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 °C. Additionally, the chilled water supply temperature for the secondary CDU can be increased to 14 °C, and for the primary chiller to 12 °C. A central chilled water system for a 30 MW reference data center was designed and analyzed, showing increased efficiency with a 12 °C supply temperature and varying condenser water return temperatures in winter, resulting in an annual PUE_cooling 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.