Data Center Cooling: Accelsius on the transition from single-phase to two-phase liquid cooling

Bernstein hosted John Hewitt, CEO of Accelsius, for a fireside chat at Bernstein's "The Road to Intelligence: A Data Center and AI Value Chain Investor Day" and summarized key takeaways. The shift toward inference workloads should not reduce (but in fact increase) the need for liquid cooling, as heat flux (W/cm²) and rack TDP (kW) are expected to keep rising regardless of whether GPUs are used for training or inference; inference may create a more consistent thermal load due to continuous high utilization. Single-phase DTC still has meaningful headroom, but extending it via higher flow rates and lower facility-water inlet temperatures consumes additional pumping and chiller power, reducing power available for compute. Two-phase DTC is unlikely to replace single-phase overnight, but gradually, with both architectures coexisting. Accelsius' testing indicated its two-phase DTC could match a single-phase system operating at 45°C when running at a 54°C facility-water inlet temperature, pote