Download or read book Investigation of Flow Boiling Phenomena in Small scale Complex Geometries written by Amir Hooshang Raeisi Dehkordi and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study concerns measurement and prediction of single-phase and flow boiling heat transfer coefficients and pressure drops in mini multi-channel geometries with and without interconnecting passages, including plate channel; parallel channel; in-line pin-fin and in-line off-set pin-fin surfaces. Experiments were performed with refrigerant R113 and deionised water at atmospheric pressure. Single-phase and flow boiling heat transfer coefficients and pressure drops were obtained over a range of effective heat fluxes and mass fluxes. For the plate and parallel channel surfaces, the results obtained have been compared with several published macro- and micro-channels correlations. For the in-line and in-line off-set pin fin surfaces, as the geometries have some similarities with tube bundles, the results obtained have been predicted using the standard correlations for tube bundles. The results also have been compared with several existing correlations developed based on macro-scale tube bundles and micro-pin-fin surfaces data. The saturated flow boiling heat transfer coefficients for the parallel channel and pin-fin surfaces were similar to within the experimental uncertainty, and considerably higher than the plate channel values, all dependent on heat flux and reasonably independent of mass flux and vapour mass fraction. This indicated that the dominant heat-transfer mechanism in the saturated boiling flow regime was nucleate boiling for all surfaces. The parallel channel, in-line and off-set pin-fin surfaces improved heat transfer by increasing the surface area and the heat transfer coefficient in comparison with the plate channel surface. The two-phase pressure drops in the parallel channel and pin-fin surfaces were considerably larger than that for the plate channel surface. Thus, the reduction in wall temperature is achieved by a significant pressure drop penalty. For the pin-fin surfaces, at low vapour qualities the heat transfer coefficients were in reasonable agreement with the conventional scale tube bundles correlations however as the vapour quality increases, the correlations were not able to predict the heat transfer coefficient as unlike the conventionally-sized tube bundles, the convective enhancement does not happen in the mini-pin-fin surfaces tested. The nucleate pool boiling correlation of Cooper (1984) provided a good agreement with the data for all surfaces tests with R113 and deionised water. The measured two-phase pressure drops for both pin-fin surfaces tests with R113 and deionised water were in a good agreement with the predicted values obtained from standard correlations for tube bundles, indicating pressure drop methods maybe transferable.
Download or read book Numerical Investigation on the Effect of Gravitational Orientation on Bubble Growth During Flow Boiling in a High Aspect Ratio Microchannel written by Jarryd Potgieter and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent technological developments, mostly in the fields of concentrated solar power and microelectronics, have driven heat transfer requirements higher than current heat exchangers are capable of producing. Processing power is increasing, while processor size simultaneously decreases and the heat flux requirements of concentrating solar power plants are being driven up by the high temperatures that produce the best thermal efficiency. Heat transfer in microchannels, specifically when utilising flow boiling, has been shown to produce significantly higher heat fluxes than their macro-scale counterparts and could have a large impact on many industrial fields. This high heat transfer characteristic is caused by a number of factors, including the large difference between the sensible and latent heat of the working fluid and the evaporation of a thin liquid film that forms between the microchannel walls and the vapour bubbles. These phenomena occur at incredibly small scales. Flow visualisations, temperature and pressure measurements are therefore difficult to obtain. Many experiments that cover a wide range of microchannel sizes, shapes and orientations, and utilise different working fluids and heat fluxes have been reported. However, the correlations between confined boiling, heat flux and pressure drop have mostly been produced for macro-scale flow. Many different criteria have been developed to distinguish the macro scale from the micro scale, but the general consensus is that macro-scale heat transfer correlations do not perform well when used in the micro scale. Heat transfer correlations are typically created by performing physical experiments over a wide range of parameters and then quantifying the effect that varying these parameters has on the performance of the system. The small scale and high