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Experimental Study Of Heat Flux Partitioning In Pressurized Subcooled Flow Boiling
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Book Synopsis Experimental Study of Heat Flux Partitioning in Pressurized Subcooled Flow Boiling by : Andrew Jonathan Richenderfer
Download or read book Experimental Study of Heat Flux Partitioning in Pressurized Subcooled Flow Boiling written by Andrew Jonathan Richenderfer and published by . This book was released on 2018 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding of subcooled flow boiling and the critical heat flux (CHF) is of the utmost importance for both safety and profitability of pressurized water nuclear reactors since they are major factors in the determination of the reactor power rating. Motivated by the emergence of a new wall boiling model by Gilman [3] and previous experimental insights from Phillips [12], a first-of-a-kind experimental investigation of pressurized steady-state subcooled flow boiling was conducted using state-ofthe- art diagnostics to gain a unique insight of the relevant mechanisms, including the partitioning of the wall heat flux. Conditions up to 10 bar pressure, 2000 kg/m2s mass flux and 20 K subcooling were explored. High-speed infrared thermometry tools were developed and used to measure the local time-dependent 2-D temperature and heat flux distributions on the boiling surface. These distributions were analyzed to determine fundamental boiling heat transfer parameters such as the nucleation site density, growth and wait times, nucleation frequency, departure diameter as well as the partitioning of the wall heat flux. While established mechanistic models can capture the trends of growth time and wait time with relatively good accuracy, this work reveals current models do not accurately predict the activation and interaction of nucleation sites on the boiling surface. This is a major roadblock, since boiling curves and CHF values obtained in nominally identical environments can be significantly different depending upon the nucleation site density which in turn is determined by the surface properties. The role of evaporation in the partitioning of the heat flux increases monotonically as the average heat flux increases, up to a maximum value of 70%, and is the dominant mechanism at high heat fluxes. At low and intermediate heat fluxes single-phase heat transfer is the dominant mechanism. Traditional heat partitioning models fail to capture these physics, but newer models with a comprehensive and physically consistent framework show promise in predicting the wall heat transfer. The data and understanding produced by this work will be essential for the development and validation of these modeling tools.
Book Synopsis An Experimental Study of Subcooled Flow Boiling at Elevated Pressure in an Annular Flow Channel by : Pervej Rahman
Download or read book An Experimental Study of Subcooled Flow Boiling at Elevated Pressure in an Annular Flow Channel written by Pervej Rahman and published by . This book was released on 2015 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental setup was developed to study the region of subcooled flow boiling. Multiple studies were carried out to investigate the effects of liquid velocity, pressure, and temperature on the boiling heat transfer of subcooled fluid flowing through a heated annular channel. Water was used as the working fluid and principle of Ohmic heating was used to raise water temperature. The system pressure, heat flux, & mass flux ranged from 101 to 912 kPa, 19 to 155 kW/m2, and 83 to 332 kg/m2-s, respectively. This report contains boiling curves, heat transfer coefficients of various studies and a description of the experimental setup.
Book Synopsis Modeling and experiments for wall heat flux partitioning during subcooled flow boiling of water at low pressures by : Nilanjana Basu
Download or read book Modeling and experiments for wall heat flux partitioning during subcooled flow boiling of water at low pressures written by Nilanjana Basu and published by . This book was released on 2003 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Study on Subcooled Flow Boiling on Heating Surfaces with Different Thermal Conductivities by : Ling Zou
Download or read book Experimental Study on Subcooled Flow Boiling on Heating Surfaces with Different Thermal Conductivities written by Ling Zou and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subcooled flow boiling is generally characterized by high heat transfer capacity and low wall superheat, which is essential for cooling applications requiring high heat transfer rate, such as nuclear reactors and fossil boilers. In this study, subcooled flow boiling on copper and stainless steel heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. Flow boiling heat flux and heat transfer coefficient were experimentally measured on both surfaces under different conditions, such as pressure, flow rate and inlet subcooling. Significant boiling heat transfer coefficient differences were found between the copper and the stainless steel heating surfaces. To explain the different flow boiling behaviors on these two heating surfaces, nucleation site density and bubble dynamics were visually observed and measured at different experimental conditions utilizing a high-speed digital video camera. These two parameters are believed to be keys in determining flow boiling heat flux. Wall superheat, critical cavity size and wall heat flux were used to correlate with nucleation site density data. Among them, wall heat flux shows the best correlation for eliminating both pressure and surface property effects. The observed nucleation site distribution shows a random distribution. When compared to the spatial Poisson distribution, similarity between them was found, while the measured nucleation site distribution is more uniform. From experimental observations, for the two surface materials investigated, which have similar surface wettability but sharply different thermal properties, bubble dynamics displayed fairly similar behavior. The obtained experimental results indicate that thermal conductivity of heating surface material plays an important role in boiling heat transfer. This is due to thermal conductivity having a significant impact on the lateral heat conduction at the heating surface and consequently temperature uniformity of the heating surface. A model was then developed and solved numerically for heat conduction at the heating surface when bubbles are present. Several key parameters which impact lateral heat conduction and surface temperature profile were studied. These parameters include material thermal conductivity, bubble size, heating surface thickness, etc. Numerical results show that, temperature profile on the heating surface tends to be more uniform and have a lower average value on a heating surface with higher thermal conductivity, which agrees well with the experimental observation.
