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Modeling And Experiments For Wall Heat Flux Partitioning During Subcooled Flow Boiling Of Water At Low Pressures
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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 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 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 Two-Phase Flow for Automotive and Power Generation Sectors by : Kaushik Saha
Download or read book Two-Phase Flow for Automotive and Power Generation Sectors written by Kaushik Saha and published by Springer. This book was released on 2018-11-03 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the two-phase flow problems relevant in the automotive and power generation sectors. It includes fundamental studies on liquid–gas two-phase interactions, nucleate and film boiling, condensation, cavitation, suspension flows as well as the latest developments in the field of two-phase problems pertaining to power generation systems. It also discusses the latest analytical, numerical and experimental techniques for investigating the role of two-phase flows in performance analysis of devices like combustion engines, gas turbines, nuclear reactors and fuel cells. The wide scope of applications of this topic makes this book of interest to researchers and professionals alike.
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 Modeling Vertical Subcooled Boiling Flows at Low Pressures by : G. H. Yeoh
Download or read book Modeling Vertical Subcooled Boiling Flows at Low Pressures written by G. H. Yeoh and published by . This book was released on 2011 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: An improved wall heat flux partitioning model at the heated surface was developed by Yeoh et al. This model, coupled with a three-dimensional two-fluid model and Multiple Size Group model, has led to satisfactory agreement being achieved between the model predictions and experimental measurements. Nevertheless, one shortcoming is the reliance on empirical correlations for the active nucleation site density in the wall heat flux partitioning model. This discrepancy brings about uncertainties, especially in appropriately evaluating the vapor generation rate, which greatly influences the model prediction on the axial and radial void fraction profiles within the bulk fluid flow. By considering the fractal model with the aforementioned subcooled boiling flow model in the absence of empirical correlations for the active nucleation site density, a comprehensive mechanistic model to predict vertically oriented subcooled boiling flows is developed. The proposed model is assessed against the experimental data of axial measurements of Zeitoun and Shoukri and the radial measurements of Yun et al. and Lee et al. for vertical subcooled boiling flows within annular channels. Improved model predictions are obtained when the model is compared against typically applied empirical correlations for active nucleation site density. Discussions on the agreement of other two-phase flow parameters are also presented.
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 Proceedings of the 2003 ASME Summer Heat Transfer Conference by :
Download or read book Proceedings of the 2003 ASME Summer Heat Transfer Conference written by and published by . This book was released on 2003 with total page 858 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of a General Purpose Subgrid Wall Boiling Model from Improved Physical Understanding for Use in Computational Fluid Dynamics by : Lindsey Anne Gilman
Download or read book Development of a General Purpose Subgrid Wall Boiling Model from Improved Physical Understanding for Use in Computational Fluid Dynamics written by Lindsey Anne Gilman and published by . This book was released on 2014 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced modeling capabilities were developed for application to subcooled flow boiling through this work. The target was to introduce, and demonstrate, all necessary mechanisms required to accurately predict the temperature and heat flux for subcooled flow boiling in CFD simulations. The model was developed using an experimentally based mechanistic approach, where the goal was to accurately capture all physical phenomena that affect heat transfer and occur at the heated surface to correctly predict surface temperatures. The proposed model adopts a similar approach to the classical heat partitioning method, but captures additional boiling physical phenomena. It introduces a new evaporation term, to truly capture the evaporation occurring on the surface while also tracking the bubble crowding effect on the boiling surface. This includes evaporation from the initial bubble inception and evaporation through the bubble microlayer. The convection term is modified to account for increased surface roughness caused by the presence of the bubbles on the heated surface. The quenching term accounts for bringing the bubble dry spot back to the wall superheat prior to bubble inception. In addition to the changes to these three classic components, a sliding conduction term is added to capture the increased heat transfer due to bubble sliding on the heated surface prior to lift-off. The sliding conduction component includes all heat removal associated with transient conduction caused by disruption of the thermal boundary layer. The new method extends the generality and applicability of boiling models in CFD through a fully mechanistic representation. The new model also tracks the dry surface area during boiling for possible application in DNB predictions. A statistical tracking method for bubble location on the heated surface provides information on the bubble merging probability and prevents the active nucleation site density from reaching un-physical values. The model was implemented in the CFD software STAR-CCM+, and the wall temperature predictions were recorded and compared against the standard model's predictions and experimental data for a range of mass fluxes, heat fluxes, inlet subcoolings, and pressures. In general, the new model predicts wall temperatures closer to experimental data for both low and high pressures when compared against the standard model. The new model also converges at higher heat fluxes and greater subcoolings than the standard model.
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 Journal of Heat Transfer written by and published by . This book was released on 2005 with total page 220 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 Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 850 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Flow Boiling in Microgap Channels by : Tamanna Alam
Download or read book Flow Boiling in Microgap Channels written by Tamanna Alam and published by Springer Science & Business Media. This book was released on 2013-08-26 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow Boiling in Microgap Channels: Experiment, Visualization and Analysis presents an up-to-date summary of the details of the confined to unconfined flow boiling transition criteria, flow boiling heat transfer and pressure drop characteristics, instability characteristics, two phase flow pattern and flow regime map and the parametric study of microgap dimension. Advantages of flow boiling in microgaps over microchannels are also highlighted. The objective of this Brief is to obtain a better fundamental understanding of the flow boiling processes, compare the performance between microgap and conventional microchannel heat sinks, and evaluate the microgap heat sink for instabilities and hotspot mitigation.
Book Synopsis Hydrodynamic Aspects of Boiling Heat Transfer by : N. Zuber
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:
