MIZUNO REPLICATION AND MATERIALS ONLY

  • exhausted where?


    I worked at the Texas Medical Center, The Methodist Hospital, for the Facilities Department making sure the Hospital passed JCAHCO certification inspections. [https://www.jointcommission.org/]


    We exhausted dirty laundry room air to the roof. Making the roof a very sketchy place to breathe.


    In the case of a hood for our purposes, the fan should pack a filter, the filter might be emptied of particulate onto a sheet of white paper. I would exhaust outdoors, where Nature, I hope, does something useful with whatever remains. Nature has talents in this area.

  • While I appreciate the concern of the moderators for possible toxic hazards of rubbing two metals together, I don't think a glove bag or box is needed for the rubbing process under discussion. Nickel is about twice the Brinell hardness of Pd, especially after having been worked hardened as woven wire. So there's no real risk of free Ni nano particles being created. Palladium is inert and considered non-toxic in elemental form, and is widely used in jewelry and in catalytic converters without associated health warnings.


    That said, use of gloves is always advisable when handling metallic Nickel, due to its known skin toxicity, and the sanding process should be done under running water to carry away any resulting Ni particles. This is common practice when sanding urethane paints and other materials with known toxicity. Adding a particulate breathing mask is a good idea if in doubt of your skills, or lack experience in mechanical fabrication.


    AlanG

  • If the sheath heater is placed inside a stainless steel tube, the sheath heater will become extremely hot at low input power. The sheath heater in the stainless steel reactor vessel is already getting borderline, because the inside is also reflective to IR. The emissivity of stainless steel is very low. Since convection inside the vessel is basically non-existent, and both the internal and external surfaces are highly reflective, the heat will be very slow to escape a stainless steel tube encapsulating the sheath heater. The stainless steel vessel is already a poor radiant emitter of heat, but at least forced air convection keeps it cool.


    I expect that a sheath heater inside a stainless steel tube would fail surprisingly quick, possibly just during calibration at fairly low input power.


    Since the sheath heater itself doesn’t seem to cause any reactor contamination problems, installing the sheath heater inside an Inconel tube may work reasonably well.



    I got the impression from the paper + Jed's explanatory comments that for the R20, the heater was coiled and than in physical contact with the reactor inner surface and/or mesh.


    For heater and mesh or reactor surface not to have good physical contact would be problematic, or at least have definite effects. As P points out convection does not happen here so we have only radiation with a relatively low emissivity.


    If the mesh is not in contact with the reactor, given the excess heat claimed emitted by the mesh even for R19 is as much as that from the heater, it will get hot, but not nearly so much because its surface area is much much higher.


    If the heater is not on good thermal contact with the reactor/mesh, then it will get very hot.


    Let's do a ball park calculation.


    For a temperature difference of 300C mesh or heater to reactor and a reactor temperature of 370C, assuming equal 0.2 emissivity in both directions, we have from law for black body radiation:


    0.2 *5.6E-8 (900^4 - 600^4) W/m^2 = 0.2*5.6E-8*5.27E11 W/m^2 ~ 6kW/m^2


    The mesh surface area (for radiation) is roughly 0.2*0.3 X 3 X 2 sq m = 0.36 sq m. So we get 250W from 150C or so difference.


    For 60cm long, 10mm circumferance heater we get 0.006 sq m = 60 X lower heat output or 36W for that 300C temperature difference.


    So: if sheath heater is not in thermal contact with reactor its surface temperature (for those who think this is significant) varies with size and input power and emissivity but will be of order 700C for these ballpark figures.


    At these temperatures (700C) the T^4 term dominates so temperature varies relatively little with the other variables.

  • I got the impression from the paper + Jed's explanatory comments that for the R20, the heater was coiled and than in physical contact with the reactor inner surface and/or mesh.


    That is not correct. The schematic drawing on pg. 14 of the R20 report clearly shows the sheath heater is positioned at the central axis of the reactor tube and not in contact with the Ni mesh. Putting it inside a thermo-well at the same location might change the calibration of temp vs. input power, but the thermal transport inside the cell would not be changed. The specified heater has a steel sheath, so quite similar in emissivity to that of a steel tube used to contain it.


    AlanG

  • Definitely not in contact. That drawing is not very accurate. It is more a schematic than a drawing. But anyway, I am sure the heater is not in contact.

    THH: "As P points out convection does not happen here so we have only radiation with a relatively low emissivity."


    Why not add an inert gas like Argon to the reactor in order to give convection an opportunity to work in our favor? Why not mount R20 vertically as in the earlier cruciform unit from 2017 in order to create convection currents?

    Then we could also plate the inside of the SS cylinder with Nickel to protect against contamination and simultaneously add potential reactor surface. Then plate it with Pd if desired. After all, Mizuno says the more Ni and Pd the better...

  • The specified heater has a steel sheath, so quite similar in emissivity to that of a steel tube used to contain it.

    The emissivity of the stainless sheath increases with temperature .. the available data suggests ..

    so an estimated sheath temperature of 700 C for a reactor inner surface T of 370C and

    RT emissivity of 0.2 may be excessive


    For an emissivity of 0.6 , Stefan' s Law gives a sheath temp. of only 530C for a sheath SA of 0.006

    and radiated power of 50W.

    https://www.engineeringtoolbox…-heat-transfer-d_431.html

    the T^4 term dominates so temperature varies relatively little with the other variables.

    Not true

    The temperature varies greatly with emissivity