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Volume 1 begins with 3 chapters on flow boiling in microchannels while the second part includes multi-microchannel evaporator cold plate studies, modeling of micro-two-phase cooling systems, their simulation, dynamic flow control and design studies.
Contents:https://doi.org/10.1142/9789814623285_fmatter01
The following sections are included:
https://doi.org/10.1142/9789814623285_0001
Mixing and advection are highly desirable to enhance flow boiling in microchannels where laminar flow prevails under typical work conditions. Additionally, flow boiling regimes are multiple and transitional. The dependence of heat transfer modes on flow regimes makes it challenging to select preferred heat transfer modes. In this chapter, two passive methodologies are developed to address these issues faced in flow boiling in microchannels. In section 3, a new mechanism in passively generating strong and sustainable mixing is developed to enhance flow boiling. Novel microfluidic transistors are developed to rapidly collapse vapor bubbles and to sustain the induced high frequency two-phase oscillations. In section 4, the stochastic flow regimes can be reduced into a single annular flow regime using novel nano-engineered walls. The controllability provides designers opportunities to select highly efficient heat transfer modes to maximize heat transfer rate of flow boiling in microchannels. By directly targeting on manipulating bubble dynamics and governing forces, consequently, the flow regimes, these two techniques can substantially enhance major flow boiling metrics (e.g. heat transfer rate, critical heat flux, and flow boiling stabilities) with water. Moreover, pressure drop can be also well managed or even be greatly reduced compared to that in smooth-wall microchannels.
https://doi.org/10.1142/9789814623285_0002
Evaporating liquid films sheared by a moving gas are a promising method of transferring large heat fluxes produced by microelectronics and power electronic equipment. In recent experimental investigations for shear-driven water films the critical heat flux was found of up to ten times higher than that for a falling film, exceeding 400 W/cm2 in experiments for moderate liquid flow rates. This chapter represents the theoretical background needed for understanding the physics of evaporating thin liquid films moving under action of gas flows, gravity, thermacapillary forces, etc., and the development of cooling techniques for electronic components based on the microchannels with thin shear-driven liquid films.
https://doi.org/10.1142/9789814623285_0003
Enhancement techniques for liquid/vapor phase-change heat transfer have been developed, commercially available, and extensively studied over many years.With the growing interest in heat transfer processes at the micro scale, adaptations of established, conventional scale techniques into micro two-phase heat sinks have been explored in recent years. As in conventional scale, the prime objectives are to reduce the surface temperature at onset of nucleate boiling, increase the heat transfer coefficient, increase the critical heat flux, and suppress flow instabilities…
https://doi.org/10.1142/9789814623285_0004
The main focus of this chapter is the detailed testing of multi-microchannel evaporators for electronics cooling and the development of operational flow maps to identify the stable operating range of such evaporators. In particular, we also wish to demonstrate and emphasize the importance of simultaneous two-phase flow and IR temperature visualizations in multi-microchannels, with the aim to categorize the types of flows observed using high-speed digital videos in tandem with assessing temperature stability using IR thermal videos. First of all, a condensed literature review of some previous experimental studies on flow imaging is given including the most recent observations of the present authors. Afterwards, a detailed description of our multi-microchannel test setup is given along with some representative heat transfer data. Then, several example micro-evaporator operational maps identifying stable and unstable operating regimes according to experimental conditions are presented, so that the most advantageous operating conditions for the safe cooling of electronics can be easily traced.
https://doi.org/10.1142/9789814623285_0005
An important challenge for the next generation of high performance computers of data centers is to guarantee sufficient and reliable cooling of the server blades. Since this seems to be unpractical with air cooling technologies due to the expected ever higher chip heat fluxes (higher than 100 Wcm−2), a novel and more effective cooling system needs to be developed. In the next chapter, it is demonstrated that simple and reliable two-phase on-chip cooling systems are attractive and provide substantial cooling rates with greatly reduced energy requirements for their operation than air cooling. In this chapter, a dynamic simulation code developed for a pump-mode on-chip cooling system is presented with 2D transient heat conduction and hot spot capabilities, applicable not only to single-phase cooling but more importantly to two-phase microchannel cooling. The present experimental validations show that both steady state and transient operating regimes agree well with the simulation code. Results of case studies considering only one heat sink, multiple heat sinks in parallel or the entire system are also shown. Simulations performed with multiple parallel microprocessors working under steady-state, transient, balanced and unbalanced work loads show the importance of such modeling to investigate the performance and reliability of the cooling system. Aspects such as flow distribution, junction temperature, critical heat flux (dry-out condition), control (safe operation) and heat recovery are investigated. Notably, this dynamic simulation code is also applicable to cooling of other electronics, such as power electronics, UPS, etc.
