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2004

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Articles 15751 - 15780 of 18252

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Single-Phase Flow And Heat Transport And Pumping Considerations In Microchannel Heat Sinks, S V. Garimella, Vishal Singhal Jan 2004

Single-Phase Flow And Heat Transport And Pumping Considerations In Microchannel Heat Sinks, S V. Garimella, Vishal Singhal

CTRC Research Publications

Microchannel heat sinks are widely regarded as being among the most effective heat removal techniques from space-constrained electronic devices. However, the fluid flow and heat transfer in microchannels is not fully understood. The pumping requirements for flow through microchannels are also very high, and none of the micropumps in the literature is truly suitable for this application. Results are reported from a wide-ranging research program being conducted on microchannel heat sinks and micropumps to understand fluid flow and heat transfer in microchannels and to identify pumping requirements and suitable mechanisms for pumping in microchannels. In particular, experiments have been performed …

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Simulation Of Ion Generation And Breakdown In Atmospheric Air, W. Zhang, T. S. Fisher, S V. Garimella Jan 2004

Simulation Of Ion Generation And Breakdown In Atmospheric Air, W. Zhang, T. S. Fisher, S V. Garimella

CTRC Research Publications

Understanding of ion generation in air provides insights to several applications, such as gas sensors, electrohydrodynamic pumping, and air purification. In this paper, ion generation processes in atmospheric air are simulated using a particle-in-cell and Monte Carlo method with emphasis on the prediction of ion generation and breakdown characteristics in microscale gaps. The simulation results are validated through comparison to Townsend’s discharge theory and experiments. The significance of each relevant electron-molecule reaction is characterized to improve understanding of ion generation dynamics. Self-sustaining discharge and ionization are predicted under sufficient voltage bias, and the predicted trends of breakdown voltage are similar …

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Investigation Of Liquid Flow In Microchannels, D. Liu, S V. Garimella Jan 2004

Investigation Of Liquid Flow In Microchannels, D. Liu, S V. Garimella

CTRC Research Publications

Liquid flow in microchannels is investigated both experimentally and numerically in this work. The experiments are carried out in microchannels with hydraulic diameters from 244 to 974 m at Reynolds numbers ranging from 230 to 6500. The pressure drop in these microchannels is measured in situ, and is also determined by correcting global measurements for inlet and exit losses. Onset of turbulence is verified by flow visualization. The experimental measurements of pressure drop are compared to numerical predictions. Results from this work show that conventional theory may be used to successfully predict the flow behavior in microchannels in the range …

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High-Field Quasi-Ballistic Transport In Short Carbon Nanotubes, Ali Javey, Jing Guo, Magnus Paulsson, Qian Wang, Mark S. Lundstrom, Hongjie Dai, David Mann Jan 2004

High-Field Quasi-Ballistic Transport In Short Carbon Nanotubes, Ali Javey, Jing Guo, Magnus Paulsson, Qian Wang, Mark S. Lundstrom, Hongjie Dai, David Mann

Department of Electrical and Computer Engineering Faculty Publications

Single walled carbon nanotubes with Pd Ohmic contacts and lengths ranging from several microns down to 10 nm are investigated by electron transport experiments and theory. The mean-free path (MFP) for acoustic phonon scattering is estimated to be lap ~300  nm, and that for optical phonon scattering is lop ~15  nm. Transport through very short (~10  nm) nanotubes is free of significant acoustic and optical phonon scattering and thus ballistic and quasiballistic at the low- and high-bias voltage limits, respectively. High currents of up to 70   μA can flow through a short nanotube. Possible mechanisms for the eventual electrical breakdown …

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A Three-Dimensional Quantum Simulation Of Silicon Nanowire Transistors With The Effective Mass Approximation, Jing Wang, Eric Polizzi, Mark S. Lundstrom Jan 2004

A Three-Dimensional Quantum Simulation Of Silicon Nanowire Transistors With The Effective Mass Approximation, Jing Wang, Eric Polizzi, Mark S. Lundstrom

