Posts by LDM

    All serious unknowns are bad for something that is characterizing a Null device.


    On the other hand, I haven't yet tried to recalculate the dummy with a lower LWIR emissivity, using the reiterative values as a start point. Note that the drop in LWIR E should affect the total emissivity also, since LWIR is the primary emissive part of the total IR spectrum for alumina-like materials.

    .

    I will still be in Italy for about another week.

    When back I want to follow some leads I have found about the thermal conductivity of castables.

    Hope that this will result in bringing the internal temperatures of my simulations more in line with those measured on your rods and also in a better understanding of what is the main factor what determines the thermal conductivity.


    However still a lot of other activities on my list.

    So it may be a while before there is anything to report.


    In the meantime looking forward to see recalculations based on lower LWIR emissivities.


    There are a lot unknowns

    Since they are unknown we can not conclude if they where bad or not for the conclusions made.

    Well, more bad news for the Lugano report...um.. to report.


    That bad news is generated by yourself. Not by the Lugano team in their report.

    In trying to explain that the Lugano measurements where faulty you are asserting that the cast was not cured.

    You have no proof of this and are not supporting it by evidence.

    It is also very unlikely

    Asserting things in this way can be done to any scientific report in order to "prove" that a report was bad.


    If you just had reported that not curing can influence the dummy run results, then I would fully agree with you.

    Stating that this is bad news without proof that it happened in order to proof your believe that the Lugano report as faulty goes for me a way too far.

    Nevertheless I respect your opinion/believe that the report was wrong, which as you know based on my own calculations, differs from yours.

    I have however no problem with people having other opinions or coming to other conclusions.

    Let's respect each other and keep to the facts without adding assertions, especially in a technical thread as this.

    That's the way these systems behave at times. And generally something breaks when it happens. I suspect that the 600 degrees you measured was actually over 1000C inside the fuel tube- heat moves too slowly to cope with recording a quick runaway.


    Is that a reason to have also an internal thermocouple ?

    I should be more careful in the future to not prepare a future cancer :)

    What i can add: fuel was compact but with big dead volume ( shongsheng spirit) , things were heated by 2 concentric coils , to have a choice between full magnetism or not. In this case, full magnetism configuration was choosen. We heat with low volt level..and minimum number of wires ( magnetism).

    Next runs should add more understanding

    Therefore stay humble :)

    I don't know if at the 1100 degree mentioned earlier you had already excess heat.

    My feeling, for what it is worth is that after you reach excess heat at the desired temperature you should heat without the magnetic field applied.

    It might possibly prevent a meltdown

    Well, the distance problem remains. I have found nobody new in the UK (so far) who is prepared to come to work with us on what could eventually prove to be a transformative technology. We have a volunteer who cleans and makes coffee now and then but he's unfortunately not a scientist. I am just amazed that there are no retired science lecturers or industrial researchers prepared to put on the robes and join the fun, there is much to do.


    ETA- if anybody can help btw, they can email me via this forum.


    ETA -again. Wyttenbach is an exceptional help, travelling here on his own dollar to help in the lab. But he has a home elswhere sadly. I said he could sleep under the bench but said it was too dusty.:)

    I am retired, but not a science teacher, nor am I a researcher.

    Just an electronic engineer.

    So I don´t know if that qualifies.

    But if I can help you out when there is really a limited period of high need {maximum 10 days} I could when I have no other activities fly over from mainland Europe.

    Good connections to Stansted.

    Don´t mind sleeping under the bench as long as I can take a daily shower.

    While repeating several power steps as used previously and checking current with the new Fluke meter, the Cylinder coil failed on one end while starting measurement of the 400 W step. After determining for a few seconds that the thermocouples were not shorting out, I turned the voltage to maximum to see if a Nernst glow could be achieved. The coil failure area glowed for an extended time, but it did not seem that it was being increased by the extra voltage. Resistance of the alumina was measured through the broken coil while still 1000 C and found to be several thousand ohms, rapidly increasing as it cooled, to the megaohm range before becoming too much to measure.


    The Kill-A-Watt was found to be reporting only about 0.1 A higher than the Fluke meter reported at low output voltages (35-50 V AC) and the gap decreased as the voltage increased. Voltage was essentially the same. The Kill-A-Watt meter is only used on the electrical outlet to power controller connection (pure sine). So for total input power, the KAW unit seems quite accurate.


    It is very unfortunately that it happened now.

    Don't know if you have still enough Durapot to make a new cylinder.

    Nevertheless you provided the data of your previous measurements. Thanks for that.


    Currently I am in the process doing FEM simulations on your rod and have discovered that there needs to be adaptions with respect to the thermal conductivity curve for Durapot .

