Exploring the Impact of CRAH Unit Partial Failure in Hybrid-Cooled Data Centers

Abstract Rising information technology loads in modern data centers (DCs) are straining traditional air-cooling systems, especially with increasing power densities and hot spots. Single-phase cold plate cooling is gaining traction but faces challenges like limited chilled water and constrained air distribution. Liquid-to-air (L2A) cooling distribution units (CDUs) offer an alternative, integrating hybrid air and liquid cooling. However, partial failure of computer room air handlers (CRAHs) disrupts this balance, causing uneven heat dissipation and reduced cooling efficiency. The interdependence of air and liquid cooling in hybrid systems makes them vulnerable to cascading failures, highlighting the need for optimized thermal management solutions. This comprehensive study delves into the implications of partial failure in the CRAH unit within the high-power density racks of a hybrid-cooled DC. The investigation explores how this partial failure impacts various critical parameters, including cooling capacity (CC), supply air temperature (SAT), air flow rate, supply fluid temperature (SFT), and thermal testing vehicle (TTV) heater case temperatures. For the purposes of this study, two L2A in-row CDUs were utilized, with a combined total heat load of 129 kW supplied to three racks. The experimental setup is meticulously equipped with the necessary instruments for monitoring and assessing tests on both the liquid coolant and air sides. By addressing these issues, the research contributes valuable insights to the ongoing efforts to optimize data center cooling solutions in the face of evolving information technology demands and technological advancements.