ATOMIZATION OF NORMAL LIQUIDS

Atomization of normal liquids has been long studied in the fields of spray combustion and spray drying. The most widespread application of the atomization of normal liquids is in spray 

This section describes the atomization processes and techniques for droplet generation of normal liquids. A comparison of the features of various atomization techniques is summarized in Table 

Emphasis is placed on the atomization processes used in spray combustion and spray drying from which many atomization processes have evolved. Advantages and limitations of the atomization systems are discussed along with typical ranges of operation conditions, design characteristics, and actual and potential applications. The physical properties of some normal liquids are listed in Table 

where Tis the temperature,p is the density, p is the viscosity, a is the surface tension, andEv is the vapor pressure. Depending upon the priority levels of application requirements, many factors need to be considered for the selection of an appropriate technique. These include, for example, (a) the cost-effectiveness, (b) the ease of operation and maintenance, and (c) the capability of producing a monodisperse spray, covering the required range of droplet sizes, accommodating various liquid properties, and achieving sufficient production rates. 

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Figure 1.6. Size ranges of droplets/particles found in nature and generated by atomization of normal liquids and melts in aerosol spray, spray combustion, powder production, and spray forming processes.

Atomization of melts has, in principle, some similarity to the atomization of normal liquids. The atomization processes originally developed for normal liquids, such as swirl jet atomization, two-fluid atomization, centrifugal atomization, effervescent atomization, ultrasonic piezoelectric vibratory atomization, and Hartmann-whistle acoustic atomization, have been deployed, modified, and/or further developed for the atomization of melts. However, water atomization used for melts is not a viable technique for normal liquids. Nevertheless, useful information and insights derived from the atomization of normal liquids, such as the fundamental knowledge of design and performance of atomizers, can be applied to the atomization of melts. 

Atomization of normal liquids has a wide range of applications, as discussed previously. In many applications, the fundamental phenomena and principles during atomization are common or similar. According to the geometry feature of bulk liquids, droplet formation may be loosely classified into the following primary idealized modes ... 

This approximate relationship is similar to those for centrifugal atomization of normal liquids in both Direct Droplet and Ligament regimes. However, it is uncertain how accurately the model for K developed for normal liquid atomization could be applied to the estimation of droplet sizes of liquid metals Tombergl486 derived a semi-empirical correlation for rotating disk atomization or REP of liquid metals with the proportionality between the mean droplet size, rotational speed, and electrode or disk diameter similar to the above equation. Tornberg also presented the values of the constants in the correlation for some given operation conditions and material properties. 

In many atomization processes of normal liquids, droplet size distributions fairly follow root-normal distribution pattern 264 ... 

In Chapter III, surface free energy and surface stress were treated as equivalent, and both were discussed in terms of the energy to form unit additional surface. It is now desirable to consider an independent, more mechanical definition of surface stress. If a surface is cut by a plane normal to it, then, in order that the atoms on either side of the cut remain in equilibrium, it will be necessary to apply some external force to them. The total such force per unit length is the surface stress, and half the sum of the two surface stresses along mutually perpendicular cuts is equal to the surface tension. (Similarly, one-third of the sum of the three principal stresses in the body of a liquid is equal to its hydrostatic pressure.) In the case of a liquid or isotropic solid the two surface stresses are equal, but for a nonisotropic solid or crystal, this will not be true. In such a case the partial surface stresses or stretching tensions may be denoted as Ti and T2-... 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

The problems involved in quantitative analysis using NMR spectroscopy, have been discussed by several authors and it is evident that it still causes a lot of problems as especially pointed out by Hays55 in his excellent review on the subject. Thus in liquid state NMR spectroscopy the quantitative estimation of atoms and groups involves the use of normal analytical method. In the case of solid state NMR spectroscopy, however, the application of the cross-polarization technique results in signal enhancements and allows repetition rates faster than those allowed by the carbon C-13 Tl. Therefore, the distortion of relative spectral intensities must always be considered a possibility, and hence quantitative spectra will not always be obtained. 

Table 2.1. Comparison of Features of Various Atomization Techniques for Normal Liquids 1 5 ...

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