complexity of microchannel-based heat exchangers make visualising the flow within them difficult and inaccurate because both the working fluid and the microchannel walls distort light. The use of numerical modelling via computational fluid dynamics software allows phenomena that occur within the channel to be simulated, which provides valuable insight into how rapid bubble growth affects the surrounding fluid, which can lead to the design of better heat exchangers. This study focused on numerically modelling the growth of a single bubble during the flow boiling of FC-72 in a microchannel with a hydraulic diameter of 0.9 mm and an aspect ratio of 10. The numerical domain was limited to a 10 mm section of the microchannel where bubble nucleation and detachment were observed in an experimental study on a similar microchannel setup. The high cost of 3D simulations was offset by an interface-tracking mesh refinement method, which refined cells not only at the interface, but also a set distance on either side of the interface. To focus on the effects of gravity, a simplified approach is used, which isolates certain phenomena. Density gradients, material roughness and multiple bubble interaction are ignored so that the effects of buoyancy and bubble detachment can be analysed. Simulations are first performed in a 2D section through the centre of the microchannel, and then in the full 3D domain. In both the 3D numerical and experimental cases (Meyer et al., 2020), the bottom heated case had the lowest maximum temperature and the highest heat transfer characteristics, which were influenced by the detachment of the bubble from the heated surface. This observation indicates that the gravitational orientation of the channel can have a significant effect on the heat transfer characteristics of microchannel-based heat exchangers, and that more investigation is required to characterise the extent of this effect.
Download or read book Heat Transfer and Fluid Flow in Minichannels and Microchannels written by Satish Kandlikar and published by Elsevier. This book was released on 2006 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: &Quot;This book explores flow through passages with hydraulic diameters from about 1 [mu]m to 3 mm, covering the range of minichannels and microchannels. Design equations along with solved examples and practice problems are also included to serve the needs of practicing engineers and students in a graduate course."--BOOK JACKET.
Download or read book Flow boiling and condensation in microscale channels written by Fabio Toshio Kanizawa and published by Springer Nature. This book was released on 2021-04-30 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers aspects of multiphase flow and heat transfer during phase change processes, focusing on boiling and condensation in microscale channels. The authors present up-to-date predictive methods for flow pattern, void fraction, pressure drop, heat transfer coefficient and critical heat flux, pointing out the range of operational conditions that each method is valid. The first four chapters are dedicated on the motivation to study multiphase flow and heat transfer during phase change process, and the three last chapters are focused on the analysis of heat transfer process during boiling and condensation. During the description of the models and predictive methods, the trends are discussed and compared with experimental findings.
Download or read book Handbook of Thermal Science and Engineering written by and published by Springer. This book was released on 2018-07-31 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Handbook provides researchers, faculty, design engineers in industrial R&D, and practicing engineers in the field concise treatments of advanced and more-recently established topics in thermal science and engineering, with an important emphasis on micro- and nanosystems, not covered in earlier references on applied thermal science, heat transfer or relevant aspects of mechanical/chemical engineering. Major sections address new developments in heat transfer, transport phenomena, single- and multiphase flows with energy transfer, thermal-bioengineering, thermal radiation, combined mode heat transfer, coupled heat and mass transfer, and energy systems. Energy transport at the macro-scale and micro/nano-scales is also included. The internationally recognized team of authors adopt a consistent and systematic approach and writing style, including ample cross reference among topics, offering readers a user-friendly knowledgebase greater than the sum of its parts, perfect for frequent consultation. The Handbook of Thermal Science and Engineering is ideal for academic and professional readers in the traditional and emerging areas of mechanical engineering, chemical engineering, aerospace engineering, bioengineering, electronics fabrication, energy, and manufacturing concerned with the influence thermal phenomena.
