Numerical analysis of rack-based data center cooling with rear door heat exchanger (RDHx): Interrelationship between thermal performance and energy efficiency

This study presents a comprehensive numerical analysis of thermal performance and energy efficiency, IT operating environment, and thermal performance of the RDHx system, a rack-based cooling solution for high-density IT power using air-cooled equipment. A 150 kW IT module and RDHx cooling system were designed and evaluated, and CFD numerical analysis confirmed that RDHx maintains a stable IT environment within ASHRAE standards at a supply air temperature of 24 degrees C. Additionally, the chilled water supply temperature for the secondary CDU can be increased to 14 degrees C, and for the primary chiller to 12 degrees C. A central chilled water system for a 30 MW reference data center was designed and analyzed, showing increased efficiency with a 12 degrees C supply temperature and varying condenser water return temperatures in winter, resulting in an annual PUEcooling range of 1.25-1.33, with an average of 1.27. The annual energy consumption distribution for rack-based cooling is approximately 46 % from chillers, 21 % from fans, and 33 % from pumps. These results provide crucial insights into data center cooling and support the application of the RDHx system in high-density data centers, with future validation involving a field mock-up test of a 150 kW IT module.