"Bob F" wrote in message
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"DerbyDad03" wrote in message
...
On Oct 23, 3:52 pm, dpb wrote:
Erma1ina wrote:
Bob F wrote:
"dpb" wrote in ...
james wrote:
My furnace was installed with a 16x20x1 pleated filter.

It looks like there is enough space to fit a 16x20x2 filter. This should
last
longer and reduce air resistance.

Is there any reason not to?
How can doubling the thickness _reduce_ resistance?
It doubles the surface area.

Keeping the CROSS SECTIONAL area (duct size) constant while increasing
the area (what you've called "SURFACE AREA")of filter material in
contact with the fluid (i.e., AIR) moving through the duct increases the
air resistance (in this case, the VISCOUS drag). QED

There ya' go...right. I was concentrating on the areas knowing at best
it could stay same.

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I was the one that brought up the issue of loading.

Would you agree or disagree that spreading the same amount of dust
over twice the surface area would "improve" the air flow over time -
by that I mean it would flatten the "degradation of air flow" curve
over the life of the filter. Not an actual increase in air flow, but a
stronger flow for a longer time due to less restriction.

That's a legitimate question on my part - I'm not trying to convince
you of anything, 'cuz i I don't know the answer. It just seems (to me)
that the system ought to act that way.

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It would do that, and lessen the drop across the brand new filter also.

If you look at the "holes per area" analogy, there are twice as many holes for
air to flow through, and twice as many holes to collect the same amount of
dust, so they plug more slowly.



Why else would they pleat filters?