On Wed, Dec 7, 2011 at 3:04 PM, Jed Rothwell <[email protected]> wrote:
> I wrote: > > >> Try placing at thermocouple on a hot pipe, in various spots, under >> various covers. You will find the differences are insignificant. >> > > I did this years ago, working at Hydrodynamics. I happen to have a nice > dual input thermocouple, with a T1 - T2 mode, so I will try it again with a > copper hot water pipe, with and without insulation and so on. I will do > this under the kitchen sink. Varying water temperatures do not matter > because I am looking for a difference between T1 and T1 (when they are > mounted differently), and the response is quick. > > I have insulated all of the hot water pipes in my house foam pipe > insulation. Look it up at Lowe's. It works remarkably well. Anyway, I'll > try it with and without that, in air, under bubble wrap and a few other > ways. > > I have different kinds of probes too. I use a shielded probe for cooking > turkey. I'll just use the regular ones for this test. > > I can compare the actual fluid temp to the pipe temp if you like. I'll bet > it is the same to within 0.3 deg C. > > You people should do stuff like this, instead of blabbing for weeks at a > time about magic pots full of water that do not cool down. > While you're at it, why don't you test using a counter-current heat exchanger in which the hot end of the primary circuit and secondary are within an inch or two of each other? Now move your test junction towards the hot end of the primary. That's where Rossi may have deliberately placed it. Put the thermocouple in contact with the copper block of the heat exchanger near the hot end of the primary. Let us know what temperature you find there. Then, compare that to the temperature of a thermocouple in the center of the flowing stream maybe a foot or so downstream of the hot end of the heat exchanger. I hope this is clear. If not, I may have to draw a **shudder** diagram. I think bad thermocouple placement on a heat exchanger can result in a large error in the measurement of T-out. But hey, do the test and prove it one way or another. If the output pipe was not embedded in a copper block and if the measurement had been downstream considerably distant from the end of the heat exchanger, it might be more credible even though it was not made inside the pipe. You can get a decent approximation of interior temperature from measuring under the insulation on an insulated pipe but only under some conditions. Why are we guessing anyway? Rossi could have heated up the system with his electrical heater, monitored the power and measured the output energy and then we'd know for sure, wouldn't we?
