Jeremy Baker wrote:I’ll second what Glenn mentions: try reducing the air intake. I made a similar stove. I placed a piece of sheet metal with a 2” hole in front of the air intake on mine and it helped.
Maybe insulate the exhaust flue??
How are the wood chips working.?
Glenn Herbert wrote:Since the water should never be in contact with the combustion core (so as not to steal heat from the fire and cool it and make it less efficient), the same setup I suggested before would work with an insulated firebrick core.
You didn't mention before that you plan to use exclusively woodchips as fuel. This makes your feed tube sensible, and also changes the parameters for how your firebox should be designed. Other people on Permies have experimented with woodchip feeders, and you might benefit from researching their efforts. An exposed metal feed which would tend to shed excess heat easily may be good, while a firebrick burn tunnel would let the heat build up for efficient combustion. I think you would want a smaller air supply opening. Reading about batch box primary and secondary air supply at batchrocket.eu should help you figure out a good system, even though it is geared to burning solid wood.