Author: Vignesh Gopal Publisher: ISBN: Category : Languages : en Pages : 80
Book Description
Adiabatic, multiple bubble formation or aperiodic bubbling in pure liquids is experimentally investigated. The process of bubble formation, coalescence, and pairing has been captured using a high-speed, high-resolution digital camera. The visual data were processed using image processing software to determine the bubble interval, bubble diameter, and coalescence distance from orifice tip, among other characteristics. The effects of orifice diameter (0.15 dsubo/sub/lsubc
Author: Deepak Saagar Kalaikadal Publisher: ISBN: Category : Languages : en Pages : 125
Book Description
The air-bubble dynamics phenomena in adiabatic liquid pools has been studied so as to present a better understanding of the parameters which that govern the process of ebullience, bubble growth and departure from a submerged capillary-tube orifice. The orifice diameter is found to directly dictate the bubble departure diameter, and the pinch-off is controlled by a characteristic neck-length. To study the role of orifice size on the growth and departure of adiabatic single bubbles, experiments were performed with different diameter capillary tubes submerged in of distilled de-ionized water as well as some other viscous liquids. A correlation has been developed based on the experimental data of this study along with those reported by several others in the literature. The predictions of this correlation agree very well with measured data for water as well as several other more viscous liquids. It is also found that the bubble departure diameter is the same as the orifice diameter when the latter equals twice the capillary length. The phenomenon of bubble necking and departure was explored experimentally and through a scaling analysis. Experiments were performed with five different liquids (water, ethanol, ethylene glycol, propylene glycol, and glycerol) to extract the departure neck-lengths for isolated gas bubbles at pinch-off from the capillary orifice. A scaling analysis of the experimental data indicated that the bubble neck-length at departure or pinch-off was predicted by a balance of buoyancy, viscous and surface tension forces. These were established to be represented by the Galilei and Morton numbers, and a power-law type predictive correlation has been shown to be in excellent agreement with the available data over a wide range of liquid properties. To characterize and model the growth and departure of single bubbles in different liquid pools, a theoretical model has been established. The motion of the gas-liquid interface has been modeled as a scaled force balance involving buoyancy, gas-momentum, pressure, surface tension, inertia and drag. With one-dimensional scaling of these forces, the model captures the incipience, growth, necking and departure of a bubble as it emerges from the orifice. Here necking and pinch-off is modeled based on the newly developed neck-length correlation. The results are compared with experimental data and are found to be in excellent agreement for a range of liquids, orifice sizes and flow rates. The predictions highlight the variations in bubble equivalent diameters at departure with orifice sizes, flow rates and fluid properties, and they further reiterate the well-established two-regime theory of bubble growth. The latter involves (a) the constant volume regime, where the bubble volume remains near constant and relatively independent of flow rate, and (b) the growing bubble regime, where the size of the bubble increases proportionately with the gas flow rate. Finally, the complex nature of ebullience in aqueous surfactant solutions has been studied using the reagents FS-50, SDS, and CTAB. The influence of the modulated liquid surface tension or more specifically, the role of the time dependent dynamic surface tension on the formation and departure of adiabatic bubbles has been investigated. Comparative studies have been undertaken to investigate the effect of time-dependent surface tension relaxation in surfactant solutions as opposed to ebullience in pure liquids with the same equilibrium surface tensions. Results highlight the effects of the surfactant's molecular weight on the adsorption-desorption kinetics, and the consequent influence on ebullience. It has been established that the bubbling characteristics in surfactant solutions are, in the first order, governed by the dynamic surface tension of the solute-solvent system.
