Maximum drop diameter

Kj= thermal conductivity of gas film surrounding the droplet, Btu/(h ft )(°F ft), evaluated at the average between diyer gas and drop temperature V = volume of diyer chamber, rP At = temperature driving force (under terminal conditions described above), °F D, = maximum drop diameter, ft to, = weight rate of liquid flow, Ib/h p, = density of hquid, Ib/ft ... 

A high velocity of the flow, Wg, an elevated density of the fluid as well as a low viscosity of the liquid phase and a low interfacial tension between liquid and fluid represent favourable conditions for high pressure spraying. Pressurised gases evidently possess characteristics similar to those of liquids with respect to the atomisation so that the relationships which are valid for liquid/liquid spraying may lead to realistic results. In the case presented here, a modified Nukiyama-Tanasawa distribution [5] has been used to specify the maximum drop diameter in the spraying process ... 

The two graphs for each medium represent the bounds of drop sizes in the range of applied extraction conditions. A maximum drop diameter in the distribution is considered (equation 5). 

Figure 4.7. Schematic representation of the interfacial tension measurements by the pendant drop method d is the maximum drop diameter, and d is the diameter located at the distance d from the drop apex.

The mathematical implementation of the dynamic boundaiy conditions at the free surface is quite involved and an exact analytical solution to these equations is impossible even for the creeping flow in this simplified case due to the free surface. However, typical simplifications and assumptions can be applied and a simple useful approximate solution to predict the maximum drop diameter can be developed. As this is an applied research paper we will continue to move... 

Figure 2 Constant property maximum drop diameter...

Figure 11 shows a comparison of numerical experimental results for maximum drop diameter. The deviation in the predictions from the measured values ranges from 20% at the lower temperature down to 7% at the high temperatures. 

As one might expect, and as seen with water, the maximum drop diameter increases rather linearly with increasing capillary lube diameter. During these simulations the drop was considered to be pinned to a location at the outside edge of the tube exit as was observed after wet out during the experiments. The dynamic contact line was not simulated in these results. 

Figure 14, shows the effect of increasing initial temperature just upstream of the outlet of the capillary tube. The maximum drop diameter inereases with increasing temperature. The higher temperature reduces the viscosity in the initial drop and allows the surface tension to... 

Pressure fiuctuations can deform the drops and they may break if the inertial forces exceed the interfacial tension forces. Kolmogoroff [27] and Hinze [31] derived an expression for the maximum drop diameter, dmax, that should be observed when turbulence is isotropic. Here, d / and the viscous forces may be neglected in comparison with the inertial forces dmax, can then be related to a critical Weber number, Wecnt, by Eq. (3). 

McManamey, W. J. (1979). Sauter mean and maximum drop diameters of liquid-liquid dispersions in turbulent agitated vessels at low dispersed phase hold-up, Chem. Eng. ScL, 34, 432-434. 

Fig. 23.19 (Top) Comparison of experimental data for mean diameter of secondary emulsion drops X5o,3/x5o,3,imaai as a function of We xnof for different emulsion systems (symbols) and model approximation function (23.12) (solid line), (bottom) similar comparison for maximum drop diameter xgo.s/Xgo.s.initiaf both diagrams fit parameters n = —0.169 and m = 0.08...

Mean and maximum drop diameters in inertial and viscous regimes. 

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