Department of Electrical and Computer Engineering Faculty Publications

The silicon nanowire transistor (SNWT) is a promising device structure for future integrated circuits, and simulations will be important for understanding its device physics and assessing its ultimate performance limits. In this work, we present a three-dimensional (3D) quantum mechanical simulation approach to treat various SNWTs within the effective-mass approximation. We begin by assuming ballistic transport, which gives the upper performance limit of the devices. The use of a mode space approach (either coupled or uncoupled) produces high computational efficiency that makes our 3D quantum simulator practical for extensive device simulation and design. Scattering in SNWTs is then treated by …

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Analysis Of A Phase Change Energy Storage System For Pulsed Power Dissipation, S Krishnan, S V. Garimella Jan 2004

Analysis Of A Phase Change Energy Storage System For Pulsed Power Dissipation, S Krishnan, S V. Garimella

CTRC Research Publications

The melting of a phase change material in a container of rectangular cross-section with multiple discrete heat sources mounted on one side is investigated for electronics cooling by latent heat energy storage. This numerical study focuses on the thermal management issues that arise when electronic components experience sudden surges in power dissipation. The transient response of the energy storage system to short pulses in power dissipation is studied. Convective cooling using air-cooled heat sinks on the sides of the containment remote from the heat sources provides for heat rejection to ambient air. The analysis is performed under different pulse frequencies. …

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Thermal Management Of Transient Power Spikes In Electronics - Phase Change Energy Storage Or Copper Heat Sinks?, S. Krishnan, S V. Garimella Jan 2004

Thermal Management Of Transient Power Spikes In Electronics - Phase Change Energy Storage Or Copper Heat Sinks?, S. Krishnan, S V. Garimella

CTRC Research Publications

A transient thermal analysis is performed to investigate thermal control of power semiconductors using phase change materials, and to compare the performance of this approach to that of copper heat sinks. Both the melting of the phase change material under a transient power spike input, as well as the resolidification process, are considered. Phase change materials of different kinds (paraffin waxes and metallic alloys) are considered, with and without the use of thermal conductivity enhancers. Simple expressions for the melt depth, melting time and temperature distribution are presented in terms of the dimensions of the heat sink and the thermophysical …

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A Two-Temperature Model For The Analysis Of Passive Thermal Control Systems, S. Krishnan, J. Y. Murthy, S V. Garimella Jan 2004

A Two-Temperature Model For The Analysis Of Passive Thermal Control Systems, S. Krishnan, J. Y. Murthy, S V. Garimella

CTRC Research Publications

Passive control of steady and unsteady thermal loads using effective thermal conductivity enhancers, such as metal foams, internal fins and metal filler particles, is being explored for a variety of electronics applications. The interstices are filled with air, phase change materials, or other fluids. Local thermal equilibrium between the solid filler and the matrix is not ensured in such systems since their thermal diffusivities are frequently very different. The use of a single volume-averaged energy equation for both the phases cannot be justified in such situations. A two-medium approach is used in the present work to account for the local …

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Design Of Flapper Valves For A Co2 Commercial Refrigeration Compressor, Douglas A. Collings, Thomas J. Weadock Jan 2004

Design Of Flapper Valves For A Co2 Commercial Refrigeration Compressor, Douglas A. Collings, Thomas J. Weadock

International Compressor Engineering Conference

No abstract provided.

