How do you cycle hydrogen into/out of the reactor kernal without blowing micro/nanopowder out of the reactor into the hydrogen system?
I agree that a type of fluidized bed of micro/nano powder might work well if uniformly distributed On Wed, Jan 25, 2012 at 4:56 PM, Robert Lynn <robert.gulliver.l...@gmail.com > wrote: > Hydrogen is amazingly good for heat transfer. Rossi and Defkalion are > both using H2 of 2.5-5MPa, and at 600°C that will have density of about > 0.7kg/m³ or greater. At that density 4µm nickel powder particles (As > defkalion are specifying) will need a hydrogen flow velocity of about > 0.5m/s to pick it up against the force of gravity (from bernoulli's > equation). > > Please Note that the following calculations are very basic, and not that > accurate, but give some indication about the size of flow speeds in the > reactor. > > If the centre of the reactor is 600°C and the walls are 350°C then there > is about 0.2kg/m³ hydrogen density difference between them, (about 2N/m³ in > earths gravitational field). > > A reactor height of 50mm with that density difference would give about > 2x0.05= 0.1Pa of driving force, and that pressure (from bernoullis equation > again with 0.7kg/m³ density) would be equal to the dynamic pressure of > hydrogen flowing at about 0.5m/s. > > So the powder is probably almost being picked up and circulated by the > hydrogen. If the reactor was (taller) then the circulation of hydrogen > would get faster and the powder would almost certainly start to get slowly > blown around making a fountain in the hot middle of the reactor that would > fall down the colder walls, gradually circulating the powder around the > reactor. Also if the powder was smaller diameter then it would take less > H2 flow speed to lift it up. > > But even without the particles moving you can see that the hydrogen will > circulate (convect) in the reactor, fountaining up in the hot middle and > dropping down the cool sides. Any hot spots will also increase the flow > speed of the hydrogen locally in that spot due to reduced hydrogen density. > The overall circulation of hydrogen will work to even out the temperatures > throughout the powder very quickly, and if you want to increase the flow > speeds and heat transfer then it is useful to have a taller reactor to > increase the driving pressure (like a thermosiphon). > http://en.wikipedia.org/wiki/Thermosiphon > > If you are very worried then you could also use a mechanical shaker to > move the powder around and limit formation of hot spots. > > > > On 25 January 2012 21:20, mårten Sundling <mar...@krteknik.com> wrote: > >> Hello >> Thanks for a great number of input. >> My concern have been that the powder might just sit there as a pile >> Be badly avaliable to the h2 and get >> so hot by the bad cooling that it melts, I'm BTW using micrometer powders >> at the moment by rossis specs, but it sounds like I will use nano powder.... >> I thought that I might overcome those hurdles by using a conductive >> porous substrate, but that might not be the case then. >> What's your opinion about using acetylene and nickel instead of >> nickel,carbon,h2 a idea that is floating around.. >> Marten >> >> Skickat från min HTC >> >> ----- Reply message ----- >> Från: "Robert Lynn" <robert.gulliver.l...@gmail.com> >> Till: <vortex-l@eskimo.com> >> Rubrik: [Vo]:Nickel honeycomb ? >> Datum: ons, jan 25, 2012 22:00 >> >> >> I think are a many potential downsides to using bulk material substrates >> (foams, foils, wires) with nickel coatings. >> - you might get large and non-homogenous transient temperature changes >> throughout the reactor and this could lead to deformation and even breakup >> of large continuous scaffolds. >> - it prevents transport of powder throughout the reactor (which may be >> important for continuous operation in terms of subjecting the nickel to >> varying temperatures or physical impacts to create hydrogen flux through >> the nickel surface) >> - a foil type substrate may constrain or otherwise limit convective flow >> of hydrogen (particularly if there is thermal deformation of the >> substrate), allowing hot-spots to form and creating worse >> temperature inhomogeneities throughout the reactor. >> - thermal expansion and material crystalline structure phase changes >> caused by temperature change or hydrogen loading can lead to large >> dimensional mismatches and stresses between substrate and nickel - leading >> to the nickel coating flaking off etc, at which point why not just use >> powder anyway? >> - the processes by which you apply the nickel coating to the substrate >> may have limitations and so not be optimal for creating the exact chemical >> alloy makeup and surface topologies required for best LENR performance. >> - making nano-powder will almost certainly be cheaper than any plating >> procedure. >> - harder to recycle substrate with nickel coating >> - very easy to replace nickel powder in a reactor. >> - one or more of the above problems will probably impose a lower >> temperature limit on the process than the nickel powder would have by >> itself. >> >> Hydrogen convection driven by buoyancy will likely slowly agitate and >> transport nickel nano-particles throughout the reactor, with radiation at >> high temperatures and physical contact of the blowing nickel particles with >> the walls also enhancing heat transfer. >> >> That does not mean nickel on a substrate won't work, but it appears to >> come with more potential problems, temperature limitations and higher >> fabrication and running costs than nickel powder, with few if any benefits >> that I can see. So unless you have other compelling reasons for a >> substrate I think you may as well just stick with the nano powder. >> >> On 25 January 2012 19:28, <mar...@krteknik.com> wrote: >> >>> Hello guys >>> I have a q, i have been reading all the posts about the problems with >>> energy transfer, core melts and so on . >>> Why not embed the nickel / catalyst mix in a honeycomb, or other >>> structure that gets easy acess for both H2 and >>> heat trasnfer to the walls of the tube ? >>> >>> >>> Is there any practical method of doing this? >>> I have thought about covering steel or other material with nickel as so >>> many other people, but in my mind that decrease the surface >>> too much, a fungi or honeycomb like structure would maybe work, but how >>> to make one ? >>> >>> Any ideas ? >>> >>> >>> Marten >>> >>> >> >
