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Author: Vysoké učení technické v Brně. Energetický ústav
Publisher:
ISBN: 9788021446984
Category :
Languages : en
Pages : 35
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Book Description
Author: Vysoké učení technické v Brně. Energetický ústav
Publisher:
ISBN: 9788021446984
Category :
Languages : en
Pages : 35
Get Book Here
Book Description
Author: Mona Hassanzadeh Jobehdar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Effervescent atomization uses the internal gas-liquid mixture to produce spray. The behavior of two-phase flow inside the atomizer influences the spray characteristics and is dependent on the atomizer internal geometry and operating conditions. The present study is conducted in two parts; study of the bubble formation from a novel submerged nozzle in a liquid cross-flow and investigation of the internal and external two-phase flows in an effervescent atomizer. The present study investigated the performance of a novel nozzle developed by Gadallah and Siddiqui (2013) in the liquid cross-flow. The impact of the nozzle shape, its configurations and orientations was experimentally investigated. The results showed that the novel nozzle generates smaller bubbles at higher detachment frequency for all cases compared to the standard nozzle. It is found that the elastic rebound of the bubble from a side hole plays a key role in the early bubble detachment. For the effervescent atomizer study, the impact of atomizer's internal geometry on the internal flow and spray droplet characteristics were studied. The results demonstrated that a conical base aerator tube and shorter mixing zone length provide more uniform bubbles in smaller size. A new type of bubble breaker was designed and tested in an effervescent atomizer. The results show that both internal and external two-phase flows in the atomizer were strongly influenced by bubble breaker configurations (diameter and number of holes). It was found that the liquid shear stress is the dominant force causing the bubble elongation and its eventual breakup.
Author: Hamed Farshchi Tabrizi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Efstathios Michaelides
Publisher: CRC Press
ISBN: 1315354624
Category : Science
Languages : en
Pages : 1559
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Book Description
The Multiphase Flow Handbook, Second Edition is a thoroughly updated and reorganized revision of the late Clayton Crowe’s work, and provides a detailed look at the basic concepts and the wide range of applications in this important area of thermal/fluids engineering. Revised by the new editors, Efstathios E. (Stathis) Michaelides and John D. Schwarzkopf, the new Second Edition begins with two chapters covering fundamental concepts and methods that pertain to all the types and applications of multiphase flow. The remaining chapters cover the applications and engineering systems that are relevant to all the types of multiphase flow and heat transfer. The twenty-one chapters and several sections of the book include the basic science as well as the contemporary engineering and technological applications of multiphase flow in a comprehensive way that is easy to follow and be understood. The editors created a common set of nomenclature that is used throughout the book, allowing readers to easily compare fundamental theory with currently developing concepts and applications. With contributed chapters from sixty-two leading experts around the world, the Multiphase Flow Handbook, Second Edition is an essential reference for all researchers, academics and engineers working with complex thermal and fluid systems.
Author: Sana Shaghaghian
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Effervescent atomization in quiescent air and in a subsonic crossflow are experimentally studied. The spray angle of an effervescent atomizer with an elliptical orifice is measured by employing the shadowgraph technique. Spray images were captured from both the minor and major axis views. The gas-liquid mass flow rate ratio (GLR) is in the range of 0.55-2.55 %. It is found that an increase in the aeration level results in an increase in the spray angle from both minor and major axis views. The results indicate that the spray angle from the minor axis view is wider than that from the major axis view and the difference increases as GLR rises. Furthermore, the effervescent atomization in a gaseous crossflow is studied using circular and elliptical orifices with aspect ratios of 1, 3, and 0.3. Gas-liquid mass flow rate ratio varies between (0-7%) and liquid-air momentum flux ratio,q, is in the range of 2-23. The high-speed shadowgraph technique and image processing were utilized to visualize the spray trajectory and measure the spray penetration height. Moreover, an empirical correlation is developed as a function of GLR, q, aspect ratio and downstream location. Additionally, the laser diffraction technique is employed to analyze the spray droplet size distribution in a crossflow.