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Optimizing Chest Compression To Rescue Ventilation Ratios During One-Rescuer Cpr By Professionals And Lay Persons: Children Are Not Just Little Adults, Charles F. Babbs, Vinay Nadkarni Jan 2004

Optimizing Chest Compression To Rescue Ventilation Ratios During One-Rescuer Cpr By Professionals And Lay Persons: Children Are Not Just Little Adults, Charles F. Babbs, Vinay Nadkarni

Weldon School of Biomedical Engineering Faculty Publications

Objective: To estimate the optimum ratio of chest compressions to ventilations for onerescuer CPR that maximizes systemic oxygen delivery in children. Method: Equations describing oxygen delivery and blood flow during CPR as functions of the number of compressions and the number of ventilations delivered over time were adapted from the former work of Babbs and Kern. These equations were solved explicitly as a function of body weight, using scaling algorithms based upon principles of developmental anatomy and physiology. Results: The optimal compression to ventilation (C/V) ratios for infants and younger children increase sharply as a function of body weight. Optimal …

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Thermal And Fluid Dynamic Behavior Of Trans-Critical Carbon Dioxide Hermetic Reciprocating Compressors: Numerical Analysis, Carlos D. Perã©Z Segarra, Joaquim Rigola, Assensi Oliva Jan 2004

Thermal And Fluid Dynamic Behavior Of Trans-Critical Carbon Dioxide Hermetic Reciprocating Compressors: Numerical Analysis, Carlos D. Perã©Z Segarra, Joaquim Rigola, Assensi Oliva

International Compressor Engineering Conference

No abstract provided.

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Turbo Water Chiller With Water As Refrigerant, Eberhard Wobst, Nikolai Kalitzin, Rainer Apley Jan 2004

Turbo Water Chiller With Water As Refrigerant, Eberhard Wobst, Nikolai Kalitzin, Rainer Apley

International Compressor Engineering Conference

No abstract provided.

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Conceptual Design Study Of A Supersonic Compressor Applied To Refrigerant Compression Cycles, Shawn P. Lawlor, Paul M. Brown, Steven G. Mackin Jan 2004

Conceptual Design Study Of A Supersonic Compressor Applied To Refrigerant Compression Cycles, Shawn P. Lawlor, Paul M. Brown, Steven G. Mackin

International Compressor Engineering Conference

No abstract provided.

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Performance Study Of A 3-Ton Residential Co2 A/C System With A Variable Flow Rate Co2 Compressor, Rodney A. Hugelman Jan 2004

Performance Study Of A 3-Ton Residential Co2 A/C System With A Variable Flow Rate Co2 Compressor, Rodney A. Hugelman

International Compressor Engineering Conference

No abstract provided.

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Vapor Injection In Scroll Compressors, Siddharth Jain, Gaurav Jain, Clark W. Bullard Jan 2004

Vapor Injection In Scroll Compressors, Siddharth Jain, Gaurav Jain, Clark W. Bullard

International Compressor Engineering Conference

No abstract provided.

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Modeling And Testing Of An Automobile Ac Scroll Compressor, Part I: Model Development, Feng Shou Yi, Eckhard A. Groll, James A. Braun Jan 2004

Modeling And Testing Of An Automobile Ac Scroll Compressor, Part I: Model Development, Feng Shou Yi, Eckhard A. Groll, James A. Braun

International Compressor Engineering Conference

No abstract provided.

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Instantaneous Frequency: Another Tool Of Source Of Noise Identification, Hubert Bukac Jan 2004

Instantaneous Frequency: Another Tool Of Source Of Noise Identification, Hubert Bukac

International Compressor Engineering Conference

No abstract provided.

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A Universal Simulation Tool For Reed Valve Dynamics, Gunther Machu, Maximilian Albrecht, Olaf Bielmeier, Thomas Daxner, Peter Steinruck Jan 2004

A Universal Simulation Tool For Reed Valve Dynamics, Gunther Machu, Maximilian Albrecht, Olaf Bielmeier, Thomas Daxner, Peter Steinruck

International Compressor Engineering Conference

No abstract provided.

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Lubrication Mechanism At Thrust Slide-Bearing Of Scroll Compressors (Experimental Study), Noriaki Ishii, Tatsuya Oku, Keiko Anami, Akinori Fukuda Jan 2004

Lubrication Mechanism At Thrust Slide-Bearing Of Scroll Compressors (Experimental Study), Noriaki Ishii, Tatsuya Oku, Keiko Anami, Akinori Fukuda

International Compressor Engineering Conference

No abstract provided.

