DIYbanter - View Single Post - High Efficiency gas furnace

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wrote:
Dave Martindale wrote:

... the thin-walled heat exchanger is more "efficient" because it's smaller.

Not much, I'd ween, if the dimensions of a forced air furnace heat exchanger
mostly depend on the air passages. With less metal, it would weigh less and
cost less, but those are different concerns.

And if the metal is a good conductor, eg steel with 50 Btu/h-ft-F, with poor
airfilm conductances on both sides, eg 5 Btu/h-F-ft^2, thinner steel won't
help much. How much, in this case, starting with 0.050" steel?

Nick

Heh, don't try to obfuscate the facts by spewing a bunch of calcs as
usual, trying to cover up. Just admit that you were wrong when you
claimed that "making the metal thinner won't help transfer the heat
more effectively." I showed you that:

1 - By the laws of physics, the heat transfered by conduction is
inversely proportional to the thickness of the metal. Despite your
well known love of spewing equations, you just completely ignored the
equation I provided, complete with reference, that says you are wrong.

2 - A manufacturer of air heat exchangers states in their heat
exchanger data sheet that they offer a metal thickness of .024 for high
efficiency applications and an increase to .050 thickeness for
applications where durability is more important.

And what's the crap about poor air film conductance on both sides of a
heat exchanger in a modern high efficiency furnace. If it's so damn
poor, how come these furnaces are 93%+ efficient? Could it be that
manufacturers know how to make heat exchangers that are efficient,
including using thinner metal and proper air flow techniques?