Download or read book Experimental Investigation on Multiscale Interactions in Intermittent Flow Boiling and a New Hybrid VOF Lagrangian Modeling Approach written by Xiang Zhang and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In flow boiling, most phase change heat transfer occurs at the smallest scales: in 1 nm -- 10 [mu]m thick liquid microlayers under nucleating bubbles and in thin thermal boundary layers around such bubbles. Nucleating bubbles evolve from microscopic cavities on heated surfaces (reaching 104 - 106 sites per cm2). Theoretical closure models have been proposed for individual bubble nucleation, growth, and departure due to hydrodynamics. However, high-fidelity integration of such microscale models and theory with full channel flow processes has proven challenging due to the large range of length and time scales. Thus, contemporary boiling engineering still relies on empirical correlations. While such models are validated by large experimental databases, they are limited to specific fluids and geometries. More rigorous descriptions are needed to predict transport with emerging configurations and fluids. The first objective of this study is to experimentally characterize the coupling between micro-scale transport and large-scale hydrodynamics in flow boiling heat transfer through high-speed photography and thermal imaging. A new hybrid volume-of-fluid (VOF)-Lagrangian multi-scale simulation approach is then proposed to directly resolve and couple these processes. Experimental data from this investigation and other publications are employed to assess this modeling approach. First, a square air-oil bubble column facility is built to track the bubble trajectories at free surface and assess the hybrid VOF-Lagrangian simulation approach. High speed videos are captured from both the front and top view to measure flow parameters including: bubble size distribution (BSD), bubble rise velocity in vertical direction, as well as bubble lifetime and propagation velocity at the free surface. A hybrid VOF-Lagrangian solver is developed to characterize the coupling between micro-scale bubble transport and macro-scale hydrodynamics in such multi-scale two-phase flows. The Lagrangian model tracks the trajectory of individual injected discrete small bubbles, accounting for effects such as buoyancy, pressure, virtual mass, drag, and turbulent dispersion. Once bubbles exceed a threshold packing density or overlap with VOF structures, they are converted to the grid-scale vapor phase. An empirical bubble-lifetime model is implemented to account for the finite coalescence times of bubbles at free surfaces. Contributions of this effort include programmable closure for bubble lifetime at the free surface (before popping/coalescence), a pinning force method for bubbles at the free surface, and Lagrangian-to-VOF transition of bubbles based on packing density. Next, a two-phase flow boiling experimental facility is developed to collect simultaneous high-speed visualization and IR temperature distribution data. The test cell channel is 420 mm long with a 10 mm square-cross section. A transparent ITO coated sapphire window serves as a heater and IR interface for measuring the internal wall temperature. The facility is charged with a low boiling point fluid (HFE7000) to reduce uncertainties from heat loss. Vertical saturated flow boiling wake-nucleation interaction experiments are performed for varying volume flow rates (0.5 -- 1.5 L min-1, laminar-to-turbulent Re) and heat fluxes (0 -- 100 kW m-2). Discrete vapor slugs are injected to explore interactions with nucleate boiling processes. By measuring film-heater power, surface temperature distributions, and pressures, local instantaneous heat transfer coefficients (HTC) are obtained. A conjugate gradient method is implemented to solve the 2-D transient inverse heat conduction problem and estimate the non-uniform heat flux distribution. For nucleate flow boiling without slug injection, visualizations show that both bubble cycle and wait time are inversely proportional to the applied heat flux. The average wall temperature displays a linear relationship with heat flux. Moreover, bubble departure diameter tends to increase with increasing the bubble nucleation temperature, and stabilizes at higher temperature. With respect to the wake-nucleation interaction experiments, it is found that small nucleate bubbles only in the core region of Taylor bubble body with a certain bubble size (1.4 to 1.6 mm) would merge into the vapor slug. IR data indicate that the wake shear effect is divided into 5 stages during the whole process. Wake heat transfer enhancement is observed due to the vortex shedding and intense mixing between in the Taylor bubble wake. In addition, the nucleate boiling is firstly suppressed in the Taylor bubble body due to the falling liquid film, then recovered after the wake region. To efficiently simulate such processes, the hybrid VOF-Lagrangian model is extended to account for heat transfer, bulk- and Lagrangian-bubble-scale phase change, and nucleation site processes. The approach tracks discrete nucleation sites on walls and simulates a contact line pinning force. Bubble growth and departure is directly predicted using grid-scale VOF velocity and temperature data rather than idealized conditions. This method is first verified with literature data for pool boiling. It is then qualitatively assessed for the Taylor flow boiling processes studied experimentally.
