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Keynote Speakers


  Jader R. Barbosa, Jr.
Polo - Research Laboratories for Emerging Technologies in Cooling and Thermophysics Department of Mechanical Engineering, Federal University of Santa Catarina, Brazil


Presentation Title: Recent Developments in Vapor Compression Technologies Ror Small Scale Refrigeration Applications
Abstract: The purpose of the talk is to review some of the current trends and research efforts associated with the development of compact (i.e., miniaturized) mechanical vapor compression refrigeration systems intended for avant-garde applications such as cooling of microprocessors. Over the past decade, there has been a significant number of studies devoted to the miniaturization of the components of the refrigeration system, the most critical being the compressor. The paper will focus on the thermodynamic and thermal aspects associated with the development of small compressors and other components of the small-scale cooling cycle. Whenever appropriate, issues and challenges associated with different cycle designs will be addressed. An overview of the ongoing efforts in competing technologies will also be presented.


Biography: Jader R. Barbosa, Jr. holds B.Sc. (1995) and M.Sc. (1997) degrees in Mechanical Engineering from the Federal University of Rio de Janeiro, Brazil, and a Ph.D. in Chemical Engineering from Imperial College, University of London (2001). He is Associate Professor at the Department of Mechanical Engineering of the Federal University of Santa Catarina, Brazil. In 2004, he received the Young Scientist Award from the European Committee for the advancement of Thermal Sciences (EUROTHERM). He also received the Dudley Newitt Award (2001) of Imperial College for a Doctoral Thesis of Exceptional Merit, and the HTFS Award (Heat Transfer and Fluid Flow Service) for the best paper at the UK National Heat Transfer Conference (Edinburgh, 1999). He has published more than 90 scientific papers in indexed journals and international peer-reviewed conferences. He carries out research on Fluids Engineering and Thermal Sciences, with a focus on Thermodynamics of Mixtures, Phase Change, Multiphase Flows, Heat Exchangers and Cooling Technologies.


 
  Dominik P. J. Barz
Queen's University, Department of Chemical Engineering, Kingston, Canada


Presentation Title: An Electrokinetic Micro Mixer for Lab-on-Chip Applications: Modeling, Validation, and Optimization
Abstract: Mixing of liquids in micro mixers at low Reynolds numbers is a challenging task since the flow regime is laminar and it is difficult to engage instabilities of the flow. In microfluidic systems based on silicone or synthetic materials, mixing can be improved by means of electrokinetic effects. A favourable but simple micro mixer design consists of a Y-junction, where the different liquid streams merge, and a subsequent twice-folded microchannel. A pressure gradient pumps the liquids to be mixed through the micro mixer. An oscillating electrical field is superimposed onto the pressure-driven base flow which generates an additional electrokinetic (electro osmotic) flow in the microchannels. These oscillating secondary flows in conjunction with the meandering geometry are responsible for stretching and folding of the contact area of the liquids to be mixed which enhance the mass transfer rates considerably. In this contribution, we present a mathematical model which allows for the numerical simulation of flow, electrical potential, and species concentration. The model is validated by experiments relying on Micro Particle Image Velocimetry (µPIV) and Micro Laser Induced Fluorescence (µLIF) for flow and concentration field, respectively. Consequently, the model is used to optimize the mode of operation of the micro mixer with respect to electrical field's signal form and frequency in order to achieve fast and high mixing even at low Reynolds Numbers.


Hendryk Bockelmann1, Vincent Heuveline1, Peter Ehrhard2, and Dominik P.J. Barz3
1Karlsruhe Institute of Technology, Department of Mathematics, AG Numerical Simulation, Optimization and High Performance Computing, Karlsruhe, Germany
2Dortmund University of Technology, Department of Biochemical and Chemical Engineering, Fluid Mechanics, Dortmund, Germany
3Queen's University, Department of Chemical Engineering, Kingston, Canada


Biography: Dr. Dominik P.J. Barz received a B.Sc. (Diplom-Ingenieur FH) in Mechanical Engineering at Aachen University (FH), Germany in 1996. Prior to chosing an academic career, he held several positions in industry and public sector in Germany. He had been working as a lab engineer at the Mercedes Benz endowed Fuel Cells Lab at FHTG Mannheim and he was a (Senior) Research Engineer working on Lab-on-Chip technologies at Forschungszentrum Karlsruhe GmbH. During these full time employments, he also graduated in 2001 with a M.Sc. (Diplom-Ingenieur) with distinction in Chemical Engineering from Dresden University of Technology, Germany. In 2005, he obtained a Ph.D. (Doktor-Ingenieur) with distinction in Mechanical Engineering from University of Karlsruhe, Germany. He joined Cornell University, US in 2007 for a postdoctoral fellowship, working on interface and transport phenomena in porous media. He then returned to Forschungszentrum Karlsruhe GmbH to assume a position as a Senior Research Engineer in the Chemical Process Technology Department in 2008. Dr. Barz joined Queen's University, Canada as an Assistant Professor of Chemical Engineering in August 2010. His academic and industrial experience has been in areas encompassing both Mechanical and Chemical Engineering subjects and, hence, his current research includes Microfluidics, Interface Phenomena, Electrochemical Engineering, and the Miniaturization of Chemical Reactors.


 
  Art Bergles
Rensselaer Polytechnic Institute, University of Maryland, Massachusetts Institute of Technology


Presentation Title: Stability and Enhancement of Boiling in Microchannels
Abstract: During the past 15 years, there has been worldwide interest in microchannel heat exchangers, particularly for cooling of microelectronic components. Boiling of the coolant is usually indicated in order to accommodate high heat fluxes and to have uniformity of temperature. However, boiling is accompanied by several instabilities, the most severe of which can sharply limit the maximum heat flux. These stability phenomena will be reviewed, and many recent studies will be discussed. Elevation of the maximum, or critical, heat flux will be discussed within the context of heat transfer enhancement. Means to improve the stability of boiling and other CHF enhancement techniques will be noted.


Biography: Art Bergles has been involved with heat transfer, particularly heat transfer enhancement, throughout his career. He has published over 400 papers, many authored/edited books, and numerous technical reports. He is the Clark and Crossan Professor of Engineering, Emeritus at Rensselaer Polytechnic Institute, Glenn L. Martin Institute Professor of Engineering at University of Maryland, and Senior Lecturer at Massachusetts Institute of Technology. He is a member of 4 engineering/scientific academies, was awarded 3 honorary degrees, and is an honorary professor at 2 foreign universities. He has received major awards from AIAA, AAAS, AIChE, ASHRAE, ASME, SAE, and other organizations.


 
  Avijit Bhunia
Teledyne Scientific Company, Thousand Oaks, CA


Presentation Title: Scalability of Liquid Micro-Jet Impingement Cooling
Abstract: The power density of the semiconductor devices used in various air, space, ship and ground-based military systems is growing rapidly with increasing push towards more electric power. The dissipation power density is also escalating proportionately, reaching hundreds, thousands, and even tens of thousands Watts/cm2 level. The device performance is often "thermally limited" due to the limitations of current cooling techniques. Multiple high heat flux cooling approaches have evolved over the past decade to meet this growing challenge. This article focuses on liquid micro-jet impingement, emphasizing on the scalability of the technique. Impingement area covered by a single micro-jet, and the jet-to-jet interaction on the impingement surface in case of a jet array, are shown to be the key parameters dictating the scalability. Results illustrate that this technique can be scaled up from the micro-scale chip level to hundreds of cm2 area sub-system or system level, with nominal non-uniformity of temperature.


