On Oct 13, 2011, at 4:11 PM, Higgins Bob-CBH003 wrote:
I think the "resistor network" and finite element approaches discussed
below are a great track for understanding the possible magnitude of
the
Tout error. The big uncertainty is the pipe thread. It may take
experiments to estimate the thermal resistance across the pipe
thread -
particularly if it is NPT instead of NPTF because NPT will require
Teflon tape to seal which would provide greater thermal isolation
of the
outlet pipe.
Can anyone discern the thread type or whether Teflon tape has been
used?
Bob Higgins
Hi Bob,
The use of teflon tape may be important, but there may be issues with
larger effects involved. There may have been electrician's tape
between the thermocouple and the steel nut. Note the tape still
present after the thermocouple is removed:
http://lenr.qumbu.com/111010_pics/111010_2_crop.jpg
I do not know to whom the credit goes for the photos referenced here.
Possibly Mats Lewan.
It appeared in one video that Rossi pulled on that wire quickly and
firmly when unwrapping the heat exchanger. Sorry I don't know which
video right now, but it might be the one in Italian. It was very
fast and at the end of a clip, so difficult to determine exactly what
happened. In a later photo it appeared the wire was bent, not taught,
between the end tape and the tape on the nut. See:
http://lenr.qumbu.com/111010_pics/111010_2_crop.jpg
It also appeared the wire segment after the end tape was long enough
to locate at least part of the Tout thermocouple out in the air
between the nut and the brass manifold edge. See:
http://www.redmatica.com/media/Thermo2.jpg
It appears to me there is enough room for the sensor to extend out
over the top of the big steel nut. You might have to blow up the
section next to the red arrow to see the sensor tip.
It is unfortunate there are not photos of the Tout location prior to
wrapping with insulation.
If the tip extended out into the air pocket under the insulation,
then it was exposed to the temperature on the edge of the big brass
manifold, or possibly even touched it.
All this uncertainty obviously could have been avoided if the
thermocouple had been located a few cm down the hose away from the
heat exchanger, preferably in a protective well exposed to the water.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