Download or read book Boiling Heat Transfer written by R.T. Lahey Jr. and published by Elsevier. This book was released on 2013-10-22 with total page 629 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the CMR at Rensselaer, a research centre specializing in the state-of-the-art in multiphase science.
Download or read book Convective Boiling and Condensation written by John G. Collier and published by Clarendon Press. This book was released on 1994-05-19 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt: * Third edition of a well-known and well established text both in industry and for teaching * Fully up-to-date and includes extra problems This book is an aid to heat exchanger design written primarily for design and development engineers in the chemical process, power generation, and refrigeration industries. It provides a comprehensive reference on two-phase flows, boiling, and condensation. The text covers all the latest advances like flows over tube bundles and two-phase heat transfer regarding refrigerants and petrochemicals. Another feature of this third edition is many new problems at chapter ends to enhance its use as a teaching text for graduate and post-graduate courses on two-phase flow and heat transfer. - ;This book is written for practising engineers as a comprehensive reference on two-phase flows, boiling, and condensation. It deals with methods for estimating two-phase flow pressure drops and heat transfer rates. It is a well-known reference book in its third edition and is also used as a text for advanced university courses. Both authors write from practical experience as both are professional engineers. -
Download or read book Translational Research in Cardio Oncology An Issue of Heart Failure Clinics written by Ragavendra R. Baliga and published by Elsevier Health Sciences. This book was released on 2022-06-23 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this issue of Heart Failure Clinics, guest editors Drs. Ragavendra R Baliga and George A. Mensah bring their considerable expertise to the topic of Translational Research in Cardio-Oncology. Top experts in the field cover key topics such as radiation-induced cardiac dysfunction; training and career development; cardiovascular imaging; CAR-T cell therapy and cardiovascular disease; and more. Contains 12 relevant, practice-oriented topics including cardio-protection of high-risk individuals; myocardial metabolism; amyloidosis; arrhythmic complications associated with cancer therapies; and more. Provides in-depth clinical reviews on translational research in cardio-oncology, offering actionable insights for clinical practice. Presents the latest information on this timely, focused topic under the leadership of experienced editors in the field. Authors synthesize and distill the latest research and practice guidelines to create clinically significant, topic-based reviews.
Download or read book Liquid Vapor Phase Change Phenomena written by Van P. Carey and published by CRC Press. This book was released on 2018-08-15 with total page 592 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 nanonchannel geometries and the effects of extreme wetting on liquid-vapor phase change processes. This edition includes significant new coverage of microchannels and nanostructures along with many other updates. More worked examples and numerous new problems have been added along with a complete solutions manual and electronic figures for classroom projection.
Download or read book Flow Boiling in Expanding Microchannels written by Tamanna Alam and published by Springer. This book was released on 2017-06-07 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief presents an up to date summary of details of the flow boiling heat transfer, pressure drop and instability characteristics; two phase flow patterns of expanding microchannels. Results obtained from the different expanding microscale geometries are presented for comparison and addition to that, comparison with literatures is also performed. Finally, parametric studies are performed and presented in the brief. The findings from this study could help in understanding the complex microscale flow boiling behavior and aid in the design and implementation of reliable compact heat sinks for practical applications.
Download or read book Handbook of Phase Change written by S.G. Kandlikar and published by Routledge. This book was released on 2019-01-22 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive coverage of the basic phenomena. It contains twenty-five chapters which cover different aspects of boiling and condensation. First the specific topic or phenomenon is described, followed by a brief survey of previous work, a phenomenological model based on current understanding, and finally a set of recommended design equa
Download or read book Encyclopedia of Two Phase Heat Transfer and Flow IV written by John R Thome and published by World Scientific Publishing. This book was released on 2018-05-18 with total page 1372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Set IV is a new addition to the previous Sets I, II and III. It contains 23 invited chapters from international specialists on the topics of numerical modeling of pulsating heat pipes and of slug flows with evaporation; lattice Boltzmann modeling of pool boiling; fundamentals of boiling in microchannels and microfin tubes, CO2 and nanofluids; testing and modeling of micro-two-phase cooling systems for electronics; and various special topics (flow separation in microfluidics, two-phase sensors, wetting of anisotropic surfaces, ultra-compact heat exchangers, etc.). The invited authors are leading university researchers and well-known engineers from leading corporate research laboratories (ABB, IBM, Nokia Bell Labs). Numerous 'must read' chapters are also included here for the two-phase community. Set IV constitutes a 'must have' engineering and research reference together with previous Sets I, II and III for thermal engineering researchers and practitioners.
