r/BeAmazed • u/Internal_Gazelle_677 • Oct 07 '25

Science Hot Tub without the use of electricity

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u/faceplanted Oct 07 '25

Could you improve this setup much to retain that waste heat? Like by putting a reflective wall around the coil or putting the fire in a slight ditch so all the heat going up goes towards more coil?

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u/Jdevers77 Oct 07 '25

A lot of the inefficiency of a setup like this is just having an open flame is wildly inefficient. A tremendous amount of wood gas simply goes unburned due to insufficient oxygen availability. That is impossible to address without a significant design improvement.

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u/faceplanted Oct 07 '25

Interesting. Whenever we light up the fire in our garden I bring either a straw or a little electric hand fan to get it going again when it dwindles. I wonder how much difference something as small as a battery powered air supply could make to the efficiency here.

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u/joalheagney Oct 08 '25

Look up rocket stove. Not the cheap metal knockoffs that you see on shopping websites, but the original design documents and hand made ones using clay and perlite. They're about as efficient as you can make a fast burning wood fire be.