Keynotes

17th Brazilian Congress of Thermal Sciences and Engineering

Prof. Moran Bercovici

Israel Institute of Technology, Technion

Moran Bercovici is an Assistant Professor in Mechanical Engineering at Technion – Israel Institute of Technology, and heads the Microfluidic Technologies Laboratory (http://microfluidics.technion.ac.il). His research combines experimental, analytical, and computational tools to study microfluidic problems characterized by coupling between fluid mechanics, heat transfer, electric fields, chemical reactions, and biological processes. A central theme in his lab is the development of novel microfluidic techniques, devices, and assays for clinical applications and for research in life and medical sciences. He received his BSc (2001) and MSc (2006) from the Faculty of Aerospace Engineering at Technion. Between 2001 and 2006 he was a Research Engineer at RAFAEL – Advanced Defense Systems, working on experimental and computational aerodynamics. He received his Ph.D. from Stanford University (2011), and spent a short postdoctoral period in the Department of Urology at Stanford School of Medicine before joining Technion. He is the recipient of the 2015 ERC starting award from the European Research Council, the Krill Prize for Excellence in Scientific Research from the Wolf Foundation, and the Yanai Prize for Excellence in Academic Education.

Abstract

Flow Control and Configurable Microstructures Using Non-Uniform Electroosmosis

Electro-osmotic flow (EOF) is the motion of a liquid due to interaction of an externally applied electric field with the net charge in the diffuse part of an electrical double layer. I will present our ongoing work leveraging non-uniform EOF to control flow patterns in a Hele-Shaw microfluidic chamber (two parallel plates separated by a small gap). By setting the spatial distribution of surface potential, we demonstrate the ability to dictate desired flow patterns without the use of physical walls. Furthermore, by replacing the rigid ‘ceiling’ (top plate) of the chamber with a thin elastic sheet, we demonstrate that internal pressure gradients formed in the liquid can be used to drive local deformations in the sheet. This opens the door to the implementation of configurable microstructures and microfluidic devices. In addition to experimental demonstrations, I will present key elements of the analytical models we developed, and discuss both future applications and limitations of the technology.

 

Prof. Luís Fernando Figueira da Silva

Pontifícia Universidade Católica do Rio de Janeiro, PUC Rio

Luís Fernando Figueira da Silva is an associate professor at the department of mechanical engineering of PUC-Rio (Brazil) and a CNRS (France) researcher. He holds an habilitation à diriger les recherches (2001) and a doctorat (1993) from the Université de Poitiers, and has received aeronautical engineering (1987) and master (1989) degrees from Instituto Tecnológico de Aeronáutica. His early works dealt with the numerical simulation of combustion in supersonic flows, and the current research activity involves numerical and experimental modelling of laminar and turbulent gas-phase combustion processes. Since 1993 he has authored 35 papers in journals, and his h-index is 9.

Abstract

Combustion research perspective at PUC-Rio

Understanding and controlling combustion processes is crucial to any society. Indeed, 85% of the energy produced and virtually all the gaseous pollutants stem from such processes. This lecture will initially provide an overview of the combustion community in Brazil and its place in the world. The, recent results from three research topics studied at PUC-Rio will be presented. First, turbulent combustion experimental results will illustrate the use of several laser-based diagnostic techniques and the role of turbulence-chemistry interactions. Then, the interplay between soot and polycyclic aromatic hydrocarbons distributions in laminar diffusion flames will be explored. Finally, a seemingly simple but overlooked issue, i.e., the thermochemical non equilibrium affecting hydrocarbon/air detailed chemical mechanisms under rich burning conditions will be detailed. Prospects for future research will also be given for each of these research topics.

Prof. Sergey Alekseenko

Novosibirsk State University

Sergey Alekseenko is a Scientific Head of the Kutateladze Institute of Thermophysics (Novosibirsk, Russia). He is a Professor and Head of Chair of Physics of Nonequilibrium Processes, Novosibirsk State University. He is Academician of Russian Academy of Sciences, member of American Physical Society, Society of Chemical Industry, Scientific Council of ICHMT (International Centre for Heat and Mass Transfer) and EUROMECH. He is a member of Assembly of World Conferences on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, member of ISMF Governing Board, and member of European Fluid Mech. Conf. Committee. His areas of expertise are the transport phenomena in two-phase flow, hydrodynamics of film flow, wave phenomena, vortex flows and turbulent jets, experimental methods for two-phase flows, power engineering, renewable energy, and energy saving. He has 130 published papers in refereed journals, 29 patents, 6 monographs including Wave Flow of Liquid Films and Theory of Concentrated Vortices. Prof. Alekseenko is the laureate of the 2018 Global Energy Prize (of The Global Energy Association).

