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510 results on '"Fedorov, Andrei G."'

103. Exergy Analysis of an Absorption Refrigeration System Using an Iconic Liquid as a Working Fluid in the Chemical Compressor

Author

Kim, Yoon Jo, Kim, Sarah, Joshi, Yogendra K., Fedorov, Andrei G., and Kohl, Paul A.

Subjects
absorption system, electronics cooling, Ionic liquid
Abstract

The first and second law of thermodynamics are applied to an ionic-liquid (IL) based absorption refrigeration system for high power electronics cooling. The IL is a salt in a liquid state usually with an organic cation and inorganic anion. It provides an alternative to the normally toxic working fluids used in the chemical compression loop, such as ammonia in conventional absorption systems. The use of ILs also eliminates crystallization and metal-compatibility problems of the water/LiBr system. In this study, mixtures of refrigerants and imidazolium-based ILs are theoretically explored as the working fluid pairs in a miniature absorption refrigeration system, so as to utilize waste-heat to power a refrigeration/heat pump system for electronics cooling. A mathematical model based on exergy analysis is employed to characterize the performance for specific refrigerant/IL pairs. Both the coefficient of performance (COP) and the exergetic coefficient of performance (ECOP) of the absorption system and components are evaluated. The thermodynamic properties of ILs are evaluated using the correlations based on group contribution methods. A non-random two-liquid (NRTL) model is built and used to predict the solubility of the mixtures. The properties of the refrigerants are determined using REFPROP 6.0 software. Saturation temperatures at the evaporator and condenser are set at 25oC and 50oC, respectively. The power dissipation at the evaporator is fixed at 100 W with the operating temperature set at 85oC, which are the benchmark conditions for high performance microprocessor chip cooling. The desorber and absorber outlet temperatures are adjusted to evaluate the system performance variation with respect to the operating condition change. The effect of the refrigerant/IL compatibility, alkyl chain length of the IL cation, and thermodynamic properties of the refrigerants, such as latent heat of evaporation, on the ECOP is investigated. Also the exergy destruction of each component of the cycle is evaluated and discussed as a means to identify the critical component(s) of the system that would require optimization.

Published
2012

112. Nanoscale design to enable the revolution in renewable energy

Author

Baxter, Jason, Bian, Zhixi, Chen, Gang, Danielson, David, Dresselhaus, Mildred S, Fedorov, Andrei G, Fisher, Timothy, Jones, Christopher W, Maginn, Edward, Kortshagen, Uwe, Manthiram, Arumugam, Nozik, Arthur, Sholl, David, and Wu, Yiying

Subjects
Nanoscale, renewable, energy, Nanoscience and Nanotechnology
Abstract

The creation of a sustainable energy generation, storage, and distribution infrastructure represents a global grand challenge that requires massive transnational investments in the research and development of energy technologies that will provide the amount of energy needed on a sufficient scale and timeframe with minimal impact on the environment and have limited economic and societal disruption during implementation. In this opinion paper, we focus on an important set of solar, thermal, and electrochemical energy conversion, storage, and conservation technologies specifically related to recent and prospective advances in nanoscale science and technology that offer high potential in addressing the energy challenge. We approach this task from a two-fold perspective: analyzing the fundamental physicochemical principles and engineering aspects of these energy technologies and identifying unique opportunities enabled by nanoscale design of materials, processes, and systems in order to improve performance and reduce costs. Our principal goal is to establish a roadmap for research and development activities in nanoscale science and technology that would significantly advance and accelerate the implementation of renewable energy technologies. In all cases we make specific recommendations for research needs in the near-term (2–5 years), mid-term (5–10 years) and long-term (>10 years), as well as projecting a timeline for maturation of each technological solution. We also identify a number of priority themes in basic energy science that cut across the entire spectrum

Published
2009

122. Using Amphiphilic Nanostructures to Enable Long-Range Ensemble Coalescence and Surface Rejuvenation in Dropwise Condensation

Author

GEORGIA INST OF TECH ATLANTA SCHOOL OF MATERIALS SCIENCE AND ENGINEERING, Anderson, David M, Gupta, Maneesh K, Voevodin, Andrey A, Hunter, Chad N, Putnam, Shawn A, Tsukruk, Vladimir V, Fedorov, Andrei G, GEORGIA INST OF TECH ATLANTA SCHOOL OF MATERIALS SCIENCE AND ENGINEERING, Anderson, David M, Gupta, Maneesh K, Voevodin, Andrey A, Hunter, Chad N, Putnam, Shawn A, Tsukruk, Vladimir V, and Fedorov, Andrei G

