Graduation Semester and Year
Summer 2026
Language
English
Document Type
Thesis
Degree Name
Master of Science in Mechanical Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Dr. Dereje Agonafer
Second Advisor
Dr. Yogesh Fulpagare
Third Advisor
Dr. Miguel Amaya
Abstract
As the power density of artificial intelligence (AI) and high-performance computing (HPC) servers escalates, air cooling is approaching fundamental scaling limits set by air's low convective heat transfer coefficient and rising parasitic fan power. This thesis presents an experimental comparison of direct-to-chip liquid cooling and air cooling for a high-density GPU server, using a Thermal Test Vehicle (TTV) that emulates the device layout and power-density regime of an 8-GPU SXM5-class baseboard (eight emulated GPU blocks and four NVLink Switch modules). The liquid configuration was tested at 8.8 kW (8.0 kW GPU, 800 W switch) across three Coolant Distribution Unit (CDU) inlet setpoints (25, 35, 45 °C) using a 25% propylene-glycol coolant; the air configuration was tested across an airflow sweep (170–370 CFM) at 1.32 kW, with flow measured per ANSI/AMCA 210 / ASHRAE 51-1999. Cooling performance is compared using average per-device thermal resistance, Rth = (mean device temperature − inlet temperature)/(average power per device), with power expressed in watts. Liquid cooling achieved GPU Rth ≈ 0.034 K/W, roughly 4.6 to 8.8 times lower than air cooling (GPU Rth ≈ 0.157–0.303 K/W across the flow sweep). Device temperature tracked coolant inlet temperature with a near-unity slope (≈0.973) across all three liquid setpoints, while GPU thermal resistance remained essentially constant as inlet temperature rose from 25 to 45 °C. This inlet-independence supports the component-level thermal feasibility of elevated-temperature coolant operation over the tested range, a prerequisite for warm-water and economizer-based cooling strategies. Even at the 45 °C inlet, mean GPU temperature remained near 80 °C. These results quantify both the magnitude of liquid cooling's thermal advantage and its robustness to elevated coolant temperatures.
Keywords
direct-to-chip cooling; data center thermal management; GPU thermal management; thermal resistance; warm-water cooling; coolant distribution unit.
Disciplines
Engineering | Heat Transfer, Combustion | Mechanical Engineering
License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Esan, Oluwagbolahan, "Experimental Thermal Characterization And Comparison Of Direct Liquid Cooling And Air Cooling For A High-Density GPU Server Thermal Test Vehicle" (2026). Mechanical and Aerospace Engineering Theses. 8.
https://mavmatrix.uta.edu/mechaerospace_theses2/8