Thermosiphon effect question

[farmerjohn]

Hello all,

Hope you can help me, thanks if you can,

I have a very small sheet metal wood burning stove in which I've placed a copper coil.

The coil has cold water coming in from house mains and warm/hot water going out towards my
outdoor bathtub. This takes forever due to the stove's small size and inefficiencies of my design, lack of knowledge, poor breeding

etc....

What I want to do is re-circulate the tub water (instead of heating direct from mains) without using a pump if possible. So hoping for a thermosiphon effect with this small wood stove boiler contraption.

Before I melt my hoses on either end of the coil I thought I'd pose the question here.

Would this system make a thermosiphon effect if both hoses were placed in the tub??

I can move the stove higher or lower than the tub if necc. but not too much maybe 1 meter.

[the coil and in-out hose inner diameter are both 6mm, flow rate of water is 1-3 liters per minute filling the tub from mains pressure, 1 L/min being hot 40C and 3L/min being coldish 30C. Mains water temp is 23C now.]

Thanks very much if you can help,

john

 

[BoilerMan]

I think the only way is to use a circulator 6mm is too small for any kind of flow from thermosiphon you'd need. I don't think you can extract much heat with that small amount of surface area in the fire anyway. Better to make a "smoke dragon" and surround the firebox with water. You could wrap the stove with something like 1/2 or 3/4" soft copper, but still not going to be much efficiency, the vast majority of the heat is going to be radiant off the stove and not transferred to the water.

BTW, if you can say and spell "thermosiphon" your breeding can't be that bad

TS

 

[farmerjohn]

Thanks for the reply TS, I'll look into the "smoke dragon"

Yeah, I know it's small, underpowered, and inefficient, just hoping for a little hot water.
It's getting there slow but sure.

Thanks again,

FJ

 

[TheMightyMoe]

Never dealt with anything like this.

But it seems like you would want more heating surface / pipe size on your tubes, and the tub should be ABOVE the stove as high as you can go. That way when it siphons, hot water will rise into tub, and cold water will take its place. So hot water tube will be at the top of tub (At water level), and bottom tube would come out of bottom of tube (Preferbly from side or bottom)

Also the coil should go from low to high to promote siphoning.

Just my thoughts.