    This hopefully will bring measured data and the simulations more in line, but the current results are not too far off either.

    I am however running out of time since I will be a few weeks away to Italy.

    So it may be some time before I can provide a new update.


    LDM


    You are being obtuse.


    The only significant "error" in that report was that TC used the same criteria as the Lugano professors, which I agree underestimated the reactor diameter.

    Incorrect,


    Besides the diameter issue, there was also the correction for the value of the view factor.

    This had an implication for the emissivity correction.

    Also the view factor had to be used in combination with the area of the finned tube, not the area of the bare tube.

    After these corrections it was shown that the COP value of 1 in TC's report was not anymore.


    If you are stating that there was too much uncertainty in this experiment, then we can not accept the conclusions of TC's report since it was based on that experiment (with much uncertanty.)

    Now, this response is 100% scientifically wrong. It is a severe misunderstanding, caused by the erroneous assumption that there is only one emissivity here. In fact there are two: total emissivity (controlling the power out) and band emissivity (controlling the IR temperature reading). The band emissivity can be high (close to 1) when the total emissivity is low (close to 0.4). That is exactly what is needed for a high false positive COP got from a much lower than expected real temperature, and TC showed that the form of this false positive closely modelled the actual Lugano results.


    See the thread rossi-lugano-early-demo-s-revisited-technica post #548


    Rossi Lugano/early demo's revisited. (technical)


    It was shown using the Optris software that the iteration with broad band emissivities did not take place on the Optris


    That was made clear in the paper sent by TC to Levi et al (as he documented here ages ago). You can find a copy on lenr-canr. It is a well-written critique, and no scientist reading and understanding it and the Lugano report would disagree. It is, also, more carefully written than the Lugano report itself. It can be checked, in detail, by anyone who wishes to do so.

    There where errors in Thomas Clarke's report which I published after discussions with .............. THHuxleynew


    See :


    Rossi-lugano-early-demo-s-revisited-technical post #90


    Rossi Lugano/early demo's revisited. (technical)


    Since you seem not to remember I wonder if you are the same THHuxleynew

    I wish we could get Levi et al. to respond to critiques such as yours, but I doubt they will.

    There has been a response by Levi in the court documents :



    On July 27, 2016, I met with Mr. Sha in Rome to have a follow-up discussion about our last meeting. Mr. Sha requested that I keep this meeting secret, but did not ask me to sign any nondisclosure agreement. During the course of this meeting, Mr. Sha told me that he wanted to make business together and that "big earnings" were possible. He then asked me a series of formal questions about the Lugano Report.

    All of the critiques and questions that Mr. Sha raised had been previously raised in blog posts that aim to discredit Dr. Rossi and the Lugano Report;

    none of Mr. Sha's questions had any scientific basis or varied from the unscientific

    attacks made in the blog posts.


    So basically levi states thatMr Sha raised the same questions (critique) which where also made on the blog posts.

    This tells us that Levis is aware of the critique on the Lugano report.

    Nevertheless he states that the critique has no scientific basis.

    Paradigmnoia


    The Cylinder is 6.6 cm long. The coil ends 2.5 mm from the ends of the cylinder.


    What is your coil diameter ?


    There are plenty of ways to improve the equipment and methods further, but that is beyond the original scope of the project.


    I really appreciate your experiments.

    They give me the feedback needed for improving the simulations.


    I am actually surprised at how much abuse this Cylinder has taken so far. It is still hooked up, so if there are any particular temperatures (within reason) or something that you would like to know or be tested, I can test them out for you.


    Thanks for that offer



    If you supply the coil diameter I will change the model to fit your dimensions and do another simulation

    However I see already that if I make my Durapot thermal conductances 50% of those currently, then as a result I get the same about 80 degree difference.

    So I wonder if Durapot 810 has a very low thermal conductance.

    A pity that Durapot does not state at what temperatures their physical values where taken.




    Paradigmnoia


    Thanks' for taking the time in answering my questions


    As you I am wondering what can be the cause of the differences in temperatures between your measurements and the simulations.

    So some thoughts, remarks :


    1. Dimensions


    For the length of the simulated rod I used 5 cm

    Don't know if that is correct.

    A longer rod would have a higher temperature in the middle


    Also I used an heating element over the full length.

    Don't know if this true for your rod.


    2. Power balance cross check


    Deviding your rod in for example 5 sections and measuring the temperature of each section we should be able to calculate the total radiated and convective power.

    That should about match the the applied power of the heating element


    If you find the effort too much then I am prepared to make a spreadsheet with the calculations based on your data.


