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jfsp 12-31-2011 10:56 AM

[Idea] Thermos (vacuum insulated) immersion BK/LT
 
This is just an idea for a DIY project, nothing concrete has been done yet, so I apologize if I'm posting in the wrong forum.

Intro: The main problem with heating a large volume of water is that you have to fight the thermal heat dissipation of your pot with the ambient air. Some insulation schemes have been used already, but none seem to be efficient enough so that one could use a 120V immersion heater with a 10g volume of liquid.

The idea came from looking at my vacuum insulated aluminum 1L Thermos pot that I use when brewing some green tea. It does a great job of keeping my tea at desirable drinking temperature during extended periods. Would it be possible to build a vacuum (aka low inner gas pressure) insulated 10g brew kettle / LT ?

Take 2 pots (12-15g outer pot and 10g inner pot). Once you remove the handles from the inner pot, it should fit into the outer pot with more then 1/2 inch space between both. The 2 pots should be joined (soldered) at the lip using a metal disk. That disk could probably be cut from the outer pot's lid. One gas pressure valve would be needed to allow to connect a vacuum pump to the thermos pot.

That pretty much sums it up. With that amount of insulation, low wattage immersion heaters could be used, limiting energy loss and scorching risks. I expect the limitation of the duo-pot would be the structural strength of the outer pot and solder region where it's more likely to crush. I guess low pressure would probably be safer then total vacuum. I have no experience in soldering or high/low pressure systems, so i'm probably years away from attempting this project. Still, i'd like to know what you all think of it.

If the basic idea is not completely bad, there there is many interesting mods possible. The first one to come to mind is to replace the low pressure air in the pot with some heavy noble gas, then reduce the pressure again for increased insulation. One could also solder a magnetic metal plate to the bottom of the inner pot (in the low-pressure inter-pot region) so that you could use induction heating (assuming that the other pot is not induction-ready). Obviously, mods that involve drilling both metal layers of the pot would be much more complicated (thermometer, liquid valves).

So what's the verdict ?

birvine 12-31-2011 01:20 PM

I think you might find that metal is flexible and will collapse into the vacuum. I think a vein to explore for this idea is along the lines of a thermal-tolerant insulation that can be put between the two pots.

B


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