Biography: Dr. Avijit Bhunia is a Research Scientist at Teledyne Scientific Company (formerly Rockwell Science Center) at Thousand Oaks, California. He is responsible for developing high heat flux cooling techniques, and leading the wide bandgap power electronics program. Dr. Bhunia was also a Faculty at the Indian Institute of Technology (IIT), Madras for an academic year. He received his Ph.D. in Mechanical & Aerospace Engineering from Case Western Reserve University, Cleveland, OH. He has extensive experience in the areas of electronic cooling, two-phase flow, surface science, instability, atomization, and microgravity fluids. He has authored over thirty articles and has four pending patent applications.


 
  Bing-Yang Cao
Department of Engineering Mechanics, Tsinghua University, Beijing, China


Presentation Title: Polymer Nanowire Arrays With High Thermal Conductivity and Superhydrophobicity Fabricated by a Nano-Injected Moulding Technique
Abstract: High thermal conductivity and superhydrophobicity are highly desired for micro/nanofluidic devices. Good thermal conductivity is helpful for thermal control and managements. Superhydrophobicity can benefit fluid friction reduction and liquid droplet control. We report on an improved nano-injection moulding technique which can prepare polymer (high density polyethylene/HDPE) nanowire arrays with high thermal conductivity (more than 10W/mK) and superhydrophobicity (contact angle >150°). This technique is promising for fabrication of micro/nanofluidics devices due to the advantages of simple fabrication, high-quality, low-cost, and mass-production.


Biography: Bing-Yang Cao received his B.S. (1998) and M.S. (2001) in engineering thermophysics from Shandong University, and Ph.D. (2005) in power engineering and engineering thermophysics from Tsinghua University. He joined Tsinghua University in 2005, and is currently an associate professor in the Department of Engineering Mechanics, Tsinghua University, Beijing, China. He also worked in Kyushu University (2005), The Hong Kong Polytechnic University (2006) and The University of Brighton (2007,2010) as a visiting researcher. His current research interests include micro- and nanoscale fluid flow and heat/mass transfer, thermomass theory and its applications, interfacial phenomena, and molecular dynamics simulation.


 
  Takemi Chikahisa
Division of Energy and Environmental Systems, Hokkaido University, Japan


Presentation Title: Microscopic Observation of Freezing Phenomena In PEM Fuel Cell at Cold Start
Abstract: In Polymer electrolyte membrane fuel cells (PEMFCs), the freezing of produced water induces the extreme deterioration of cell performance below zero. We have investigated ice distribution in the catalyst layer and in the gas diffusion layer (GDL) to clarify the freezing mechanism using an optical microscope and a CRYOSEM. The observation result shows the apparent difference in the ice formation characteristics between -10oC and -20oC. Ice formation difference was also found for the GDLs with and without micro-porous layer. It was observed that cell performance after melting was not recovered to the original level before freezing depending on the freezing temperatures. Therese results together with the ice observation with microscope implies the water transport phenomena though micro-porous layers.


Biography: I was a researcher of internal combustion engines, and I proposed a similarity theory of combustion in diesel engines. Recently I have been working on the water transport behavior in PEM fuel cell and trying to find optimal design structure of gas channel and gas diffusion layer (GDL). I am also interested in the analysis of effective strategy of reducing CO2 emission from a country with keeping employment by using MARKAL model.


 
  Adam Donaldson
Department of Chemical and Biological Engineering, University of Ottawa


Presentation Title: Enhancement of Inter-Phase Transport in Mini/Mico-Scale Applications Using Passive Mixing
Abstract: Structured mini/micro-scale reactors continue to receive attention from both industry and academia due to their low pressure drop, high mass transfer rates and ease of scale-up when compared to conventional reactor technology. Commonly considered for heat and mass transfer limited reactions such as hydrogenations, hydrodesulphurization, oxidations and Fischer-Tropsch synthesis, the performance of these systems is highly dependent on mixing and interfacial surface area between multiple phases. While existing literature describes the initial flow patterns generated by a broad range of two-phase contactors, few studies have explored the dynamic impact of downstream passive mixing elements on flow patterns and inter-phase mass transport. Two-phase flow pattern transitions, pressure drop and mixing in planar serpentines with circular cross-sections and venturi-based passive mixing elements are explored both experimentally and computationally for moderate flow conditions. The serpentine and venturi employ different mechanisms of inducing bubble breakup (viscous shear and inertial impingement, respectively), providing an illustration of the efficacy of each at the mini/micro scale. The conditions leading to significant flow pattern transitions are discussed, along with design considerations for the maintenance and/or modification of the flow pattern when curvature is introduced into the flow path. Challenges associate to the characterization of multi-phase flow through these systems are highlighted, and strategies suggested for both experimental and computational analysis of dynamic flow patterns and fluid-fluid interactions.


Biography: Adam Donaldson is a part-time professor and postdoctoral fellow at the Department of Chemical and Biological Engineering at the University of Ottawa. He received his doctorate under the guidance of D.M. Kirpalani and Prof. A. Macchi at the National Research Council and University of Ottawa for his work on two-phase flow in mini-scale passive mixing designs and the simulation of bubble coalescence and breakup in surface tension dominated flow. His research interests include interfacial phenomena, mixing and mass transfer in micro/mini-scale multiphase flow, reactor design and process intensification, biomass conversion and alternative energy systems.


 
  Debashis Dutta
Department of Chemistry at the University of Wyoming


Presentation Title: Microfluidic Devices for Enhancing the Sensitivity of Elisa Methods
Abstract: Enzyme-linked immunosorbent assays (ELISA) are critically important tools in biological research, allowing the presence and concentrations of a wide variety of key biochemical intermediates to be determined. While the signal amplification that is the core advantage of ELISA methods is impressive, it is nevertheless the case that it is insufficient for some particularly demanding challenges in terms of sensitivity, assay time, or sample size. In this talk, I will discuss three different approaches developed in our laboratory that can improve the sensitivity of ELISA methods by 2-3 orders of magnitude. Two of these approaches have been shown to reduce the minimum detectable concentration of the target analyte in the system through trapping of the analyte species and the enzyme reaction product around a semi-permeable membrane. The third approach, on the other hand, focuses on reducing the sample volume requirement in these assays by implementing multiplex ELISA methods in a single microfluidic channel using the same enzyme label. This multiplex technique relies on the slow diffusion of the enzyme reaction product across adjacent assay segments for accurate quantitation and has been demonstrated to have a limit of detection substantially better than that of commercial microtiter plates. We believe the combination of these approaches could significantly extend the applicability of the ELISA technique to more challenging assays than is currently possible.


Biography: Prof. Debashis Dutta is currently an assistant professor in the Department of Chemistry at the University of Wyoming. He received his Bachelors and Doctoral Degree in Chemical Engineering from Indian Institute of Technology, Bombay, India, and the University of Notre Dame respectively. He joined his faculty appointment in 2006 following a post-doctoral experience at the University of North Carolina at Chapel Hill in Prof. J. Michael Ramsey's group. Prof. Dutta has co-authored over 10 journal articles as an independent researcher and is currently the principal investigator on multiple research grants from the National Science Foundation. His research interests include microfluidic separations, immunoassays, sample preparation and fuel cells.


