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rocket barrel oven - position of exhaust?

 
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Hi. I asked this on a different forum, but due to no responses there I am posting here.

My rocket oven experiment (super rustic demo unit) worked out excellently, and I'm moving on to a portable (or at least movable) unit.

I suspect that the position of the exhaust underneath the barrel (combined with a very tall chimney flue) plays a major role in the superb functionality of the stove. But I am not sure. Here is the exhaust config:



QUESTION: do you think there would be a considerable difference of heat transfer into the inner barrel if the exhaust exit were positioned on the back of the oven, along its vertical and round end at the bottom? As indicated by the red circle here...



Thanks.
 
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Hi David,    I'm a little lost with your question. Is there a reason why something already with a "superb functionality" would need to be changed?
 
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Hi David;
I think??? you are asking if there will be a noticeable difference in oven temperature, by moving the outlet from the very bottom to coming out the end?
If so then my opinion is it will work just as well as it does now. Maybe even better.
That 180 degree turn is a collection point for ash or moisture. By changing that to a 90 degree turn your system should flow even smoother.
 
thomas rubino
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Hi David;
Here's another idea for you.
Use a "plunger" tube exhaust . Come straight down from the top, no bends at all.
Leave 6" or so open from the floor for flow to start.  You could increase your oven temp the closer to the floor the plunger goes or raise the plunger and decrease oven temp...
Monitor your temps and choose a sweet spot that works best or slide it up or down to vary.
 
david pittaway
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Gerry Parent wrote:Hi David,    I'm a little lost with your question. Is there a reason why something already with a "superb functionality" would need to be changed?



Hi Gerry, and thanks for the reply. Yes, there is a reason. The 'portable' (or movable) unit I have under construction would be much easier to transport if the flue elbow protrudes from back of the barrel instead of underneath it. The unit I have designed will be relatively easy to dismantle into 4 parts: burn chamber and barrel frame, riser, oven, and flue pipe. The big 180 degree bend stemming from underneath the barrel makes the oven part far more awkward to move during transportation than the 90 degree bend - at least that's what I think. The rustic unit, pictured in my first post, will stay as it is - no need to change that (though it might get dismantled in what could be an extension to my cabin sometime...)

@Thomas_Rubino: thanks for your comments. The plunger tube exhaust is a great idea, but it won't work in this application. The gap between the back of the two barrels (or outer barrel and inner drum) will be too small - I am maximising space inside the oven.

My speculation is that the "superb functionality" of the unit may have something to do with the exhaust exit underneath, a position that I imagine 'wraps' the extremely hot air around the back of the oven, heating the bottom on the back of the barrel. My only concern is that an exhaust exit in the 'new' position would mean that the bottom of the back of the barrel won't get as hot. @Thomas_Rubino I'm curious to hear why you think the new position would be better. I can see why you would say that the flow would be even smoother - there would be less of an obstruction with the new position. But I imagine that I'm looking for a sweet spot where the heat doesn't exit too quickly or from a position that may mean the entire inner drum is not totally 'wrapped' in heat. I don't have a problem with flow because I compensate for the 180 degree bend with a very tall flue pipe. By changing the position of the exhaust exit position, however, there could be a possibility that I am introducing the 'problem' of sub-maximum heat transfer into the oven.

Any other thoughts or comments welcome...    

     
 
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