Effective cooling is crucial for high-power liquid-cooled servers to ensure optimal performance and reliability ofcomponents. Thermal characterization is necessary to ensure that the cooling system functions as intended, is energy efficient, and minimizes downtime. In this study, a proposed methodology for thermal characterization of a high-powerliquid-cooled server/TTV [server and TTVs (thermal test vehicle) are used interchangeably] is presented. The server layout includes multiple thermal test vehicle setups equipped with direct-to-chip cold plates, with two or more connected in series to form a TTV cooling loop. These cooling loops are connected in parallel to the supply and return plenums of the cooling loop manifold, which includes a chassis-level flow distribution manifold. To obtain accurate measurements, two identical server/TTV prototypes are instrumented with sensors for coolant flow rate and temperature measurements for every TTV cooling loop. Four ultrasonic flow sensors are installed in the flow verification server/TTV to measure the coolant flow rate to each TTV cooling loop. In the thermal verification server, thermistors are installed at the outlet of each GPU heater of TTV cooling loop to log temperature measurements. The amount of heat captured by the coolant in each TTV cooling loop is subsequently estimated based on the flow rates determined from the flow verification server.This methodology enables precise characterization of the thermal performance of high-power liquid-cooled servers,ensuring optimal functionality, energy efficiency, and minimized downtime.
This content will become publicly available on December 1, 2025
A significant number of investigations have been performed to develop and optimize cold plates for direct-to-chip cooling of processor packages. Many investigations have reported computational simulations using commercially available computational fluid dynamic tools that are compared to experimental data. Generally, the simulations and experimental data are in qualitative agreement but often not in quantitative agreement. Frequently, the experimental characterizations have high experimental uncertainty. In this study, extensive experimental evaluations are used to demonstrate the errors in experimental thermal measurements and the experimental artifacts during testing that lead to unacceptable inconsistency and uncertainty in the reported thermal resistance. By comparing experimental thermal data, such as the temperature at multiple positions on the processor lid, and using that data to extract a meaningful measure of thermal resistance, it is shown that the data uncertainty and inconsistency are primarily due to three factors: (1) inconsistency in the thermal boundary condition supplied by the thermal test vehicle (TTV) to the cold plate, (2) errors in the measurement and interpretation of the surface temperature of a solid surface, such as the heated lid surface, and (3) errors introduced by improper contact between cold plate and TTV. A standard thermal test vehicle (STTV) was engineered and used to provide reproducible thermal boundary conditions to the cold plate. An uncertainty analysis was performed in order to discriminate between the sources of inconsistencies in the reporting of thermal resistance, including parameters such as mechanical load distribution, methods for measuring the cold plate base, and TTV surface temperatures. A critical analysis of the classical thermal resistance definition was performed to emphasize its shortcomings for evaluating the performance of a cold plate. It is shown that the thermal resistance of cold plates based on heat exchanger theory better captures the physics of the heat transfer process when cold plates operate at high thermodynamic effectiveness.
more » « less- Award ID(s):
- 2209691
- PAR ID:
- 10537555
- Publisher / Repository:
- ASME
- Date Published:
- Journal Name:
- Journal of Electronic Packaging
- Volume:
- 146
- Issue:
- 4
- ISSN:
- 1043-7398
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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