When I say "precise method" I mean the inclusion of the specific
data to be obtained, where it is obtained, and the formulas applied.
You wrote: "Indeed, continuous experiments easiest way is to use
enthalpy sensors, that gives as total enthalpy for any given moment.
Even more simple is to measure the steam pressure inside E-Cat,
because it gives directly the total enthalpy, but of course we need
to first calibrate this kind of enthalpy sensors."
There is no such thing as an actual enthalpy sensor. Only specific
enthalpy is sensed. Only incremental enthalpies (delta H) of a
system can be measured. To obtain energy of a mass of steam, relative
to that mass at some temperature, you need to know the mass of the
steam. The mass of an army tank differs from the mass of a small
car. Measuring only pressure, or specific enthalpy, provides an
insufficient amount of information. To obtain thermal power you need
to know the mass flow. The water overflow is a significant part of
the flow by volume, more than 2% in some cases by volume. This
means the specific enthalpy of the steam is almost insignificant in
those cases.
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 which I posted
here last January:
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
I consider the big deal about the definition of "steam quality" to be
a red herring, a diversion from the important issues of measurement
of the thermal power carried by the mass flow of a water steam mixture.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
On Sep 27, 2011, at 9:16 PM, Jouni Valkonen wrote:
First I would add to my previous message, that I think that Peter's
method is more accurate than measuring pressure. That is because in
order to find out correlation between pressure and enthalpy we need
to do very careful calibration. In short run high accuracy may be
difficult to archieve, but if experiment lasts for example 10 years
continuously, then of course calibrating pressure sensor for
enthalpy calculations will give great pay off.
Horace wrote:
« You have again not specified the precise method you would use.
It would appear you have a case of missing variables. The principle
missing variable is mass flow, m dot, which is best to isolate and
measure directly. »
Actually I have defined but it is so simple that you have probably
missed it. First of course, we need to know that system is at
equilibrium, i.e. water massflow in and massflow out are both
matching. If water inflow rate varies a lot then calculations and
calibrations are difficult, if system is overflowing. That means
that for sure massflow must be known and it must be measured in
calibration.
But if system is a kettle boiler that does not overflow, then
calibration is very easy. In industrial water boilers this is the
most reasonable situation because this ensures high steam quality
because we can easily superheat steam to remove that 1-2% natural
wettness of steam. This reduces the corrosion. Superheating can
also be considered in calculations so this does not reduce the
accuracy of method.
Pressure can be measured either directly with pressure sensor
(easiest and most reliable and it is always available in pressure
boilers.) or in kettle boilers boiling water temperature can be
measured or last method is to measure steam temperature (this works
only if steam is not superheated and is thus wet. I.e. steam
quality must be measured, therefore this method is not universal).
—Jouni
On Sep 28, 2011 7:41 AM, "Horace Heffner" <hheff...@mtaonline.net>
wrote:
>
> On Sep 27, 2011, at 9:35 AM, Jouni Valkonen wrote:
>
>> 2011/9/27 Peter Gluck <peter.gl...@gmail.com>:
>>> The simplest solution is to use a Steam Water mixing valve,in
>>> which the
>>> heated mixture coming out from the demo is mixed with a constant
>>> flow of
>>> cold water, you can know the enthalpy performance in any moment.
>>
>> Indeed, continuous experiments easiest way is to use enthalpy
sensors,
>> that gives as total enthalpy for any given moment. Even more
simple is
>> to measure the steam pressure inside E-Cat, because it gives
directly
>> the total enthalpy, but of course we need to first calibrate
this kind
>> of enthalpy sensors.
>>
>> –Jouni
>>
>
>
>
> You have again not specified the precise method you would use.
>
> It would appear you have a case of missing variables. The principle
> missing variable is mass flow, m dot, which is best to isolate and
> measure directly.
>
> Best regards,
>
> Horace Heffner
> http://www.mtaonline.net/~hheffner/
>
>
>
>