 
  Justin Gao
Corporate Research and Engineering, Eastman Kodak Company


Presentation Title: Fluid Dynamics of Microfluidic Devices (Justin Gao and Kam Ng)
Abstract: The subject of fluid dynamics of microfluidic devices such as instability, droplet formation, and control has gained considerable momentum in recently years. This is due partially to the fact that modern developments in the design and utilization of microfluidic devices for fluid transport have found many applications such as drug design and diagnostic devices in biomedicine and microdrop generators for image printing. Furthermore, the new development of nonlinear dynamics of droplets has created a new paradigm of scaling and instability theory that opened a new approach to this classic phenomenon. The utility of a microfluidic device is linked directly to its ability to control microdroplets in precision and speed for desired functionalities. The talk will begin with an overview of Micro-Electro-Mechanical Systems (MEMS) based microfluidic devices. An example of such a device is Kodak's Continuous Inkjet System, which is capable of stimulating drop breakup of jets of complex fluids with unprecedented precision, speed, and selectivity. We will utilize such a microfluidic device to discuss some of the fluid dynamics topics in microfluidic devices, and to illustrate that the fluid dynamic behavior of such a device is not only influenced by the device architecture, but also by the fluidic properties and by the way the fluid is energized to induce the drop formation and movement. The topics will include a discussion of fluid properties relative to jet modulation, wavelength dependencies, thermal modulation schemes, satellite drop formation, and aerodynamic effects.


Biography: Justin Gao received his Ph. D. in Theoretical & Applied Mechanics from Northwestern University. He was a Research Associate at Virginia Tech, an Assistant Professor at Clarkson University for four years before he joined Kodak in 1995. He is currently the Head of the Fluidics Department in Kodak Corporate Research and Engineering. Dr. Gao has conducted extensive research in the areas of micromechanics of materials, microfludics design and physics. He has been invited to give keynote presentations at many international conferences. He has served as the Associate Editor for AMSE Journal of Machine Design, and symposium chair for many international conferences. Dr. Gao has over 100 publications in patents, journal and conference papers, book chapters and technical reports. He has written chapters for Encyclopedia of Analytical Chemistry: Instrumentation and Applications (John Wiley & Sons, Chichester, UK, 2000), and Numerical Analysis and Modeling of Composite Materials (Chapman and Hall, Dec. 1995). He currently holds 26 US patents and has many other pending US patent applications.


 
  Terry Hendricks
Pacific Northwest National Laboratory, MicroProducts Breakthrough Institute, Corvallis, OR


Presentation Title: Micro- and Nano- Technologies: Roadmap Enabling More Compact, Lightweight Thermoelectric Power Generation and Cooling Systems
Abstract: Advanced thermoelectric (TE) energy recovery and cooling systems have critical benefits in transportation, industrial process, and military applications because of rising or uncertain energy costs and subsequent need for energy efficiency, geopolitical uncertainties impacting basic energy supplies worldwide, and the need for electrified, distributed cooling and heating systems in automotive applications. Advanced TE energy recovery and cooling technologies will require high-performance heat transfer characteristics to achieve system performance targets and requirements. However, TE energy recovery systems generally have high-temperature thermal transfer requirements (i.e., as high as 750 - 800 °C), while TE cooling systems require low temperature thermal transfer (i.e., 25 °C - 100 °C). Investigations have compared system power and cooling benefits and system thermal integration challenges of energy recovery and cooling systems using microchannel heat exchangers to provide high heat transfer performance in both high-temperature, high-enthalpy energy streams and low-temperature cooling streams. This work explores the roadmap and vision for using micro-technology solutions integrated with advanced thermoelectric materials in advanced TE power generation and cooling systems. Integrated system-level TE power generation and cooling system analyses demonstrate that inter-related system-level requirements on weight, volume, and performance lead to derived requirements for micro-technology solutions. Nano-technologies and micro-technologies will be presented that demonstrate where and how these technologies impact TE system designs. Of course, micro-technology manufacturing cost is critical in all energy recovery and cooling applications. Recent progress in microtechnology cost-modeling elucidates and quantifies key cost-manufacturing interdependencies, relationships, and sensitivities that will be explored in this presentation. This provides critical information on manufacturing processes, production volume dependence, material selections, and ultimately pathways forward leading to low-cost microtechnology heat and mass transfer devices that improve advanced TE energy recovery and cooling system performance (specifically including weight and volume impacts).


Biography: Dr. Hendricks is currently a Business Development Manager & Senior Program Manager at the MicroProducts Breakthrough Institute of U.S. Department of Energy (DOE) Pacific Northwest National Laboratory (PNNL) in Corvallis, OR, where he is responsible for developing and managing programs and initiatives in Energy Recovery, Micro-Electro-Mechanical Technologies, Advanced Thermoelectric Systems, Advanced Nano-scale Heat Transfer, and Fuel Cell Systems. Prior to joining PNNL, Dr. Hendricks was the Field Program Manager for the DOE Advanced Heavy Hybrid Propulsion Systems project and the Power & Propulsion Task Leader in the Center for Transportation Technologies and Systems at the DOE National Renewable Energy Laboratory. His 27 years of professional experience and expertise span technical interest areas of thermal & fluid systems, energy conversion systems, terrestrial and spacecraft power systems, micro electro-mechanical systems, design optimization, probabilistic methods, and project management. He was awarded the Midwest Research Institute / Battelle Memorial Institute Chairman's Award in October 2003 for outstanding performance while at the National Renewable Energy Laboratory and the ASME Columbia Basin Engineer of the Year Award in February 2009. Dr. Hendricks received his Ph.D. and Master of Science in Engineering from the University of Texas @ Austin, where he was also awarded a University Fellowship in 1992. He also holds a Bachelor of Science (Summa Cum Laude) in Physics from the University of Massachusetts @ Lowell. He has written more than 57 technical papers and reports in heat transfer, power systems, thermoelectrics, and cryogenics for national and international conferences, ASME journals and IEEE transactions, and the DOE. He has served as reviewer for the ASME Journal of Heat Transfer, ASME Journal of Energy Resources Technology, Journal of Electronic Materials, and AIAA Journal of Thermophysics and Heat Transfer; holds 8 patents, and one ADVISOR software copyright. He is a registered Professional Engineer in the states of California and Texas.


 
  T. G. Karayiannis
School of Engineering and Design, Brunel University, West London, Uxbridge, Middlesex, UK


Presentation Title: Flow Boiling Heat Transfer of R134a in Small to Micro Diameter Tubes: Effect of Heated Length and Inner Surface Characteristics (T. G. Karayiannis, M. M. Mahmoud, D. B. R. Kenning)
Abstract: Flow boiling in small to micro diameter tubes and channels has been the subject of numerous investigations in the last few years. Examination of past papers reveals a significant scatter of the reported data and disagreement on the dependence of the local heat transfer coefficient on vapour quality, mass and heat flux and system pressure. The reasons for this scatter or disagreement were not clearly or conclusively discussed. As a result, various suggestions were reported on the dominant heat transfer mechanism(s) in small to micro diameter tubes. The work described in this paper is part of an extensive study of up-ward flow boiling of refrigerants in small to micro diameter vertical tubes. The effect of the tube inner surface characteristics and tube heated length were particularly studied because they may contribute, at least in part, in explaining the discrepancies between past works and help elucidate the heat transfer mechanism(s) that prevail. The effect of the tube inner surface characteristics was investigated through examining, under identical conditions, two stainless steel tubes manufactured by two different methods: a welded and a seamless cold drawn tube. The tubes had an inner diameter of 1.1 mm and were 150 mm long. The system pressure was 8 bar, the mass flux was 300 kg/m2 s and the heat flux was varied from 12.6 to 102 kW/m2. A scanning electron microscope was used to examine the inner surfaces of the tubes. The welded tube had a smooth surface with some scattered fragments or debris. However, the texture of the cold drawn tube was completely different; rough, with uniformly distributed scratches or channels. The heat transfer results, presented as local heat transfer coefficient versus local vapour quality or distance from the tube entrance, in the two tubes were completely different with the welded tube demonstrating a more complex and difficult to explain behaviour. In addition, the effect of heat flux was not clear in the welded tube but obvious in the cold drawn tube. Three heated lengths were investigated, again under similar conditions, using a seamless cold drawn tube with diameter of 1.1 mm over a wide range of experimental conditions covering: mass flux 100 - 500 kg/m2 s, system pressure of 6 - 10 bar, inlet sub-cooling value of about 5K and exit quality up to about 0.95. The results indicated that the heated length strongly influences the magnitude as well as the local behaviour of the heat transfer coefficient. There is a progression from nucleate boiling to convective boiling as the heated length increases indicating that this is a parameter that needs to be included when assessing different results and comparing with past correlations.