Book Synopsis Modeling and Experiments for Wall Heat Flux Partitioning During Subcooled Flow Boiling of Water at Low Pressures by : Nilanjana Basu
Download or read book Modeling and Experiments for Wall Heat Flux Partitioning During Subcooled Flow Boiling of Water at Low Pressures written by Nilanjana Basu and published by . This book was released on 2003 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modelling Subcooled Boiling Flows by : Guan Heng Yeoh
Download or read book Modelling Subcooled Boiling Flows written by Guan Heng Yeoh and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the context of computational fluid dynamics (CFD), modelling low-pressure subcooled boiling flow is of particular significance. A review is provided in this book of the various numerical modelling approaches that have been adopted to handle subcooled boiling flow. The main focus in the analysis of such a challenging problem can be broadly classified according into two important categories: (i) Heat transfer and wall heat flux partitioning during subcooled boiling flow at the heated wall and (ii) Two-phase flow and bubble behaviours in the bulk subcooled flow away from the heated wall. For the first category, details of both empirical and mechanistic models that have been proposed in the literature are given. The enhancement in heat transfer during forced convective boiling attributed by the presence of both sliding and stationary bubbles, force balance model for bubble departure and bubble lift-off as well as the evaluation of bubble frequency based on fundamental theory depict the many improvements that have been introduced to the current mechanistic model of heat transfer and wall heat flux partitioning. For the second category, details of applications of various empirical relationships and mechanistic model such as population balance model to determine the local bubble diameter in the bulk subcooled liquid that have been employed in the literature are also given. A comparison of the predictions with experimental data is demonstrated. For the local case, the model considering population balance and improved wall heat partition shows good agreement with the experimentally measured radial distributions of the Sauter mean bubble diameter, void fraction, interfacial area concentration and liquid velocity profiles. Significant weakness prevails however over the vapor velocity distribution. For the axial case, good agreement is also achieved for the axial distributions of the Sauter mean bubble diameter, void fraction and interfacial area concentration profiles. The present model correctly represents the plateau at the initial boiling stages at upstream, typically found in low-pressure subcooled boiling flows, followed by the significant rise of the void fraction at downstream.
Book Synopsis Materials with Extreme Wetting Properties by : Majid Hosseini
Download or read book Materials with Extreme Wetting Properties written by Majid Hosseini and published by Springer Nature. This book was released on 2021-02-17 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book aims at identifying novel advanced materials of extreme wetting properties (MEWP) for practical, industrial applications. The state-of-the art superhdyrophobic, superhdyrophilic, superoleophobic, superoleophilic, and superomniphobic materials, that are MEWP, with respect to their technological and emerging industrial applications are discussed in this book. MEWP offer new perspectives providing numerous potential applications. Hence, these advanced MEWP have the potential to lead to a new generation of products and devices with unique properties and functionalities. Despite the large scientific progress on MEWP there are still some obstacles which have to be solved to make these materials available for real life applications. Recent advances on the production strategies, including methods and materials, of MEWP has shown that the durability and sustainability obstacles can be addressed thus offering the possibility for industrial exploitation. MEWP with wettabilities ranging from superhydrophobicity to superhydrophilicity provide promising avenues for several and important applications, which sometimes are crucial for the humankind. This book also discusses a large variety of other potential applications of MEWP, thus providing new ideas to scientists and engineers for further exploitation of these novel materials. Moreover, the whole spectrum of the recent technological developments, current research progress, future outlook, and the modern trends in the applications of MEWP are discussed in a consistent approach.