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Friction Factor Under Transient Flow Condition, Fernando A. Ribas, Cesar J. Deschamps Jan 2004

Friction Factor Under Transient Flow Condition, Fernando A. Ribas, Cesar J. Deschamps

International Compressor Engineering Conference

No abstract provided.

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Computer Simulation And Experimental Validation Of Scroll Compressors, Yu Choung Chang, Ching Eeng Tsai, Ching Huan Tseng, Guang Der Tarng, Lung Tsai Chang Jan 2004

Computer Simulation And Experimental Validation Of Scroll Compressors, Yu Choung Chang, Ching Eeng Tsai, Ching Huan Tseng, Guang Der Tarng, Lung Tsai Chang

International Compressor Engineering Conference

No abstract provided.

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Simulation Of An Innovative Rotary Compressor With Variable Speed Displacers, A. R. Barreto, Julio Kopelowicz, Jose A. R. Parise Jan 2004

Simulation Of An Innovative Rotary Compressor With Variable Speed Displacers, A. R. Barreto, Julio Kopelowicz, Jose A. R. Parise

International Compressor Engineering Conference

No abstract provided.

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Cfd For Positive Displacement Compressors, B. G. Shiva Prasad Jan 2004

Cfd For Positive Displacement Compressors, B. G. Shiva Prasad

International Compressor Engineering Conference

No abstract provided.

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A Study On Lubrication Characteristics Of Journal And Thrust Bearings In Scroll Compressors, Atsuo Okaichi, Hiroshi Hasegawa, Fumitoshi Nishiwaki Jan 2004

A Study On Lubrication Characteristics Of Journal And Thrust Bearings In Scroll Compressors, Atsuo Okaichi, Hiroshi Hasegawa, Fumitoshi Nishiwaki

International Compressor Engineering Conference

No abstract provided.

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A Uniform Property Region Method For Screw Compressor's End-Face Leakage Prediction, Calim Zamfirescu, Carlos A. Infante Ferreira Jan 2004

A Uniform Property Region Method For Screw Compressor's End-Face Leakage Prediction, Calim Zamfirescu, Carlos A. Infante Ferreira

International Compressor Engineering Conference

No abstract provided.

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Modeling Capacity And Coefficient Of Performance Of A Refrigeration Compressor, Hubert Bukac Jan 2004

Modeling Capacity And Coefficient Of Performance Of A Refrigeration Compressor, Hubert Bukac

International Compressor Engineering Conference

No abstract provided.

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Design Optimization Of An Oil-Flooded Refrigeration Single Screw Compressor, Hong Qi Li, Li Wen Jin Jan 2004

Design Optimization Of An Oil-Flooded Refrigeration Single Screw Compressor, Hong Qi Li, Li Wen Jin

International Compressor Engineering Conference

No abstract provided.

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Improving Centrifugal Compressor Performance By Optimizing Diffuser Surge Control (Variable Diffuser Geometry) And Flow Control (Inlet Guide Vane) Device Settings, Lee G. Tetu Jan 2004

Improving Centrifugal Compressor Performance By Optimizing Diffuser Surge Control (Variable Diffuser Geometry) And Flow Control (Inlet Guide Vane) Device Settings, Lee G. Tetu

International Compressor Engineering Conference

No abstract provided.

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Impact Fatigue On Suction Valve Reed: New Experimental Approach, Michele Libralato, Andrea Contarini Jan 2004

Impact Fatigue On Suction Valve Reed: New Experimental Approach, Michele Libralato, Andrea Contarini

International Compressor Engineering Conference

No abstract provided.

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Thermal Expansion Prediction Of Compressor Piston, Mario Lavella, Paolo Valero, Roberto Doglione, Marek Zgliczynski Jan 2004

Thermal Expansion Prediction Of Compressor Piston, Mario Lavella, Paolo Valero, Roberto Doglione, Marek Zgliczynski

International Compressor Engineering Conference

No abstract provided.

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