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.
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Abstract Free, publicly-accessible full text available December 1, 2025 -
Plastic optical fibers (POF) possess the potential to occupy a distinctive role in contemporary communication systems, bridging the gap between the attributes of copper cable and glass fiber. POF stands out as a more lightweight and cost-effective alternative to glass fiber, while concurrently offering significantly enhanced communication bandwidth compared to traditional copper cables of equivalent cost or weight. However, the novelty of this technology introduces a challenge, as there is limited understanding of how POF cables may behave under specific bending conditions, particularly in the case of the latest multi-core fibers. This paper outlines a research endeavor aimed at establishing a cost-effective and reproducible testing framework for assessing the light transmission properties of plastic optical fibers during various bending conditions. The methodology involves partial automation using National Instruments LabVIEW for servo motor control, and optical power measurements were taken using the Thorlabs PM100USB. The investigation encompassed measurements across diverse bending angles and radii for five distinct types of fibers: Eska MH, Eska BH, Eska GH, a Graded Index fiber, and a Multi Core Fiber.more » « lessFree, publicly-accessible full text available March 15, 2025
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This study investigates the impact of under-filled and over-filled launching configurations on the transmission properties of Plastic Optical Fiber (POF). Experimental analyses on step and graded index fibers reveal differences in spatial and frequency properties under these launching conditions. Results show that the under-filled configuration leads to narrower radial profiles and Encircled Angular Flux (EAF) compared to the over-filled configuration. Additionally, under-filled launching produces better frequency response and larger bandwidth, particularly notable in shorter fibers. Results show that the under-filled launching significantly improves transmission properties, offering potential improvements in POF applications.more » « lessFree, publicly-accessible full text available March 15, 2025
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We proposed a Client Server Based Plastic Fiber Optic Network for an Elderly Support system in a smart home environment. The network will incorporate multimodal dialogue systems (MDS) and Artificial Intelligence (AI) systems. Existing AI models like GPT and Vicuna will be used and further trained to support the elderly in a smart home. The MDS systems, Whisper and Lavis, will act as intermediaries between the POF network of sensors and the AI systems. The systems will convert video and audio files into information that the AI systems can process and respond to. The POF network, consisting of sensors and a client-server architecture, will serve as the system's backbone. Its primary purpose is to gather data for the AI system and act based on its output. This research aims to enhance the safety, well-being, and independence of the elderly by leveraging advanced network technologies.more » « lessFree, publicly-accessible full text available March 15, 2025
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Semiconductor thermal management is becoming a bottleneck challenge that restricts further development in the electronics industry. Compromising processor thermal requirements will impact the processor performance and reliability. Heat sinks are designed to increase the available surface area of an electronic component and allow for more heat to be easily dissipated. As a result, the thermal characterization of the heat sinks plays a critical role in electronics thermal management. In this study, a flexible experimental apparatus is designed, built, and assembled to characterize and test various electronics components in different aerodynamics and thermal conditions. This novel experimental apparatus allows for controlled characterization of the various heat sinks with different heights as well as realistic scenarios with air bypass at server level. Moreover, a general guideline on precise experimental procedure to characterize air cooled heat sinks is developed. The results show that introduced method reduces the experimental error by 26%.more » « less
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Abstract Impingement split flow liquid-cooled microchannel cold plates are one of several flow configurations used for single-phase liquid cooling. Split flow or top-in/side-exit (TISE) cold plates divide the flow into two branches thus resulting in halved or reduced flow rates and flow lengths, compared to traditional side-in /side-exit (SISE) or parallel flow cold plates. This has the effect of reducing the pressure drop because of the shorter flow length and lower flow rate and increasing the heat transfer coefficient due to thermally developing as opposed to fully developed flow. It is also claimed that the impinging flow increases the heat transfer coefficient on the base plate in the region of impingement. Because of the downward impinging and turning flow, there are no exact analytical models for this flow configuration. Computational and experimental studies have been performed, but there are no useful compact analytical models in the literature that can be used to predict the performance of these impingement cold plates. Results are presented for novel physics-based laminar flow models for a TISE microchannel cold plate based on an equivalent parallel channel flow approach. We show that the new models accurately predict the thermal-hydraulic performance over a wide range of parameters.
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Forecasting data center cooling demand remains a primary thermal management challenge in an increasingly larger global energy-consuming industry. This paper proposes a dynamic modeling approach to evaluate two different strategies for delivering cold air into a data center room. The common cooling method provides air through perforated floor tiles by means of a centralized distribution system, hindering flow management at the aisle level. We propose an idealized system such that five overhead heat exchangers are located above the aisle and handle the entire server cooling demand. In one case, the overhead heat exchangers force the airflow downwards into the aisle (Overhead Downward Flow (ODF)); in the other case, the flow is forced to move upwards (Overhead Upward Flow (OUF)). A complete fluid dynamic, heat transfer, and thermodynamic analysis is proposed to model the system’s thermal performance under both steady state and transient conditions. Inside the servers and heat exchangers, the flow and heat transfer processes are modeled using a set of differential equations solved in MATLAB™. This solution is coupled with ANSYS-Fluent™, which computes the three-dimensional velocity, temperature, and turbulence on the Airside. The two approaches proposed (ODF and OUF) are evaluated and compared by estimating their cooling effectiveness and the local Entropy Generation. The latter allows identifying the zones within the room responsible for increasing the inefficiencies (irreversibilities) of the system. Both approaches demonstrated similar performance, with a small advantage shown by OUF. The results of this investigation demonstrated a promising approach of data center on-demand cooling scenarios.more » « less