I found these old videos on youtube and started putting together a playlist "Flow Visualization".
The concepts of laminar flow, flow stall, reverse flow, pressure vs velocity etc. are demonstrated. While this is done in a liquid medium and we are generally interested in gas, the concepts are presented clearly. I enjoyed watching these so much, I just had to share.
The segment below immediately made me think of the P-Channel, and so potentially adding to the theory of why it works. Where gas of higher density is added into the flow at the top of a lower density gas.
Fresh air entering the burn tunnel through the P-Channel is presumably cooler than the air (flames) already in the burn tunnel. This causes instability which provides for turbulent mixing, as shown below. Although, in our situation we may want the air to be preheated in order to prevent excessive cooling of the burn and aid in efficient combustion, it won't ever be preheated to equal temperature as the combustion itself. Thus the effect still has potential, in theory. Whether or not this actually has a significant effect, I don't know.
I figure this concept in combination with Peter's idea of the volatile gasses tending to flow at the top of the burn tunnel makes for efficient mixing and a nice clean burn.
I've embedded the video set to start at 23:05, where the example I reference is demonstrated-
Last Edit: Nov 15, 2014 3:03:38 GMT -8 by PNW Dave
For fuck sake mate! Whay haven't you dug that before!
Well, the sound seems to be a little wonky!
Thanks a lot anyway!
HA! I've only recently found these myself! But physics and conceptual understanding is one of my favorite late night pastimes. For anyone with similar interest, I highly recommend Richard A. Muller's course "Physics for Future Presidents" from Berkley, CA. (though not rocket stove related at all). All lectures from the course are available to view for free. I've seen every one since the 2006 semester at LEAST once, so long as it is Muller or Bob Jacobsen... I didn't care for the more recent lecturers. Here is a playlist on YouTube- Physics for Future Presidents
Yes, who ever did the video conversions did not compensate for differing video and audio rates, so the video progressively lags more and more behind the audio. In some places you'll hear the narrator describe something that won't be on screen for a few seconds. So it is good to keep that in mind while watching.
Getting grumpy with people who don't understand fluid mechanics. I had to research few other videos, here they are.
Despite the funnel end, this can well illustrate what the exhaust of the heat riser does.
This one is even better,
If you immagine what happens in, a T, the two blue regions are increased, even more turbulent, and the gases crashing on a flat surface instead of a sharp point, create even more turbulence. Mixing with the stalling blue adds more and more drag on the gases.
vesuvius: Do any of you have experience with using the glass from home oven doors on a rocket stove? I'd like to have a viewing port on my stove but don't want to fork out for new ceramic glass. Any thought as to whether it would take the heat of a rocket stove?
Jan 4, 2019 16:30:40 GMT -8
yaya: you dont need the blowair for that temp..
Jan 13, 2019 16:43:57 GMT -8
flybywire: Glass window from an old washing machine is designed to take high temps. Cheap solution to your need.
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jlmtech: GADGET: CONSIDER USING A JET PUMP INSTEAD OF A BLOWER FAN TO INDUCE DRAFT; NO CLOGGING.
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deadstarsstillburn: Hi there. I was directed this way by folks on the Permies.com website and am hoping I can get some information on how a total newbie can get started designing, siting, building, and not-dying-in-a-horrible-house-fire with a new RMH in a 160-year old home
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deadstarsstillburn: The people over there recommended either a 6" batchbox or an 8" J-tube. I don't know what those are but am going to try to figure that out. What I need is a blueprint that I can scale to fit the need for my house. I have something likne 5000 square feet
Oct 21, 2020 6:53:00 GMT -8
deadstarsstillburn: but I do not need to heat all of it by any means. probably only need to heat half of that, maybe less.
Oct 21, 2020 6:53:15 GMT -8
deadstarsstillburn: moreover, the house has 3 storeys (large attic) so I assume if I get very efficient heating on the ground floor, that will go a long way toward heating the upstairs as well, no?
Oct 21, 2020 6:53:59 GMT -8