Before we break into the data, we'd like to establish a bit of nomenclature for clarification. This experiment is being carried out in V 1.3 cells, however it is using V 2.0 protocol. This may be an important distinction in the future, so we'd like to be clear now. Remember that in V 1.0 the first two versions of replication cells were in H2 atmosphere whereas the key distinction in protocol V 2.0 is the ~1 mBar dynamic vacuum.
We've power-cycled both active (A) and control (B) cell NiCr wire with independent power supplies using the same control script. Also remember that neither of these cells have Celani wire installed yet. Luckily the power steps only rise to a 25W max in 5W steps with 1hr time constant, so we can finish a complete cycle in ~5 hours and it doesn't take too long to really narrow our confidence interval.
That being said, running 6 calibration cycles has cut the confidence margin roughly in half as we doubled from 3 cycles. The environment is relatively static but not perfect, so we're unsure of how much this margin will improve with more cycles. We mentioned in an earlier post that the direct flow of air from inlet window to vacuum hood easily tainted our validity, but this offset has been fixed with a polycarbonate spoiler on the inlet window to disperse the current. It wasn't really exciting enough to warrant a photograph.
Below is the table of calibration data. The values in bold represent the power margins that we must exceed to suggest anomalous energy in our active cell. Cell A's calibration results are displayed above Cell B's at 95% confidence to the left and 99% to the right. It's also important to note that T_Ext Rise values are the difference of the external glass temperature above the ambient. This is all just a refresher (plus we're trying to make blogs a little more lay-person friendly).
Cell A | Cell A | |||||||||||
Input Power (W) | T1_Ext1 Rise (°C) | 95% CI (°C) | 95% CI as Percent | Degrees/Watt | 95% CI (W) | Input Power (W) | T1_Ext1 Rise (°C) | 99% CI (°C) | 99% CI as Percent | Degrees/Watt | 99% CI (W) | |
0.00 | -0.14 | 0.14 | -100.80 | -74.14 | 0.00 | 0.00 | -0.14 | 0.23 | -158.08 | -74.14 | 0.00 | |
5.00 | 15.61 | 0.27 | 1.75 | 3.12 | 0.09 | 5.00 | 15.61 | 0.43 | 2.74 | 3.12 | 0.14 | |
10.00 | 30.93 | 0.36 | 1.18 | 3.09 | 0.12 | 10.00 | 30.93 | 0.57 | 1.85 | 3.09 | 0.18 | |
15.00 | 44.79 | 0.56 | 1.26 | 2.99 | 0.19 | 15.00 | 44.79 | 0.89 | 1.98 | 2.99 | 0.30 | |
20.00 | 57.16 | 0.69 | 1.21 | 2.86 | 0.24 | 20.00 | 57.16 | 1.08 | 1.90 | 2.86 | 0.38 | |
25.00 | 68.65 | 0.91 | 1.33 | 2.75 | 0.33 | 25.00 | 68.65 | 1.43 | 2.09 | 2.75 | 0.52 | |
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Cell B | Cell B | |||||||||||
Input Power (W) | T2_Ext1 Rise (°C) | 95% CI (°C) | 95% CI as Percent | Degrees/Watt | 95% CI (W) | Input Power (W) | T2_Ext1 Rise (°C) | 99% CI (°C) | 99% CI as Percent | Degrees/Watt | 99% CI (W) | |
0.00 | -0.08 | 0.13 | -152.39 | -43.97 | 0.00 | 0.00 | -0.08 | 0.20 | -238.99 | -43.97 | 0.00 | |
5.00 | 14.27 | 0.39 | 2.72 | 2.85 | 0.14 | 5.00 | 14.27 | 0.61 | 4.26 | 2.85 | 0.21 | |
10.00 | 28.14 | 0.58 | 2.05 | 2.81 | 0.20 | 10.00 | 28.14 | 0.90 | 3.21 | 2.81 | 0.32 | |
15.00 | 40.78 | 0.83 | 2.03 | 2.72 | 0.30 | 15.00 | 40.78 | 1.30 | 3.19 | 2.72 | 0.48 | |
20.00 | 52.00 | 0.85 | 1.63 | 2.60 | 0.33 | 20.00 | 52.00 | 1.33 | 2.55 | 2.60 | 0.51 | |
25.00 | 62.46 | 0.86 | 1.37 | 2.50 | 0.34 | 25.00 | 62.46 | 1.35 | 2.15 | 2.50 | 0.54 |
We can reasonably operate with the 95% CI and call anything above a third of a Watt excess energy, but there will always be elusive contributors to error that reduce this interval even further. Bearing this in mind, a 99% CI is our preferred standard, and we have a ~0.5W resolution in its widest margin. We think we could do better.