Author: Publisher: ISBN: Category : Languages : en Pages : 108
Book Description
The growth dynamics of a single gas bubble from inception to departure, emanating from a submerged capillary tube orifice in quiescent liquid pools has been theoretically modeled. The mathematical model represents a fundamental balance of forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport, and the consequent motion of the evolving gas-liquid interface. Theoretical solutions describe the dynamic bubble behavior (incipience, growth, necking and departure) as it grows from the tip of a capillary tube orifice in an isothermal pure liquid pool. Also complete Navier Stokes equations are solved using VOF model to simulate the different stages in the evolution of the bubble. Variations in bubble shapes and sizes, equivalent diameter, and growth times with capillary orifice diameter and air flow rates are outlined. These results are also found to be in excellent agreement with the experimental data available in the literature. The parametric trends suggest a two-regime ebullient transport: (a) a constant volume regime where the bubble diameter is not affected by the flow rate, and (b) a growing bubble regime where bubble size increases with flow rate. The experimental data available in the literature for a wide range of liquids, flow rates and orifice sizes are analyzed to develop regime maps that characterize these two regimes. For a given liquid, the transition from the constant volume regime and the growing bubble regime is determined by the non-dimensional parameter, BoFr0.5 = 1, that defines the interaction between buoyancy, surface tension and inertial forces. Correlation for isolated adiabatic bubble departure diameters is also developed based on a non-linear regression analysis of experimental data. The correlation considers the effects of thermo physical properties of the gas and liquid phases, orifice diameters and gas flow rates, and describes the experimental data published in the literature with in " 10 percent.
Author: Publisher: Springer ISBN: 9783319266947 Category : Science Languages : en Pages : 0
Book Description
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.
Author: J.R.A. Pearson Publisher: Springer Science & Business Media ISBN: 9400966342 Category : Technology & Engineering Languages : en Pages : 351
Book Description
Large, fast, digital computers have been widely used in engineering practice and their use has had a large impact in many fields. Polymer processing is no exception, and there is already a substantial amount of literature describing ways in which processes can be analysed, designed or controlled using the potentialities of modern computers. The emphasis given varies with the application, and most authors tend to quote the results of their calculations rather than describing in any detail the way the calculations were undertaken or the difficulties experienced in carrying them out. We aim to give here as useful and connected an account as we can of a wide class of applications, for the benefit of scientists and engineers who find themselves working on polymer processing problems and feel the need to undertake such calculations. The major application we have in mind is the simulation of the dynamics ofthe various physical phenomena which arise in a polymer process treated as a complex engineering system. This requires that the system be reasonably well represented by a limited number of relatively simple subprocesses whose connections can be clearly identified, that the domi nant physical effects relevant to each subprocess can be well defined in a suitable mathematical form and that the sets of equations and boundary conditions developed to describe the whole system can be successfully discretised and solved numerically.
Author: Martin Sommerfeld Publisher: Springer Science & Business Media ISBN: 3642185401 Category : Science Languages : en Pages : 354
Book Description
The book summarises the outcom of a priority research programme: 'Analysis, Modelling and Computation of Multiphase Flows'. The results of 24 individual research projects are presented. The main objective of the research programme was to provide a better understanding of the physical basis for multiphase gas-liquid flows as they are found in numerous chemical and biochemical reactors. The research comprises steady and unsteady multiphase flows in three frequently found reactor configurations, namely bubble columns without interiors, airlift loop reactors, and aerated stirred vessels. For this purpose new and improved measurement techniques were developed. From the resulting knowledge and data, new and refined models for describing the underlying physical processes were developed, which were used for the establishment and improvement of analytic as well as numerical methods for predicting multiphase reactors. Thereby, the development, lay-out and scale-up of such processes should be possible on a more reliable basis.
Author: Joseph Katz Publisher: Cambridge University Press ISBN: 1139490087 Category : Technology & Engineering Languages : en Pages :
Book Description
The objective of this introductory text is to familiarise students with the basic elements of fluid mechanics so that they will be familiar with the jargon of the discipline and the expected results. At the same time, this book serves as a long-term reference text, contrary to the oversimplified approach occasionally used for such introductory courses. The second objective is to provide a comprehensive foundation for more advanced courses in fluid mechanics (within disciplines such as mechanical or aerospace engineering). In order to avoid confusing the students, the governing equations are introduced early, and the assumptions leading to the various models are clearly presented. This provides a logical hierarchy and explains the interconnectivity between the various models. Supporting examples demonstrate the principles and provide engineering analysis tools for many engineering calculations.
Author: Vignesh Gopal
Author: Deepak Saagar Kalaikadal
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Author: J.R.A. Pearson
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Author: Martin Sommerfeld
Author: Winslow Hobart Herschel
Author: Joseph Katz