We are in a phase where we are developing and testing our methods before we test the next active Celani Wire. Per some excellent suggestions from our followers we are trying several new little experiments while we work towards some calorimetry also.
Stepping up and down
First, we are testing a new way of doing the calibration where we step the power up and then back down again. This is simple and easy to do and will help determine if the cell was at adequate equilibrium for the calibration test. It was suggested by Ed Storms. The results look like this:
When we plotted the upgoing curve vs the downgoing curve and found them to overlap pretty closely. To see the difference, we subtracted one set of points from the other, and got the following graph.
Here is the resulting data set in an xls format stored in google drive: https://docs.google.com/open?id=0ByUU8sU37DYsbVRLRnFyQ2JMODg
Better thermal connection to the glass:
Second, we are trying to enhance the validity of the temperature measurements. Towards this end, we took a small piece of aluminum (roughly 12mm X 36mm X 2.0mm), rolled it to match the glass, and carved a groove for the thermocouple tip to fit into.
Then we installed it on the glass with a little thermal grease under it and some some kapton tape over it. That should make some good thermal contact. Too bad we can't do that inside the glass, too.
Third, more temperatures sensors to explore more about the ambient
Then we also added more temperature sensors. Due to the limitations of the number of columns in the instrumentation software and the fact that we don't know if we'll keep these sensors, we put them in a different test. That test should be available in the data viewer today.
In Summary:
- T_A1 - Left side of air stream in vent hood
- T_A2 Middle of air stream in vent hood
- T_A3 - Right side of air stream in vent hood
- T_G1 - Exterior of glass on the left side (plumbing side)
- T_G2 - Exterior of glass in the middle
- T_G3 - Exterior of glass on the right side
- T_F1 - Middle of the flange on the plumbing side
- T_F2 - Middle of the flange on right side
Look for the range of variation in each part of the air stream. The sensors may have slight offsets. I guess we'll see.
Look for the variation of the temperatures on the glass and the range of noise on each one. Compare that to T_glassout which is now under a piece of aluminum with thermal grease between it and the glass.
Look for the slope of the temperatures on the flanges when the glass looks constant - expect different time constants
Results of Pressure Sweeps at a (mostly) Constant Power
The violet line was a sweep done with the new borosillicate cell with Macor ceramic wire supports. The orange line and light blue line below are with the insulation at the ends of the cell. The orange line is at 48 W and the light blue line is 47W. It showed a tiny amount of improvement in the slope, but definitely shows a trend for the temperature to rise as the pressure decreases. There are still some differences in the geometry between our cell and Celani's but I was expecting the insulation we put in to make more of a difference than it did. I don't really know why the T_glassout sensor seemed to read lower after the insulation was in place, though.
When we divide by the input power, we get a slightly smoother shape. It shows the two runs after the insulation was in place to behave very similarly, but shows the other run in violet to be of a significantly different baseline.
Next steps:
We have been advised to try to mount the cell in a vertical orientation in order to facilitate more consistent convection currents on the inside of the glass. We are going to try to figure out how to do that next.
Update #1:
From the Euro Team: As the team in Switzerland wait for the Celani wire in the EU cell to de-load, we see Nicolas working on a Mizuno type cell and Mathieu talking to Dr. Edmond Storms who is offering his assistance to the project.
Update #2:
With our Euro Cell, we are trying to unload hydrogen from Celani's wire as much as possible.
Unfortunately, we have broken the Nichrome wire 2 days ago.
So we cannot heat the wire indirectly, but rather by applying current into it while pumping the cell to vacuum.
As we do not want to put too much current in the wire, we wrapped a copper sheet around the cell to maximize the internal temperature.
Obviously, in these conditions we are far from the calibration baseline.
Therefor all excess heat data that you might have seen during the last 2 days are not correct.
Comments
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I think what's really needed is a way to completely thermally isolate the cell from external temperature influences.
I concur. I found some silver wire for K type thermocouplers that was only $13 on Amazon, so seems price isn't too bad. Also found this information on silver thermocouplers, isotech.co.uk/.../... where it could measure upwards of 970 C with an accuracy around 1 to 4 mK. I think that's rather acceptable for our purposes if they decide to go that route.
Though, if they stick with the copper wrap, then we should be good with none of those worries with our current ones.
At 11:49 Power Blue was set from 0 to 125MW
At 11:50 Resistance dropped from 18Ohms to -3200 ??
At 11:56 Pressure raised from 0 to 150 and t-mica jumps to over 500C.
