For some of the deviations, there was no good excuse. For some, there is good reason. MFMP has had difficulty replicating the Parkhomov seals, and does not yet have the right size alumina parts for proper Parkhomov replication. And in the Parkhomov design, it is hard to tell if the seal failed or the device just didn't work. The best data from the experiment just completed is that the sealing of the compression fitting with the aluminum ferrule was good. This is a serious win, because it permits analytical plumbing to be attached to a Parknomov-like device. This analytical plumbing will allow real time pressure measurement, post experiment gas sampling for analysis, gas venting to safely open the reactor, and an ability to open the reactor without cutting the tube (but it is not clear that it will be possible to sample the Ni materials without sectioning). And, the plumbing will subtend no significant expansion volume.
MFMP is getting ready to publish my proposed plumbing design for attaching to a Parkhomov-like reactor, probably on Facebook. On Sun, Feb 8, 2015 at 10:56 AM, James Bowery <[email protected]> wrote: > In an experiment where replication is everything, it takes a pretty > compelling reason to deviate from the exact protocol and the justification > for such deviation should be carefully documented prior to the experimental > run. > > Where is this documentation for the justification for departure > from Parkhomov's protocol? > > On Sun, Feb 8, 2015 at 11:02 AM, Bob Higgins <[email protected]> > wrote: > >> I think estimations of the gas pressure inside the dogbone reactor tube >> at failure are probably substantial over-estimates. We don't really know >> how much volume was displaced by the Ni, so the volume estimate for the >> chamber is probably only accurate +100%/-50%. The volume of the system can >> and should be measured prior to start of the experiment. This can be done >> with a calibrated piston plumbed into the system. Decrease the volume by >> 1cc using the piston and see how the pressure changes. >> >> Second, there is a hot volume and a cold volume, but only one pressure. >> Third, we don't know what is happening chemically inside the hot chamber. >> Sure there is decomposition, but there are probably also other hydride >> formations occurring at that pressure and temperature (note that there was >> added zirconium). Perhaps there was even ammonia formation which would >> reduce the pressure; and this could condense in the cold side. Fourth, the >> LiAlH4 weight added is probably only known +/- 20%. >> >> The summary is we really won't know what the pressure profile was in this >> experiment and we won't know until it is carefully measured. There is no >> real point to the wild speculation. It will just have to be measured. >> >> On Sun, Feb 8, 2015 at 9:47 AM, Jones Beene <[email protected]> wrote: >> >>> Yes, that is the good news - that the compression fitting works, and >>> if the problem relates to thermal stress, there is an easy way to fix that >>> also. >>> >>> To minimize thermal stress – the heater wire could be “feathered in” >>> from both ends, when it is wound so that there is an intermediate zone >>> of heat which is less than the fully wound wire, but greater than the >>> unheated zone. The idea is to spread out the areas of highest >>> temperature gradient, to reduce thermal stress. >>> >>> *From:* *Bob Higgins* <[email protected]> >>> >>> Ryan Hunt reports that the failure mode was NOT the compression fitting >>> giving way under pressure - the fitting remained intact. This experiment >>> was of the "easier Parkhomov" design, posted previously where the seal was >>> made with a compression fitting, in this case with the use of a soft >>> aluminum ferrule at the suggestion of Alan Goldwater. Alan's tests >>> suggested the compression fitting would hold and it did! \ >>> >> >> >