Biography: Tassos G. Karayiannis is a professor of thermal engineering in the School of Engineering and Design of Brunel University, where he is co-director of the Centre for Energy and Built Environment Research (CEBER). He obtained a BSc in Mechanical Engineering from City University (UK) in 1981 and a PhD from the University of Western Ontario (Canada) in 1986. He has carried out research in single-phase heat transfer, enhanced heat transfer and thermal systems. He has been involved with research in two-phase flow and heat transfer for about 20 years. He is a fellow of the Institution of Mechanical Engineers and the Institute of Energy.


 
  Dong-Pyo Kim
National Creative Research Center of Applied Microfluidic Chemistry, Chungnam National University, Daejeon, Korea


Presentation Title: Lab-on-a-Chipsystems for Microchemical Synthetic Applications
Abstract: Lab-on-a-chip microchemical systems were fabricated from PDMS, polyimide film and functional polymers by different lithographic techniques to look for microreactor applications in the areas of organic, polymer and inorganic syntheses. In detail, efficient gas-liquid reactions in dual-channel microreactor, continuous recovery and recirculation of catalyst-immobilized magnetic particles in microfluidic system, hydrophilic glass-like microchannels for electrokinetic activity and a flexible film microreactor will be discussed.


Biography: Prof. Dong-Pyo Kim received Ph.D. in Chemistry (Temple Univ.) at 1991 and shifted to Materials Sci. & Eng (UIUC) as a post-doctoral position. In 1993, he joined as a senior researcher at Korea Research Institute of Chemical Technology. Since 1995, he has worked at Department of applied chemistry, Chungnam National University in Korea. He began his career at the area of materials chemistry including inorganic polymers. Since 2004 he devotes to lab-on-a-chip microreactors under National Research Lab grant, and currently as a head of Center of Applied Microfluidic Chemistry under Creative Research Initiatives program for 9 yrs.


 
  Ali Kosar
Dept. of Mechatronics Engineering, Sabanc? University, Istanbul


Presentation Title: Flow Boiling in Microscale at High Flowrates
Abstract: Boiling heat transfer is an important heat removal mechanism for cooling applications in micro scale and finds many applications. Many studies were conducted to shed light on boiling heat transfer in microchannels. They were concentrated on saturation boiling at low mass fluxes (G<1000 kg/m2s). With the enhancement in micro pumping capabilities, flow boiling could be performed at higher mass velocities so that high cooling rates (>1000 W/cm2) could be possibly attained. Due to the increasing trend in critical heat flux and suppression of boiling instabilities with increasing mass velocity flow boiling is becoming more and more attractive at higher mass velocities, where subcooled boiling conditions are expected at high mass velocities. With the shift from low to high flow rates, a transition in both boiling heat transfer (saturated boiling heat transfer to subcooling boiling heat transfer) and critical heat flux (dryout type critical heat flux to departure from nucleate boiling critical heat flux) from one mechanism to another is likely to occur. Few experimental studies are present in the literature related to this subject. In this paper, it is aimed at addressing to the lack of information about boiling heat transfer at high flow rates and presenting experimental data and results related to boiling heat transfer and Critical Heat Flux (CHF) at high flowrates. New emerging technologies resulting in local heating such as nano-scale plasmonic applications and near field radiative energy exchange between objects could greatly benefit from boiling heat transfer at high flow rates in micro scale.


Biography: Ali Kosar received the B.S. degree in Mechanical Engineering from Bogazici (Bosphorus) University, Istanbul, in 2001. He pursued his graduate study in the Department of Mechanical Engineering at Rensselaer Polytechnic Institute, where he completed his M.S. and Ph.D. degrees. He worked at Rensselaer Polytechnic Institute as a post doctorate research associate and adjunct faculty before joining Mechatronics Engineering Program at Sabanci University in Fall 2007. He is one of few pioneers in the design and development of new generation micro heat sinks and microfluidic devices. His research interests constitute a wide spectrum covering heat and fluid flow in micro/nano scale, forced convection, two-phase flow, and cavitation. He aims at contributing to the literature by removing the lack of information about micro/nano scale heat transfer and fluid flow and providing experimental data and design guidelines for futuristic cooling technologies. The results of his research have already generated more than 25 published/accepted journal research articles which have been published in prestigious journals such as Journal of Heat Transfer, Journal of Microelectromechanical Systems and International Journal of Heat Transfer. He also has more than 30 conference papers in prestigious and well attended international conferences such as International Conference on Minichannels and Microchannels (ICNMM) and ASME International Mechanical Engineering Congress. He is currently an Associate Professor at Sabanci University.


 
  Kohei Koyama
Institute of Ocean Energy, Saga University, Japan


Presentation Title: A Constant-Wall-Temperature Model for Prediction of Thermal Performance of Gas-to-Gas Counter-Flow and Parallel-Flow Microchannel Heat Exchangers
Abstract: Thermal performances of gas-to-gas counter-flow and parallel-flow microchannel heat exchanger have been investigated. Working fluid used is air. Heat transfer rates of both heat exchangers are compared with those calculated by a conventional log-mean temperature difference method. The results show that the log-mean temperature difference method can be employed to a parallel-flow configuration whereas that cannot be employed to a counter-flow configuration. This study focuses on the partition wall which separates hot and cold passages of the microchannel heat exchanger. The partition wall is negligibly thin for a conventional-sized heat exchanger. In contrast, the partition wall is thick compared with channel dimensions for a microchannel heat exchanger. A model which includes the effect of the thick partition wall is proposed to predict thermal performances of the microchannel heat exchangers. The heat transfer rates obtained by the model agree well with those obtained by the experiments. Thermal performances of the counter-flow and parallel-flow microchannel heat exchangers are compared with respect to one another based on temperature of the partition wall. The comparison results show that thermal performances of the counter-flow and parallel-flow microchannel heat exchangers are identical. This is due to performance degradation induced by the thick partition wall of the counter-flow microchannel heat exchanger. This study reveals that the thick partition wall dominates thermal performance of a gas-to-gas microchannel heat exchanger.


Biography: Kohei Koyama is an assistant professor in Institute of Ocean Energy, Saga University. He received Ph. D. from Tokyo Metropolitan University in 2010. The thesis was entitled "Heat Transfer Characteristics of a Gas-to-Gas Microchannel Heat Exchanger." He studied at Aichi Institute of Technology, where he received bachelor and master degree. His research interest includes high-performance compact heat transfer equipment and heat transfer enhancement techniques. His interest also involves multi-phase flow. He is currently working on investigations of boiling heat transfer for ocean thermal energy conversion.


 
  Kaoru Maruta
Institute of Fluid Science (IFS), Tohoku University, Japan


Presentation Title: Flame Chromatography: Toward Fuel Indexing Based on Multiple Weak Flames in a Meso-Scale Channel With a Prescribed Temperature Profile
Abstract: Swiss roll microcombustors for general purpose heat sources with the thermal efficiency nearly twice that of resistive heaters and the temperature controllability within one degree Celsius have been developed. For understanding the flame stability in the microcombustors, fundamental studies on the combustion characteristics in a meso-scale channel with a prescribed wall temperature profile are conducted. Results showed that the existence of dynamic oscillatory flames and weak flames in addition to the normal propagating flames for the first time. It is recognized that the weak flame phenomena can be applied for examining multi-stage oxidation of hydrocarbon fuels in wide temperature region. Based on the preliminary experiments with primary referenced fuels, Research Octane Number (RON) of the test fuels can be clearly described by the stabilized stationary multiple weak flames. The methodology is applied for fuel indexing of future alternative fuel characterization.


