Water droplet size, factors affecting

Another important factor is the size of the overhead product liquid accumulator. Ten minutes liquid residence time based on net product rate is common however, aromatic gasoline fractions may require 5 to 8 min settling time for clarification because water vapor tends to condense in small droplets. The required accumulator size is also affected by the type of process equipment downstream. 

In addition, a quantitative mathematical model was introduced to examine the evaporative cooling effect of micron-sized water droplets under low-pressure conditifHis [23]. From the experiment, the temperature of the gas-droplet mixture decreased significantly depending on the pressure appUed. The cooling rate of the aerosol was found to be about 2 x 10 K/s at 20 Torr. The simulation results suggested that a constant low-pressure, the droplet size, and the flow rates of the carrier gas and solutimi were the major factors that affected droplet cooling. 

Although the stability of emulsions containing micron-size droplets has been studied using a variety of emulsions in the past no unified and quantitative approach based on the physico-chemical properties of the system has been achieved. Obviously, this lack of understanding can be attributed to the complexity of the systems which invariably contain several species. A substantial contribution to the factors affecting emulsion stability has been made by Boyd et al. (9) using Spans or Tweens with Nujol and water. Some aspects of energy barriers associated with emulsion stability have been considered by several authors. The details can be found in the reference, Davies and Rideal (10). We will consider the electrical barrier-effects encountered with the oil-water and water-oil emulsion systems in a later section. 

Since all the emulsions presented very similar DSD, with a mean diameter centered at about 8 pm the water droplet size was not considered as an important factor affecting the stability behaviors of the emulsions stabilized by different silica nanoparticles. 

The dispersed oil droplet size distribution may vary from point to point in a produced water system, and from one system to another. The size distribution is affected by interfacial tension, turbulence, temperature, system shearing (pumping, pressure drop across pipe fitting, etc.), and other factors. The droplet size distributions should be measured in the field when troubleshooting and/or upgrading systems, whenever possible. 

The reverse microemulsion method can be used to manipulate the size of silica nanoparticles [25]. It was found that the concentration of alkoxide (TEOS) slightly affects the size of silica nanoparticles. The majority of excess TEOS remained unhydrolyzed, and did not participate in the polycondensation. The amount of basic catalyst, ammonia, is an important factor for controlling the size of nanoparticles. When the concentration of ammonium hydroxide increased from 0.5 (wt%) to 2.0%, the size of silica nanoparticles decreased from 82 to 50 nm. Most importantly, in a reverse microemulsion, the formation of silica nanoparticles is limited by the size of micelles. The sizes of micelles are related to the water to surfactant molar ratio. Therefore, this ratio plays an important role for manipulation of the size of nanoparticles. In a Triton X-100/n-hexanol/cyclohexane/water microemulsion, the sizes of obtained silica nanoparticles increased from 69 to 178 nm, as the water to Triton X-100 molar ratio decreased from 15 to 5. The cosurfactant, n-hexanol, slightly influences the curvature of the radius of the water droplets in the micelles, and the molar ratio of the cosurfactant to surfactant faintly affects the size of nanoparticles as well. 

Drop size measurements were made on water sensitive papers exposed inside cooling towers at various levels. Results are given for samples taken under eliminators, over eliminators and high in towers. Design and operational factors which affect the values are discussed. Droplet removal efficiencies are given for conventional louvre eliminators and for louvre eliminators modified with plastic meshes. 

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