On Mon, Jul 18, 2011 at 8:03 PM, Mark Iverson <[email protected]> wrote:
> Abd wrote: > "Whatever is the cause, that the temperature is nailed shows that there is > steam and water in > equilibrium." > > It's only been recently that Rossi admits to achieving completely dry > steam, The claim is implicit in the power calculation from the very first demo. > and from Kullander's > report we can estimate that the steam has less than 2% liquid content (1.4% > from his report). How > you ask??? If the Relative Humidity is below saturation, the one can use > that and the temperature > and pressure to give you the mass of water vapor per volume of steam. But Rossi doesn't measure the volume of the steam, so you still don't know the mass of the steam. And if you assume that all the water is converted to steam to get the steam volume, then you're arguing in a circle. Again. I know this is beating that > dead horse again, but the absolute certainty with which some argue the > opposite point is, in my > opinion, not justified. If the steam is nearing saturation (>95% RH) then > I might agree that its > use is seriously questionable. I don't remember seeing any figures for the > RH when the Testo probe > was used inside the chimney... If it was over 95% then I would concede the > skeptic's point. > Steam at the boiling point is 100% saturated by definition. What else could you have other than water vapor? So you should concede. I found a paper on measuring steam quality. It's a tricky (and important) business, but the classical method is to use calorimetry. That is, determine the heat content and deduce the liquid content. Rossi is using the liquid content to get the heat content. But how does he get it. If a testo probe was effective, why would others bother with calorimetry. Newer methods use optical and microwave techniques. There is no mention of capacitive methods. Nor does the literature on the probe itself claim to be able to determine steam quality. The paper is Mitra et al. "...Steam Quality Measurement ...", IEEE Sensors Journal 11 (2011) 1214. Here's a snippet from the intro: "Various methods for determining the steam quality (wetness fraction) and the enthalpy of the partially condensed steam at the last stages of a turbine have been under development for over many years. Several types of calorimetry probes based on extraction and analysis of wet steam from the main flow exist [6]. In order to carry out an accurate measurement process and analysis, the sampling procedure should be iso-kinematical. Iso-kinematical sampling in the running turbines is extremely difficult due to unsteady flow in the last stages, and the local thermodynamic and aerodynamic parameters are also disturbed. Also, the probe must be well heat insulated to achieve accurate results. Every measurement takes several hours as full thermal equilibrium of the whole probe body should be established from one operating condition to another. This results in the probe missing the transient data of the turbine during a startup and shutdown condition. Thus, a calorimetry probe is mostly used to make measurements well beyond the last stage of a turbine. [...] "Recently, some work has been done on the development of optical methods, primarily based on light scattering techniques and microwave resonant cavities [7]–[9]. The optical techniques mentioned in the above-mentioned references provide informa- tion of the size of the water droplets, render fast measurements, and enable measurement between the different stages in a tur- bine. They also do not disturb the local thermodynamic pa- rameters. However, the estimation of steam quality with these technique depends on the droplet size classification. Individual monochromatic light sources of different wavelengths are used in the measurement. Hence, the measurement accuracy for the steam quality is highly dependent on the water droplet size dis- tribution which can be reliably measured only with appropriate wavelengths being used to probe the steam." One wonders why they would go to all that trouble if a testo probe could be used. In the paper they show how their technique can measure steam quality to within a few per cent between 5% and 80%. 5% corresponds to 5 % steam by mass, and yes, that means 95% liquid by mass. So not only is very wet steam with 95% liquid by mass possible, but there are ways to measure it accurately. Not with an RH probe, though.