https://doi.org/10.1142/9789814623285_0006
Thermal designers of data centers and server manufacturers are showing an ever greater concern regarding the energetics of cooling of the newgeneration data centers beyond today's conventional air cooling of the chips/servers. One potential large term scalable solution is to make use of on-chip two-phase cooling, which, besides improving the cooling performance at the chip level, also adds the capability to reuse the waste heat in a convenient manner, since higher evaporating and condensing temperatures of the two-phase cooling system (up to 60° in a pump-driven system and up to 95° in a compressor-driven) are possible with such a “green” cooling technology…
https://doi.org/10.1142/9789814623285_0007
In this chapter a dynamic model and efficient solution algorithm is elaborated for a compact two-phase cooling system using microchannel evaporators to cool high performance electronic devices. The focus is put on model development and solution algorithm implementation, as these can then be easily applied to other two-phase cooling systems and applications. First, a practical overview is provided on the various two-phase modeling and related numerical solution techniques. The temporal and spatial discretizations are then discussed in detail, with a focus on the discretization of the convective terms using TVD schemes. The fully discretized flow conservation equations are also presented. At the end of the chapter, the verification of the model using the method of manufactured solutions is discussed. This method is particularly well suited for two-phase models as exact analytical results are often difficult to obtain for two-phase flow. Some illustrative results of the model are then presented. In summary, the system model described in this chapter provides a tool to dynamically simulate a complete two-phase microchannel electronics cooling system. Furthermore, the chapter provides a concise overview of some state-of-the-art numerical techniques and, by their application, serves as an excellent starting point to develop efficient dynamic numerical models of two-phase systems.
Fanghao Yang is a postdoctoral researcher in IBM T J Watson Research. Dr Yang received the BEng degree from Beijing University of Aeronautics and Astronautics, Beijing, China, in 2008 and the PhD in mechanical engineering from University of South Carolina in 2013. From 2009 to 2013, he was a Research Assistant with the department of mechanical engineering in University of South Carolina. His research focuses on thermal fluidics, phase-change heat transfer in Microsystem and electronics cooling. He has authored or co-authored 15 articles in prestigious journals and international conferences. He is also an inventor of 4 US patents.
Chen Li is an associate professor in the Department of Mechanical Engineering at the University of South Carolina (USC), Columbia, USA. He received his PhD in mechanical engineering in Rensselaer Polytechnic Institute, Troy, NY, USA in 2006. He conducts research in micro/nano-scale two-phase heat and flow physics, prediction, control and modeling and aims at basic research in developing and verifying theories based on new two-phase transport behaviors observed in experiments. Dr Li's research is sponsored by NASA, NSF, ONR, and DARPA.
Professor, PhD Oleg A Kabov graduated from the Tomsk Polytechnic State University, Russia, in 1978 and received the Ph.D. degree from the Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences (IT) in 1987. In 1999 he received the degree of Doctor of Sciences in Physics and Mathematics (habilitation) from the same institute. In 2007 he has been granted the diploma of Professor on thermal physics and thermal fluids science of Russian Academy of Sciences. Since 1987, he has been the Head of Laboratory of Enhancement of Heat Transfer in IT (Novosibirsk). His current research interests include: shear-driven and falling liquid films and rivulets, two-phase flows in microgravity and hypergravity, drop spreading and drop evaporation, condensation, evaporative and thermocapillary convection. From 1997 till 2012 he was in a research staff of the Universite Libre de Bruxelles and has been managing the "Two-Phase Systems Group" of the Microgravity Research Center of ULB. He was involved as a coordinator and researcher in the several experiments performed under microgravity conditions (Parabolic Flights, Sounding Rockets, International Space Station). Experiments in 10 parabolic flights campaigns of the European Space Agency have been performed. He has authored and coauthored 271 papers in referred journals and conference proceedings, 7 patents, has delivered 60 keynotes, plenary, and invited lectures at technical conferences and institutions. He is a member of National Committee on Heat and Mass Transfer of Russian Academy of Sciences. In 2006 Prof. Kabov initiated the permanent yearly Workshop on Two-Phase Systems for Ground and Space Applications. Since 2013 he is serving as Editor-in-Chief of the Journal "Interfacial Phenomena and Heat Transfer" published by Begell House.
Professor Dr. Sc. Vladimir V Kuznetsov is the Head of the Laboratory of Applied and Computational Fluid Dynamics in the Institute of Hydrodynamics SB RAS, Novosibirsk, Russia. He is a member of the Scientific Council of the Institute of Hydrodynamics SB RAS, scientific expert of Krasnoyarsk regional fund of science. Since 1994 V V Kuznetsov is teaching at Novosibirsk State University. He is a specialist in the field of boundary layers, fluid motion with interfaces, fluid dynamics and heat-mass transfer at zero gravity conditions, author and co-author of 80 scientific works, including two patents.