I'm having a hard time trying to figure out what this is telling me. Did the mica really see over 500C for several minutes?
Great find! I had been digging everywhere, but only found a graph for copper metal that went as long as the 800 nm range. That graph did seem a little different, as it showed copper as having an absorption peak around 800 nm, but who knows.
Either way, you're absolutely right that there will be no other way for heat to escape, so it won't matter (IR, like most of the electromagnetic spectrum, cannot pass through metal). This is also why the copper wrap will help the cell to be warmer per input power, which is also something we very much want.
We definitely want that copper wrap around the cell, in my opinion; much for much cleaner, more consistent, and far simpler data.
I think that in the case of complete metal wrapping any metal is good (because heat "has no other way to escape", I can't find a good way to explain that now), that's not the case if we make a small probe which is touching a piece of metal.
I found a reflectance a curve for copper by the way (even if it is about "metal films" I think it's ok anyway)
www.tvu.com/PNextGenTFWeb.html.
I'm still looking for a reflectance chart for NiCr 90% 10% (the meaterial of which a thermocouple type K is made).
@Alan G
Low reflectance for the probe is perhaps desirable, but what we need is constant reflectance all along the IR range. That way we are sure that the power absorbed is independent from the wire temperature.
Silver seems a good choice.
See figure 3 at noao.edu/.../SDN0003-26.htm
Because it conducts heat far better than the glass, a larger piece of aluminum carefully fitted over T_GlassOut would reduce the possible error from turbulent convection inside the cell, and if black anodized it would also eliminate the unknown energy leak of IR radiation at the point of measurement.
123star wrote:
I noticed that aluminum absorbs shorter wavelengths better, I don't know if this effect is negligible or not. What is your opinion? Remember that the glass is a poor heat conductor after all. (to read the graph, remember that IR spectrum starts from 750 nm)
thanks for the clarification about this. At the first look, I did not found a deeper description in your files and the connection cables could be made of copper too. I pointed you to this, because I do not want that anyone could critizese your results
picking up this point. And I want this wonderful project to be a 100% success.
23 years of critizism and suppression is enough !
BR Dieter
Oh, do you have a graph like that for copper? I want to see if we can convince the MFMP team to keep that copper wrap around the cell!
That is an option - we are going to have to re-build this cell as the NiChrome wire is broken. That means we will have to re-calibrate and so this all becomes a possibility.
Hmm, interesting, thanks for that graph. It mildly absorbs the very highest range of short wavelength IR right before the visible color Red, which starts at 600 nm or so. That would then be sent as conduction to the coupler. The rest of the IR is reflected back into the cell.
At the temperatures we're dealing with, we should be emitting a spectral wavelength peak around 4 um, which is definitely well reflected, but also absorbed by the borosilicate. Fascinating to see what this will do. I would hypothesize that indeed, any IR that the glass doesn't absorb and then conduct, would be absorbed or reflected by the aluminum. What happens with the reflected IR that the glass doesn't absorb? It seems like that would be lost energy, so as the cell heated up, we'd lose some detection? Or would we still catch it fully? Such interesting questions!
Probably the piece aluminum and the thermal grease will improve the spread in the calibrations, even if mounted this way.
I noticed that aluminum absorbs shorter wavelenghts better, I don't know if this effect is negligible or not. What is your opinion? Remember that the glass is a poor heat conductor after all. (to read the graph, rememeber that IR spectrum starts from 750 nm)
shop.perkinelmer.com/NR/rdonlyres/DA3DA7CB-7171-45C7-966F-9C5AEE521AFC/2315/fig_18.gif
Is the cell wrapped completely or just partially? Please put a thermocouple on the outside surface of the copper and then make your calibration/exp erimental runs using that value!
This will more than probably flatten all the calibration curves together!
Oh... wait I see from the live data that you have removed the copper?!?
It should completely nullify the issue. Either the glass absorbs the power in the IR range and conducts it to the coupler, or the aluminum absorbs the power in the IR range and conducts it to the coupler. Just trading one absorber for another, but the energy from the IR is accounted for either way. And, now the coupler is sandwiched, so no issues of contact for conduction.
@Robert and all,
Maybe you should leave that copper around the cell and just rebaseline with it :D? Copper is a great thermal spreader for more uniformity, no worries about IR that way, and it should help the cell maintain higher temperatures at lower input power (which is why you're using it I see). I totally motion for keeping that copper, but it's up to you guys, as it's a lot of work doing baselines -again-.
Mizuno Type Experiement
and you might need to search for
Mathieu Valat
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