Refrigerant to Air Cooling for High Heat Density Two-Phase Cooled Data Centers

Two-phase cooling is actively being investigated as an alternate solution for the thermal management of data centers since it is projected that thermal dissipation from high-power density chips would exceed the capabilities of single-phase cooling. The restricted availability of a chilled water source in many legacy data centers is one of the obstacles to the adoption of two-phase. This study introduces a potential system to help adopt two-phase cooling when a chilled water source is not available in IT rack location of a data center. This system consists of an in-rack two-phase Cooling Distribution Unit (CDU), rack manifolds, server cooling loops, and an air-cooled condenser. High-power-density Thermal Testing Vehicles (TTVs) with 2.5 kW rated heaters are used to simulate the thermal load of real servers of up to 10kW in a 3U server platform. To transfer heat from the two-phase cooled TTVs into the room air, a two-phase CDU along with a refrigerant-to-air condenser and a rack manifold is used. This work begins with a description of the system design process, followed by an introduction to the Flow Network Modeling (FNM) of the system, then a detailed explanation of the system commissioning procedure, and the work concludes with a discussion of experimental findings when operating the system with heat application to TTVs to replicate a server's thermal load. Thermal testing is performed using R1234yf green refrigerant as a potential replacement for R134a.