On Sat, Jun 25, 2011 at 5:36 PM, Mark Iverson <[email protected]> wrote: > > First, here is my conclusion based on the methodology and resoning below: > > "If certain conditions are present, one can reduce this to a mass-in, mass > out problem, and you > don't need to measure the volume of steam exiting in order to estimate > dryness" > > I don't think anyone here was suggesting that the instrument used by > Galantini could measure steam > quality directly. What I am attempting to do is ascertain if there is a way > to make an indirect > measurement with what variables we DO have, and I think I may have the answer. > > Let's discuss whether this method will work, and under what conditions... > > 1) we know the flow-rate of water going in; can't remember but say its > 10g/sec. > 2) assume the entire mass of water IS vaporized; > 3) we can easily calculate the volume of steam that would be generated each > second; > 4) *IF* the pressure inside the chimney is ambient, then the entire volume of > steam is exiting the > chimney each second, else pressure would build up inside; > 5) assume that overall the process is relatively stable, with constant flow > of steam out the chimney > and only minor fluctuations in temp and pressure inside; > 6) Given the above, the mass on the instrument's display of mass of water in > the steam MUST equal > the mass of water going in. > > If the instrument is reading 10g/m^3, then ALL the inlet water is being > converted to vapor, and the
This is wrong. I wrote in a another thread that the Relative Humidity detector is pegged at 100% for any saturated steam with a quality between 0 and 100%. The capacitance reading will not change as the steam quality changes, it is not sensitive to steam quality. So you can't measure 10 g/m^3 as vapor because the relative humidity meter only tells you that there is saturated vapor in contact with it. Are you trained in science in anyway? The Relative Humidity meter will never give you steam quality. Jed in particular needs understand this because people seem to listen to him. > steam is dry. Volume is irrelevent *IF* the pressure inside the chimney is > ambient. This also > assumes the instrument's humidity sensor isn't getting bombarded by liquid > water, as we have > discussed recently in our postings about how the polymer/capacitive sensor > works. > > The only critical elements here are #4 and #5. > I propose that it is REASONABLE to accept these assumptions because of these > FACTS: > 1) There is only one place for the water vapor to go... Out the chimney! > 2) The pressure inside the chimney is the same as ambient as measured by the > instrument in question. > > If pressure was higher in the chimney then this would not be a valid > methodology. > > As I said very early on, there is a specific reason why both Rossi and > Galantini always specified > the temperature AND pressure when being asked about how they measured the > steam quality. I've > explained why the pressure is important, and I assume that the temperature is > important for the > reasons stated by Finlay McNab, > > "If the temperature of the vapor is above 100C and the pressure is 1 atm, > then an examination of the > phase diagram of water suggests that no liquid water can be entrained in the > vapor." How sure are we that the temperature is above 100 C? Rossi made a crude measurement with a thermocouple, there is very likely to be calibration error. The steam exhaust could be anywhere between 99 and 101 C (assuming he has a halfway decent temperature measuring instrument). Also, is Rossi measuring the steam or does he have it too close to the source of heat? Or is the thermocouple too close to the edge of the pipe so that the room is cooling it? We don't know. This is rough measurement for a public demonstration, not a properly done experiment to be peer reviewed and published. There is no proof that they did a proper temp probe calibration and put it at the right location. So it is easily possible that there is a water vapor / water micro droplet mixture (i.e. wet steam) with most of the mass in the form of micro droplets (i.e. liquid) and a small fraction in the form of vapor. We can't use a crude temperature measurement to determine that it is all vapor - because that measurement was crude with no proof of calibration. > > CONCLUSION: > If certain conditions are present, one can reduce this to a mass-in, mass out > problem, and you don't > need to know the volume of steam exiting in order to estimate dryness... > > -Mark > > >