Abstract

Controlling coalescence events in a heterogeneous ensemble of condensing droplets on a surface is an outstanding fundamental challenge in surface and interfacial sciences, with a broad practical importance in applications ranging from thermal management of high-performance electronic devices to moisture management in high-humidity environments. Nature-inspired superhydrophobic surfaces have been actively explored to enhance heat and mass transfer rates by achieving favorable dynamics during dropwise condensation; however, the effectiveness of such chemically homogeneous surfaces has been limited because condensing droplets tend to form as pinned Wenzel drops rather than mobile Cassie ones. Here, we introduce an amphiphilic nanostructured surface, consisting of a hydrophilic base with hydrophobic tips, which promotes the periodic regeneration of nucleation sites for small droplets, thus rendering the surface self-rejuvenating. This unique amphiphilic nanointerface generates an arrangement of condensed Wenzel droplets that are fluidically linked by a wetted sublayer, promoting previously unobserved coalescence events where numerous droplets simultaneously merge, without direct contact. Such ensemble coalescences rapidly create fresh nucleation sites, thereby shifting the overall population toward smaller droplets and enhancing the rates of mass and heat transfer during condensation., Published in ACS Nano, v6 n4 p3262-3268, 2012.

Published
2012

123. Foro virtual como una estrategia metodológica para el desarrollo del pensamiento crítico en la universidad

Author

Fedorov, Andrei G. and Fedorov, Andrei G.

Abstract

Las grandes complejidades y vertiginosas transformaciones del mundo actual imploran que los ciudadanos tengan, usen y perfeccionen el pensamiento de alta calidad. En este contexto, la demanda de desarrollo del pensamiento crítico en los futuros profesionales que acuden a la universidad, requiere no solo de una evolución de contenidos sino, también, de una transformación de los métodos y medios de la enseñanza y el aprendizaje.Para cumplir con este cometido, la pedagogía universitaria debe redefinir en la práctica los roles de los actores del proceso formativo y ofrecer las estrategias metodológicas adecuadas. En el presente artículo, el desarrollo del pensamiento crítico se enfoca a través de la aplicación de la metodología del foro virtual. Se presenta una breve contextualización del tema y se expone una parte de los resultados de una investigación original de corte descriptivo, llevada a cabo en el Instituto Tecnológico de Costa Rica, entre los años 2005 y 2006.Así, se demuestra que, según la opinión de los estudiantes, la estrategia metodológica del foro virtual incide positivamente en el desarrollo de diferentes elementos del pensamiento crítico. Al mismo tiempo, se esclarece la estructura del constructo, donde la dimensión actitudinaly la autorregulativa poseen roles preponderantes y logran potenciar las operaciones cognitivas llevándolas al más alto nivel de competencia en el desarrollo del pensamiento crítico.

Published
2008

126. Three-Dimensional Integrated Circuit With Embedded Microfluidic Cooling: Technology, Thermal Performance, and Electrical Implications.

Author

Xuchen Zhang, Xuefei Han, Sarvey, Thomas E., Green, Craig E., Kottke, Peter A., Fedorov, Andrei G., Joshi, Yogendra, and Bakir, Muhannad S.

Subjects
THERMAL analysis, MICROPROCESSORS, HEAT sinks (Electronics), SILICON research, ANTENNA arrays
Abstract

This paper reports on novel thermal testbeds with embedded micropin-fin heat sinks that were designed and microfabricated in silicon. Two micropin-fin arrays were presented, each with a nominal pin height of 200 µm and pin diameters of 90 µm and 30 µm. Single-phase and two-phase thermal testing of the micropin-fin array heat sinks were performed using de-ionized (DI) water as the coolant. The tested mass flow rate was 0.001 kg/s, and heat flux ranged from 30 W/cm² to 470 W/cm². The maximum heat transfer coefficient reached was 60 kW/m² K. The results obtained from the two testbeds were compared and analyzed, showing that density of the micropin-fins has a significant impact on thermal performance. The convective thermal resistance in the single-phase region was calculated and fitted to an empirical model. The model was then used to explore the tradeoff between the electrical and thermal performance in heat sink design. [ABSTRACT FROM AUTHOR]

Published
2016
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137. Ensilla un caballo para que hale un Porsche

Author

Fedorov, Andrei G. and Fedorov, Andrei G.

Abstract

El artículo pretende coadyuvar en la creación de conciencia sobre la necesidad de redimensionar la potencialidad de las TIC en su papel de transformador de la educación superior en el contexto de un país pequeño en vías de desarrollo, como lo es Costa Rica.

Published
2004

138. ¿Cómo poner a funcionar un proyecto de virtualización?

Author

Fedorov, Andrei G. and Fedorov, Andrei G.

Abstract

El presente artículo pretende presentar y debatir el rol del asesor académico, como coordinador del equipo interdisciplinariode acuerdo con las experiencias políticas, administrativas, pedagógicas, técnicas y personales generadas en las primeras etapas del desarrollo del proyecto pedagógico de virtualización de la enseñanza y el aprendizaje del Instituto Tecnológico deCosta Rica.

Published
2004

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