Biography: Kaoru Maruta is professor and head of Energy Dynamics Laboratory (EDL) at Institute of Fluid Science (IFS), Tohoku University, Japan. He received his Bachelor (1988), Master (1990) and Doctoral degrees (1993) in Engineering from Sophia University, Tokyo. He worked at IFS, Tohoku University as a research associate and assistant professor from 1993 to 1999. He got an associate professor position at Akita Prefectural University in 1999. After his one-year visiting scholarship at University of Southern California and UC Berkeley, he went back to IFS, Tohoku University as associate professor in 2002 and currently serving as professor and head of EDL.


In 1990's, he has been active in the field of combustion under microgravity, particularly on combustion limit of gaseous fuels. He found radiative extinction which clarified the intrinsic mechanism of the existence of the flammability limit. He extended his fields to combustion in micro scales during his stay in the U.S. In 2002, he has started developing "Swiss roll microcombustors as heaters." He also addressed fundamentals of microscale combustion in a micro channel with a prescribed temperature profile. The approach led to the development of flame chromatography which is being expected to be used for the design and development of flexible alternative fuels.


He is a member of the Combustion Institute, Japanese Society of Mechanical Engineering, and Heat Transfer Society of Japan. He is currently an Editorial Board Member of Combustion and Flame, Progress in Energy and Combustion Science, and Combustion Explosion and Shock Waves. He is the author of over 70 peer reviewed journal papers in combustion and thermal engineering fields.


 
  O. K. Matar


Presentation Title: Pattern Formation and Hydrothermal Waves in Evaporating Drops With and Without Nanoparticles
Abstract: We study the dynamics of a droplet undergoing evaporation focusing on the onset and evolution of pattern formation. We consider situations in which the droplet contains nanoparticles and others wherein these particles are absent. For droplet laden with nanoparticles, we demonstrate the methodology required to model the evaporative dynamics reliably. We use lubrication theory, valid for slender droplets, and account for the effects of these particles on the structural intermolecular forces, which are significant at the contact line. We show that the evaporation process is influenced significantly by the presence of the nanoparticles accompanied by the formation of `terraces' at the contact line. In the absence of particles, we use a combination of boundary-layer theory in conjunction with the Karman-Polhausen approximation to derive a set of evolution equations that govern the droplet shape and temperature. A linear stability analysis of these equations demonstrates the presence of fingering phenomena near the contact line; this analysis also reveals the presence of hydrothermal waves, which correspond to wave travelling in the azimuthal direction, over a range of the system parameters.


Biography: Prof. O. K. Matar (OKM) is an Exxon-Mobil Fellow and Professor of Fluid Mechanics in the Department of Chemical Engineering, Imperial College London. OKM's current research interests include the modelling of multiphase flows driven by Marangoni stresses, surface and bulk diffusion, gravitational, capillary, intermolecular forces and parametric forcing, placing emphasis on hydrodynamic instabilities and pattern formation, with industrial and biomedical applications. These include intensive processing, coating flow technology, surfactant replacement therapy, Marangoni drying, micro-fluidics and microelectronics manufacturing. OKM has recently published a review of the filed of thin films in Rev. Mod. Phys. (impact factor 33). OKM is the current coordinator of the Fluid Mechanics Focus Area at Imperial and has received Research Council and industrial funding to study surfactant transport on non-Newtonian layers, phase inversion in concentrated emulsions, thin film flows over rapidly rotating discs, nonlinear bubble sound interactions, fouling in heat exchangers in crude oil distillation units, dynamics of liquids spreading on compliant substrates, multiphase flow in large-diameter pipes, the prediction of complex vapour liquid annular flows, interfacial behaviour in stratified and stratifying annular flows, in addition to the removal of soft-solids adhering to solid substrates. He has co-authored well over 100 articles in prestigious journals, is on the Editorial Board of the International Journal of Multiphase Flow, Editor-in-Chief of Multiphase Science and Technology.


 
  Koji Miyazaki
Department of Mechanical and Control Engineering, Kyushu Institute of Technology


Presentation Title: Heat Conduction in a Nano-Porous Material and its Application
Abstract: We calculated heat conduction in a nano-porous material by using a molecular dynamics simulation and phonon bolzmann transport equations to understand the extremely low thermal conductivity of the nano-porous materials. We also intend to enhance the figure of merit of thermoelectric materials by using low thermal conductivity of a nano-porous material.


Biography: Koji Miyazaki is an Associate Professor of Department of Mechanical and Control Engineering at Kyushu Institute of Technology. He received the Ph.D in Department of Mechanical Science and Engineering at Tokyo Institute of Technology in 1999. He had stayed in University of California Los Angeles in 2000-2001 and Massachusetts Institute of Technology in 2001-2002 as a visiting scholar. He was also a JST PRESTO researcher from 2004 to 2008, and currently a senior researcher of NEDO BEANS project from 2008. His research interests focus on thermophysical properties of a nano-structured material.


 
  Y. S. Muzychka
Memorial University of Newfoundland, Faculty of Engineering and Applied Science, St. John's, Newfoundland, Canada


Presentation Title: Generalized Models for Laminar Developing Flows in Heat Sinks and Heat Exchangers
Abstract: Laminar flow fluid friction and heat transfer in non-circular ducts occurs quite frequently in low Reynolds number flow heat exchangers such as compact heat exchangers, microchannel heat sinks, and other mini-scale systems such as electronic cooling applications as a result of the miniaturization of packaging technologies. While traditional approaches rely heavily on the use of tabulated and/or graphical data, the ability to design thermal systems using robust and simple methods is much more desirable. Most modern fluid dynamics and heat transfer texts rarely present correlations or models for more complex geometries, which appear in many engineering systems. Rather, a subset of data for miscellaneous geometries is usually presented after detailed discussion and analysis of simple geometries such as the circular duct and parallel plate channel. Very little effort is made to unify and understand the general characteristics of internal flows from the standpoint of passage geometry, thermal boundary condition, and flow development. In this paper, flow friction and heat transfer characteristics are considered in detail, and a review of new models applicable to micro and mini-channels is presented. These models can be used to predict the required hydrodynamic and thermal characteristics of laminar internal flows.


Biography: Yuri Muzychka is a Professor of Mechanical Engineering at Memorial University of Newfoundland, Canada. He obtained his Ph.D. in Mechanical Engineering from the University of Waterloo in 1999. From 1993-2000, he worked in the Microelectronics Heat Transfer Laboratory at the University of Waterloo, on numerous problems in electronic packaging, heat exchangers, tribology, and heat transfer and fluid flow fundamentals in internal flows. Before joining Memorial University in 2000, he was a part time research consultant for R-Theta, Inc., a manufacturer and developer of electronics cooling systems. As a thermo-fluid analyst, his research is focused on the development of robust models for characterizing transport phenomena in complex systems using fundamental theory. These models are validated using experimental and/or numerical results. He has published approximately 50 papers in refereed journals along with another 50 papers in international conference proceedings in these areas. He is also co-author of two chapters to be published in the 2011 CRC Press Microfluidics/Nanofluidics Handbook. Current interests include: transport in porous media, compact heat exchangers, two phase flows, micro-channel flows, slip flows, non-Newtonian flows, electronics packaging, contact heat transfer, and thermal design/optimization of energy systems. He is a member of the American Institute for Aeronautics and Astronautics (AIAA) and the American Society of Mechanical Engineers (ASME).


