On Sep 1, 2011, at 8:01 AM, Jouni Valkonen wrote:
Hallo!
I made simple steam sparging experiment by measuring the steam quality
and enthalpy of my Espresso machine's steam wand (for making
capuchino).
– 200ml cool water (11°C) was measured into tea cup.
– Steam was sparged into mug for 32 seconds and there was not
observed
splattering or escaping steam
– After sparging temperature was measured at 38°C, thus ΔT was 27K
– the total enthalpy was calculated 4160J×27×0.20 = 22.5 kJ and
power 0.70 kW.
– Water level rose approximate 15ml ± 5ml.
As my instruments were too crude, I could not calculate steam quality
in any reasonable accuracy. If it is assumed 100% quality steam, then
total enthalpy should be 22.7–45.4 kJ therefore steam quality was
something between 99.1% and 49.6%. Therefore I failed with steam
quality measurements.
However for calculating enthalpy, steam quality is irrelevant. And
also I did not observe any reasons why there should not be two or even
three significant digits, if measurements were done carefully. Horace
has said that there are numerous potential errors, but I did not
observe any of his objections:
Horace wrote: «I would note that steam sparging can have large errors
due to steam escaping, due to variability in measuring the temperature
decline curve, due to variations in the calorimetry constant with
temperature, and due to imperfect stirring techniques.»
There was not significant steam escaping. Temperature decline was
irrelevant, because experiment lasted only 32 seconds. And stirring is
irrelevant, because sub-boiling water needs to be stirred only before
final temperature is measured. Steam sparging is very accurate, fast
and simple to do method for calorimetry, therefore Horace's objections
are out of proportions.
–Jouni
PS. I also calibrated my thermometer and I noticed that it was very
poor. 0°C water was -6°C. I have also some doubts if the scale is
accurate, because 11°C was somewhat reasonable temperature for cold
tap water. However 38°C was too small value, because water was
somewhat hotter than hand, although it was not burning hot. Anyways, I
guess that this thermometer is good for measuring temperature at
Incineration plant.
This test shows your true colors. It indicates that you actually
expect the steam power to be on the order of 100 watts, not 10,000
watts or even 1,000 watts. If you put a wand issuing 10,000 watts
steam power into the bucket you will get a notion of what I mean.
Beyond that, this "bucket method" works only for a brief snapshot of
power. It does nothing to accomplish an overall energy balance for a
test. It also is not useful for providing traces for computerized
data acquisition. It *is* admittedly a far better check than what was
done in the public tests.
This specific test of course is of no use as a control test, because
the amount of steam energy introduced into the bucket is unknown,
unless you measured the watts input when it reached steady state. I
assume it can reach a steady state.
The problems I discussed were real problems I encountered and fixed
in a real calorimetry run. I know for a fact they are real problems
for extended time calorimetry.
A much better test would involve a much larger reservoir.
A somewhat amateurish, but still effective long term test of a Rossi
device might be condensing the steam in a condenser, and collecting
the condensed liquid output separately. Flow calorimetry can then be
done on the condenser cooling water. The condenser cooling water can
then be recycled through an ice barrel to reset its temperature. The
ice melt water flow can then be measured to proved confirming
calorimetry data by an independent method, which is useful for error
magnitude determination. There are then two thermal flows to measure
and add, the device water thermal flow and the condenser cooler water
thermal flow. This kind of test (less computerized data
acquisition) is fairly easily accomplished by amateurs. The main
problem might be getting a sufficient quantity of ice delivered and/
or stored, provided the Rossi device is actually outputting on the
order of 10,000 watts. If it is outputting on the order of the input
power, it should not take a very long run to determine this.
One thing nice about the above method is it can handle thermal
dynamics, and thus permits use of a calibration pulse during a test,
and can take meaningful data if a momentary heat excursion takes place.
I take it this kind of discussion is all academic now NASA is involved.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