Dr Yulia Kabova is a senior scientist in the Institute of Thermophysics Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia. She joined in many projects associated with the intensification of heat exchange with phase changes as a supervisor and principal investigator. Her current research interests include the hydrodynamics and heat-mass transfer in shear-driven and falling nonisothermal liquid films, evaporation and rivulet flows.
Professor Yoav Peles is an international leader in the field of convective heat transfer in micro domains. He published more than 90 peer reviewed journal papers, about 50 conference papers, has several patents, written four book chapters, and is the author of a book. Professor Peles organized several international conferences and workshops including the first Gordon Research Conference (GRC) on Micro and Nanoscale Phase Change Heat Transfer to be held in January 2015. He is a fellow of the American Society of Mechanical Engineering (ASME).
Dr Sylwia Szczukiewicz is a scientific collaborator at the Laboratory of Heat and Mass Transfer, École Polytechnique Fédérale de Lausanne (LTCM, EPFL). She received her master's degree in mechanical engineering from the Kielce University of Technology (PŚk), Poland, in 2009. Her PhD thesis, as a part of the Nano-Tera RTD project CMOSAIC, was focused on the two-phase flow operational stability of refrigerants in multi-microchannels for cooling of future high-performance 3D stacked architectures with interlayer cooling. She has been involved in designing and setting up an experimental test loop to investigate a passive thermosyphon cooling system for high heat flux datacenter servers. Since 2009, she has authored over 10 journal and conference papers
John R Thome is Professor of Heat and Mass Transfer at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland since 1998, where he directs the two-phase flow and heat transfer research laboratory (LTCM) with 20 some post-docs and PhD students, see http://ltcm.epfl.ch/. His work focuses on visual investigations of the fundamental phenomena of microchannel two-phase flows (in channels as small as 85 microns), new experimental and image processing techniques for microscale two-phase flows, mechanistic two-phase flow pattern based heat transfer and pressure drop models for microscale evaporating and condensing flows, computerized flow control of two-phase microcooling systems, the development of multi-microchannel evaporators for electronics cooling with up to 1200 parallel microchannels, and the numerical modeling of two-phase phenomena. He received his PhD at Oxford University, England in 1978.
Nicolas Lamaison received his master's degree in energy from the National Institute of Applied Sciences (INSA) in Lyon, France, in 2010. He is currently finishing his PhD in the Laboratory of Heat and Mass Transfer (LTCM) at the Swiss Federal Institute of Technology in Lausanne (EPFL). His current research interests are dynamic modeling and experimental evaluation of pumped or gravity driven controlled two-phase on-chip cooling systems. It includes fluid mechanics and heat transfer in parallel microchannels evaporators/condenser, analysis of system dynamics and investigation of energy recovery.
Dr Jackson Braz Marcinichen is a Research Post Doc at the Laboratory of Heat and Mass Transfer at the EPFL (Lausanne-Switzerland) and has over 20 years experience in HVAC & R systems. He received his BE in Mechanical Engineering from the Federal University of Santa Catarina, Brazil in 1996, and his PhD in Mechanical Engineering from the same university in 2006. He has authored over 30 scientific and technical papers in indexed journals and international peer-reviewed conferences, book chapters and US patents. He has designed and evaluated several experimental facilities characterizing the thermo-hydrodynamic and control of cooling systems (calorimeters, wind tunnel, hybrid systems etc). Today he is engaged in the development of new novel hybrid cooling systems (passive and active) to cool high heat flux electronics components using on-chip cooling.
Dr Tom Saenen is a Research Post Doc at the Laboratory of Heat and Mass Transfer at the EPFL (Lausanne-Switzerland). He received his ME in Mechanical Engineering from the University of Leuven, Belgium in 2007, and his PhD in Mechanical Engineering from the same university in 2013. His main research interests are dynamic modeling of two-phase cooling and refrigeration systems including their components, with a focus on flow and heat transfer in microchannel evaporators. He has authored several papers in indexed journals and international peer-reviewed conferences on these topics.
Martine Baelmans is Professor at the Department of Mechanical Engineering at the KU Leuven in Belgium, where she leads the group on thermal-fluid engineering since 1996. She graduated from the same university and obtained her PhD in Engineering in 1993. She has authored or co-authored more than 200 papers in applications on fluid mechanics and heat transfer. Research topics are presently focusing on automated optimization in thermal design. Starting from dedicated component and system models, parameters, shapes and topologies are improved. Applications range from liquid and two-phase microelectronics cooling over thermal management in power electronics, power transformers and energy systems.