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About this book

​​This book advances a new view of phenomena associated with the spray of liquids from a nozzle in a gas. New results of experimental studies and numerical simulation of the hydrodynamics of an emerging two-phase flow and accompanying interphase heat and mass transfer therein are presented. The book is ideal for specialists who develop and use technologies involving the spraying of liquids in a gas, such as burning and pyrolysis of liquid hydrocarbons, granulation and drying of polymers, and dust and gas scrubbing.

Table of Contents

Frontmatter

Chapter 1. Introduction: Analysis of the Problems of Modeling of Hydrodynamics and Interphase Heat and Mass Exchange in the Processes with Spraying of Liquid in a Gas

Abstract
Spraying of liquid in a gas, for example, using nozzles, is one of the three ways to increase the surface of phase contact and the intensity of interfacial heat and mass transfer processes. Spray processes are widely used in chemical technologies, energy, and transport. At the same time, theoretical methods for calculating such processes are not developed enough, which in turn does not allow reliably designing high-efficiency spray devices and is therefore a serious scientific problem.
Nikolay N. Simakov

Chapter 2. Experimental Study of a Free Two-Phase Flow Generated by Spraying of Water in Air Using a Mechanical Injector

Abstract
The basis of the method for calculating the processes of heat and/or mass transfer in a two-phase gas-droplet system consists of equations describing the hydrodynamics of such a system, taking into account the interfacial interaction. Knowledge and understanding of the mechanism of interaction of phases in a two-phase flow, which is created by spraying a liquid in a gas, is definitely not sufficient (as will be shown below). This is one of the main reasons for the abovementioned problem (see Chap. 1 ).
Nikolay N. Simakov

Chapter 3. Analyses of Experimental Results: Physical Picture of a Free Two-Phase Flow Generated by a Mechanical Nozzle

Abstract
An analysis of the experimental data for a two-phase spraying stream showed that it has a number of features. In particular, such a flow is strongly turbulent; the average velocities of phases differ markedly at all points of the flow; there is a noticeable rarefaction of gas in the root zone of the spray; the hydrodynamic drag coefficient of each drop is smaller than of a single spherical particle at the same value of the Reynolds number.
Nikolay N. Simakov

Chapter 4. Mathematical Modeling of Hydrodynamics of an Axisymmetric Two-Phase Flow Produced by a Nozzle

Abstract
Now, two approaches are known for simulating a two-phase flow of sprayed liquid in a gas by using an injector. These are a method of mutually penetrating continua and the method of turbulent jets. Taking into account the flow peculiarities revealed in the analysis of the experimental results, it turned out that none of the abovementioned approaches taken separately can be used to model the spray flow. But it is possible to use their combination.
Nikolay N. Simakov

Chapter 5. Testing Hypotheses About Reasons of Anomaly-Crisis of Particles Drag

Abstract
To determine the cause of the anomaly (crisis) of drag for droplets in the spray flow, some hypotheses were tested on the effect of the group movement of droplets and the circulation motion of the liquid in them, the influence of geometry, and the strong turbulence of a gas flow around a droplet.
Nikolay N. Simakov

Chapter 6. Calculation of Drag Coefficient of a Sphere and Heat Transfer from It to a Gaseous Flow

Abstract
The hypothesis about the influence of the early drag crisis of sphere on its heat exchange with gas was confirmed by mathematical modeling. First, the numerical simulation of the gas flow around the sphere in a cylindrical channel was carried out with the calculation of the drag coefficient of sphere and heat transfer from it to a gas. Second, the same was done for the case of flow around the sphere by a free gas stream, both laminar and strongly turbulent. In the latter case, it was found that the early crisis of drag for the sphere is accompanied by a crisis of its heat exchange with gas. In addition, the numerical simulation of the heat exchange of a drop of liquid with a gas stream was carried out without taking into account its evaporation.
Nikolay N. Simakov

Chapter 7. Numerical Simulation of Two-Phase Flow Produced by a Nozzle Taking into Account the Early Crisis of Drag for Droplets and Interphase Mass Transfer

Abstract
A numerical experiment on the simulation of the two-phase flow formed during spraying of a liquid in a gas by a nozzle has been described. The distinguishing feature of the mathematical model is that it employs the differential equations describing the nonstationary flow of a compressible fluid as the initial equations. To transit to their difference analog, the known Lax–Wendroff algorithm has been used. The same numerical model was used to calculate the interfacial mass transfer in spray flow. For this purpose the basis differential equations of the proposed model have been supplemented by the equation of impurity mass transfer from gas to droplets.
Nikolay N. Simakov

Backmatter

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