On Thu, Jul 14, 2011 at 10:19 PM, Abd ul-Rahman Lomax <a...@lomaxdesign.com>wrote:
> > Semantics. Yes, steam can be much wetter than 20%, particularly after > condenstation, under marginal conditions it could approach 100%. This, > however, wouldn't be called "steam." It would be called "hot water." Yes, 100% liquid would be called hot water. But 99% liquid by mass is 94% gas by volume, and if the liquid is in the form of a fine mist, then that is called steam -- very wet steam. The conditions under which such wet steam can exist may not be met in the hose, but they certainly could be met in the chimney. My objection to what you wrote was because you seemed to suggest that wetter than 20% was not plausible without any basis for such a suggestion. Storms based a similar suggestion on the wetness of steam in a boiler, but that is a very different situation. > We are here talking about what amounts to a boiler, Ah, so you were basing it on the same reasoning Storms used, but no, we're not talking about what amounts to a boiler. A boiler produces steam that then flows through connected pipes. The amount of fluid that flows through the pipes is governed by the amount of steam that is produced. Some liquid is carried along with the steam because the turbulence involved in the boiling produces droplets or a mist. In the ecat, the amount of fluid that flows in the conduit is governed by the amount of water that is pumped in. So liquid water is forced into the pipes along with fast-flowing steam, regardless of how much steam is produced. In that case, depending on the ratio of steam to liquid and the size of the conduit, you could have very much wetter steam. In fact 1% steam quality is perfectly plausible in the chimney. and I was looking for a "low" value for steam quality, for steam at the port > of such a boiler. Obviously, with various devices or arrangements, one could > get much wetter steam. Right, with an ecat, for example. Especially since we don't know what is inside the chimney. A coil of small diameter pipe would produce very wet steam or mist, as would a nozzle of some sort. I agree that 2 mL/s of water (liquid) would be flowing through the hose, but >> I think your description of it is not apt. If 1% of the liquid (by mass) >> were vaporized, then 94% of the fluid would be gas (by volume), and what you >> would see would be dominated by this steam. >> > > 2 ml/s is the input flow rate. I.e., if the water is at 100 C., and there is > the "minimum boiling," which means there is an infinitesimal amount of > boiling -- or, we could say, none -- then the water flowing out would be 2 > ml/s. If you say "none" or infinitesimal, then I agree. But the chance that there is infinitesimal boiling at the boiling point is, well, infinitesimal. And if only 1 part in 1000 by mass is boiling, then you already have more gas than liquid by volume. And then the ordinary concept of liquid flowing would not apply. > The much less voluminous water would come out as a mixture of mist and >> larger sputtered droplets. It's hard to think of it as flowing out steamily, >> when steam occupies 94% of the volume. >> > > If there is overflow water, it would flow into the hose, over the threshold > of the hose outlet, steam would flow above this water. See, this is what I have trouble picturing. When you say overflow water, I picture the chimney filling up with water, and then running out of the hose. But then how is the steam getting through the chimney? Some people talk about it bubbling through, but remember, the steam occupies much more volume than the liquid. You used the same description in your reply to Rothwell when the flow rate is just above the level at which all the water is vaporized. In that case >99.9% of the volume is occupied by gas. That would be one enormous bubble rising in a tiny drop of water. Can you see why this doesn't make any sense? If the fluid is 90+% gas by volume, which is almost certainly going to happen if there is any boiling at all, I can't see the liquid filling the chimney; I see it as a very turbulent mixture of mostly gas and a little liquid (by volume) forced through the chimney as droplets or perhaps a film of water along the walls or something like that. I'm just speculating of course, and I think we agree on the crucial point, which is that a mixture of liquid and gas has to come out of the hose, one way or another, if the power is too low to vaporize all of it. Both would be at 100 C. The steam would transfer more heat to the hose, > however, and would cool. The water would build up in the hose, with > condensed steam adding to it. There would be some condensation, but we know that some steam survives to the end of the hose, and that means that a 100W or more worth of steam probably was produced in the ecat, meaning a few per cent of the water by mass, meaning in the ecat, the fluid is close to 99% gas by volume. That's likely to be wet steam. Yes. So Rossi has a perfectly good reason for emptying the hose, and this is > so even if there is no overflow water, because of condensed steam cooled by > passage through the hose. If the hose dissipates 150W or so, then the amount of condensation would represent only a few per cent of the total flow by mass, and could be easily entrained in the flowing steam. This would not be a significant concern. The water that collects, I suspect, is mainly from the the unboiled component settling out into a liquid component in the hose, where the steam velocity could be lower than in the ecat. This could represent a much larger fraction of the input flow. In fact, if we can believe Lewan, then about 1/2 of the input water came out as a liquid at the end of the hose in his demo. He concludes that that means that at least half of the water was vaporized (and conceivably all of it, depending on how much condenses), but I think it means that half of the water escapes as a mist. > The hose won't block, exactly, rather, water would flow instead of steam. > Exactly what happens would depend on the balance. There is an extremely narrow range of power where the "water would flow instead of steam", because if only 1 part in 1000 by mass survives as steam, then it already takes up more volume than the water, and it would be blocked by the water filling the hose, and then it would sputter out of the hose. So, the power would have to be accurate to within maybe 10 to 100 ppm for water to flow without sputtering, if any steam at all is visible before the water flows. > >> > Maybe. I was originally imagining better separation between the steam and > water. It could be frothy. It might not be very misty. > Water doesn't froth. If it's more than 90% gas by volume, a misty component seems pretty likely to me.