 
  Yoav Peles
Rensselaer Polytechnic Institute (RPI)


Presentation Title: Heat and Mass Transfer Enhancement by Active Flow Control in Micro Domains
Abstract: A new method to enhance heat and mass transfer in micro domains by active flow control is presented. Controlling the flow can significantly enhance mixing and early transition to a turbulent flow. Since heat transfer mechanisms are closely linked to flow characteristics, the heat transfer coefficient can be significantly enhanced with rigorous mixing.


The flow field of water around a low aspect ratio micro circular pillar of diameter 150 ?m entrenched inside a 225 ?m high by 1500 ?m wide microchannel with active flow control is studied and its effect on mixing is discussed. A steady control jet emanating from a 25 ?m slit on the pillar was introduced to induce favorable disturbances to the flow in order to modify the flow field, promote turbulence, and increase large-scale mixing. Micro Particle Image Velocimetry (µPIV) was employed to quantify the flow field, the spanwise vorticity, and the turbulent kinetic energy (TKE) in the microchannel. Flow regimes (i.e., steady, transition from quasi-steady to unsteady, and unsteady flow) were elucidated. The turbulent kinetic energy was shown to significantly increase with the controlled jet and is therefore, expected to significantly enhance the heat transfer coefficient.


Biography: Dr. Peles is an associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering (MANE) at Rensselaer Polytechnic Institute (RPI). His research at RPI mainly concerns heat and fluid flow (single-phase as well as two-phase) and power systems with emphasis on micro domains. The research is funded by several government and industrial agencies including ONR, DARPA, and NSF.


Dr. Peles has been at RPI since 2002. Prior to joining RPI, he was a post-doctoral associate and later a research engineer at the Massachusetts Institute of Technology (MIT) working on the Micro Engine Project. There he worked on a miniature Brayton cycle, micro rocket, and auxiliary power components.


Professor Peles received his Ph.D. degree from the Mechanical Engineering Department at the Technion - Israel Institute of Technology. There he studied fundamental processes governing flow boiling in micro-channels. The studies conducted at RPI, MIT, and the Technion were disseminated in about 60 journal publications and about 40 conference papers. He is a recipient of the 2005 ONR Young Investigator Award and the 2007 DARPA/MTO Young Faculty Award. As a member of the American Society of Mechanical Engineering (ASME) he has served on numerous professional committees and help organized several conferences.


 
  Jason Reese
Imperial College London, University of Oxford, Technische Universitaet Berlin, University of Cambridge, University of Aberdeen, King's College London, University of Strathclyde, Glasgow, Scotland


Presentation Title: Perspectives on the Simulation of Micro Gas and Nano Liquid Flows
Abstract: Micro- and nano-scale fluid systems can behave very differently from their macro-scale counterparts. Remarkably, there is no sufficiently accurate, computationally efficient, and - most importantly - generally agreed fluid dynamic model that encapsulates all of this important behaviour. The only thing that researchers can agree on is that the conventional Navier-Stokes fluid equations are unable to capture the unique complexity of these often locally non-thermodynamic-equilibrium flows. In this talk I will outline the range of international work on developing and exploring new models for these flows, highlighting particular simulations that display, in my opinion, the most interesting fluid dynamic behaviour. I will describe the successes and failures of various hydrodynamic and molecular models in capturing the non-equilibrium flow physics, and give examples of current test applications in micro and nano engineering.


Biography: Born in London in 1967, Jason Reese graduated in Physics from Imperial College London, and completed his Masters and Doctoral research in Applied Mathematics at the University of Oxford in 1993. After postdoctoral work at the Technische Universitaet Berlin and the University of Cambridge, he became a Lecturer in Fluid Dynamics at the University of Aberdeen, and subsequently Lecturer and ExxonMobil Engineering Fellow at King's College London. In 2003 he was appointed the Weir Professor of Thermodynamics and Fluid Mechanics in the University of Strathclyde, Glasgow, Scotland. He is a Fellow of the Royal Society of Edinburgh, of the Institution of Mechanical Engineers, and of the Institute of Physics in the UK. His scientific interests focus on non-equilibrium fluid dynamics, in particular, how the molecular nature of fluids affects the behaviour of micro- and nano-scale flows. His other interests are in the industrial application of fluid dynamics research: he co-founded Brinker Technology Ltd in 2002, which commercialises and operates a novel leak detection and sealing system for oil/gas pipelines and wellheads, and water mains pipes.


 
  Masahiro Shoji
Professor of Kanagawa University, Professor emeritus of The University of Tokyo


Presentation Title: Boiling Heat Transfer of Butanol Aqueous Solution
Abstract: Some aqueous solutions such as butanol aqueous solution are sometime called as "self-rewetting liquid" and yield high critical heat flux with very small generating bubbles. It is a promising liquid for the application to micro-structured cooling devices. In this talk, the results of fundamental experiments of pool saturated and subcooled boiling as well as of flow boiling inside a mini-tube are presented.


Biography: Boiling heat transfer, Surface tension driven heat and fluid flow, Chaotic thermal and fluid phenomena.


 
  Tracey Stokol
College of Veterinary Medicine, Cornell University


Presentation Title: Little Channels, Big Disease: Using Microfluidics to Invetsigate Cancer Metastasis
Abstract: The leading cause of death in human patients with malignant cancer is the dissemination of the primary tumor to secondary sites throughout the body. It is well known that cancers metastasize to certain tissues (e.g. breast cancer typically spreads to the lungs. brain and bone), in a pattern that cannot be explained by blood flow from the primary tumor or simple mechanical arrest. Circulating tumor cells usually arrest in the microvasculature of target tissues. At these sites, they must adhere to the endothelium, survive, proliferate and extravasate in order to form a secondary tumor. In vitro tools that appropriately mimic the microvasculature in which cancer metastasis occurs have been largely unavailable. With the advent of microfluidic and nanotechnology, we can now more accurately model the complexity of the microvascular environment, in terms of representative endothelial cells, geometry, shear stress and exposure to organ-specific environmental cues. This talk will focus on the use of microfluidic devices to explore mechanisms involved in tumor-endothelial cell interactions that govern cancer metastasis to organ-specific sites.


Biography: I am a veterinary clinical pathologist and associate professor in the College of Veterinary Medicine. I received my veterinary degree and PhD from the University of Melbourne in 1987 and 1993, respectively. I obtained specialist status in veterinary clinical pathology through board certification by the American College of Veterinary Pathologists in 1995 and have over 15 years of experience in diagnostic clinical pathology. My research interests encompass mechanisms of thrombosis in animals and cancer metastasis in humans and animals. The focus of my cancer studies is to understand how circulating cancer cells interact with vascular endothelium to establish secondary tumors. To facilitate these studies, I have developed a microfluidic model of the microvascular endothelium in collaboration with Dr. Michael Shuler of the Department of Biomedical Engineering. This microfluidic system is being used to explore mechanisms governing tumor cell-endothelial interactions in the metastatic process.