Download or read book Interface Capturing Simulations and Analysis of Boiling Phenomenon in Complex Geometries written by Christopher B Landis and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Two Phase Flow Boiling and Condensation written by S. Mostafa Ghiaasiaan and published by Cambridge University Press. This book was released on 2014-08-07 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text is an introduction to gas-liquid two-phase flow, boiling and condensation for graduate students, professionals, and researchers in mechanical, nuclear, and chemical engineering. The book provides a balanced coverage of two-phase flow and phase change fundamentals, well-established art and science dealing with conventional systems, and the rapidly developing areas of microchannel flow and heat transfer. It is based on the author's more than 15 years of teaching experience. Instructors teaching multiphase flow have had to rely on a multitude of books and reference materials. This book remedies that problem by covering all the topics that are essential for a graduate first course. Among the important areas that are discussed in the book, and are not adequately covered by virtually all the available textbooks, are: two-phase flow model conservation equations and their numerical solution; condensation with and without noncondensables; and two-phase flow, boiling, and condensation in mini and microchannels.
Download or read book Lattice Boltzmann Method written by A. A. Mohamad and published by Springer Science & Business Media. This book was released on 2011-06-27 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lattice Boltzmann Method introduces the lattice Boltzmann method (LBM) for solving transport phenomena – flow, heat and mass transfer – in a systematic way. Providing explanatory computer codes throughout the book, the author guides readers through many practical examples, such as: flow in isothermal and non-isothermal lid driven cavities; flow over obstacles; forced flow through a heated channel; conjugate forced convection; and natural convection. Diffusion and advection-diffusion equations are discussed with applications and examples, and complete computer codes accompany the coverage of single and multi-relaxation-time methods. Although the codes are written in FORTRAN, they can be easily translated to other languages, such as C++. The codes can also be extended with little effort to multi-phase and multi-physics, if the reader knows the physics of the problem. Readers with some experience of advanced mathematics and physics will find Lattice Boltzmann Method a useful and easy-to-follow text. It has been written for those who are interested in learning and applying the LBM to engineering and industrial problems and it can also serve as a textbook for advanced undergraduate or graduate students who are studying computational transport phenomena.
Download or read book Heat Transfer written by Aziz Belmiloudi and published by BoD – Books on Demand. This book was released on 2011-01-28 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past few decades there has been a prolific increase in research and development in area of heat transfer, heat exchangers and their associated technologies. This book is a collection of current research in the above mentioned areas and discusses experimental, theoretical and calculation approaches and industrial utilizations with modern ideas and methods to study heat transfer for single and multiphase systems. The topics considered include various basic concepts of heat transfer, the fundamental modes of heat transfer (namely conduction, convection and radiation), thermophysical properties, condensation, boiling, freezing, innovative experiments, measurement analysis, theoretical models and simulations, with many real-world problems and important modern applications. The book is divided in four sections : "Heat Transfer in Micro Systems", "Boiling, Freezing and Condensation Heat Transfer", "Heat Transfer and its Assessment", "Heat Transfer Calculations", and each section discusses a wide variety of techniques, methods and applications in accordance with the subjects. The combination of theoretical and experimental investigations with many important practical applications of current interest will make this book of interest to researchers, scientists, engineers and graduate students, who make use of experimental and theoretical investigations, assessment and enhancement techniques in this multidisciplinary field as well as to researchers in mathematical modelling, computer simulations and information sciences, who make use of experimental and theoretical investigations as a means of critical assessment of models and results derived from advanced numerical simulations and improvement of the developed models and numerical methods.
