MIZUNO REPLICATION AND MATERIALS ONLY

  • Forgive me, but I'm still not clear who 'our' is. Are you still collaborating with Mizuno? He does not seem to have confirmed your prior comment that the two of you are still working together.


    Not trying to be difficult, but I'm genuinely confused. You seem to be working with Mizuno, but not Mizuno Tech..?

  • It’s quite simple actually. It’s simple a titanium double walled box filled with ceramic insulation to prevent the walls from collapsing and then removing the air with a vacuum pump to further reduce heat flow.

  • Forgive me, but I'm still not clear who 'our' is. Are you still collaborating with Mizuno? He does not seem to have confirmed your prior comment that the two of you are still working together.


    Not trying to be difficult, but I'm genuinely confused. You seem to be working with Mizuno, but not Mizuno Tech..?

    There will be an official announcement soon

  • It’s quite simple actually. It’s simple a titanium double walled box filled with ceramic insulation to prevent the walls from collapsing and then removing the air with a vacuum pump to further reduce heat flow.

    the ceramic insulation will have a large outgassing. Is the gasses from the ceramic insulation exposed to the active metal (nickel or whatever you have)?

  • the ceramic insulation will have a large outgassing. Is the gasses from the ceramic insulation exposed to the active metal (nickel or whatever you have)?

    or may use something like that:

    Properties of Macor | Morgan Technical Ceramics


    MACOR® Machinable Glass Ceramic (MGC) has a continuous use temperature of 800oC and a peak temperature of 1000oC. Its coefficient of thermal expansion readily matches most metals and sealing glasses. It is non-wetting, exhibits zero porosity, and unlike ductile materials, won't deform. It is an excellent insulator at high voltages, various frequencies, and high temperatures. When properly baked out, it won't outgas in vacuum environments.

  • As Alan says outgassing isn’t an issue. We are just reducing the gas pressure inside the VIP to reduce kinetic energy transfer between the walls. There are more exotic materials available such as aerogel insulation but that’s overkill in this application.

  • As Alan says outgassing isn’t an issue. We are just reducing the gas pressure inside the VIP to reduce kinetic energy transfer between the walls. There are more exotic materials available such as aerogel insulation but that’s overkill in this application.

    the surface area of ceramic fiber insulation with plastic binders is enormous and will outgas (any ceramic fiber insulation having stiffness has some plastic binders), the fact that you say it's a double wall means these gases are not exposed to your active material (nickel?).


    It may not be worth the aggravation to put a vacuum in those titanium panels - because of outgassing and risks that the panel insulation coefficient will change - this is just a gut feeling.


    It's important to make sure the calibration experiment matches the active experiment as much as possible. I had a situation where I used more nickel mesh in the active experiment compared to the calibration experiment. It was probably twice or three times the amount of nickel mesh in the active experiment compared to stainless steel mesh in the calibration experiment - plus the mesh opening size was smaller in the active experiment compared to the calibration. As result, the average temperature was something around 10 C colder for the active experiment compared to the calibration experiment at the same power level (and thus this was a failed reproduction). I attribute the colder temperature to the amount and size of the mesh being different between the active and calibration experiment (and no excess heat) which redirected the heat flow to other parts of the calorimeter and away from the thermocouples, there were 10 thermocouples on the outside of the vessel.


    I assume you will base your excess heat on the thermocouples in the hottest areas right next to the active vessel (i.e. the center of the insulated box). I would say small amounts of excess heat could be due to differences between active and control experiments. But if you get a big result, then it is more likely real. My initial assumption is the insulation you use around the vessel will minimize any problem with the control being different than the active. I did not have insulation around my vessel.

  • All valid points. It’s not a hard vacuum in the panels, normally between 50 and 100mbar. Yes the innermost section is where the temperature is measured. Also calibration runs are done both before and after the active run so any effect of outgassing would become apparent between the two calibrations.

  • Paper comparing panels made of various materials.

    I had to download the paper to see the tables correctly formatted - otherwise it can be confusing especially table 7 which made little sense otherwise.


    https://www.degruyter.com/document/doi/10.1515/secm-2013-0162/pdf



    In table 7, the thermal conductivity of the panels at atmospheric pressure is 3 to 5 times the thermal conductivity at 1 mbar (i.e. 1/1000 of an atmosphere).


    The question is: What is the thermal conductivity change after the core insulation outgases? I think there is risk it could be as much as 5% or 10%.


    You say that you will verify the calibration constant using a dummy cell before and after the active cell to confirm that the calibration has not changed. Prior to any calibration run, you may want to bake the fully finished vacuum panels at some high temperature so as to get the outgassing and whatever else out of the way so that your calibration constant changes the least during experimentation. You could even run the calibration before and after this bakeout to see any changes.

  • Yes I think it probably makes sense to do a bake out at maximum operating temperature and then reapply the vacuum. I’m not sure how much vacuum we can apply before the titanium box starts to collapse with the ceramic wool inside. They is why I was considering just about 50mbar maximum vacuum so any possible outgassing should result in a minimal increase in heat transfer, but the overall thermal conductivity will be higher but the variation will be minimal. We will have to see but as I want to remove any source of variability more than achieve the best possible vacuum. I agree as we move forward and we start to aim for infinite COP operation then minimizing thermal conductivity will be a higher priority.

  • They is why I was considering just about 50mbar maximum vacuum so any possible outgassing should result in a minimal increase in heat transfer, but the overall thermal conductivity will be higher but the variation will be minimal. We will have to see but as I want to remove any source of variability more than achieve the best possible vacuum.

    As far as a mechanical structure is concerned the the difference between 50 mB and 0 mB is just 5% more load. It might be more significant at the kind of temperatures you want to reach.



    An external file that holds a picture, illustration, etc.<br>Object name is materials-14-06432-g012.jpgThis is for the common Ti6Al4V alloy. See also...https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Ti%206Al-4V.pdf

  • Thank you Alan. Ideally we will want to reduce the pressure to about 1mbar if this doesn't introduce additional variability which we definitely want to avoid. Its very helpful to have these discussions here. We are planning to use commercial grade 2 Ti sheets.

  • Yes I think it probably makes sense to do a bake out at maximum operating temperature and then reapply the vacuum. I’m not sure how much vacuum we can apply before the titanium box starts to collapse with the ceramic wool inside. They is why I was considering just about 50mbar maximum vacuum so any possible outgassing should result in a minimal increase in heat transfer, but the overall thermal conductivity will be higher but the variation will be minimal. We will have to see but as I want to remove any source of variability more than achieve the best possible vacuum. I agree as we move forward and we start to aim for infinite COP operation then minimizing thermal conductivity will be a higher priority.

    This is not a solution because it will just outgass again - you have to bake the panel *after* the final application of the vacuum.


    In other words, the bake out is the last step in manufacturing the panels, not applying vacuum.

    Edited 2 times, last by j9381 ().

  • I hope, this is the right spot to ask some more specific technical questions on reactor design. However, I (we) are not doing an exact MIZUNO replication, but similar.


    I would be pleased, if we could have an exange here, since I believe participants in this thread have similar technical challenges. Otherwise please mods advice the best thread.

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