On Sat, Nov 19, 2011 at 3:34 PM, Peter Heckert <[email protected]>wrote:
> > If we assume steam was 50% wet, which is physically impossible, then we > still get a COP of about 3. > 50% wet is rain and not fog or steam. > > In 2-phase flow, steam (or vapor) quality is simply the ratio of the mass of steam to the total mass of the fluid, and that can range continuously from 0 to 100%, and experimental plots include data points for 1 % steam quality, so there is no question 50% steam quality is physically possible. When you consider that the volume of steam is about 1700 times that of water for the same mass at atmospheric pressure, 50% quality steam is more than 99.8% gas by volume, so it would not have to look like rain at all. The mist coming out of an ultrasonic mister would be a very low quality vapor. Note that the actual void ratio in 2-phase flow -- the geometrical ratio of steam volume to liquid in the conduit at any instant --also depends on the slip ratio, the ratio of the speed of the gas to that of the liquid. There are well characterized modes of 2-phase flow that depend on the speed and the quality. Low quality steam in the output conduit of the megacat would probably fall in the annular/mist regime, where some liquid flows along the walls of the conduit, and a mist flows in the center. But if a fine mist is formed earlier by some mechanism, it could be largely mist flowing in the pipe. And it could easily be only a few per cent steam by mass.
