Improved Cooling of Electromagnetics by Directed Airflow

2013 ◽  
Author(s):  
Scott Downing ◽  
Adam Fain ◽  
Pradip Majumdar
Keyword(s):  
High Performance ◽  
Experimental Testing ◽  
Hot Spot ◽  
Test Methods ◽  
Cfd Modeling ◽  
Air Cooling ◽  
Low Velocity ◽  
Article Surface ◽  
Two Phases ◽  
Geometrical Dimensions

The transformers in aircraft power conversion are often very heavy and represent a significant fuel or range penalty. Being thermally sized, improved cooling methods would allow downsizing and thereby reduced weight. Since the conductive paths in these metal “dense” devices are good, the controlling thermal resistance is typically the convective coefficient. The goal of this study was to optimize the convective air cooling across transformers by parametrically testing candidate shroud geometries to minimize average and hot spot surface temperatures with minimal fan power. Experimental results from a low velocity wind tunnel were well correlated by CFD modeling, providing confidence in continued shroud development with only CFD or experimentally. A simple cubic test block was selected as surrogate to generalize and simplify both test methods and results. A new “goodness” parameter was developed that included both the heat transfer performance and pressure penalty for a comparative index of shroud designs. The work was divided into two phases. Phase-A used numerical modeling to study a variety of different shapes to select the best for experimental testing. Phase-B included the testing and further parametric evaluation with CFD studies. A parameter was developed that quantified the effect of conductive spreading on the test article surface. Presented here are the results of these studies, where several general shroud shapes emerged as high performance in comparative evaluation. Following the down select, specific geometrical dimensions relative to the duct and mock transformer sizes were further optimized.

CFD Modeling of the Distribution of Airborne Particulate Contaminants Inside Data Center Hardware

2020 ◽  
Author(s):  
Satyam Saini ◽  
Kaustubh K. Adsul ◽  
Pardeep Shahi ◽  
Amirreza Niazmand ◽  
Pratik Bansode ◽  
...  
Keyword(s):  
Data Center ◽  
High Performance ◽  
Phase Particle ◽  
Cfd Modeling ◽  
Air Cooling ◽  
Ambient Conditions ◽  
Particle Modeling ◽  
Free Air ◽  
Discrete Phase ◽  
Particulate Contaminants

Abstract Modern-day data center administrators are finding it increasingly difficult to lower the costs incurred in mechanical cooling of their IT equipment. This is especially true for high-performance computing facilities like Artificial Intelligence, Bitcoin Mining, and Deep Learning, etc. Airside Economization or free air cooling has been out there as a technology for a long time now to reduce the mechanical cooling costs. In free air cooling, under favorable ambient conditions of temperature and humidity, outside air can be used for cooling the IT equipment. In doing so, the IT equipment is exposed to sub-micron particulate/gaseous contaminants that might enter the data center facility with the cooling airflow. The present investigation uses a computational approach to model the airflow paths of particulate contaminants entering inside the IT equipment using a commercially available CFD code. A Discrete Phase Particle modeling approach is chosen to calculate trajectories of the dispersed contaminants. Standard RANS approach is used to model the airflow in the airflow and the particles are superimposed on the flow field by the CFD solver using Lagrangian particle tracking. The server geometry was modeled in 2-D with a combination of rectangular and cylindrical obstructions. This was done to comprehend the effect of change in the obstruction type and aspect ratio on particle distribution. Identifying such discrete areas of contaminant proliferation based on concentration fields due to changing geometries will help with the mitigation of particulate contamination related failures in data centers.

Study on Heat Conduction in a Simulated Multicore Processor Chip—Part II: Case Studies

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Wataru Nakayama
Keyword(s):  
Hot Spots ◽  
High Performance ◽  
Thermal Environment ◽  
Hot Spot ◽  
Air Cooling ◽  
Multicore Processor ◽  
Temperature Contrast ◽  
On Chip ◽  
Heat Spreading ◽  
Level Analysis

