At 10:38 PM 6/22/2011, Daniel Rocha wrote:
Do you expect water droplets above 100C? This is like expecting microscopic ice to not immediately melt above 0C.
Wrong question. Do we expect water droplets above the boiling point of water? No, not except transiently. Is Mr. Rocha assuming that the boiling point of water is 100 C?
If we can tell that the steam is above the boiling point, yes, water droplets, if they exist at all, would very rapidly evaporate, absorbing energy from the steam to do so. This will tend to maintain the steam at exactly the boiling point, only very slightly above because of rate considerations, it takes time for a droplet to heat....
The measurements apparently show that the steam is at the boiling point for the atmospheric pressure (part of the measurement must be the pressure inside the measurement space, as well as the temperature. From this, we cannot tell the percentage of water droplets.
Basically, the appearance is that any droplets in the steam are in equilibrium with the steam, which is precisely why the temperature seems to be nailed at boiling.
Ice is a similar situation. If you have a mixture of ice and water, the temperature of the water will be stabilized at the melting point (which also varies with pressure, I think, though I think that is not so much). Cool it, more ice will form. Heat it, ice will melt, maintaining the constant temperature until the whole thing is frozen or the whole thing melts.
We cannot, from the temperature, tell how much of the water is ice! For the same reason, we can't, from the temperature, tell how much of the steam is water, if we have a mixed phase condition. If the temperature of the ice goes above the melting point, we know that the ice is all gone, and if it goes below the melting point, we'd know that it all froze. In between the extremes, we can't tell.
In addition, there is another very serious problem. The steam could be very dry, but water could still be running out the hose underneath the steam. That the feed rate is fixed leads to a serious suspicion of this, for matching the feed rate to the evolution of steam is tricky, a fixed rate would probably be too much or too little.
The water running out, if there is steam being evolved, would be at the same temperature. It would take quite a while to fill the hose, so the hose could be displayed as this one was, provided that the hose was first emptied into the drain, which Rossi took care to do.
That's not an indictment of Rossi at all, because even if the steam is completely dry, water would accumulate in the hose from condensation and cooling over that very significant length.
Bottom line: the demonstration did not show what was apparently intended. People may have completely independent reasons for believing or disbelieving, hence, as people often do, they line up in "sides," attempting to support or reject what is, in this case, a bogus claim, that steam quality has been conclusively determined. It may have been determined, but not by the means that have been shown.
(Kullander and Essen report examining steam directly. That's interesting, confirming steam quality, but unfortunately does not appear to have ruled out water running out the hose without having evaporated.)
