lsayre wrote:I'm tempted to suggest breathing in through the open air and then breathing in (simulating draft) through a bed of coal ash to see which is easier to do, but I won't.
I think the confusion is because people look at the coal bed as a restrictive object. Truth is, the little bit of air coming in the primary hardly notices the coal in the way at all, since the coal bed is just a huge pot of air passage ways.. At high volumes, sure it would slow it down, but dealing with the minute pressures and volumes in a coal bed, its un noticed.. Imagine blowing thru an air filter or blowing thru a Christmas tree. The only time the coal bed gets restricted enough to make a difference is when its completely clogged with ash. And at that point yer fire is goin bye bye..
That's why I see a -.005 stronger under the coal bed. It actually creates some of its own draft by heating the air that is coming up thru it. That's another best guess...
OK, the Christmas Tree was silly... Here's a more likely analogy... Imagine a gentle breeze oozing thru a screened window on a warm summer night. Is it likely the screen is slowing it down much? Would there be much difference in volume if the screen wasn't there? Probably not, right?
Then all of a sudden a thrashy thunderstorm moves in and a 60 MPH wind hits the screen. You here the screen whistle and click the light on to see it bowing inward. Is it likely the screen is slowing it down much? I would say yes. At high volume, the screen limits some air since its whistling and bowing are evidence. Would there be much difference if the screen wasn't there? I say yes again, since there is noticeable drag on the screen from a huge volume of air trying to get thru it.