I think it is great you are pursuing this Alan.
I think the temperature of the thick brass part may play a similar or
even larger role than the steel nut.
I noted on page 4 of my review:
http://www.mtaonline.net/~hheffner/Rossi6Oct2011Review.pdf
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This photo by Mats Lewan of NyTeknik of the 6 Oct Rossi Tout
thermocouple that it can and probably did extend beyond the steel
nut, toward the brass manifold:
http://www.mtaonline.net/~hheffner/LewanTcoupleClose.jpg
It was thus subject to the air temperature in the volume underneath
the insulation and between the brass manifold and steel nut. It is
especially notable that the frayed insulation, cut from around the
probe tip, was not trimmed. This is very unusual. The frayed
electrical insulation may have prevented good thermal contact of the
thermocouple with the steel nut, and thus exposed the thermocouple
primarily to the air temperature in the vicinity, which would be
expected to be higher than that of the steel nut.
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On Oct 27, 2011, at 1:05 PM, Alan J Fletcher wrote:
At 06:51 AM 10/27/2011, Higgins Bob-CBH003 wrote:
I examined pictures of the manifold and created a diagram to
capture the
important features. [I made a small .png version of the diagram
that I
am trying to include.] I am not sure it is schematically correct
yet.
A characteristic that I believe is very important in the analysis
of the
possible temperature contamination is the issue of the fittings
used in
the manifold. These use pipe threads, and appear to be NPT
because of
the use of pipe dope. At each junction of pipe threads, there
will be a
large thermal resistance compared to continuous brass. Analysis of
these across-the-thread resistances are going to be hard,
particularly
with pipe dope and or Teflon tape present as is required to seal NPT.
The resistance across the thread boundaries will be high and the net
effect will be to significantly decouple the Tout thermocouple
from the
manifold.
These thread boundary effects don't appear to be included in your
model.
Thanks for the diagram.
So far I've just widened my original model to 12 cm ... and get
results which are closer to the measured value.
http://lenr.qumbu.com/rossi_ecat_oct11_spice.php
Update information is copied below :
http://lenr.qumbu.com/lenr_spicepics/111027_spice_0001.png
The bottom pane shows the new schematic. A is the extreme right,
and B and C are the centers of the two steps. The thermocouple is
on step C.
The center pane shows the temperature across the manifold. A is now
at 33.4 C (compared to the secondary water temperature of 30 C).
The top pane shows the OFFSET in temperature from A.
This new result shows that the result varies dramatically with the
geometry -- and since the actual measurements are not known, the
results are speculative.
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I can easily add in a "thread boundary" as resistors between the
steps.
But I don't think I can draw any REAL conclusions from this
model ... except to say that the thermocouple should not be
ANYWHERE on the manifold!
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