The best answer right now is to make changes to the hood and surrounding environment to make conditions a little more constant. Our first step is to pull down the hood sash to eliminate sporadic eddies in air current. We are certainly open to more practical suggestions. What do you think?
This is the exact reason we're making moves to improve our calorimetry! The explicit goal is to better insulate the cell from ambient.
Our next step will be to gather SEM images of Celani wires before installing them in the V 1.3 cells.
Thanks for reading!
Comments
Nice work.
This graph from accelconf.web.cern.ch/accelconf/e06/PAPERS/THPCH073.PDF suggests that the copper bands are reflecting most of the IR from the cell interior, resulting in a lower measured temperature:
If this is true, the measurement would potentially change over time as the copper oxidizes in air. Some darkening can be seen in the photos recently posted. To correct this, the copper bands should be given a black oxide treatment like Ebanol C, yielding lower reflectivity:
A heat-resistant paint or even treatment with liver of sulfur might be enough to reduce this possible error.
Yes they are sitting at room temp and below atmospheric pressure. Our plans for these cells would include analyzing the celani wire with our SEM. That is all we have planned right now.
As far as your idea for and experiment goes, we will have to figure out the priorities on these cells. It may be that the leak is so small that we wouldn't be able to see the bubbles. That is, if the rate of leakage is smaller than the rate of diffusion into the water. I will put the idea on the list!
We haven't written up what we know from this last experiment, but that is on our list as well :). We know now the sensitivity of the sensors to ambient changes like air current and absolute temp. We also know that the sensor placement is key and that the vertical orientation is not ideal. We saw that the pressure and gas composition inside the cell makes a difference in the readings. Other observations are welcome for the official write up!
There is a difference in the contact to the outer glass temp between the US and the EU cells. Here in the US we are using the copper bands (all are the same dimensions) and the tip of the TC is in the same spot, but mirrored, on each of the cells.
In Europe, Mathieu is using carbon sticky dots to keep the TC adhered to the outside glass.
We are using the same glass and other mechanical parts. The outer temp sensors are the only difference between the cells.
We are going to use the outside or exterior TC 1. This is the TC in the middle of the cell, horizontally.
As far as the difference goes, we are working with Mathieu to find why his exterior TCs are noisy. More updates will follow on that situation.
I see that you pulled the plug on the 2 1.0 cells (macor and mica). Are they just sitting at room temp now with the less than 1atm of H2?
I'm still very curious about the H2 leak. Is it possible to design a passive experiment with one of the cells that's not be used? Pump it up with H2 and put it into a tank of water and watch for bubbles? It works for inner tubes :)
We've spent many hours over the last 5 months watching the data from these two cells. What is it that we learned from this?
CellA CellB
-US (138 138)
-EU (198 199)
But the external glass temps are different, even though you have ruled out any ambient differences(for the US cell atleast).
-US ( 86 79)
-EU (103 110 )
Tamb is 27 for EU and 31/31 for US
These temps are at times 04-18 17:00 for both EU&US
How come there is a difference in temperatures?
Is there different types/thickness of the glass that contributes to different IR absorbtion? Or is the copper band that holds the sensors of different size?
Btw, are you planning to use the mica temp or the external temp for measuring output power?
Even though you are going to compare each cell to itself it would be good for the validity of this experiment to identify the reason for this difference.
Yes it does have active control. Pictures will be released soon on the temperature control box around the cells. We have noticed this problem. The box uses a space heater and its' built in fan. Air may not be flowing fast enough to take the heat created by the cell out as exhaust, more updates to come as we know.
Whatever you did has made a nice improvement in the cell thermal environment. T_Amb is very stable (active control?). It does now show a small effect from the cell heat, about 2% of delta T_Out1 or 1% on T_Mica. The T_Amb settling time after a power change appears to be in the range 30-60 minutes and this should be considered in the ongoing calibration.
