At 09:44 AM 6/21/2011, Jed Rothwell wrote:
Abd ul-Rahman Lomax wrote:
Jed, these devices measure a number of things
directly, and others are calculated. I see no
sign that the device is designed to measure
steam quality. It's not a described application.
Yes, it is. The Delta Ohm meter with an HP474AC
probe, the meter is intended to go up to 150°C.
That's steam temperature. The meter is intended to measure enthalpy.
Look, I don't know the reality here, I could be
way out in left field. But I see you making many
assumptions, Jed, such as "temperature" meaning
that this thing will function under all
conditions as long as the temperature is below
150 C. Temperature of what? If the device is
intented to measure relative humidity in air, it
will do so in *air* up to 150 C.
Why would they make a meter that goes up to
steam temperatures, which specifically says it
measures calories per gram, but it does not do that? What would be the point?
The meter has all kinds of uses.
Look, Abd, you need to get real. I honestly have
no idea how these meters work.
That's right. I can tell you this: the brochure
is quite specific as to what is measured, and it
ain't enthalpy. Enthalpy is calculated from what
*is* measured, with some assumptions.
Electronic instruments are often black boxes
that work by black magic. But these meters are
made by several different companies and it is
reasonable to assume they work as advertised. They measure enthalpy.
The enthalpy of what? Hot molten salt?
(seriously, not that, the temperature is too
high. But obviously the meter needs to know what substance is being measured!)
Otherwise, some agency would go after the
companies for false advertising. If the gadget
did not work with steam, what possible use
would it be? Who would buy it? You would not
use one of these single-probe instruments to
measure the enthalpy of hot water. You use these nifty things:
http://www.dynasonics.com/products/tfx-ultra.php
You are right you would not use it to measure the
enthalpy of hot water. Bingo! Wet steam is,
partly, hot water! It is not a uniform material,
it will separate out into hot water and water
vapor. I don't think the probe is measuring the hot water at all.
If Rossi would incorporate the Testo 650 with
the printer option, and have it print enthalpy
every minute, he would have a bang-up,
irrefutable demonstration. He could measure the
reservoir before and after, power input, and
then show that the printed record of enthalpy
does not vary much, so the flow rate and power
level is reasonably stable. That would prove his
point. Just multiply the average enthalpy by the
total mass of water consumed and Bob's your uncle.
That would be nice touch, but the video demo was
impressive enough. Rossi is a more impressive in
person, in the video, then he is in his blog.
Sorry, you just convinced me that you aren't
seeing this objectively. The Krivit video has
seriously damaged my impression of Rossi, it was
his explanation of hot steam. He's explaining
away, incorrectly, an obvious problem, the weak
steam plume from the hose. You and I know a
possible explanation, but, assuming he knows it,
he didn't want to say it, perhaps because it
would reveal that the demonstration was weak. Or
whatever. I don't claim to understand Rossi, I
only know that he *might* have a number of
different possible motives to be deceptive. Legally deceptive.
I've seen nothing in print that allows me to
believe that these RH meters can be used to
measure steam quality. They do not claim it as an
application. Your sputtering that nobody would
buy them if they didn't work to measure steam quality is very strange.
If they were being sold to measure steam quality,
don't you think they would mention it?
These are *relative humidity meters.* From the
MAC humidity/moisture handbook,
http://www.macinstruments.com/pdf/handbook.pdf,
relative humidity is a measure of the amount of
water vapor that is mixed with other gases. That
is, it is a gas-phase measurment.
A thought experiment. You have a box, in it is
steam, unknown quality. That is, this steam may
contain suspended water droplets. You have a port
in the side of the box and you insert your
instrument probe. Your instrument is supposedly
designed to tell you the "steam quality." Notice
something: water droplets are not exactly mixed
with the steam, they can and will condensed
together and fall to the bottom of the box.
Obviously, your probe can only measure what it
contacts. Your "steam quality meter" results will
depend on how well the steam and water droplets
are mixed, the droplet size, etc. (If the
droplets are large, they will obviously fall to
the bottom of the box. If your probe happens to
lie within the condensed water, it will tell you
that the steam is 100% liquid water! If above it,
it will not tell you the total water content of
the box. How could it? Only with an assumption
that the water droplets are thorough mixed and
dispersed so that the probe physics detects the
phase difference between the water and the steam.
This isn't a relative humidity meter, which is
only measuring the gas phase. Remember that HP
manual? It specified that it only worked up to a
certain humidity level, and it assumed, for the
accuracy provided, the absence of condensed
water. Condensed water isn't gas, obviously.
Relative humidity measures the gas phase only.
You don't want your probe tip to be wet because
it will then tell you that you have pure water. No steam at all!
This could all be quite moot, except for the fact
that RH meters were used to indicate -- by
unknown measurements and an unstated process -- steam quality.
Krivit has asked Kullander about the steam
measurements, but, in typical Krivit style, he's
looking for a contradiction, and he gets one. As
far as I can tell, Kullander is scratching his
head wondering why Krivit is asking this
question. Volume or mass? Geez, Louise, an RH
meter doesn't measure either one, it determines,
from certain assumptions, the mass of water per
unit volume. Volume of gas, by the way. So? This
mass/volume question is only an issue because of
that silly discussion with Krivit and Levi.
Krivit has his contradiction, he can now play
football with it, and ends the interview. Instead
of actually clarifying the issue by deeper questioning.
I'll separately look at that interview.
