Some questions on the thermography: Did they do thermography on all sides or only from front? If so how do we know that there wasn't some insulation internal to the alumina that restricted the heat output from the sides + bottom that were not recorded?
The tube radiation would have heated the frame underneath the tube a lot, and that would have meant that the air rising through that frame and past the tube would not be at room temperature, but rather at higher temperature and lower density, so the convection calculations are likely to be significantly in error - but would require modelling in CFD to give an idea as to how much. Did they observe significantly cooler sides on the tube compared to the top and bottom? natural convection should cool the sides a lot more than the top or bottom of the tube due to the higher air flow velocities in those regions. In fact the heat transfer and temperature differences created by natural convection could be modelled with CFD and would be a way to validate the power output via radiation. Still wishing they had done some simple air-flow calorimetry with a hood and chimney instead. On 12 October 2014 17:39, Robert Lynn <[email protected]> wrote: > -Max average Ecat temp recorded in test 1412°C, 2.8kW heat output. > - 20mm diameter, 200mm long, thermal conductivity of alumina 6W/m/K at > 1400°C means for 1mm wall thickness would have 40°C through-wall temp > differential, for 2mm would be 80°C. > -So assuming 1mm wall thickness (probably conservative) the internal > reactor temp is at least 1450°C > > Through wall temperature differentials like that induce large stresses as > external surface is subject to tensile stress and inner wall subject to > compressive stress. > http://www.ceramics.nist.gov/srd/summary/scdaos.htm > Alumina at 1400°C has thermal expansion of 8.5e-6/K, tensile strength of > 22MPa, 343GPa elastic modulus so 40K temp difference means 33MPa > compressive stress at inner surface and 33MPa tensile at outer surface. It > would crack and break letting oxygen in, particularly if made thicker > walls. The external surface crenellations would create stress > concentrators that would only make this worse. > > Resistive heating wires inside the alumina tube must necessarily be a lot > hotter than 1450°C in order to push 900W heat into reactor. But there are > no non-refractory heating wires that can survive such high temperatures. > Refractorys can't handle oxygen exposure, and in some cases are no good > with lithium or hydrogen. The wires have to be joined to non=refractory > wires before they contact air and yet at those joints must not melt the > non-refractory wire either. I am also not aware of electrical > feed-throughs that can handle such high temperatures. > > 1455°C Ni melting point, but nano particles of metal have depressed > melting points. > http://en.wikipedia.org/wiki/Melting-point_depression > > The fuel/reaction particles as the source of all the heat would need to be > at a temperature far above the internal reactor surface temp of 1450°C, > probably at least 50-100°C higher, in order to radiate/convect the heat > away to the walls. > > So at 1450°C we can expect that the Ni fuel particles are much hotter, and > liquid, making for rapid mixing. Forget special crystalline structures > created by secret processes. LENR in a liquid matrix seems to run counter > to a lot of theories. > > Lithium vapour pressure at 1450°C is around 5-10 bar, with approximately > .01g of lithium in reactor and perhaps 20-30mL volume that means nearly all > lithium is in vapour state or as Li liquid condensate on relatively cooler > reactor walls. This reactor is mostly nickel droplets in lithium gas (the > hydrogen will all diffuse away through porous sintered alumina rapidly at > such high temperatures, but perhaps is useful to create reducing conditions > initially). > > This internal lithium vapour pressure would also add to the physical > stress on the alumina - probably 5-10MPa, which would likely cause a > failure given any other stresses (such as aforementioned heat flux induced > differential expansion stresses). > > Nickel vapour pressure is around 1Pa at 1500°C, so in a month long test we > can expect that along with liquid state of Ni fuel droplets' continual > evaporation and condensation, dissolving in lithium condensate of Ni within > the reactor vessel will lead to steady mixing between the droplets. > > Li + Ni vapour will condense into a thin layer on the cool walls of the > reactor - basically acting as a lithium heat pipe and create very > consistent all-over temperatures. Perhaps with small drops of lithium > condensing and rolling down sides with some dissolved Ni, or otherwise > simply leaving a thin coating of Ni and Li on walls. > > Alumina is strongly attacked by liquid lithium reacting with it to form > new compounds - I would expect it to be quickly consuming the available > lithium in the slightly porous alumina. > > And we do see that Nickel "ash" has very little Lithium (.03%, down from > 1.17%) > > Basically all fuel should end up very homogenous. > > Liquid Nickel dissolves alumina and oxygen to a small degree- about 1.8% > and 1.6 % respectively, but only 0-.05% aluminium in analysed ash - that > probably indicates something in error > > http://docs.sadrnezhaad.com/papers/176%20(Interaction%20Crucible%20NiTi).pdf > > If there is a secondary smaller sealed reactor vessel within the alumina > tube then if must be even hotter. > > So so questions that need to be answered: > 1/ Why isn't there more aluminium in ash given claimed temperatures? > 2/ How does theory deal with liquid Ni as the LENR matrix? > 3/ How do heater wires survive these temps without melting - it is well > beyond temps that non-refractory metals can withstand, particularly given > that they must be a lot hotter than the reactor itself, and refractory > metal wires would fail at external joints. Not to mention non-leaking > feed-throughs of heater wires into reactor while maintaining seal integrity > is probably not possible at such high temps due to differential thermal > expansion of metal vs ceramic and limited strength of materials. > 4/ If within the reactor itself how do heater wires survive exposure to > 1450°C lithium without dissolving/disintegrating. > 5/ Given claimed heat flux and internal pressure why didn't alumina tube > fail? > > PS: can anyone calculate hydrogen diffusion rates through the alumina tube? > > http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1979.tb19114.x/abstract > quoted eqn+units in this abstract aren't clear to me. >
