Download or read book Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Building written by Eduardo Aktinol and published by . This book was released on 2014 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed--including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates. The numerical predictions show reasonable agreement with the results from experiments performed at microgravity. For nucleate boiling at microgravity the simulations predict a drastic change in vapor removal pattern when compared to Earth normal gravity. The predictions match well with experimental results. However, simulated heat transfer rates were significantly under-predicted.
Download or read book Numerical Simulation of the Dynamics and Heat Transfer Associated with a Single Bubble in Subcooled Pool Boiling and in the Presence of Noncondensables written by Jinfeng Wu and published by . This book was released on 2007 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study, a numerical procedure coupling level set function with moving mesh method is established. Test problems have been chosen to validate this developed method. The numerical results show that the current adaptive method can achieve the equivalent accuracy to the methods based on more uniform grids do. The results from the above-mentioned numerical procedure coupling level set function with moving mesh method for comparing cases in the presence of noncondensables with ones in the absence of noncondensables show the evidence of effects of noncondensable air imposed on heat transfer and the induced flow pattern is presented as well.
Download or read book Direct Numerical Simulations of Bubbles in Turbulent Flows with Heat Transfer written by Claudio Santarelli and published by Tudpress Verlag Der Wissenschaften Gmbh. This book was released on 2015-08-12 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bubbly flows are essential in many industrial and environmental applications and several methodologies have been employed to investigate the complex phenomena involved. In the present book Direct Numerical Simulations of bubble swarms in channel flow configuration are reported and several cases are presented. The focus is on the mutual interaction between fluid turbulence and bubble dynamics and the impact on the heat transfer in the two-phase mixture. This analysis concerns flow visualizations and quantitative statistical data regarding the fluid as well as the bubbles which can now be used as reference data for model developing and validation.
Download or read book Microscale Heat Transfer Fundamentals and Applications written by S. Kakaç and published by Springer Science & Business Media. This book was released on 2006-05-20 with total page 517 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains an archival record of the NATO Advanced Institute on Microscale Heat Transfer – Fundamental and Applications in Biological and Microelectromechanical Systems held in Çesme – Izmir, Turkey, July 18–30, 2004. The ASIs are intended to be high-level teaching activity in scientific and technical areas of current concern. In this volume, the reader may find interesting chapters and various Microscale Heat Transfer Fundamental and Applications. The growing use of electronics, in both military and civilian applications has led to the widespread recognition for need of thermal packaging and management. The use of higher densities and frequencies in microelectronic circuits for computers are increasing day by day. They require effective cooling due to heat generated that is to be dissipated from a relatively low surface area. Hence, the development of efficient cooling techniques for integrated circuit chips is one of the important contemporary applications of Microscale Heat Transfer which has received much attention for cooling of high power electronics and applications in biomechanical and aerospace industries. Microelectromechanical systems are subject of increasing active research in a widening field of discipline. These topics and others are the main themeof this Institute.
Download or read book Heat Transfer in Boiling written by Erich Hahne and published by . This book was released on 1977 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Modeling of Bubble Dynamics and Heat Transfer on Flow Boiling Within Microchannels written by Konstantinos Vontas and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubble Dynamics and Heat Transfer in Pool Boiling on Wires at Different Gravity written by Jian-Fu Zhao and published by . This book was released on 2011 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of experimental studies on bubble dynamical behaviors and heat transfer in pool boiling on thin wires in different gravity conditions have been performed in the past years, including experiments in long-term microgravity aboard the 22nd Chinese recoverable satellite RS-22, in short-term microgravity in the drop tower Beijing, and in normal gravity on the ground. Steady pool boiling of degassed R113 on thin platinum wires has been studied using a temperature-controlled heating method. A voltage-controlled heating method has also been used in normal gravity. A slight enhancement of nucleate boiling heat transfer is observed in microgravity, while dramatic changes of bubble behaviors are very evident. Considering the influence of the Marangoni effects, the different characteristics of bubble behaviors in microgravity have been explained. A new bubble departure model including the influence of the Marangoni effects has also been proposed, which can predict the whole observation both in microgravity and in normal gravity. The value of CHF (critical heat flux) in microgravity is lower than that in normal gravity, but it can be predicted well by the Lienhard-Dhir correlation, although the dimensionless radius, or the square root of the Bond number, in the present case is far beyond its initial application range. A further revisit on the scaling of CHF with heater radius in normal gravity, which is focused on the case of a small Bond number, has also been performed in our laboratory using different kinds of working fluids at different subcooling conditions. Interactions between the influences of the subcooling and heater radius will be important for the case of a small Bond number. In addition to the Bond number, there may exist some other parameters, which may be material-dependent, that play important roles in the CHF phenomenon with a small Bond number.
Download or read book Encyclopedia Of Two phase Heat Transfer And Flow Iii Macro And Micro Flow Boiling And Numerical Modeling Fundamentals A 4 volume Set written by John R Thome and published by World Scientific. This book was released on 2018-03-13 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous 'must read' chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a 'must have' reference together with Sets I and II for thermal engineering researchers and practitioners.
