From: 72240.1256@compuserve.com (Jed Rothwell)
Newsgroups: sci.physics.fusion
Subject: From Gene Mallove
Date: 21 Jul 92 19:55:55 GMT
Reply-To: Jed Rothwell <72240.1256@compuserve.com>
Organization: Sci.physics.fusion/Mail Gateway

To: >INTERNET:fusion@zorch.SF-Bay.ORG

Gene Mallove's Response to Tom Droege's posting:

	I think Tom has jumped to many unwarranted conclusions in his
analysis of Takahashi's initial results.  Jed has addressed many of these
incorrect conclusions in his response, with which I fully concur. But I have
a few comments of my own.

	Takahashi has clearly seen anomalies that we have not yet seen --
healthy indications of *temperature elevation* in his cell as a function of
time (sweep). This has nothing to do with postulated convection variations in
calibration. Both his high and low end cell temperatures rise. As long as we
can trust his thermocouple and his ambient temperature drift correction,
he's got excess heat. This is the main point of his work.  I agree that it is
better to also have a coolant loop inlet-outlet delta-T measurement, and that
is what we and he have recently been doing, with the assistance of Tom's
wonderful thermoelectric delta-T gadget. Takahashi apparently is getting
excess heat with such measurements; we have not yet seen it
unambiguously.

	I agree that at Takahashi's high current input there is something like
0.07 C delta-T (electrolyte-to-coolant) per input watt to the cell. And I
agree that his number would be extremely difficult and unreliable to model
because of the complexity of convective heat transfer. The problem in
Tom's analysis, however, is the comparison of this 0.07 with another
number, 0.61 C/watt, which was obtained by Tom in an entirely different
way. Tom seems to think that 0.61 C/watt contradicts 0.07 C/watt.  It
doesn't, because 0.07 is right and 0.61 is wrong.

	As I understand Tom's analysis, he takes the *initial* slope of the
temperature decline from Hi to Lo and measures it. I will assume that he
has measured it correctly and that it is 34 C/hour or 0.0094 C/second.  He
then uses this number multiplied by the thermal capacity of the cell (575cc)
*(1 cal/C cc) * (4.1 joules/cal) to to get an *initial* heat outflow of 22.1
watts. That may be a fine estimate of the initial heat outflow. But then
Tom's analysis breaks down when this initial slope-derived number (22.1)
is divided into the total temperature difference drop from 33.5 to 20 C.
That results in the 0.61 C per watt. But this makes no sense because the
slope of the power curve is changing throughout the 45 minutes to an hour
to reach the lo-phase equilibrium.

	Basically, one can't use a complex time history of temperature decay,
which may be strongly dependent on the convective heat transfer history,
to infer anything about the initial high-phase cell resistance. Dividing
(33.5-20 by 22.1) gives a meaningless number. So there is no basis, in my
view, for comparing 0.61 with 0.07.

	On the basis of this, in my view, bogus comparison, Tom suggests
that stirring must be changing drastically as the current is shut down. He
winds up concluding that Takahashi has not calibrated properly because of
this supposed changed stirring.  Let me point out that that Takahashi did
not calibrate with a pure resistance heater. He used a dead cathode and
calibrated with electrolysis fully under way, so his cell was always stirred
That's what he emphasized in his MIT talk. So it seems to me that on that
misunderstanding alone Tom's entire argument collapses. I do not believe
Tom's assertion that the conduction resistance of the calorimeter increases
that much when the power drops.

	A final point:  both the Bow, NH, experiment and Takahashi's new
one have time history data for heat outflow as the cell switches from Hi to
Lo. There is no need to do computations based on curve slopes,  we have
the raw measurements in hand.

- Gene Mallove