 
  Kripa K. Varanasi
Massachusetts Institute of Technology


Presentation Title: Dynamic Wetting and Phase Change Interactions on Nano-Engineered Surfaces
Abstract: In this talk, we show how surface/interface chemistry and structure can be engineered to fundamentally alter thermal-fluid-surface interactions for dramatic performance enhancements and prevention of catastrophic instabilities in various engineering systems. We study the wetting energetics and wetting hysteresis of droplets as a function of surface texture and surface energy and establish various wetting regimes and conditions for wetting transitions. We extend these concepts to dynamic wetting and establish optimal design space for droplet shedding, impact resistance, and drag reduction. We then present the behavior of surfaces under phase change, such as condenation, and freezing using an environmental SEM. We find that surfaces can be engineered to promote dropwise condensation but result in a mixture of wetting states on textured hydrophobic surfaces. Heat transfer measurements indicate significant enhancement in the heat transfer coefficient on these surfaces when compared to baseline surfaces. Further optimization of the surface by considering nucleation-level phenomena leads to hybrid wetting architectures similar to the one found on a Namib beetle. The last portion of the talk will focus on ice and hydrate mitigation. Clathrate hydrates are an important flow assurance challenge for deep-sea oil and gas exploration and was recently a challenge in the Gulf of Mexico oil spill. Similarly, ice poses a key challenge to operational performance of wind turbines and aircraft engines. We show how interfaces can be designed to significantly reduce adhesion of both ice and hydrates. Fundamental studies of Van der walls and acid-base interactions on adhesion are presented. Applications of these nanoengineered surfaces to power turbines, engines, power and desalination plants, oil and gas, microfluidics, and electronic cooling will be highlighted.


Biography: Kripa Varanasi is a d'Arbeloff Assistant Professor of Mechanical Engineering at MIT. He received his B.Tech from IIT, Madras and his MS (ME and EECS) and Ph.D from MIT. Prior to joining MIT, Dr. Varanasi was a lead research scientist and project leader in the Energy & Propulsion and Nanotechnology programs at the GE Global Research Center, Niskayuna, NY, and was the PI for the DARPA Advanced Electronics Cooling program. The primary focus of his research is in the development of nano-engineered surface, interface, and coating technologies that can dramatically enhance performance in energy, water, agriculture, transportation, buildings, and electronics cooling systems. Dr. Varanasi has filed more than 25 patents in this area. He was awarded the First Prize at the 2008 ASME Nanotechnology Symposium and won several awards at GE Research Labs including Technology Project of the Year, Best Patent Award, Inventor Award, and Leadership Award. Most recently he received the MIT-Deshpande Award, 2010 IEEE-ASME Itherm best paper award, NSF CAREER Award and DARPA Young Faculty Award.


 
  Evelyn Wang
Mechanical Engineering, MIT


Presentation Title: Nanoengineered Surfaces for Efficient Energy Systems
Abstract: Nanoengineered surfaces offer new possibilities to manipulate fluid transport and enhance heat dissipation characteristics for the development of energy efficient systems. In particular, nanostructures on these surfaces can be harnessed to achieve superhydrophilicity and superhydrophobicity, and to control liquid spreading and droplet wetting. In this talk, I will discuss two topics: 1) liquid spreading on superhydrophilic surfaces, and 2) droplet dynamics on superhydrophobic surfaces. In the first study, we fabricated three-dimensional nanopillars that can control spreading behavior and directionalities. In the presence of asymmetric nanopillars, uni-directional spreading of water droplets can be achieved where the liquid spreads only in the direction of the pillar deflection and becomes pinned on the opposite interface. In the presence of fine features on the pillars, we observed a multi-layer spreading effect due to their associated energy barriers. For both cases, we have developed energy-based models to accurately predict the liquid behavior as functions of pertinent parameters. In the second study, we fabricated hierarchical structures with both micro and nanoscale features. The motivation is to mimic the surface of a lotus leaf, such that the mechanisms for its superior non-wettability can be investigated. The fabricated surfaces demonstrated excellent resistance to wetting where droplets rebound at velocities greater than 4 m/s. In addition, a two-fold increase in heat transfer coefficients was observed when compared with flat surfaces with identical surface chemistries. These studies provide insights into the complex physical processes underlying liquid-nanostructure interactions. Furthermore, this work shows significant potential for the development and integration of advanced nanostructures to achieve efficient energy systems.


Biography: Evelyn Wang is the Esther and Harold E. Edgerton Assistant Professor in the Mechanical Engineering Department at MIT. She received her BS from MIT in 2000 and MS and PhD from Stanford University in 2001, and 2006, respectively. From 2006-2007, she was a postdoctoral researcher at Bell Laboratories, Alcatel-Lucent. Her research interests include fundamental studies of micro/nanoscale heat and mass transport and the development of efficient thermal management, water desalination, and solar thermal energy systems. Her work has been honored with awards including the 2008 DARPA Young Faculty Award, the 2011 Air Force Office of Scientific Research Young Investigator Award, and a best paper award at 2010 ITherm.


 
  Liqiu "Rick" Wang
Department of Mechanical Engineering, University of Hong Kong


Presentation Title: Research and Engineering Practice in Nanofluids: Key Issues
Abstract: Unlike the past century that was blessed with ever-abundant cheap oil, this century energy has been rated as the single most important issue facing humanity. A global-scale energy crisis looms ahead. Nanotechnology will figure centrally in providing technological solutions. Nanofluid technology, one of the enabling technologies of the nanotech revolution, holds the promise of significantly enhancing the thermal properties of fluids and thus providing high quality heat-transfer fluids of the future that are vital for solving the terawatt challenge facing us.


Nanofluids, fluid suspensions of nanometer-sized (<100nm) particles, tubes and fibers, are research challenges of rare potential but daunting difficulty. The potential comes from both scientific and practical opportunities in many fields. The difficulty reflects the issues related to multiscales. Nanofluids involve at least four relevant scales: the molecular scale, the microscale, the macroscale and the megascale. The molecular scale is characterized by the mean free path between molecular collisions, the microscale by the smallest scale at which the law of continuum mechanics apply, the macroscale by the smallest scale at which a set of averaged properties of concern can be defined and the megascale by the length scale corresponding to the domain of interest. By their very nature, research and engineering practice in nanofluids are to enhance fluid macroscale and megascale properties through manipulating microscale physics (structures, properties and activities). Therefore, interest should focus on addressing questions like: (i) how to effectively manipulate at microscale, (ii) what are the interplays among physics at different scales, and (iii) how to optimize microscale physics for the optimal megascale performance. In this talk, we summarize our work on addressing these key issues with powerful microfluidic technology, thermal-wave theory and constructal theory.


Biography: Prof. L. Q. "Rick" Wang received his PhD from University of Alberta (Canada) and is currently a full professor in the Department of Mechanical Engineering, the University of Hong Kong. He has over 25 years of university experience in thermal & power engineering, energy & environment, transport phenomena, nanotechnology, biotechnology and applied mathematics in Canada, China/Hong Kong, Singapore and the USA. He is the author and co-author of 9 books/monographs and over 280 technical articles in these areas.


Prof. Wang has been a visiting professor at the Harvard University, a visiting professor at the Duke University, a chair professor at the Shandong University, and a guest professor at the Tianjin University. He serves as the editor-in-chief for the Advances in Transport Phenomena (Springer annual review series), the associate editor for the Current Nanoscience, the guest editor for a special issue on nanofluids for the Nanoscale Research Letters and annual issues on heat transfer in nanofluids for the Advances in Mechanical Engineering, and serves on the editorial boards of ten international journals.


 
  Mimami Yoda


Presentation Title: Studying Interfacial Transport With Evanescent Wave-Based Particle Velocimetry
Abstract: Interfacial phenomena due to surface forces are important in microfluidic devices with their relatively large surface areas and small volumes. Most experimental studies of interfacial transport estimate flow velocities from the motion of tracer particles less than 1 m in diameter, and assume that the particle displacements over a known interval are due to the fluid velocity field. This talk discusses some of our research on measuring fluid velocities in Poiseuille and electrokinetically driven flows over the first ~0.5 m next to the solid wall from the motion of an ensemble of O(105) fluorescent spheres as small as 100 nm illuminated by evanescent waves. Because the evanescent-wave intensity decays exponentially with wall-normal distance, the particle-wall separation can be determined from the brightness of each particle image, and used to estimate the steady-state distribution of the tracers near the fluid-solid interface.


