Owing to the dramatic increase in IT power density and energy consumption, the data center (DC) sector has
started adopting thermally- and energy-efficient liquid cooling methods. This study examines a single-phase
direct-to-chip liquid cooling approach for three high-heat-density racks, utilizing two liquid-to-air (L2A)
cooled coolant distribution units (CDUs) and a combined total heat load of 128 kW. An experimental setup was
developed to test different types of CDUs, cooling loops, and thermal testing vehicles (TTVs) for different
operating conditions. IR images and the collected data were used to investigate the effect of air recirculation
between cold and hot aisle containments on the CDU’s performance and stability of supply air temperature
(SAT). Three different types of cooling loops (X, Y, and Z) were characterized thermally and hydraulically.
Results show that Type Y has the lowest cold plate thermal resistance and pressure drop, among others. In a later test that included a single rack at a heat load of 53 kW and a single CDU, the heat capture ratio for fluid was found to be 94%. Experiments show that using blanking panels on the back of the racks limits hot air recirculation and maintains a steady SAT in the cold aisle. Finally, the CDU performance was evaluated at a high heat load for the three racks at 128 kW, and the average cooling capacity of the units is 58.6 kW, and the effectiveness values for CDU 1 and CDU 2 are 0.83 and 0.82, respectively.
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This content will become publicly available on December 1, 2025
Performance Analysis of Liquid-to-Air Heat Exchanger of High-Power Density Racks
The ability of traditional room-conditioning systems to accommodate expanding information technology loads is limited in contemporary data centers (DCs), where the storage, storing, and processing of data have grown quickly as a result of evolving technological trends and rising demand for online services, which has led to an increase in the amount of waste heat generated by IT equipment. Through the implementation of hybrid air and liquid cooling technologies, targeted, on-demand cooling is made possible by employing a variety of techniques, which include but are not limited to in-row, overhead, and rear door heat exchanger (HX) cooling systems. One of the most common liquid cooling techniques will be examined in this study based on different conditions for high-power density racks (+50 kW). This paper investigates the cooling performance of a liquid-to-air in-row coolant distribution unit (CDU) in test racks containing seven thermal test vehicles (TTVs) under various conditions, focusing on cooling capacity and HX effectiveness under different supply air temperatures (SAT). This test rig has the necessary instruments to monitor and analyze the experiments on both the liquid coolant and the air sides. Moreover, another experiment is conducted to assess the performance of the CDU that runs under different control fan schemes, as well as how the change of the control type will affect the supply fluid temperature and the TTV case temperatures at 10%, 50%, and 100% of the total power. Finally, suggestions for the best control fan scheme to use for these systems and units are provided at the conclusion of the study.
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- Award ID(s):
- 2209776
- NSF-PAR ID:
- 10529824
- Publisher / Repository:
- ASME
- Date Published:
- Journal Name:
- Journal of Electronic Packaging
- Volume:
- 146
- Issue:
- 4
- ISSN:
- 1043-7398
- Subject(s) / Keyword(s):
- data center high heat density rack liquid cooling liquid-to-air heat exchanger cold plate
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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