Semi-snorkel stove heat transfer

[AlwaysDan]

TL;DR Summary

How to catch heat from top of stove using circulating water.

Hi! Came across this forum while researching my project, and this seems like a good place to ask. Thanks in advance!

I'm building a hot tub that will use a 55 gallon steel drum wood stove as a heat source. The drum is built into one of the sides so that the majority of the stove is surrounded by water, with a small opening on the outside of the tub to load firewood/cleanout. The top of the drum is about 4 inches above water level, with a chimney coming from the top. I have an old pool pump that draws water from the side farthest from the drum, and plan to have that water run over the top of the stove down into the tub as a water feature/means to collect some heat from the top of the stove and bring it back into the tub.

I'm looking for suggestions of the best way to accomplish this, or if there are other ways of achieving the same result that I haven't thought of.

 

[BvU]

Hello Dan, !

Pleasant project !

You might want to organize some circulation, perferably natural convection.
Or else have some screen separating you from the hot drum.
I google 'hot tub with external coil' and get lots of links and images

 

[Rive]

I'm looking for suggestion...

Just one small warning: if you overdo the utilization of the heat from the stove you can end with the exhaust having too low temperature and the stove choked (danger of having CO produced). Your idea with the pump (in some configuration) is fundamentally OK as enforced circulation, but make sure that you can hold back when that's what needed.

 

[AlwaysDan]

Thank you both.

BVU - The external coil over the fire was one option that I looked at, and I might still be able to incorporate that into the flue. And there will definitely be a screen of some sort around the stove. (Although the stove below the water line stays cool)

Rive - I haven't had that problem yet, but while I can't control the flow rate of the water, I'll be able to adjust the amount that flows over the stove.

Right now, my problem is creating water tight seals where tank meets chimney; water has been leaking down and suppressing the fire. I might just place a metal pot on top of the drum for now to run the water through

 

[anorlunda]

Just one small warning: if you overdo the utilization of the heat from the stove you can end with the exhaust having too low temperature and the stove choked (danger of having CO produced). Your idea with the pump (in some configuration) is fundamentally OK as enforced circulation, but make sure that you can hold back when that's what needed.

Rive - I haven't had that problem yet, but while I can't control the flow rate of the water, I'll be able to adjust the amount that flows over the stove.

Slow down. CO is a flaw that can kill people. You can't just wave your hands.

How will you know when it is adjusted correctly?
Is the stove outdoors or indoors?

 

[AlwaysDan]

It's outside. Any fire will produce CO if it's overloaded or choked, so I'll look for a clean burn from the flue. Or if that doesn't work I can just wave my hands by the air intake.