Droplet generation processes

Many droplet size distributions in random droplet generation processes follow Gaussian, or normal distribution pattern. In the normal distribution, a number distribution function/(D) may be used to determine the number of droplets of diameter D ... 

To characterize a droplet size distribution, at least two parameters are typically necessary, i.e., a representative droplet diameter, (for example, mean droplet size) and a measure of droplet size range (for example, standard deviation or q). Many representative droplet diameters have been used in specifying distribution functions. The definitions of these diameters and the relevant relationships are summarized in Table 4.2. These relationships are derived on the basis of the Rosin-Rammler distribution function (Eq. 14), and the diameters are uniquely related to each other via the distribution parameter q in the Rosin-Rammler distribution function. Lefebvre 1 calculated the values of these diameters for q ranging from 1.2 to 4.0. The calculated results showed that Dpeak is always larger than SMD, and SMD is between 80% and 84% of Dpeak for many droplet generation processes for which 2left-hand side of Dpeak. The ratio MMD/SMD is... 

Essentially, the reason for the appearance of varied interfacial tension is the variable reagent concentration of the interface. When using a surfactant in the droplet generation process, the low adsorption rate of the surfactant is caused by its low mass transfer rate, even for small-molecule surfactants... 

WangXY, Riaud A, WangK, etal Pressure drop-based determination of dynamic interfacial tension of droplet generation process in T-junction microchannel, ARcrrJIuid Nanojluid 18 503-512, 2015c. 

The capability of the developed software covers the operation conditions of typical encapsulation processes, which from the application point of view defined the goal of our corresponding research. The developed software has been enriched with an additional module being responsible for the operational aspects of the droplet generation process by means of a flowrate modulation of the introduced dispersed phase(s). Thanks to the corresponding modulation mechanisms being also introduced into experimental setups in the form of periodic volumetric flowrate disturbances suggests an increased reproducibility of the numerical predictions with respect to experimental observations. 

Fig. 13.8 Sequence of a simulated droplet generation process compared to experimental observation Fd Fc = 2.5/123.1—top row and Fd Fc = 3.0/148.7—bottom row. Corresponding time differences between the images arc 1.15s (top row) and 0.80 s (bottom row)...

Fig. 13.9 Sequence of a simulated (top row) droplet generation process compared with experimental (bottom row) measurement. Colorscale of the computational results corresponds to the velocity magnitude. Timestep between the images is 0.29 s. Adapted from [4] with permission...

In this chapter, various processes and techniques for droplet generation are described in detail, along with their applications and associated materials systems. 

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... 

Droplet properties have an important impact on the transport phenomena in associated droplet processes. A thorough understanding of fundamental phenomena, principles and mechanisms in droplet processes is therefore needed in order to enhance efficiency of droplet generation, and to control droplet properties. In this chapter, the mechanisms governing droplet generation and deformation in various droplet processes are reviewed in detail. 

Atomization, or generally speaking droplet generation, is an extremely complex process that cannot yet be precisely predicted theoretically. The lack of general theoretical treatment of droplet processes has led to the development of numerous empirical correlations for droplet properties as a function of process parameters and material properties. In this chapter, empirical and analytical correlations for the prediction of droplet properties, such as droplet size distribution and droplet deformation characteristics will be summarized from experimental observations and theoretical analyses in available literature. 

Droplet generation is typically a random process. Droplet sizes are usually characterized by a wide spectrum. In many... 

In this chapter, basic theoretical calculations and numerical modeling of droplet generation and deformation processes of both normal liquids and melts will be discussed in detail. The review of modeling efforts will outline the current status and recent developments... 

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