It was actually a fun little project, the ambient around each cell can be controlled to above 25 C, without warming the whole room up. This will be handy in summer when the room will be up above 25 C.
We also have a motion sensor in the lab, it shows the times of the day when we are walking around in there. It will go from 0 to 0.08 when there is motion. This should be up in each test for the US cells soon, we can then correlate movement to different artifacts in the data.
Wonderful news!
Now I can put my club away.
Sorry for all the ruckus!
I hope the horse is ok...
This might help
quantumheat.org/.../...
Your concerns have been headed. In the US they have been fashioning a shield for the cells and will reveal this in an up and coming blog entry.
In general we note when people have been close to the cells and logbook those events so that the times can be ignored.
I know that the open, visible nature of these cells are one of the strong points of appeal, and I understand that cumbersome, opaque radiant shielding detracts from that appeal. I believe we can be clever in the design of the isolation barriers to maintain decent observer visibility, and can hinge open the shielding for reactor access.
BTW, for 25mm wire-only cylinder, 200mm long (33% open, 300mm), recalculated flux delta for:
35C person: 0.3W
65C equipment rack: 1W
2 people: 0.6W
1 person, 1 rack: 1.3W
I wish to conclude my previous comment post by adding that while the smaller surface area of the actual wire will reduce the incoming radiated flux received by my current model, it will only be by a linear proportion. The glass has significant mass, transmissivity and emissivity, and while it will certainly participate in determining the net system heat flux, I believe it will not present a significant radiant isolation barrier, such as becoming the effective "cavity" ambient walls (which must be opaque, btw).
I believe my models already reveal about as much useful information as we're likely to extract from this exercise:
the effect of likely variations in environmental radiant coupling to our cells is not negligible within our experiment's measurement domain.
Yes! The coupling of environmental radiators onto the cell is what effects the net flux variance. The actual cell wire temperature does not have an effect (using these first-order models), only the temperature of the external body (but to the fourth power! ) and the area of the apparatus exposed to the radiation from that body.
I believe the radiated power difference between the vacuum vs air environment will be negligable.
The glass cylinder creates a complex model. I don't know what the spectral absorption curves look like for that material, but I can say that the combination of reflectance, transmission, refraction, absorption and emission will all be strongly dependent on angle-of-incide nce and wavelength. We'd likely need more empirical data than exists to model it accurately.
Following your input, I checked the contact of the T_out TCs with the tube on Cell A. It should be a little better now.
The cell is running precalibration runs. I want to verify that everything is working fine on continuous conditions.
The temperature variation should be solved by this week with the use of SEM carbon sticky tape between the tube and the T_out TCs. A video detailing the entire system/environm ent/instrumenta tion will be published in the coming week.
Thanks for you patience ;)
Thanks for this contribution Robert, it just goes to show how important it is to look at every aspect. If we can show 4+ watts on 15ish then we should be good.
We will be publishing the wire temperature estimation basis soon.
First there is temperature for current applied in free air conditions.
Then there is estimated temperature of the wire in the vacuum cell. This is calculated on a Stefan–Boltzman n basis, with the initial cell temp being room temp. Over time the cell wall temp will effectively become the wire's environment temperature due to back radiation and because of IR thermalisation in the glass, will be significantly higher over time. We predict that the wire temperature at 20W will be in the many hundreds of degrees centigrade and the cell wall temperature will be more than 100 degrees above ambient after an extended run which will raise the wire temperature further.
Given that the ultimate cell temperature may be 140+ degrees and there will be a vacuum between the hot wall of the cell and the extremely hot wire - and the wire is, in effect the ultimate target of the IR emitting from a 35 degree body, the incident IR on the exposed surface area of the wire may be minimal.
When we have published this work, we would really appreciate you re-running your calculations.
About the EU dual cell V1.3 calibrations.
You are very observant. There is an issue with the building AC that Mathieu is in the process of resolving. He is getting the local unit in the lab to be uniquely controllable. Due to change of season in southern France, the overall buildings thermal management is not conducive to the lab environment and is causing swings in room temp.
Additionally, the vacuum pump, now that is on all the time is presenting itself as a localised heat source and this issue also needs to be designed out.
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