Abstract

Vortex reconnection in the swirl flow

Vortex reconnection seems to be a fundamentally important phenomenon resulting in the drastic change in the topology of vortex structures. This paper presents the results of experimental study of vortex reconnection processes on the spiral vortex tube formed in a swirl flow in a conical diffuser with sufficiently large swirl parameter values. The experimental setup is a simplified model of a draft tube of hydroturbine. The result of reconnection can be either formation of an isolated vortex ring while preserving the basic spiral vortex tube or formation of a system consisting of the vortex ring linked with the spiral tube. On the original spiral in the reconnection zone, the left-handed Kelvin wave, running up the vortex tube, is generated consistently. A number of topological features of vortex reconnection, such as asymmetry of the process near the ring and spiral tube, formation of two bridges and two threads, as well as formation of external bridges, not associated with the vortex reconnection process, were revealed. The obtained results are useful for understanding and describing the processes in a draft tube of hydroturbine, quantum turbulence, and solar flares.

Prof. Matteo Bucci

Massachusetts Institute of Technology, MIT

Matteo Bucci is Assistant Professor of Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), where he teaches graduate and undergraduate courses on nuclear energy systems and nuclear reactor thermal-hydraulics. He received his MSc (2005) and PhD (2009) in Nuclear Engineering from University of Pisa, Italy. Thereafter he was research scientist at CEA (Commissariat à l’énergie atomique), France, where he led several research projects in experimental and computational thermal-hydraulics. Matteo has published over 40 articles in the areas of reactor safety and design, two-phase flow and heat transfer, and surface engineering technology. His research currently focuses on nuclear reactor thermal-hydraulics, two-phase heat transfer and surface-engineering innovations to improve the safety and the economic competitiveness of existing and future advanced nuclear reactors. Matteo is also an active member of the Consortium for Advanced Nuclear Energy Systems (CANES), one of the eight MIT Low-Carbon Energy Centers (LCEC).

Abstract

Advanced diagnostics to resolve long-lasting controversies in boiling heat transfer

Boiling heat transfer has been investigated for several decades, but still there are many open questions and controversies about the mechanisms associated with this process and particularly its limit, known as critical heat flux (CHF). Specifically, there is still no general agreement on the mechanisms that lead to CHF enhancement with micro- and nano-engineered surfaces, let alone a universal model or correlation. CHF enhancement on such surfaces has been attributed to a variety of factors including nucleation site density change, surface area increase, contact line pinning, microlayer evaporation, micro- convection, surface wettability and wickability. The lack of understanding, which results in controversies about the physical mechanisms, is due to a lack of experimental capabilities to perform high-quality measurements of all the parameters that affect the boiling process. Such parameters include nucleation site density, bubble departure frequency, bubble growth time and wait time, dry area fraction, contact line density, as well as the partitioning of the heat flux on the boiling surface. Experimental devices used in the literature studies are typically very simple and enable measurements of the average boiling surface temperature and heat flux only. As such, they cannot provide the information required to reveal what are the first principles and eventually to build mechanistic boiling heat transfer models. Today, new horizons can be discovered thanks to unique diagnostics recently developed in Nuclear Science and Engineering (NSE) at MIT. This technique leverages high-speed video and high-speed infrared cameras and advanced post-processing algorithms developed in-house. Using such diagnostics, it is possible to measure both time-dependent temperature and heat flux distributions on the boiling surface with unprecedented space (~100 µm) and time (2500 to 4000 fps) resolutions, together with all the fundamental boiling parameters listed before. In this talk, we presentcutting-edge investigations enabled by these advanced diagnostics. The list of addressed controversial issues includes: wall heat flux partitioning in boiling heat transfer, CHF in steady-state and transient conditions and, last but not least, CHF enhancement on micro- and nano-engineered surfaces.

