Thermal performance analysis of next generation high performance computing data centers using waterfall diagrams

Thermal management in high-density computing data centers is crucial for maintaining performance, reliability, and energy efficiency. As computing power demands surge, traditional air-cooling methods face limitations in handling increasing heat loads, while liquid cooling offers a feasible solution. However, a system-level metric and analysis assessing the energy efficiency of liquid cooling remains absent. This paper introduces a novel waterfall diagram (WFD) framework to provide a comprehensive system-level analysis of liquid cooling performance. The WFD evaluates energy efficiency using total-power usage effectiveness (TUE) derived from analytical calculations. A comparative analysis of coolant distribution unit (CDU) designs identified the 3U CDU architecture as the most suitable configuration for WFD analysis due to its optimal power consumption, TUE, and power density. The WFD analysis also incorporates the Sankey and heat load diagrams to visualize energy flow and heat load accumulation across the cooling system. Results indicate that the secondary side yields the highest pressure drop, which emphasizes opportunities for hydraulic performance optimization. In addition, at the component level, the cooler’s low pressure drop highlights its energy efficiency while, at the system level, the cooler and tube connections make a significant contribution to system TUE, suggesting areas of improvement for energy efficiency. This framework relies on analytical methods without empirical validation and assumes steady-state conditions, which may limit its applicability. Future work should focus on experimental validation and transient thermal analysis. Additionally, the WFD methodology can be extended to different data center cooling methods and other thermal management systems such as hybrid air-liquid cooling, immersion cooling, HVAC, and battery cooling.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Lee, Donggun

Contributors dc:contributor

• Miljkovic, Nenad

• Data Center
• Liquid Cooling
• Thermal Management

Statement dc:rights

• Copyright 2025 Donggun Lee

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130013

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130013