[SEL] Thermo-syphon Question

[John Culp]

> I found this on google. Doesn't say anything about the water having to 
> be above either radiator or tank opening. Could this be wrong?

Of course it could. It's not, though, just incomplete. What they're not 
mentioning, taking it as a given, is that there must be a complete 
circuit for the flow to occur, just as with a DC electrical circuit.

Let a large enough air bubble into the system to open the liquid 
circuit, and thermosiphoning can't occur. Percolation driven by rising 
steam bubbles still can. Remember the old fashioned coffee percolators?

The heat input to a thermosiphoning system doesn't have to be at the 
bottom, or the cooling at the top, for convection to occur. It just 
needs to be asymmetrical so that one side of the system contains warmer 
liquid than the other. That liquid's less dense than the cool liquid in 
the other line, so it will rise and be displaced by the cooler liquid, 
that then is heated.

John Culp
Bristol, Tennessee, USA