Author: Seyed Milad Mousavi
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
Atomization is a process where the bulk of liquid jet disintegrates into liquid sheets, ligaments and droplets. It has enormous applications in industries and processes such as combustion, heat transfer systems, transport, biological systems and particularly our interest, coating processes. The Effervescent nozzle is a type of twin-fluid atomizer and has shown a superior performance in handling and spraying different liquids without any clogging issues; which is particularly interesting in thermal spray. In spite of significant number of experimental works, a few numerical works have been carried out. That makes it crucial to conduct a comprehensive numerical study on Effervescent atomizer. The complex internal and external behaviors of Effervescent atomizer are governing the behavior of the flow. The latter is a turbulent and compressible multiphase flow. It is studied numerically by employing a three-dimensional compressible Eulerian method along with Volume of Fluid (VOF) surface-tracking method coupled with the Large Eddy Simulation (LES) turbulence model. The numerical study is conducted by using OpenFoam library, an open-source package introduced by Open-CFD. In this study, the effect of varying the gas to liquid ratio (GLR) and the suspension (i.e. effect of viscosity, density and surface tension), on the structure of internal flow and consequently, the external flow is studied numerically. It is observed that the increase in GLR is accompanied with an evolution of the internal flow from a complex bubbly flow to an annular flow. This reduces the liquid film thickness at the discharge orifice. Further studies on internal pressure illustrated the critical condition, choked flow and pressure oscillations at the discharge orifice. The examination of increasing the GLR and evolving of internal flow resulted in changing in primary atomization parameters such as shortening the breakup length and widening the spray cone angle. Furthermore, the existence of a slip velocity between the two phases in the external flow results in dominant aerodynamic forces at high GLRs. Moreover, alternation of the liquid properties illustrated the higher spray velocity and wider cone angle of the spray, which demonstrates the superior performance of the Effervescent atomizer.
Author: L.P. Bayvel
Publisher: Routledge
ISBN: 1351434950
Category : Science
Languages : en
Pages : 488
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Book Description
Covering the basics of liquid atomization, this book familiarizes readers with the physical processes of liquid atomization, the main types of atomizers and their design, measurements of spray characteristics, experimental investigations of atomizers, and application of atomizers. It demonstrates how to calculate and design atomizers and how to mea
Author: Miguel A. Balzán
Publisher:
ISBN:
Category : Atomizers
Languages : en
Pages : 314
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Book Description
An experimental investigation was conducted with the purpose of studying the effects of selected operating and design variables in the flow inside an effervescent atomizer. A series of tests were performed in a horizontally oriented, square conduit of 12.7 mm in diameter which constituted the mixing chamber of the effervescent atomizer. The operating fluids were water and air. The air was injected perpendicularly into a fully developed, turbulent water flow, whose bulk water velocity values ranged between 1.1 and 4.3 m/s. The gas mass flow rate values were in the range between 8 and 60 × 10-3 g/s. Three different gas injectors, with diameters of 0.27 mm, 0.52 mm and 1.59 mm were used. The combination of variables allowed the operation of the atomizer within the limits of what constitutes a bubbly flow in pipes. High-speed shadowgraphy was the technique used to investigate thoroughly the dynamics between the gas and liquid phases near the gas injection region as well as upstream the discharge nozzle. A set of original, empirical expressions used to estimate the incipient centerline and borderline trajectories of the gas phase, during its initial interaction with the liquid and based on dimensionless parameters, were introduced. The assessment of the correlations gave a strong prediction of the initial centerline and borderline trajectories of the gas jet in the flowing liquid. The effects that the gas injection velocity, liquid mean velocity and injection gas injection diameter have on the process of bubble generation were investigated. Four distinct regimes were identified: Single Bubbling (SB), Pulse (P), Elongated Jetting (EJ) and Atomizing Jetting (AJ). It was observed that the shift between regimes occurs gradually, producing the need to identify transitional regions: SBP and PTJ. Sets of independent dimensionless variables were used to categorize the proposed regimes in bubble formation maps. Empirical correlations that delimit the boundaries between ordered and chaotic bubble generation were determined. An introductory description of the forces involved in the bubbling process was conducted. The results indicated that the form-induced drag and added mass force were dominant detaching and cohesive force respectively. While there was agreement with previous works regarding the dominant breakup effect, the results obtained for the main attaching force were unique. Also, a novel methodology for the estimation of dynamic shape based drag and added mass coefficient was included. The morphological features of the gas jet were described through empirical correlations based on relevant dimensionless numbers associated to the variations of three fundamental design parameters: liquid cross-flow velocity, gas mass flow rate and the nozzle dimensions. The gas jet features were compared with representative statistical diameters from the population distribution, resulting in an estimation of the averaged Sauter mean diameter and maximum bubble diameter as a function of the gas jet dimensions. It was determined that the gas injection conditions play a fundamental role in the internal flow characteristics for an effervescent atomizer.
