Are we getting close to a Stirling engine running as a frig? Don Joe Gwinn > A dodge occurs to me - a homebrew heat pipe: > <http://en.wikipedia.org/wiki/Heat_pipe>. > > Make the cold plate of copper, to which is soldered a meandering > piece of copper tubing, which tubing is also soldered to a copper > radiator plate that is above the coldplate, forming a closed loop > with a fill tube attached by a T. Braze all tubing connections, as > for freon refrigeration systems. (Soft solder is too porous to work > for the joints, but is OK for attaching tubes to plates.) > > Insulate the two tubes running between coldplate and radiator plate > from one another. > > Put enough working fluid into the system to fill the tubing that is > soldered to the coldplate, but no more. Warm the system up so the > vapor drives all the air out, pinch the fill tube off and fold it > back, and braze the end shut. (It's not critical to get absolutely > all the air out.) > > Making the radiator plate be above the coldplate (the boiler) > implements what amounts to an oldtime two-pipe water vapor heating > plant. Vapor goes up one pipe, condensed fluid returns via the > other. I lived in a house with such a system. The difference > between a vapor plant and a steam plant is pressure: the vapor plant > runs below atmospheric pressure, while the steam plant runs at or > slightly above. > > Make sure that things are arranged so the returning fluid does not > pool anywhere but in the coldplate, or the heat pipe will bang like > an old steam heating system. > > There is a brazing filler metal intended for copper-to-copper joints > that is widely used for freon systems: > <http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm>. > The zero silver phos stuff is adequate, cheap and widely available. > While copper-to-copper needs no flux, copper-to-brass does, so also > get the flux. Plumbing supply houses and welding equipment stores > are likely sources. You will also need a torch or pair of torches > able to raise the tubing joints to an orange heat in a reasonable > length of time. > > Depending on the chosen working fluid, the cold plate temperature > will not rise above the boiling point of the fluid unless the system > is too small (in radiator heat removal capacity) to easily handle the > 10 or 20 thermal watts that are passing through. > > What fluid to use? Anything common and thermally stable that does > not attack copper. Alcohol (methyl or ethyl) and water are common > choices, as are the various freons. I bet acetone would also work. > Anyway, one controls the coldplate temperature by a combination of > choice of working fluid and internal pressure. > > > I have seen commercially made heat pipes for cooling Intel CPUs > advertised, but I don't know that these units can be adapted. > > Anyway, a heat pipe system will stabilize the coldplate temperature > fairly accurately despite variations in thermal load, has no moving > or electrical parts, and may be sufficient by itself. If not > sufficient, it can be used as the outer stage in a two-stage ovening > scheme. > > > Joe Gwinn > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >
-- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