Biography: Minami Yoda is Professor and Woodruff Faculty Fellow in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. She received a B.S. from Caltech and a M.S. and Ph.D. from Stanford University, and was a von Humboldt and National Science Foundation postdoctoral fellow at the Technical University of Berlin in Germany. Dr. Yoda is Associate Editor for the journal Experiments in Fluids, the Vice Chair and Chair-Elect of the American Nuclear Society Fusion Energy Division, and has served on the Executive Committee of the American Physical Society Division of Fluid Dynamics. She is a Fellow of the American Society of Mechanical Engineers and a former member of the Defense Science Study Group of the Institute for Defense Analyses. Dr. Yoda's research interests include experimental fluid mechanics, optical measurement techniques, microfluidics, colloid science, liquid films, and the thermal-hydraulics of fusion energy.


 
  M. Michael Yovanovich
University of Waterloo, Ontario, Canada


Presentation Title: Models for Pressure Drop for Poiseuille Flow in Trapezoidal and Triangular Microchannels in Silicon
Abstract: Models, numerical and experimental results for developed laminar flow in long isosceles trapezoidal and triangular microchannels etched in < 100 > silicon will be reviewed and compared. The equivalent rectangle model (ERM) baed on a novel model fo rth effective aspect ratio was developed for non-circular microchannels; it will be compared with the numerical and experimental data (62 points) will presented. The equivalent rectangle model is accurate with rms difference of 3.1%. A maximum difference of -7% occurs for data obtained for flow through four very narrow trapezoidal microchannels.


Biography: Dr. M. Michael Yonanovich is Distinguished Professor Emeritus at the University of Waterloo. Michael is a recognized authority on thermophysics and heat transfer. Over the past 12 year Dr. Yovanovich and his collaborators: Dr. Majid Bahrami, Dr. Zhipeng Duan and Dr. Yuri Muzychka have developed accurate compact models for developing and developed laminar flow of liquids an dgases in numerous non-circular microchannels. The models for gas flows are based on first order slip and compressibility effects are taken into account. The compact models are based on the square root of the flow area rather than the conventional hydraulic diameter and the introduction of an effective aspect ratio to replace the conventional nominal aspect ratio. An accurate fully-developed turbulent flow model for smooth non-circular ducts and microchannels has been developed. The various compact models for laminar and turbulent flow will appear in the chapter, Fluid Friction and Heat Transfer in Microchannels, for the CRC Handbook of Microfluidics and Nanofluidics (2011).


 
  Peng Zhang
Shanghai Jiao Tong University, Shanghai, China


Presentation Title: Flow and Heat Transfer Characteristics of Liquid Nitrogen in Mini/Micro-Channels
Abstract: Flow and heat transfer in mini/micro-channels have been intensively investigated due to its capacity of dissipating large heat flux, which therefore has inspired many applications in the cooling of high power electronic devices. Previous researches focused mostly on the room-temperature liquids as the working fluids, such as water, Freon refrigerants and so on. However, with the advancement of superconductivity science and technology, the superconducting transition temperature has been elevated to liquid nitrogen temperature (77 K) range. Consequently, there arise requirements for the effective cooling for high temperature superconducting magnet or devices, for example, CICCs (Cable-In-Conduit Conductors), in which many small channels are generally embedded. Such situation requires that the flow and heat transfer characteristics of cryogen, like liquid nitrogen, are well known in mini/micro-scale; meanwhile, such investigation will apparently provide the database for enriching the understanding of flow and heat transfer in mini/micro-scale because the thermal properties of liquid nitrogen is different from those of room-temperature fluids in that the latent heat, viscosity and the ratio of liquid density to vapor density, etc. are much smaller, which will definitely affect the flow and heat transfer characteristics.


In the present study, we presented the investigation of flow and heat transfer characteristics of liquid nitrogen in mini/micro-channels. The small viscosity enables the flow state in mini/micro-channels to be turbulent state, which proves that the classical theory for pressure drop is still valid if the roughness of the passage is properly taken into consideration. Experiments of flow boiling of liquid nitrogen were conducted under both adiabatic and diabatic conditions. It was shown that confinement number Co=0.5 can be applicable in classifying the heat transfer characteristics of liquid nitrogen in macro- and micro-channels. Flow visualization in micro-channels at low temperatures poses big challenges in image magnification and illumination. These two problems have been subtly overcome in our investigation and clear images have been obtained. The flow patterns and flow regimes of two-phase nitrogen flow indicated different features. Furthermore, we proposed and implemented a very simple but effective method for 3D flow visualization by one high-speed camera. Finally, numerical analysis of the flow boiling of liquid nitrogen in mini/micro-channel was carried out to deepen the understanding of mechanism.


Biography: Peng Zhang was born on 9th May, 1973. He graduated from Shanghai Jiao Tong University in 1995 with a Bachelor degree, and he completed his Ph.D. study in 1999 from the same university. He then joined Institute of Refrigeration and Cryogenics at Shanghai Jiao Tong University as an 'Assistant Professor. He was honored as JSPS Postdoctoral Research Fellow in 2002 and spent two years at University of Tsukuba in Japan to conduct the research on heat transfer of superfluid helium. He is now the full Professor in Mechanical Engineering at Shanghai Jiao Tong University.


Dr. Peng Zhang's research interests are thermal and fluidic phenomena at low temperatures, energy saving through thermal/cold storage. He is the principle investigator of many projects from National Natural Science Foundation of China, Ministry of Education, etc. He has coauthored more than 100 referred journal and conference papers in above research fields. Many of the papers have been published in the prestigious journals, like, Physical Review B, Physical Review E, International Journal of Heat and Mass Transfer, Cryogenics and so on. He is the receipt of CEC-ICMC Meritorious Student Paper Award (1999), National Excellent Ph. D. Dissertation Award (2002), and Young Investigator Award of Chinese Association of Refrigeration (2007); and was honored Danfoss Honoring Professor (2005).


 
  Giuseppe Zummo
ENEA - Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Rome, Italy


Presentation Title: Flow Boling in a Microtube: Flow Pattern and Heat Transfer
Abstract: This paper presents the results of the flow boiling patterns of FC-72 in a microtube. The internal diameter of the tube is 0.48 mm, with a heated length of 73 mm. The mass flow rate varies from 50 to 3000 kg/m2-s. The microtube is made of Pyrex in order to obtain the visualisation of the flow pattern along the heated channel. Different types of flow pattern have been observed: bubbly flow, deformed bubbly flow, bubbly/slug flow, slug flow, slug/annular flow, and annular flow. The flow pattern map is compared with those obtained for larger tubes (2.0, 4.0, and 6.0 mm). Flow patterns in the microtube present less chaotic behaviour and regular vapour-liquid interfaces. Besides, as the tube diameter decreases, the intermittent flow regime shifts from the saturated boiling region towards the subcooled boiling region. The experiments show the presence of flow instabilities in a large portion of the tests at low mass flow rates and low subcooling. Flow patterns in presence of flow instabilities are mainly characterized by bubbly/slug flow and slug/annular flow. The experimental results of flow pattern are compared with the flow pattern maps of McQuillan and Whalley (1985), Mishima and Ishii (1984), and Ong and Thome (2010).


Biography: Dr. Zummo is a leading researcher in the area of multi-phase flow and heat transfer at ENEA C.R. Casaccia Energy Department, Institute of Thermal Fluid Dynamics in Rome Italy.


 

 
 
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