Measurements droplet size

The flow artifacts detected in the droplet size measurements are similar to those reported by Goux et al. [79] and Mohoric and Stepisnik [80]. In their work natural convection effects led to an increase in the decay of signal attenuation curves, causing over-prediction in the self-diffusion coefficient of pure liquids. In order to avoid flow effects in droplet size distributions, flow compensating pulse sequences such as the double PGSTE should be used. It has been demonstrated recently that this sequence facilitates droplet size measurements in pipe flows [81]. 

Mathematical representation of droplet size distribution has been developed to describe entire droplet size distribution based on limited samples of droplet size measurements. This can overcome some drawbacks associated with the graphical representation and make the comparison and correlation of experimental results easier. A number of mathematical functions and empirical equations1423 427 for droplet size distributions have been proposed on the basis of... 

Derived from spray data for high-viscosity liquids (mixtures of glycerine and water) of 50flows through discharge slots and impacts both sides of a flat liquid sheet from a discharge slot inbetween the air slots) Droplet size measured by Malvern 2600HSD Spray Analyzer Effects of air slot thickness included... 

SMD = U— COrpsd Derived from water droplet size measurements No liquid properties included Applicable only to water Oyama Endou [472]... 

The studies on the performance of effervescent atomizer have been very limited as compared to those described above. However, the results of droplet size measurements made by Lefebvre et al.t87] for the effervescent atomizer provided insightful information about the effects of process parameters on droplet size. Their analysis of the experimental data suggested that the atomization quality by the effervescent atomizer is generally quite high. Better atomization may be achieved by generating small bubbles. Droplet size distribution may follow the Rosin-Rammler distribution pattern with the parameter q ranging from 1 to 2 for a gas to liquid ratio up to 0.2, and a liquid injection pressure from 34.5 to 345 kPa. The mean droplet size decreases with an increase in the gas to liquid ratio and/or liquid injection pressure. Any factor that tends to impair atomization quality, and increase the mean droplet size (for example, decreasing gas to liquid ratio and/or injection pressure) also leads to a more mono-disperse spray. 

Electrical methods involve the detection and analysis of electronic pulses generated by droplets in a measurement volume or on a wire. The electronic signals are then converted into digital data and calibrated to produce information on droplet size distribution. A detailed review of electrical methods for droplet size measurements has been made by Jones.[657]... 

Wiscombe and Welch, 1986). Cloud absorption is related to droplet size in a complex way (Stephens and Tsay, 1990) so that errors in droplet size measurements can alter the model-predicted absorption by a cloud. The treatment of absorption due to water vapor is another possibility. As discussed by Crisp (1997), the treatment of water vapor in models is simplified and may not properly reflect, for example, continuum absorptions between major bands in the near-IR. Model calculations suggest that the presence of a thin, saturated layer of water vapor above the clouds, for example, leads to increased absorption by 2-6% (Davies et al., 1984 Podgorny et al., 1998). However, the Crisp calculations indicate that this cannot account for all of the observed excess absorption. 

Figure 7.17 Influence of i-carrageenan on the state of flocculation of BSA-stabilized emulsions (20 vol% oil, 1.7 vt% protein. pH = 6, ionic strength = 0.005 M) stored at 25 °C for 40 hours. The average droplet size measured by static light scattering (Malvern Mastersizer), d32, is plotted against the polysaccharide concentration ch added to the freshly made emulsion. Reproduced from Dickinson and Pawlowsky (1997) with permission.

Droplet-Size Measurements in Reacting Flows by Laser Interferometry... 

In conclusion, droplet size measurements in the range 10 to 100 m can be performed, also in hostile environments, from the visibility of individual scattered signal. Advantages of this method are simultaneous measurement of particle size, concentration and velocity no calibration is necessary good spatial resolution up to less than 1 mm-3 the visibility is independent on particle trajectory. Limitations are individual scattered signal can be obtained only with moderate particle concentration it is difficult to automatically process scattered signals to extract the visibility value and to check validation conditions it seems very difficult to extend the technique to cover the entire spray distribution the lower limit in the small particle end of the distribution curve depends upon experimental sensitivities and V(d) curve flatness... 

On the basis of measurements of velocity, temperature, and gas concentration in spray flames and droplet size measurements in isothermal sprays, the following conclusions have been reached. 

A new method for droplet size measurement, using a bench-top pulsed-field-gradient NMR spectrometer operating in the time domain, has been reported (18). The continuous water phase is successfully suppressed by gradient pulses in order to measure the dispersed oil phase. Simulations show that for most common oil/water food emulsions the influence of droplet diffusion is negligible due to a rather large droplet size or a high viscosity of the continuous water phase. 

Smart J, Berg E, Nerbrink O, Zuban R, Blakey D, New M. TouchSpray technology Comparison of the droplet size measured with cascade impaction and laser diffraction. In Respiratory Dmg Delivery V Dalby RN, Byron PR, Farr SJ, eds. Interpharm Press Phoenix, AZ, 2002 525-532. 

Zhang, G. J., and Ishii, M., "Isokinetic Sampling Probe and Image Processing System for Droplet Size Measurement in Two-phase Flow", Int. J. of Heat and Mass Transfer, 38, 2019 (1995). 

Battan, L. J., and Reitan, C. H. (1957) Droplet size measurements in convective clouds, in Artificial Stimulation of Rain, Pergamon Press, New York, pp. 184—191. 

Figure 14 In vitro assessment of droplet size measurement in the European Standard. Simulated patient inhalation at 15 L/min draws air over (or through) the nebulizer where entrained ambient air mixes with nebulized aerosol. A sample of the air at 2 L/min is drawn into a Marple Series 290 cascade impactor, which sizes aerosol droplets in relation to aerodynamic diameter. Impacted aerosol solute (e.g., NaF or drug) can be subsequently desorbed and quantified from each impaction stage.

A low thermal capacity to warm the cooled nebulizer output air-aerosol mixture, which has been reported with other cascade im-pactors to further evaporate liquid aerosol and confound interpretation of droplet size measurements (32). 

Figure 16 Comparison of mean droplet size measured using acoustic spectroscopy, neutron scattering, and X-ray scattering.

Table 14.3 Droplet size distribution of the spray generated by the three different atomisers obtained from offline droplet size measurements by laser diffraction [31]...

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