The objective of this study is to understand the effects of various parameters involved in the chip design and cooling on the occurrence of hot spots on a multicore processor chip. The thermal environment for the die is determined by the cooling design which differs distinctly between different classes of electronic equipment. In the present study, like many other hot spot studies, the effective heat transfer coefficient represents the thermal environment for the die, but, its representative values are derived for different cooling schemes in order to examine in what classes of electronic equipment the hot spot concern grows. The cooling modes under study are high-performance air-cooling, high-performance liquid-cooling, conventional air-cooling, and oil-cooling in infrared radiation (IR) thermography setup. Temperature calculations were performed on a model which is designed to facilitate the study of several questions that have not been fully addressed in the existing literature. These questions are concerned with the granularity of power and temperature distributions, thermal interactions between circuits on the die, the roles of on-chip wiring layer and the buried dioxide in heat spreading, and the mechanism of producing temperature contrast across the die. The main results of calculations are the temperature of the target spot and the temperature contrast across the die. Temperature contrasts are predicted in a range 10–25 K, and the results indicate that a major part of the temperature contrast is formed at a granularity corresponding to the size of functional units on actual microprocessor chips. At a fine granularity level and under a scenario of high power concentration, the on-chip wiring layer and the buried oxide play some roles in heat spreading, but their impact on the temperature is generally small. However, the details of circuits need to be taken into account in future studies in order to investigate the possibility of nanometer-scale hot spots. Attention is also called to the need to understand the effect of temperature nonuniformity on the processor performance for which low temperature at inactive cells makes a major contribution. In contrast to the situation for the die under forced convection cooling, the die in passively cooled compact equipment is in distinctly different thermal environment. Strong thermal coupling between the die and the system structure necessitates the integration of package and system level analysis with the die-level analysis.

scholarly journals Experimental Investigation and CFD Modeling of Slush Cryogen Flow Measurement Using Circular Shape Capacitors

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2117 ◽  
Author(s):  
Bogdan Florian Monea ◽  
Eusebiu Ilarian Ionete ◽  
Stefan Ionut Spiridon
Keyword(s):  
Flow Measurement ◽  
High Performance ◽  
Solid Phase ◽  
Experimental Testing ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cfd Modeling ◽  
Two Phase ◽  
Circular Shape ◽  
Experimental Stand

The measurement of two-phase cryogenic fluid mixtures flow, also known as slush cryogen flow, with its most attractive form (liquid and solid) is of great interest for various applications, due to its thermodynamic advantages. This paper presents a newly developed device, under the form of a circular capacitor prototype, together with an experimental stand for slush formation. Slush nitrogen was used as testing fluid during the experimental work. Then, the experimental data for slush cryogen flow measurement using the proposed circular shape capacitor were compared with theoretical results obtained by simulation. A three-dimensional flow field model was built and solved for the innovative design slush flowmeter using a computational fluid dynamic (CFD) model. Nitrogen slush density of 874 kg/m3, representing approximately 30% solid fraction, was reported for both the modeling and experimental testing, although the numerical investigation is not limited to these values. By comparing experimental vs. simulation results, a deeper view on the designed configuration can be achieved, thus improving the progress in producing high-performance next generation devices for two-phase flow measurement in terms of physical dimensions, length and space between armatures. Even so, the mathematical model has limitations when mixtures with higher percentages of solid phase and particle sizes are encountered.

Topology Optimization, Additive Layer Manufacturing, and Experimental Testing of an Air-Cooled Heat Sink

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Ercan M. Dede ◽  
Shailesh N. Joshi ◽  
Feng Zhou
Keyword(s):  
Topology Optimization ◽  
Heat Sink ◽  
Computer Aided Design ◽  
Experimental Testing ◽  
Jet Impingement ◽  
Coefficient Of Performance ◽  
Air Cooling ◽  
Additive Layer Manufacturing ◽  
Cloud Data ◽  
Layer Manufacturing

Topology optimization of an air-cooled heat sink considering heat conduction plus side-surface convection is presented. The optimization formulation is explained along with multiple design examples. A postprocessing procedure is described to synthesize manifold or “water-tight” solid model computer-aided design (CAD) geometry from three-dimensional (3D) point-cloud data extracted from the optimization result. Using this process, a heat sink is optimized for confined jet impingement air cooling. A prototype structure is fabricated out of AlSi12 using additive layer manufacturing (ALM). The heat transfer and fluid flow performance of the optimized heat sink are experimentally evaluated, and the results are compared with benchmark plate and pin-fin heat sink geometries that are conventionally machined out of aluminum and copper. In two separate test cases, the experimental results indicate that the optimized ALM heat sink design has a higher coefficient of performance (COP) relative to the benchmark heat sink designs.

Research on In Situ Anionic Polymerization of PA6/PI Alloy

2011 ◽  
Vol 295-297 ◽  
pp. 21-25
Author(s):  
Hong Kai Zhao ◽  
Li Guang Xiao ◽  
Hong Jie Wang
Keyword(s):  
Molecular Weight ◽  
Bisphenol A ◽  
High Performance ◽  
Hot Spot ◽  
Microscopic Analysis ◽  
Infrared Analysis ◽  
Elongation At Break ◽  
System Temperature ◽  
Lamellar Crystals

