"bq340" wrote in message
...
Smitty Two wrote:

The part I'm having trouble with is the completely unjustified and
unsubstantiated claim that doubling surface area doubles (or improves by any
factor) air flow, given the same cross-sectional area of duct.

Sounds like you are envisioning a fiberglass filter, not the fan-fold paper
ones.

If you have a fan-fold one that has 1" thick folds then we will arbitrarily
say it has 2000 tiny holes in it (although it really has more, obviously).
Now if we make the pleats 2" thick we now have twice as many holes in it,
allowing twice as much air to pass thru it.

The outside dimensions stay the same, but the thickness of the filter paper
pleats (surface area) is doubled.

That's was going to be my analogy also.