Download or read book Heat Transfer Vapour Bubble Dynamics and Sound Emission in Subcooled Nucleate Pool Boiling written by Andreas Bode and published by . This book was released on 2004 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Liquid Vapor Phase Change Phenomena written by Van P. Carey and published by CRC Press. This book was released on 2020-02-28 with total page 731 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the second edition of Liquid-Vapor Phase-Change Phenomena was written, research has substantially enhanced the understanding of the effects of nanostructured surfaces, effects of microchannel and nanochannel geometries, and effects of extreme wetting on liquid-vapor phase-change processes. To cover advances in these areas, the new third edition includes significant new coverage of microchannels and nanostructures, and numerous other updates. More worked examples and numerous new problems have been added, and a complete solution manual and electronic figures for classroom projection will be available for qualified adopting professors.
Download or read book Journal of Heat Transfer written by and published by . This book was released on 2007 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advances in Heat Transfer written by George A. Greene and published by Elsevier. This book was released on 2006-10-17 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Heat Transfer fills the information gap between regularly scheduled journals and university level textbooks by providing in-depth review articles over a broader scope than in journals or texts. The articles, which serve as a broad review for experts in the field, will also be of great interest to non-specialists who need to keep up-to- date with the results of the latest research. It is essential reading for all mechanical, chemical and industrial engineers working in the field of heat transfer, graduate schools or industry. Provides an overview of review articles on topics of current interest Bridges the gap between academic researchers and practitioners in industry A long-running and prestigious series
Download or read book Hydrodynamic Aspects of Boiling Heat Transfer written by N. Zuber and published by . This book was released on 1959 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulation of Bubble Growth in Subcooled Pool and Flow Boiling Under Microgravity Conditions written by Benjamin Franz and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical Science Under Microgravity Experiments on Board the SJ 10 Recoverable Satellite written by Wenrui Hu and published by Springer Nature. This book was released on 2019-10-16 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the physical science experiments in a space microgravity environment conducted on board the SJ-10 recoverable satellite, which was launched on April 6th, 2016 and recovered on April 18th, 2016. The experiments described were selected from ~100 proposals from various institutions in China and around the world, and have never previously been conducted in the respective fields. They involve fluid physics and materials science, and primarily investigate the kinetic properties of matter in a space microgravity environment. The book provides a comprehensive review of these experiments, as well as the mission’s execution, data collection, and scientific outcomes.
Download or read book Transport Phenomena in Microgravity written by S. S. Sadhal and published by . This book was released on 2004 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: The plans for an international space station, long distance space travel (perhaps to Mars), and the potential for commercial production of ultra pure silicon or polymer crystals are what make these topics of current relevance. The program includes topics such as transport in biological systems (relevant to bone loss associated with long-duration space travel), acoustic levitation, electromagnetic phenomena, crystal growth, protein crystallization, and boiling.
Download or read book Bubble Dynamics and Boiling Heat Transfer written by Samuel Siedel and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since boiling heat transfer affords a very effective means to transfer heat, it is implemented in numerous technologies and industries ranging from large power generation plants to micro-electronic thermal management. Although having been a subject of research for several decades, an accurate prediction of boiling heat transfer is still challenging due to the complexity of the coupled mechanisms involved. It appears that the boiling heat transfer coefficient is intimately related to bubble dynamics (i.e. bubble nucleation, growth and detachment) as well as factors such as nucleation site density and interaction between neighbouring and successive bubbles. In order to contribute to the understanding of the boiling phenomenon, an experimental investigation of saturated pool boiling from a single or two neighbouring artificial nucleation sites on a polished copper surface has been performed. The bubble growth dynamics has been characterized for different wall superheats and a experimental growth law has been established. The interaction between successive bubbles from the same nucleation site has been studied, showing the bubble shape oscillations that can be caused by these interactions. The forces acting on a growing bubble has been reviewed, and a complete momentum balance has been made for all stages of bubble growth. The curvature along the interface has been measured, and indications concerning the mechanism of bubble detachment have been suggested. The rise of bubble after detachment has been investigated, and the maximum velocity reached before a change of direction has been estimated and compared to existing models from the literature. The interaction between bubbles growing side by side has been studied: the generation and propagation of a wave front during the coalescence of two bubbles has been highlighted. As boiling heat transfer enhancement techniques are being imagined and developed, this study also focuses on the electrohydrodynamic enhancement technique. Boiling experiments have been performed in the presence of electric fields, and their effects on heat transfer and bubble dynamics have been characterized. Although the volume of the bubbles at detachment and the relationship between the bubble frequency and the wall superheat were not affected, the bubble growth curve was modified. The bubbles were elongated in the direction of the electric field, and this elongation was estimated and compared to other studies from the literature. The rising velocity of the bubble was reduced in the presence of electric field, and the behaviour of bubbles growing side by side was modified, the electric field causing the bubbles to repeal each other. These results, obtained in a fully controlled environment, provide compelling evidence that electric fields can be implemented to alter the bubble dynamics and subsequently heat transfer rates during boiling of dielectric fluids.
