Rocket barrel oven - exhaust exit position

[whazzatt]

My rustic rocket barrel oven has served me excellently. It's this one: donkey32.proboards.com/thread/3610/basic-tube-rocket-barrel-oven

Next up - a portable unit. Or at least a movable one.  

CFB 6 inch J's burn chamber is already encased, and the oven component is in development.



drive.google.com/file/d/1-I53-pLbxvC-Ria13Phf3IahsB7AraNr/view?usp=sharing

Question

I often wonder if the excellent performance of the oven as a cooker has anything to do with the positioning of the exhaust hole in the oven's outer barrel. I think that perhaps its position underneath likely results in circulation of the heat around the entire barrel, creating a thoroughly hot oven. But would it make much difference if the exhaust hole were positioned on the back of the oven (pictured), along its vertical and round end at the bottom ('proposed' position in red)? This would require only 1 elbow join instead of two, as pictured.  

[whazzatt]

For my rocket barrel oven, I went with an exhaust exit as indicated by the red circle in the final picture of the previous post.

Here's the exit hole of my portable rocket oven:




As for performance, I'm not sure there's much of a difference between the J-shaped and U-shaped exits into the flue pipe. My preference is for the U because I think the immobile oven performs marginally better than the portable one, but that could be for other reasons, so the jury remains out.

J is easier and uses fewer materials, U may be needed in some applications. At least I can confirm that the U approach works excellently, though I should point out that the flue pipe attached to the U is rather tall.

[martyn]

I wonder if the entry and exit were to be set at a tangent it would then form a spinning air flow inside?