Author: Amr Abdelaziz Mostafa Saleh
Publisher:
ISBN:
Category :
Languages : en
Pages : 141
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Book Description
Atomization of liquids (pure liquids and suspensions) plays an important role in numerous industrial fields and applications. One of the main important applications is in thermal spraying processes which is the primary motivation for this study. The main trend in thermal spray processes is to coat with sub-micron and nano sized particles due to the superior performance of fine microstructured coatings. Recently, thermal spraying processes are using the suspension spraying technique. The breakup of a suspension in the atomization process differs from that of a pure liquid by the influence of the suspended particles on the fragmentation kinetics. In suspension spraying process, different types of atomizers are used but clogging problems can occur due to the suspension properties. Effervescent atomizers have shown to be a good alternative to the conventional atomizers to solve clogging issue when liquids with large variety of viscosity and density such as suspensions are atomized.In this study, effervescent atomization of suspensions in a crossflow of air is investigated experimentally. The tests have been performed at different liquid-to-gas momentum flux ratios (q) and different gas to liquid ratios (GLR). Hydrophilic and hydrophobic particles are used in the experiments. Shadowgraphy and image processing have been used in order to capture the penetration height of the spray. New correlations have been developed to predict the spray penetration height of suspensions in case the non-aerated liquid jet (GLR= 0) and for the aerated liquid jet (GLR ≠ 0).Moreover, suspensions properties such as viscosity and surface tension have a crucial effect on the atomization process. Because the atomization process and droplet formation occur in a very short timescale of the order of milliseconds, it is necessary to analyze the rapid change of the affecting suspension properties related to this timescale especially surface tension. Therefore, the time changing (dynamic) surface tension is more appropriate to be analyzed than static surface tension. In this work, the dynamic surface tension of suspensions is investigated using a combined analytical and experimental approach based on the physics governing the oscillation of elliptical jets. The dynamic surface tension of suspensions liquids in the timescale of milliseconds is calculated. The effect of the dynamic surface tension of suspension on its atomization process has been analyzed.
Author: Nasser Ashgriz
Publisher: Springer Science & Business Media
ISBN: 1441972641
Category : Technology & Engineering
Languages : en
Pages : 922
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Book Description
Atomization and sprays are used in a wide range of industries: mechanical, chemical, aerospace, and civil engineering; material science and metallurgy; food; pharmaceutical, forestry, environmental protection; medicine; agriculture; meteorology and others. Some specific applications are spray combustion in furnaces, gas turbines and rockets, spray drying and cooling, air conditioning, powdered metallurgy, spray painting and coating, inhalation therapy, and many others. The Handbook of Atomization and Sprays will bring together the fundamental and applied material from all fields into one comprehensive source. Subject areas included in the reference are droplets, theoretical models and numerical simulations, phase Doppler particle analysis, applications, devices and more.