High performance trend of plastics has become a hot spot of current research. Select bisphenol A dianhydride and bisphenol A diamine with excellent water resistance as the reactant monomers to obtain anhydride-terminated polyimide with very high molecular weight by two-step polymerization, graft the active radicals of acyl caprolactam using the activity of anhydride and obtain PI modified nylon resin by polymerization.When the system temperature is above 160 °C and the added modifiers are greater than 10%, the system viscosity increases very fast; when the system temperature reaches 140 °C and the added modifiers are at 5%, the system viscosity increases very slowly. It is proved that the reaction in each above step is successful through infrared analysis. The mechanical properties of modified PI nylon increases with the increase of consumption and molecular weight of polyimide, when the molecular weight is selected to be about 8000~10000 and the adding amount is 10wt%~15 wt%, the tensile strength reaches over 85MPa, the notch impact strength is increased to 19.6kJ.m-2 and the elongation at break reaches 18%, which are remarkably better than general engineering plastics.Through microscopic analysis, the molecules of polyimide does not enter crystallization phase of nylon resin, but forms compact lamellar crystals existing in nylon matrix.

AN OVERVIEW OF MOISTURE DAMAGE PERFORMANCE TESTS ON ASPHALT MIXTURES

2016 ◽  
Vol 78 (7-2) ◽  
Author(s):  
Fauzan Mohd Jakarni ◽  
Muhammad Fudhail Rosli ◽  
Nur Izzi Md Yusoff ◽  
Md Maniruzzaman A Aziz ◽  
Ratnasamy Muniandy ◽  
...  
Keyword(s):  
Moisture Damage ◽  
Test Methods ◽  
Asphalt Mixtures ◽  
Performance Tests ◽  
Cohesive Failure ◽  
Modified Bitumen ◽  
Traffic Loading ◽  
Construction Methods ◽  
Evaluation Phase ◽  
Two Phases

This paper presents a review of moisture damage performance tests on asphalt mixtures. The moisture damage remains to be a detriment to the durability of the Hot Mix Asphalt (HMA) pavement. Moisture damage can be defined in forms of adhesive failure between bitumen and aggregates and cohesive failure within bitumen. Aggregate mineralogy, bitumen characteristics and anti-stripping additive dominantly influence the performance of asphalt mixtures towards moisture damage alongside construction methods, climate and traffic loading. Various laboratory test methods have been developed to quantify the moisture damage performance of asphalt mixtures by resembles the action in the field, including qualitative test such as Boiling Water Test (ASTM D3625) and quantitative tests such as Modified Lottman Test (AASHTO T283). Both of these tests consist of two phases, which are conditioning and evaluation phase. This paper will review the effectiveness of the selected available tests based on various asphalt mixtures materials. Generally, this study indicates that asphalt mixtures consisted of limestone aggregates, modified bitumen and addition of anti-stripping additives will provide more resistant towards moisture damage. 

scholarly journals Experimental Behavior of Precast Bridge Deck Systems with Non-Proprietary UHPC Transverse Field Joints

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6964
Author(s):  
Mohamed Abokifa ◽  
Mohamed A. Moustafa
Keyword(s):  
High Performance ◽  
Bridge Deck ◽  
High Performance Concrete ◽  
Experimental Testing ◽  
Bridge Decks ◽  
Transverse Field ◽  
Full Scale ◽  
Bridge Construction ◽  
Vertical Loading ◽  
Precast Bridge Deck

Full-depth precast bridge decks are widely used to expedite bridge construction and enhance durability. These deck systems face the challenge that their durability and performance are usually dictated by the effectiveness of their field joints and closure joint materials. Hence, commercial ultra-high performance concrete (UHPC) products have gained popularity for use in such joints because of their superior mechanical properties. However, the proprietary and relatively expensive nature of the robust UHPC mixes may pose some limitations on their future implementation. For these reasons, many research agencies along with state departments of transportation sought their way to develop cheaper non-proprietary UHPC (NP-UHPC) mixes using locally supplied materials. The objective of this study is to demonstrate the full-scale application of the recently developed NP-UHPC mixes at the ABC-UTC (accelerated bridge construction university transportation center) in transverse field joints of precast bridge decks. This study included experimental testing of three full-scale precast bridge deck subassemblies with transverse NP-UHPC field joints under static vertical loading. The test parameters included NP-UHPC mixes with different steel fibers amount, different joint splice details, and joint widths. The results of this study were compared with the results of a similar proprietary UHPC reference specimen. The structural behavior of the test specimens was evaluated in terms of the load versus deflection, reinforcement and concrete strains, and full assessment of the field joint performance. The study showed that the proposed NP-UHPC mixes and field joint details can be efficiently used in the transverse deck field joints with comparable behavior to the proprietary UHPC joints. The study concluded that the proposed systems remained elastic under the target design service and ultimate loads. In addition, the study showed that the use of reinforcement loop splices enhanced the load distribution across the specimen’s cross-section.

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