The caps must be resistant to hydrogen exfiltration, i.e. not sintered. Is there some mention in the test report that says that the outer alumina tube is hydrogen proof? Does it say that the outer tube is sintered alumina?
On Tue, Oct 14, 2014 at 11:15 AM, Bob Higgins <[email protected]> wrote: > Robert, I think a lot of your observations are spot on. I would like to > continue discussion of the likely construction of the latest IH hotCat. > You are likely correct that the corrosion of liquid and vapor phase lithium > would be terrible for use of a metal reactor vessel. That is probably why > they switched to alumina. > > Alumina is a wonderful ceramic from a thermal, mechanical, and electrical > properties standpoint. Its only drawback is that it has to be fired at a > very high temperature to form it, but Coors has been doing it for decades. > It is high thermal conductivity, very low electrical conductivity (a good > dielectric), and extremely chemically stable. It is mechanically tough, > even in thin wafers (it has been used as a substrate for hybrid electronic > circuits also for decades). > > One thing that strikes me is that heater wires at this temperature have 2 > related constraints: a) they must be sealed away from oxygen, and b) there > must be a good way to remove the heat from the wire to prevent hot spots > from run-away temperature rise. Regarding a) - long before these wires > melt, they will oxidize and burn up in oxygen. Usually this means that the > wires must be sealed inside a ceramic oxide to prevent exposing the hot > metal heater wire to free oxygen. For b), it is necessary to spread the > heat from the wire. This is usually done by bonding the wire to another > ceramic body, usually with a refractory cement. > > Now lets consider the issue of using a refractory cement to bond the > heater wire to the inside of a ceramic tube. You would need to have the > coils pre-formed and slipped inside such a tube and then paint them inside > with the refractory ceramic. This would be very painful. Instead, I > imagine a central alumina tube with the heater wires wrapped on its > outside. This could then be painted with a refractory cement to seal out > the oxygen and help thermally spread the wire's heat over the ceramic tube. > > Normally such refractory cements have an organic binder that dries in air > at room temperature. They also contain both low temperature glass and > ceramic fibers. As the cement is heated, it would first drive off any > organic. Then the glass melts and further binds the joint. Then as > temperature gets hotter the glass wicks into the ceramic fiber and a > glass-ceramic hybrid is formed. The joint can be air tight at basically > all temperatures until the ceramic itself melts. > > Also, because we are talking about 3-phase coils, there will be > cross-overs of the wire that must be brought out to the ends of the > reactor. These will have to be very carefully managed so as not to short. > This is another practical reason why I believe the coils must be created > wound on the outside of an alumina tube; that tube being coaxially internal > to the alumina tube that is visible on the outside. Probably after a first > heating of the coil (either self-heating or having been placed in a curing > furnace), the inner alumina tube with the wrapped coils could be coated > with a similar refractory cement and slipped (glued) inside the outer > tube. Imperfect cement contact between the inner and outer alumina tubes > could cause the appearance of uneven heating on the outside tube. > > Another point has to do with how the heat is conveyed from a LENR > reaction. Since the LENR reaction is likely a nano-scale event, heat must > be conveyed from the reaction in a way that doesn't make the NAE the > hottest spot. Otherwise, none of the reported melt-downs would be possible > - the NAE would evaporate itself before it could create enough heat to melt > the macro apparatus. This implies that the heat is conveyed from the NAE > by photons - not such high energy that they readily escape the reactor, but > high enough that it can penetrate through a mm or so of the surrounding > materials (which could be LENR powder), depositing heat as the photons are > attenuated in penetration. The important take-away is that the NAE cannot > be the hottest spot - it must heat its surroundings more than itself. > Given this, it is possible that the heat from the LENR is being absorbed in > the alumina in a distributed way, causing the LENR powder to be largely the > same temperature as the surrounding ceramic. I don't believe it is > necessary or probable that the core must be much higher temperature than > the shell. > > Can we refocus this thread into discussion about the construction of the > latest reactor? For example: > > - Why do we think the end caps are so big? Are they part of a lower > temperature insulated mounting system? > - Why do we think the 3-phase drive is used? > - What else? > > Bob Higgins > > On Sun, Oct 12, 2014 at 9:43 PM, Robert Lynn < > [email protected]> wrote: > >> 1% lithium in 1g fuel, so 0.01g, boils at 1342°C. At 1 bar,1342°C would >> fill about 180mL volume, reactor volume probably about 30-50mL so will be >> filled with lithium gas under pressure - operating as a heat-pipe to >> equalise pressure. >> >> I have just realised that we can probably infer the existence of an inner >> reactor vessel because we see helical wires or wire shadows of only one >> angle - we can't see both sides of wire helix through an open core because >> there is an inner core vessel in the way. I had thought there was no such >> vessel, so my conclusion about the wires being hotter no longer stands up. >> The wire temperatures are electrically controlled to alter the amount of >> radiative heat flux that leaves the inner vessel - a crude method of >> controlling heat flux that suggests great improvements in COP if better >> methods of heat flux control are employed (high temp coolant fluid or >> moveable insulating shields). >> >> That inner vessel must be crazy hot! around 300°C higher than the >> already hot outer wall in order to radiate the heat to the outer wall and >> hot wires; eg if Ø20mm outer wall is at 1200°C (approx max given revised >> COP of around 2 from temp reading that is obviously in error due to >> non-melting of inconel, though could be significantly lower) then an inner >> alumina tube of Ø12mm outer diameter radiating 1kW would need to be more >> than 1500°C surface temperature (Actually higher given hot wires >> surrounding it), so again it seems temperature within vessel must be up to >> range where nickel is melted and lithium is gas at 5-10bar. >> >> I wonder if that smaller hotter inner tube and translucence of outer >> alumina tube is what is screwing up the thermographic calorimetry? If the >> camera is picking up the inner tube at 300°C temp higher than the outer >> then the exterior tube temp might only be 1100°C and the COP could be a lot >> lower >> >>
