[Stoves] Sidewinder not

[Crispin Pemberton-Pigott]

Dear Lanny

I like your analysis and the acuity of your observations.

>The vortex does seem to contain the heat.

I think this is obvious but there have to be reason for it, right?  The combustion is taking place there and if the flames cannot spread out into the combustion chamber, the heat stay concentrated which helps burn the CO and particulates.

>If you will notice in the video, the flames are pulled away from the 
>edges of the fuel and are concentrated in the center. 

I did notice.  The vortex is also keeping the flame small in diameter as it hits the pot.  I was hoping to continue the conversation we had a while ago about the length of the gas path between contacting the pot and reaching the edge of it.  Dale Andreatta, in an experiment about which I had some reservations, showed that the heat transfer along the sides of the pot was pretty minimal compared with the bottom.  This is (I guess) partly because of a low gas temperature by that time, and because the hottest gas does not hug the side of a pot the way it hugs the bottom.

You may be able to test the contribution of the vortex alone be running the fire through a cone to produce a non-vortexed stove with the same diameter contact point.  Compare that with the vortexed one....

I expect that a well established vortex will spin the gases as they pass under the pot in a radial fashion increasing the contact length.  I built a stove with a long (200mm) gas path under a smallish pot.  Instead of the gases passing along 85mm of pot, they passed under 200mm.  There was a 60% increase in the heat transfer.  I was so surprised by this that I was loathe to report it because it seemed impossible but it is a reproducable effect.  I reduced the gas path sectional area to compensate for reduced gas temperature/volume along its length to maintain a constant gas velocity.

It might be that your efficiency of the stove is mostly because the vortex simultaneously combining several efficiency-promoting ideas:

- better mixing
- lower losses to the walls
- burning the CO to generate extra heat
- small contact point at the pot center
- radially rotating gas path (accidentally)
- pot skirt

>....and how about some video now that I have DSL.

You live in Dreamland!

It is really hard for me to watch (or send) video on a Swazi dial-up.  I was impressed with the video system Tom Miles has in place on the REPP site.  I clicked and it ran!  Amazing.

Regards
Crispin