At 12:02 AM 6/22/2011, Jeff Driscoll wrote:
http://www.testosites.de/export/sites/default/datalogger2011/en_INT/local_downloads/brochure_EN.pdf yes, this device, and its probes, measure the relative humidity of *air* !!!!. It does not measure steam quality!!!!. What is Galantini doing?
I don't know. A visible steam cloud will have an RH of 100%, as will live steam. Wet steam will have a water content of g/m^3 greater than that of dry steam at the same temperature and pressure. However, the question is whether or not the meters in question will measure this, I suspect that when they indicate g/m^3, they are assuming dry steam, or they may read erratically if it's wet steam. I see no specification or guidance on this from the manufacturer literature, and no indication that this device measures the water burden of air when the water is as liquid instead of vapor.
In wet steam, the probe, being initially cooler, would heat up from condensation of steam onto it, so it would become wet, covered with liquid water. If the steam is wet, it will not evaporate this water, thus skewing the readings toward higher water, depending on how the humidity measurement is made. It might be possible, from this, to infer that steam is dry.
That, however, would seem to be an "off-label" usage of the meter, and would require much more information from the expert user than a simple result.
In confirming his results to Krivit, Galantini did not state his results, beyond temperature and pressure. He didn't state the actual pressure, it was stated as "ambient," which is not quite enough for an accurate understanding (of the meaning of the temperature measurement). The meter does have a mode which indicates g/m^3, but that is grams of water vapor per cubic meter of gas. I think. The meter is not specified for accuracy at 100% RH.
I'm not seeing any clarification of this appearing, except for confirmation that there are grounds to think the meter can't be used for the kind of measurement asserted, which concern has been widespread and goes back, I think, to January. One would think that in all this time, and all this discussion, if this meter could be used for measuring steam quality in a direct way, it would have come out. Have I missed something?
And if it is used indirectly, how? What's the procedure?