Download or read book Boiling written by Yasuo Koizumi and published by Elsevier. This book was released on 2017-06-22 with total page 849 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boiling: Research and Advances presents the latest developments and improvements in the technologies, instrumentation, and equipment surrounding boiling. Presented by the Japan Society of Mechanical Engineers, the book takes a holistic approach, first providing principles, and then numerous practical applications that consider size scales. Through six chapters, the book covers contributed sections from knowledgeable specialists on various topics, ranging from outlining boiling phenomena and heat transfer characteristics, to the numerical simulation of liquid-gas two phase flow. It summarizes, in a single volume, the state-of-the-art in boiling heat transfer and provides a valuable resource for thermal engineers and practitioners working in the thermal sciences and thermal engineering. Explores the most recent advancements in boiling research and technology from the last twenty years Provides section content written by contributing experts in their respective research areas Shares research being conducted and advancements being made on boiling and heat transfer in Japan, one of the major research hubs in this field
Book Synopsis The Effects of Concave Curvature on Subcooled Flow Boiling from a Small, High-heat-flux Region by : Pey-Shey Wu
Download or read book The Effects of Concave Curvature on Subcooled Flow Boiling from a Small, High-heat-flux Region written by Pey-Shey Wu and published by . This book was released on 1994 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Wall Heat Flux Partitioning During Subcooled Flow Film Boiling of Water on a Vertical Surface by : Phani Kiran Meduri
Download or read book Wall Heat Flux Partitioning During Subcooled Flow Film Boiling of Water on a Vertical Surface written by Phani Kiran Meduri and published by . This book was released on 2007 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Subcooled Flow Boiling for High Heat Flux Applications by : Ronald D. Boyd
Download or read book Experimental Subcooled Flow Boiling for High Heat Flux Applications written by Ronald D. Boyd and published by . This book was released on 1989 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Basic Experimental Studies on Boiling Fluid Flow and Heat Transfer at Elevated Pressures for Month of ... by :
Download or read book Basic Experimental Studies on Boiling Fluid Flow and Heat Transfer at Elevated Pressures for Month of ... written by and published by . This book was released on 1960-09 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Study on the Subcooled Boiling Flow Via Optical Measurement Techniques by : Jun Soo Yoo
Download or read book Experimental Study on the Subcooled Boiling Flow Via Optical Measurement Techniques written by Jun Soo Yoo and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of experimental work to investigate the subcooled boiling flow in a vertical square upward flow channel is described. As experimental methods, high-speed photography and infrared (IR) thermometry were employed simultaneously. The research scope explored includes (i) measurement issues of fundamental bubble parameters through visualization, (ii) experimental methodology to achieve both enhanced two-phase flow visualization and accurate wall temperature measurement, and (iii) measurement of diverse aspects of bubble dynamics as well as wall heat transfer by applying the verified experimental approach. Before producing the actual data, substantial effort was first made to identify the critical measurement issues of fundamental bubble parameters in a forced convective boiling system. Those issues have never been explicitly addressed in previous studies despite the possibly critical impacts on the experimental results. Thus, a series of systematic experimental investigations was performed to uncover those issues and to verify the errors created by not addressing them, based on which more suitable ways of observing and characterizing such parameters through experiments were discussed. Then, an experimental strategy to achieve high-fidelity optical measurements using both high-speed photography and IR thermometry was established. To attain the goal, the important issues such as test section design, IR thermal imaging issues, visualization strategy, wall temperature tracking method, and experimental validations were extensively addressed. Also, the feasibility of current experimental approach was demonstrated through the subcooled flow boiling experiment. Finally, by employing the experimental strategy established, an experimental investigation of the subcooled boiling flow was conducted. The experiment was performed in a vertical square upward flow channel using refrigerant NovecTM 7000, in which a single nucleation site was purposely activated for a fundamental study of subcooled flow boiling process. The various aspects of bubble behavior under different subcooled flow boiling conditions were examined using both micro- and macroscopic views of high-speed cameras while measuring the wall temperature/heat flux with IR thermometry. Additionally, based on the measurements of various bubble parameters as well as wall heat transfer, relevant relations among those parameters and the underlying mechanisms were intensively discussed. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155042
