Median droplet diameter

Median Diameter. The median droplet diameter is the diameter that divides the spray into two equal portions by number, length, surface area, or volume. Median diameters may be easily determined from cumulative distribution curves. 

An empirical relationship between median droplet diameter and atomizer conditions has been demonstrated [30]. The relationship is described in the following expression. 

Analytical and empirical correlations for droplet sizes generated by ultrasonic atomization are listed in Table 4.14 for an overview. In these correlations, Dm is the median droplet diameter, X is the wavelength of capillary waves, co0 is the operating frequency, a is the amplitude, UL0 is the liquid velocity at the nozzle exit in USWA, /Jmax is the maximum sound pressure, and Us is the speed of sound in gas. Most of the analytical correlations are derived on the basis of the capillary wave theory. Experimental observations revealed that the mean droplet size generated from thin liquid films on... 

Regarding the effects of process parameters on gas atomization of melts, modeling and experimental studies l63 l64 324l revealed that the mass median droplet diameter decreases with increasing atomization gas pressure and gas to metal mass flow rate ratio. The standard deviation decreases with increasing gas to metal mass flow rate ratio. As the melt superheat increases, both the mass median droplet diameter and the standard deviation decrease. 

Since 5 is measured in percent supersaturation, 5 = 1 corresponds to 1% supersaturation, and c is the CCN concentration activated at 1% supersaturation, k is an empirical parameter. Approximate values of c and k determined in different environments have been given in Table 17.4. The number of CCN that are activated to cloud droplets increases as the peak supersaturation in the air increases. Based on (24.44), the larger the value of c, the larger the ultimate droplet concentration. Since the liquid water contents of continental and marine clouds do not differ greatly, the average size of droplets in continental clouds should be less than that in marine clouds. Marine cumulus clouds have a median droplet concentration of about 45 cm-3 and a median droplet diameter of about 30 pm continental cumulus clouds have a median droplet concentration of about 230cm-3 and a median diameter in the vicinity of 10 pm (Hobbs 1993). 

A specialized case of when two liquid jets of the same substance impinge each other to atomize was investigated by Bayvel and Orzechowski [57]. The angle between the two jets and the diameter of the liquid jets play an important role in the degree of atomization. It is predicted that the mass median droplet diameter will be proportional to... 

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