisle, where hot air is collected and returned to the cooling units, minimizing air mixing and improving efficiency. Air cooling is currently a prevalent choice for some data centers as it requires less capital upfront, easier installation compared to liquid cooling as well as having a lower maintenance burden. Although air cooling methods are typically less efficient than liquid cooling methods in power-demanding environments, it remains well suited for a spectrum of less intensive applications within data centers of all sizes.

Beyond Air: Why Are Data Centers Embracing Innovative Liquid Cooling?

Liquid cooling represents an advanced approach that brings a cooling fluid much closer to the heat source, offering significantly more efficient heat transfer. Liquid’s superior thermal conductivity allows for targeted heat removal, dramatically improving cooling efficiency, reducing energy consumption, and enabling higher computing power densities. This includes several sophisticated techniques:

• Direct-to-chip cooling: Circulates dielectric fluid directly over or through cold plates attached to high-power components like CPUs, GPUs, and memory modules. Heat transfers from the component to the fluid, which then carries it away to a heat exchanger, offering highly efficient, localized cooling.
• Immersion cooling: IT equipment (servers, storage, networking gear) is submerged directly into a non-conductive dielectric fluid.
  • Single-phase immersion cooling: IT equipment is submerged in a specialized dielectric fluid that consistently remains in its liquid phase. Heat transfers directly from the components to this fluid, which is then circulated to a heat exchanger to release the absorbed heat before being recirculated back to cool the equipment.
  • Dual-phase immersion cooling: Uses dielectric fluid with a very low boiling point. As components heat up, the fluid boils and turns into vapor, carrying away significant latent heat. Vapor rises, condenses on a cooled coil, and drips back into the liquid, completing the cycle. This phase change process is extremely efficient.
• Rear Door Heat Exchangers: These units, while cooling air, leverage a liquid loop for highly efficient heat capture. They are large heat exchangers integrated into the rear door of a server rack. Hot air exiting servers is immediately drawn into the heat exchanger, cooled by a circulating fluid (often chilled water), and returned as cooler air to the data center aisle. This allows for very efficient heat capture directly at the rack level, reducing the overall heat load on the main data center cooling infrastructure and enabling higher rack densities than traditional air cooling alone.

These methods promise reduced energy consumption and the ability to pack more processing power into smaller footprints. The shift to liquid cooling fundamentally changes thermal management demands. This transition shifts focus from moving vast volumes of air to precisely controlling fluid dynamics, requiring high-efficiency, low-noise power and control technologies. Challenges move from managing turbulent airflow to ensuring laminar liquid flow and precise pressure regulation.

How Do 48V Systems Power Efficiency in Data Center Operations? 

Driving these next-generation cooling systems, whether advanced air or liquid, requires equally advanced power delivery and control. The shift to 48V power distribution within data centers is a key enabler. By moving from traditional 12V to 48V, data centers can achieve:

• Reduced current: Lower current means less power loss through resistive heating in power delivery infrastructure, enhancing overall system efficiency.
• Smaller cabling: 48V systems can deliver more power through smaller and fewer cables compared to lower voltage systems, which reduces the bulk of cabling required for power distribution within racks and frees up physical space for additional hardware.
• Higher efficiency: Converting from high voltage AC power to lower voltages incur conversion losses. A 48V system reduces the step-down conversion losses compared to 12 V systems, leading to improved overall energy efficiency.  

This higher voltage system provides a more efficient backbone for powering powerful fans or pumps needed for both advanced cooling solutions. Innovative power management and control solutions leverage these 48V systems, ensuring optimal performance for components that orchestrate complex cooling architectures, enabling higher power delivery with enhanced efficiency from the power delivery itself.

Building a Cooler, More Efficient Future

As data center power demands continue to rise, the evolution from traditional air cooling to advanced liquid cooling and 48V systems is vital.  Advanced thermal management solutions seamlessly integrate with both air and liquid cooling architectures, often forming hybrid systems that provide essential control to manage fluid and airflow precisely.  By leveraging innovative power and control technologies, the industry is helping to build a cooler, more efficient, and sustainable future for the digital infrastructure that powers our world.

More information about data center solutions from Allegro MicroSystems