Book Synopsis Direct-Contact Heat Transfer by : Frank Kreith
Download or read book Direct-Contact Heat Transfer written by Frank Kreith and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: to increase the use of direct contact processes, the National Science Foundation sup ported a workshop on direct contact heat transfer at the Solar Energy Research Insti tute in the summer of 1985. We served as organizers for this workshop, which em phasized an area of thermal engineering that, in our opinion, has great promise for the future, but has not yet reached the point of wide-spread commercial application. Hence, a summary of the state of knowledge at this point is timely. The workshop had a dual objective: 1. To summarize the current state of knowledge in such a form that industrial practi tioners can make use of the available information. 2. To indicate the research and development needed to advance the state-of-the-art, indicating not only what kind of research is needed, but also the industrial poten tial that could be realized if the information to be obtained through the proposed research activities were available.
Book Synopsis Experimental Study on the Identification of Heat Transfer Characteristics for Subcooled Flow Boiling of Novec 649 by : Moritz Till Bruder
Download or read book Experimental Study on the Identification of Heat Transfer Characteristics for Subcooled Flow Boiling of Novec 649 written by Moritz Till Bruder and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Investigation of Subcooled Flow Boiling Using Synchronized High Speed Video, Infrared Thermography, and Particle Image Velocimetry by : Bren Andrew Phillips
Download or read book Experimental Investigation of Subcooled Flow Boiling Using Synchronized High Speed Video, Infrared Thermography, and Particle Image Velocimetry written by Bren Andrew Phillips and published by . This book was released on 2014 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Subcooled flow boiling of water was experimentally investigated using high-speed video (HSV), infrared (IR) thermography, and particle image velocimetry (PIV) to generate a unique database of synchronized data. HSV allowed measurement of the bubble departure diameter. IR thermography allowed measurement of wall superheat (local distribution and surface-averaged values), heat transfer coefficient, nucleation site density, and bubble frequency. Particle image velocimetry allowed for the measurement of velocity profiles in the liquid phase for single bubble nucleation events. The tests were performed at pressures of 1.05, 1.5, and 2.0 bar and at subcoolings of 5, 10, and 15 °C. The mass flux values explored were 150-1250 kg/m2/s. The heat flux values explored were 100-1600 kW/m2. As expected, the heat transfer coefficients increased with increasing mass flux in the single-phase convection and partial boiling regions, and converged to a fully-developed boiling curve for high heat fluxes. The bubble departure diameter decreased with increasing mass flux and decreasing heat flux; in accordance with Sugrue's model. The nucleation site density increased with increasing superheat and decreasing mass flux, as predicted by Kocamustafaogullari and Ishii's model. The nucleation site density models under-predicted the nucleation site density for a given wall superheat. Wait time and frequency models did not reproduce the data accurately, and underestimated wait time by an order of magnitude. A new mechanistic model for calculating the wait time was developed that split the wall heat flux into the component that is transferred to the fluid, and the component that is transferred as sensible heat into the heater wall. Significant localized cooling was observed underneath bubbles sliding along the wall after departure from a nucleation site, an effect which should be considered in advanced models of subcooled flow boiling. The sliding bubble thermal effects were found to be insensitive to system conditions and were limited by the thermal conduction within the substrate. Bubble growth front velocities, and regions of flow influence of departing bubbles were measured with PIV. The database generated in this project can be used to inspire or validate mechanistic models and/or CFD simulations of subcooled flow boiling heat transfer.
Book Synopsis Experimental Study on the Identification of Heat Transfer Characteristics for Subcooled Flow Boiling of Novec 649 by : Moritz Bruder
Download or read book Experimental Study on the Identification of Heat Transfer Characteristics for Subcooled Flow Boiling of Novec 649 written by Moritz Bruder and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
