[Greenbuilding] stealing heat from a woodstove for water heating

[Reuben Deumling]

The further from the firebox one chooses to steal the heat the fewer
+ negative repercussions for the combustion process, and
+ BTUs per hr transfer into the water

But are there nonlinear solutions? Methods for stealing heat close to the
firebox that do not negatively effect the combustion process?

My ideal scenario relies on (1) below. http://www.axeman-fireflue.com/ My
reason for looking beyond that solution is that the average length of time
I burn a fire/day is a little over 2 hrs. The fellow who is advising me on
the flue water jacket (at link above) thinks this may not yield very much
hot water. My inclination is to have him make the water jacket taller (more
surface area), and find a smaller tank (less cold water volume to dilute
the heat), but in the absence of some empirical work, or others'
experiences, this would be somewhat of a crap shoot . If moving things
closer to the firebox increases the rate at which heat transfers into the
water, then laying the 'water jacket' right on top of the stove (2) seems
almost too easy. Frank Tettemer has spoken up the most on this subject in
the past. Anyone else have thoughts on this?

(1) external stainless flue water jacket
(2) external 'water jacket' laid on top of stove

Obviously the more effective this system is at robbing heat from the stove
for DHW purposes, the less heat goes into the room, which leads
(dynamically) to incrementally longer burn times to reach the same desired
air temperatures. This is not a bad thing.
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