Prof. Christian Hermes

Universidade Federal de Santa Catarina, UFSC

Christian Hermes received his bachelor (1996) and doctoral (2006) degrees in mechanical engineering, all from the Federal University of Santa Catarina, Brazil. He worked as a senior engineer for Whirlpool Corp., and held a professorship in mechanical engineering at the Federal University of Paraná, Brazil. Currently, he is with the POLO Research Laboratories for Emerging Technologies in Cooling and Thermophysics of the Department of Mechanical Engineering of the Federal University of Santa Catarina as an associate professor. He holds two international patents and authored more than 50 journal papers on Thermodynamics and Transport Phenomena focusing on frost formation, heat exchangers, and refrigeration systems and their components.

Abstract

Frost formation in refrigerating appliances: fundamentals and applications

Evaporator frosting is a major issue in modern refrigeration design as it depletes the cooling capacity thus increasing the energy input needed to accomplish the same refrigerating effect. To tackle with such a multivariable engineering problem, simulation models have been developed to predict the frost build-up on the surfaces of complex geometries, such as tube-fin evaporators. Frost models, however, rely not only on the mass and energy balances on and within the frost layer, but also on the thermophysical properties of the frosted media, such as density and thermal conductivity. To put forward reliable and accurate frost accretion models to be used as engineering design tools on industrial grounds has demanded a substantial research effort, which is on the focus of this presentation. This keynoteis, therefore, aimed at the fundamental and applied research on frost formation carried out in the past decade at the POLO Labs, evolving from the experimental evaluation of the thermophysical properties of frost to the experimental validation of homemade mathematical models for fan-supplied tube-fin evaporators running under frosting conditions. The semi-empirical correlations, tailor-made models, and purpose-built wind- tunnel facilities devised for this end are also described, together with some recent optimization results focusing on robust evaporator geometry and optimal defrost cycle.

Prof. Jerzy Maciej Floryan

University of Western Ontario

Dr. Jerzy M. Floryan is a Professor at Department of Mechanical and Materials Engineering at the University of Western Ontario in Canada. He received PhD from Virginia Tech, US, and postdoctoral training from the Northwestern University, US. He is Fellow of the American Society of Mechanical Engineers, Canadian Society of Mechanical Engineers, Canadian Aerospace and Space Institute, Engineering Institute of Canada, Japanese Society for the Promotion of Science and American Physical Society, and Associate Fellow of the American Aeronautics and Space Institute. He has been awarded Humboldt Research Prize in Germany, Senior NATO Research Award in France, Science and Technology Fellowship in Japan and Humboldt Fellowship in Germany. His Canadian Awards include Robert W. Angus Medal (Engineering Institute of Canada) and Canadian Pacific Railway Engineering Medal (Canadian Society of Mechanical Engineers). He is also Canadian delegate to IUTAM. Dr.Floryan has held visiting appointments at the Los Alamos National Laboratory (US), German Aerospace Research Establishment (DVLR, Gottingen), French Aerospace Research Establishment (CERT-ONERA, Toulouse), National Aerospace Laboratory (Tokyo, Japan), Paul Sabatier University (Toulouse, France), Ohio University (USA) and National University of Singapore (Singapore).

 

Abstract

On the structured convection

Natural convection driven by heating patterns is referred to as the structured convection. Its understanding is required for a reliable prediction of the local contaminant transport in urban environments where the form of the convection is dictated by the surface topography (building pattern) and thermally-relevant features of this topography like color variations (color patterns of roofs, streets and parks). Similar conditions can be encountered in rural environments where local circulation can be driven by different heating rates of patterns of forests and lakes, and can be significantly modified by the rural terrain topography. Heating patterns can be used to induce proper structure in the flow to improve mixing and thereby would provide an excellent tool to design efficient heat exchangers. Other examples include patterns of local fires, patterns of computer chips, thermal patterning in micro-fluidic devices, and so on. The important unifying features of all these problems is the existence of a certain spatially distributed pattern of external heating applied to the system of interest. The structured convection occurs in systems heated from below as well as in systems heated from above. It occurs regardless of the intensity of heating and thus is of interest in system with small temperature differences. A review of the recent results will be presented with focus on the super-thermo-hydrophobic effect which provides means for drag reduction.