On Jan 22, 2011, at 5:24 PM, Jeff Driscoll wrote:
Rossi used this electronic device for electronic measurement (as
was reported) - model HD37AB1347. Relative Humidity probe model
HP474AC was attached to it.
Page three of this link (thanks to Horace) shows details of that
probe connected to the electronic device. HP474AC has the
following specifications:
http://tinyurl.com/45rwsvh
HP474AC Relative Humiditiy Probe specifications:
5% to 98% RH >>> -40C to 150 C
+/- 2.5% (5%...95%RH)
+/-3.5%(95%...99%RH)
Temp +/-0.3C
This probe does not measure the amount of liquid water droplets in
the "steam" (ie. mass fraction of water vapor to to total water).
It measures Relative Humidity (Relative Humidity measures how
saturated the air is for a given temperature).
What we want is a a device that measures "quality" of the steam.
For reference, 100% quality = 100% vapor.
How did they confirm that the water vapor was truly vapor?
Yes, good question.
I believe the HP474AC probe actually measures the capacitance of the
air, and converts that to relative humidity. The more the
capacitance, the more water in the air, by volume. Another
important thing is heat content is carried in proportion to mass,
not volume. I have appended the computations I posted earlier
showing the huge proportion of mass that is contributed by a small
volume of liquid, and that estimates of the heat flow from the device
can be off by 96%, i.e only 4% of the estimated heat value due to
vaporization, if only 1.4% of the volume flow is liquid water
droplets. Therefore a very small error, less than 1%, in measuring
capacitance can produced huge errors in calculated heat flow. The
stated error of the probe is +-3.5% where it counts, at 99% water
content.
It is also notable the meter/probe requires calibration:
http://tinyurl.com/4z5985v
Most important is the fact the probe is designed to detect the
percent of water vapor in air, not percent of water microdrops in
pure steam. Pure vapor should have more capacitance than 100% humid
air, and be way beyond the meter's measuring limits. Adding water
droplet should push the capacitance even higher. Once the meter is
maxed, the question arises: can extra water droplets make any
difference to an already maxed out 100% reading? The +-3.5% error
could thus actually be irrelevant.
This whole issue may be of academic interest only. Even if all the
heat flow due to vaporization is negated, the COP is still over
unity, assuming the water is not heated much above 13 °C by ambient
conditions before entering the device. Further, if the device can
run without energy input at all, then none of this matters, provided
the total energy to start up the device is way less than the device
produces. This would clearly be the case if the device can run 6
months as stated.
Here again is my analysis showing the importance of the huge
difference in mass vs volume ratios:
From:
http://en.wikipedia.org/wiki/Water_(properties)
http://en.wikipedia.org/wiki/Specific_heat_capacity
http://en.wikipedia.org/wiki/H2o
http://hypertextbook.com/facts/2007/DmitriyGekhman.shtml
The following approximate values for water can be used from the above
refs:
Liquid Density: 1000 kg/m^3 = 1 gm/cm^3
Heat of vaporization: 40.6 kJ/mol = 2260 J/gm
Heat capacity: 4.2 J/(gm K)
Molar mass: 18 gm/mol
Density of steam at 100 C and 760 torr: 0.6 kg/m^3 = 0.0006 gm/cm^3
Now to examine the importance of mass flow vs volume flow
measurements for the steam.
If x is the liquid portion by volume, then x/((x+(1-x)*0.0006)) is
the portion by mass. This gives the following table:
Liquid Liquid Gas
Portion Portion Portion
by Volume by Mass by Mass
--------- ------- -----------
0.000 0.0000 100.00
0.001 0.6252 0.3747
0.002 0.7695 0.2304
0.003 0.8337 0.1662
0.004 0.8700 0.1299
0.005 0.8933 0.1066
0.006 0.9095 0.0904
0.007 0.9215 0.0784
0.008 0.9307 0.0692
0.009 0.9380 0.0619
0.010 0.9439 0.0560
0.011 0.9488 0.0511
0.012 0.9529 0.0470
0.013 0.9564 0.0435
0.014 0.9594 0.0405
We can thus see from this table that if 1 percent by volume of the
steam is entrained water micro-droplets, easily not seen in tubing or
exhaust ports, that only 5.6 percent of the heat of vaporization is
required to produce that mixture.
Rough calculations based on Rossi specifics:
Suppose for the Rossi experiment the mass flow of a system is 292 ml/
min, or 4.9 gm/s, the inlet temperature 13 °C.
The delta T for water heating is 100 °C - 13 °C = 87 °C = 87 K.
If the output gas is 100% gas, we have the heat flow P_liq given by:
P_liq = (4.9 gm/s)*(87 K)*(4.2 J/(gm K))= 1790 J/s = 1.79 kW
and the heat flow H_gas for vaporization given by:
P_gas = (4.9 gm/s)*(2260 J/gm) = 11.1 kW
for a total thermal power P_total of:
P_total = 1.79 kW + 11.1 kW = 12.9 kW
Now, if the steam is 99% gas, we have:
P_liq = 1.79 kW
P_gas = (0.1066)* (11.1 kW) = 1.18 Kw
P_total = 1.79 kW + 1.18 kW = 2.97 kW
or 23% of the originally estimated power out.
It thus seems reasonable to do calorimetry on the steam-liquid out.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
