Originally Posted by Carbon
Ok, I can see that. Then how about eight 1/2" holes on a flat drum top? The total area of those eight exhaust holes are significantly smaller than a single 2" exhaust.
Originally Posted by foam2
The idea of thermo dynamics on a domed lid vs flat with regards to the size of the exhaust is absurd.
The whole effect of heat rising and creating a draw up through an exhaust stack is thermo dynamics and fluid dynamics at work. If you think its absurd, your absurd....
I have personally experimented with diferent length exhaust tubes from the barrel flat top and I can with the exact same inlet openings, change the temp by as much as 50degrees with a longer exhaust tube. I currently use a 6" exhaust but with a 12" stack the drum will run 50 degrees hotter than the 6" with the exact same setup....
with the normal offset location of the bung hole on a flat top drum the heat on the side oposite the exhaust will rush up against the top of the flat lid and turbulate causing a high pressure zone(turbulent flow), where the heat that rises adjacent to the exhaust opening will rocket straight up and out the 2" exhaust (laminar flow) causing a vaccum(low pressure) and thus a positive flow or a draft in the upward orientation....
With a domed lid the heat all rushes up toward the center exhaust and out, thus the webber lids usually can get by with a much smaller exhaust because of this effect. (the eight circumferential holes would eliminate the turbulence since the hole are all equidistance from the center thus requireing less voulmetric flow)
If you notice the exhuast on a weber usually comes out with a fairly high flow rate and a nice amount of force. Conversely try looking at a drum with an offset exhaust, where the exhaust comes out a failry low flow rate.... but with a higher volume. It's all about volumetric displacement, how much air can you move thru the inlets up through the coals across the food grates and out through the exhaust..
Now, Im done with this. This place was not meant to argue or point finger at each other and call each others ideas absurd, Instead we should be considering all the things each other have to say in the intrest of our mutually shared hobby and passion... This was not meant for the person who simply wanted to discuss this topic
, have a nice day..
Heres a little light reading for you...