Alice Givan wrote- >In my comment on calculating the volume of a droplet, I "guessed" that >the diameter of >the drop might be approximately the diameter of the nozzle orifice. I >knew this was a >rough approximation --- as the stream can contract a bit as it leaves the >orifice and >then the droplet that forms can have a diameter greater than the diameter >of the stream. >Joe Trotter (whom I always trust) says that the droplet diameter is >approximately 1.89 >times the nozzle diameter. In fact, I just went and measured the drop and >the stream >on my monitor screen and I got about 1.6 (using a bad ruler and a roughed >up piece >of paper). So my approximation that the drop diameter was equal to the >nozzle orifice >diameter was, obviously, grossly wrong either way. I wouldn't have gone that route. > Perhaps the best way to calculate >the volume of a drop is by Dirk Van Bockstaele's method (calculating the >volume >of the "column" of liquid coming out of the nozzle in one second and then >dividing >that volume into however many drops are being generated in one >second). However, in >order to do this from first principles you need to know the diameter of >the stream and >also the velocity of the stream.....possible, but awkward. Velocity for a stream-in-air nozzle, in m/sec, should be 3.7 * (sheath pressure(in psi))^(1/2). This is from Pinkel and Stovel, also on p. 139 of the 3rd Ed. of PFC. Page 140 has the "column" volume calculation. > I suppose you could also >do it simply by measuring the volume flowing from the stream in 10 minutes >and then >calculating the volume for one second (I might be missing something here >-- Howard, >where are you (I know, he is working on the fourth edition just when I >need him). I'm still here, obviously. And you can probably limit the calculation of stream volume to 1 minute; you'll divide by 60 to get the volume per second, and you'll get enough volume out in a minute (or two) to get an accurate enough calculation. And there's time (but not much) to clear this up in the 4th Edition. Do you have a reference to Dirk van Bockstaele's calculation? -Howard
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