    3. Thermal conductance


    Maybe the thermal conductance is higher then the values I used.

    This will lead to smaller temperatures drops and thus higher temperatures.

    Against this is that the thermal conductance is also an important factor in the transient time constant.

    And we have seen that in the simulation this about matches your transient profile.


    4. Possibility that Durapot has lower broadband emissivities


    Against this is that Durapot is less dense then Alumina, or it has more pores.

    And the pores increase the emissivity


    5. Pyrometer emissivity


    For 735 C I have following my derived curve an Optris in band emissivity of about .93.

    Since I believe your Pyrometer works with the 8 to 14 uM band, it covers less of the high emissivity values of the Alumina spectrum.

    As a result I expect your Pyrometer should have a value less then .93.

    My calculated value for that temperature is .90.

    But that would only result in a difference of about 10 degree C on the pyrometer.


    That you measured in your calibration a value higher then .90 can indeed be due to the pores increasing the emissvity somewhat compared to dense Alumina.



    There is some theory about the heat distribution in round cylinders.

    I will see if I can use that for some calculations and see if that will give some answers.











    Paradigmnoia


    I may have been confused as to where edge of the cylinder was in the slice image. So the lines are the coil?


    Indeed, the double lines are the coil.

    In the simulation the coil is running over the full length.


    The core temperature still seems low compared to the real thing, but no need to split hairs at the moment


    What is your measured temperature data ?

    What is your difference between inside and outside ?

    And where is your internal thermocouple located ? In the center ?


    Also, is your cast resting on the floor (tiles) or is there room between the tiles and the cast so that no heat is leaking away by contact ?

    In any case it is preferred to have the cast at at least such a height above the floor that a normal convective heat flow can develop and that almost no radiated heat is reflected from the floor upwards again.


    Another point about your 17 minute stabilzation time.

    That time frame is large enough that your room temperature may have changed.

    Did you keep track of the room temperature and if it changed in that time frame compensated for it ?


    And what was the emissivity setting used on your Pyrometer ?

    Did you calibrate the Pyrometer with a thermocouple ?


    The emissivity question is about something else, which is best tackled after the simulation behaves as good as is reasonable.


    What do you mean by reasonable ?



    LDM ,

    Why does your simulation show a cooler inside than the middle of the outside?


    In the picture below a temperature profile taken in the middle from the center to the outside perpendicular to the axis is shown.

    Distance 0 is the center of the rod, distance 0.0125 is the surface.





    As can be seen the temperature in the middle is about 770 degree C while the temperature at the outside surface is about 735 degree C.

    Thus the middle is not cooler then the outside.


    The temperature in the middle is lower then the temperature near the heating element.

    This is due to the short length of the rod which causes heat in the middle for a large degree also to flow to the sides of the rod and thus cooling the middle.






    Do you suppose it is the hollow area in the center of the Lugano device that speeds up the settling time (less mass in the hardest place to heat)?


    As Alan already stated that is certainly a factor.

    Some other thoughts (But no proof)


    Maybe the position of the heater coil plays also a role.

    In my Lugano ECAT model it is wound on an inner tube with a diameter of 1 cm

    So much closer to the center.

    Also as you can see from the heat distribution of the central cut, even in the middle of your cast ther is still influence of the sides while in the Lugano ECAT due to it's much longer length, in the middle the heat leaking to the sides is much less. (Maybe you can test your Durapot cylinders with the sides isolated)

    This results in the middle, where the transient is measured much less heat leaking away to the sides.


    I can't see the ribs helping, but instead hindering the settling time a bit.


    The outher surface, wether there are ribs are not are together with emissivity and convective heat transfer coefficient are determining the surface temperature.

    But that does in my opinion not influence the settling time but only the height of the step.

    The settling time will be mostly determined by the internal thermal capacitances and thermal resistances

    Also, how hard is it to change the emissivity settings for your simulation?


    Not that difficult, especially not for your cast.

    For my ECAT simulations it is more cumbersome since the FEM program does not take into account view factors and reflections from the ribs.

    So I have to correct the emissivities to take these effects into account before applying them to the model.


    Concerning that I used the same Durapot physical properties as a function of the temperature as for the Lugano ECAT simulation the following.

    That ECAT simulation was not published but was the one showing the third bump.

    The curve was however close to the one of standard Alumina with the following differences.

    In the beginning it rose almost as fast as the curve for dense Alumina but then went slightly under it.

    Then at about the point of the third bump it started to rise somewhat exponentional again and ended at the same level as the Alumina simulation.

    So in general the deviation from the Alumina curve was not much and the settling time stayed the same.